Food Hygiene and Control PDF

Food Hygiene and Control By Dr. Eglal Ghoneim Salem Definition Food hygiene may be defined as the sanitary science which aims to study methods for production, preparation and presentation of food which is safe for...

Food Hygiene and Control By Dr. Eglal Ghoneim Salem Definition Food hygiene may be defined as the sanitary science which aims to study methods for production, preparation and presentation of food which is safe for the consumer and of good keeping quality. Objectives The broad objective of food control program is to promote a safe and honestly presented food supply to protect consumers against being offered foods which are: (1) Injuries to health. (2) Unfit for human consumption. (3) Adulterated or presented in a deceived manner. The need for food control services Food control is needed to encourage the production and handling of food under hygienic conditions to prevent microbiological contamination which now causes most outbreaks of food born illnesses, and at the same time to deal with the increasing risks of chemical contamination and attendant health hazard. Other important needs are: 1. Food control programmes reduce food losses 2. Laws are still needed to control gross adulteration and contamination 3. Microbiological contamination causes most food-borne illnesses 4. Centralized food processing increases importance of controls 5. Environmental contamination creates new problems 6. Control of “Dumping” 7. Uniform and accurate weights and measures are essential to marketing 8. Pesticides usage increases need for food control 9. Food additives use must be controlled 10. The need to control zoonoses 11. The problem of aflatoxins and other mycotoxins 12. Atomic energy and food irradiation present new problems 13. The need for food standards 14. The role of food control in nutritional improvement Chemical contamination of foods 1- Radioactive fallout Nuclear fission generates over 200 radioisotopes of some 60 different elements. Many of these are harmful to man because they may be incorporated into body tissues. 1 2- Pesticides Contamination of food with residue of pesticides may result from the application of these chemicals in agriculture, industry or household. The most likely compounds to appear as food contamination are the insecticides. 3- Fertilizers and plant growth regulators 4- Asbestos It is widely distributes in the environment as a result of industrial pollution. An additional source of asbestos fibers may be the use of asbestos filtration pads. 5- Antibiotics May occur incidentally through the treatment of diseased animals or added during processing to aid in the preservation of foods. 6- Trace metals A variety of trace metals may become components of foods through industrial contamination of the environment as mercury, cadmium and lead, where they may be accumulated in fish and shellfish as a result of marine pollution. Also, they may be introduced into foods through pickup from equipment and containers, especially tin cans as (tin and lead). 7- Fungal toxins (mycotoxins) The most common are the aflatoxins formed by members of the Aspergillus flavus group. Sources of food contamination with Micro-organisms The original forms of the biological materials of animals or plants which serve as the basis of natural foodstuffs usually carry none or very few micro-organisms. Examples are tissues and organs of living animals and plants, the milk within the udder, the egg in the oviduct of the hen, etc. Exposure to contamination however starts when the natural biological materials are collected and turned into manufactured foodstuffs (from the process of slaughter, harvesting of vegetables, milking, the laying of the egg, etc.) and will continue until the food is consumed. The sources from where this contamination with micro-organisms originate are the principle reservoirs of micro-organisms in nature. Many reservoirs of the bacteria which cause food born gastro enteric illnesses could be listed. Some important ones are man and the animals he keeps, sewage, manure, soil, water, air, rodent, insects, and the food supply. Water and soil frequently acquire pathogens from sewage (human source); in turn, the food supply may acquire pathogens from all the above-named sources, thus, man and animals emerge as the fundamental sources of the organisms which are responsible for food borne gastrointestinal illnesses. I- The human reservoir 2  The area of the mouth, nose, and throat of a healthy man are bound with micro-organisms of various kinds. It was found that 30-50 percent of healthy people carry staphylococci in their nose, in patients and working personnel in hospitals, the nasal carriage may be as high as 60-80 percent. The human clean skin and hands carry some organisms. But when the skin and hands are not clean, or if there are lesions on the hands such as boils, ulcers, abrasions, septic cuts and burns, an impressive number and variety of micro-organisms are present and a small speck of pus could inoculate food with millions of organisms The un-guarded cough or sneeze can disperse from the nose, mouth, or throat numbers of bacteria suspended in droplets of moisture. These droplets serve to pass infection directly from one person to another; they may also contaminate foodstuffs. The habit of licking the finger to pick up paper is a bad one, particularly when the paper, contaminated with saliva, is used for wrapping food. Nose picking or fingering the nose may leave staphylococci or other harmful organisms on the hands. The intestinal tract of man may harbours a variety of bacteria in large numbers such as coliforms and Escherichia coil. The faecal excreta of diseased person or carriers harbour the infecting agents such as Salmonellae and Glostridium perfringens. The intestinal organisms may get attached to the hands of the food handler when he visits the toilet and does not thoroughly wash his hands before returning to work. Thus contaminated hands may pass infection to food, however, washing hands by soap and water can eliminate the organisms that are not harboured in the skin like staphylococci. Aerosol sprays from flushed lavatory, soiled seats, door handles may also pass infection from person to person. The more fluid the stool, the more danger from spread. II- The animal reservoir 1- Livestock Animals may become infected through eating contaminated feeding meals, grazing on contaminated pasture land, or by contact with animals, human, or bird excretes on the farm and during transport. Thus the meat animals may contain, in addition to the natural surface flora, a contamination with important kinds of microorganisms from their intestinal tract, and from hides, hoods, and hair which usually contain not only large number of pathogenic organisms from soil, manure, feed and water, but also important kinds of spoilage organisms. The slime that covers fish, gills and the intestine of fish, skin, feathers and feet of poultry, all contain large numbers of different kinds of micro-organisms 2- Vermins Rats and mice are destroyers and polluters of foods particularly the raw materials and the finished stored products. They can suffer from infection due to types of salmonellae which can survive for long time in rat faeces. The organisms will be picked up on farms, in sewers, and from garbage. Thus their droppings are a source of danger to food which they soil. 3  Cockroaches are able to contaminate food, equipment and utensils by carrying filthy materials on their legs and bodies. Also, while feeding on food, cockroaches may regurgitate filthy material previously eaten which may be laden with bacteria. Flies carry disease-causing organisms in their mouth parts, intestinal tract and on their leg hairs and feet. Since flies feed on faeces, animal manure, and human filth, all of which may contain intestinal pathogens of human and animal origin, they are an important reservoir of micro-organisms causing many food borne illnesses. 3- Domestic animals Cast and dogs are sometimes kept in food establishments for controlling rodents. They may be also found around the factories as pet animals. Their hair and excreta may contaminate the foods III- The environment 1- Soil Soil is considered the main natural reservoir for micro-organisms whether regarding the number or the kinds. Micro-organisms present on soil particles contaminate the surfaces of growing plants, animals, the air, and the running natural waters. Animals contribute their wastes and finally their bodies to the soil. Sewage going onto soils contributes to their microflora. These are potential sources for pathogenic and enteric microorganisms. Soil may enter the areas of food preparation and storage in many ways: with the food and its wrapping, on the employees’ shoes, and in the air. 2- Water Water is used in large volumes in food industry for several purposes, by employees, for washing and preparation of raw materials, for cleaning purposes, for processing, and as a major ingredient in certain foods. Ground water from springs and wells usually have a small number of bacteria (few to several hundreds/ml), since they are filtered by passing through layers of rook and soil. On the other hand, surface waters in lakes and rivers vary considerably in their microbial content depending on water composition, the soil it contacts, surface pollution and many other factors that affect self-purification. 3- Sewage The micro flora of sewage varies greatly depending on its age and method of disposal. Fresh sewage contains the flora of the intestinal tract which may contain human pathogens. Consequently the usage of untreated domestic sewage as fertilizer or for watering the soils as it is practices in certain areas make it quite probable that raw plant foods, i.e., fresh fruits and vegetables, may become contaminated with pathogens particularly those causing gastrointestinal disturbances. Fish and other sea foods may be also contaminated with pathogens through sewage going to water. 4- Air Spoilage organisms as well as human pathogens may contaminate the food through the air. There is no natural micro flora for air. The micro-organisms present in air are generally accidental and usually present on solid particles or moisture droplets suspended in the air. 4  The general sources of micro-organisms found in the air of food establishments are: 1) Dust and dry soil. 2) Sprays from natural waters, liquid foods and liquid ingredients. 3) Droplets from coughing, sneezing, etc. 4) Dust from dry food products or ingredients. 5) Mold spores growing on the surroundings such as walls and ceilings. Molds, bacteria and yeasts merely persist in the air. The number varies widely depending on location, movement, sunshine, humidity and amount of suspended matter Generally speaking, the means of transmission of micro-organisms to foodstuffs in the factory, shop, and kitchens are by direct contacts with the microbial reservoirs themselves or by indirect contacts through other dead or living objects which have become contaminated from the same sources (containers, utensils, equipment, ingredients and the human hand). Relation of food contamination to public health The growth of micro-organisms in the foods causes the breakdown of its constituents and the produced of certain changes. These changes could be: 1. Desirable changes Such as the fermentation processes in the production of beer or wine and the manufacture of cheese. Also production of fermented milks, e.g. Yoghurt, Kefir etc. depends completely on activities of desirable micro-organisms added to milk in the form of starters. 2. Undesirable changes (spoilage) As the souring of milk, molding of bread, putrefactions, rancidity, discoloration and gassy fermentation of dairy products. 3. Harmful changes (poisoning) A few are harmful, as the growth of pathogenic bacteria in foods. The growth of pathogenic micro-organisms in food may cause food poisoning (intoxication) due to ingestion of toxins elaborated by the organisms in the food or food infection caused by invasion, growth and damage to the tissue of the host by pathogens carried by the food. Food Spoilage Spoiled food may be defined as: Food that has been damaged or injured so as to make it undesirable or unfit for human consumption. However, it is difficult to sharply define spoilage because different people have different concepts about edibility or fitness to eat, and for what one person eat, another will not. 5 Criteria for assurance of fitness: 1. The desired stage of development or maturity of the food. 2. Freedom from pollution at any stage in the production and subsequent handling of the food. 3. Freedom from objectionable chemical and physical changes resulting from action of food enzymes; activity of microbes, insects, rodents; invasion of parasites, and damage from pressure, freezing, heating, drying, and the like. Causes of spoilage Spoilage may be due to one or more of the following: 1- The growth and activity of microorganisms. 2- Insects. 3- Action of enzymes of plant or animal food (Autolysis). 4- Chemical reactions not catalyzed by enzymes. 5- Physical changes as those caused by freezing, burning......etc. Classification of foods on ease of spoilage 1- Stable or nonperishable foods; these foods which do not spoil unless handled carelessly, include products such as sugar, flour, and dry beans. 2-Semiperishable foods: If these foods are properly handled and stored, they will remain unspoiled for a fairly long period as potatoes and nutmeats. 3- Perishable foods: This group includes most of our daily foods that spoiled readily unless special preservative methods are used as meat, poultry, fish, milk, eggs and many fruits and vegetables. Factors affecting the growth of microorganism in food The rate of growth of existing organisms in food is affected by intrinsic and extrinsic factors present in food. I- Intrinsic factors They are the expression of the physical properties, the chemical composition, and some biological attributes of the food itself. 1) Hydrogen-ion concentration (pH) Most microorganisms grow best at pH values around 7.0, while few grow below 4.0. Bacteria tend to be more fastidious in their relationships to pH than molds and yeasts, with the pathogenic bacteria being the most fastidious. The pH of fruits, soft drinks, vinegar and wines all fall below the point at which bacteria normally grow. Thus the excellent keeping quality of these products is due in great part to pH. However, fruits generally undergo mold and yeast spoilage due to the ability of these organisms to grow at pH values below 3.5. 6  At the same time, most of the meats and sea foods have a final ultimate pH of about 5.6 and above. This makes these products susceptible to bacterial as well as mold and yeast spoilage. 2) Moisture content The preservation of foods by drying is a direct consequence of removal or binding of moisture without which microorganism do not grow. The water requirements of microorganisms defined as water activity (aw). Just as yeast and mold grow over a wider pH range than bacteria, the same is true for aw, as most Spoilage bacteria do not grow below aw of 0.91, while spoilage yeast and molds can grow as low as 0.80.  Dry foods (bread and milk powder) is likely to spoil by molds.  Foods of low water content (condensed milk) are spoiled by yeasts.  Most natural food (milk, meat,) is spoiled by bacteria.  I.e. bacteria need more moisture than yeasts followed by molds. 3) Oxygen tension and oxidation-reduction potential The oxygen tension or partial pressure of oxygen about a food and the oxidation-reduction (O/R) potential or reducing and oxidizing power of the food itself influence the type of organisms to grow and hence the changes produced in the food. 4) Nutrient content The kinds and proportion of the nutrients are important to determine what spoilage organisms are most likely to grow. Generally, microorganisms require water, source of energy, source of nitrogen, vitamins and minerals for their growth and function. 5) Antimicrobial constituents The stability of some foods against attack by microorganisms is due to the presence in these foods of certain naturally occurring substances with antimicrobial activities, e.g. Lactenin and anticoliform factor in fresh milk, lysozyme in egg white. Also microorganisms growing in a food may produce one or more substances inhibitory to other organism as acids, alcohols, peroxides or antibiotics. As alcohol fermentation inhibits bacteria, nisin by Strepto lactis inhibit gas forming Clostridium. 6) Biological structure The natural covering of some foods provides excellent protection against the entry and subsequent damage by spoilage organisms, e.g. the outer covering of fruits, the shell of nuts, the hide of animals and the shells of eggs. II- Extrinsic factors Are those properties of the storage environment that affect both the foods and the micro-organisms. 1- Temperature of storage There is a likelihood of spoilage at any temperature between 5°C and 50°C, since microorganisms differ so widely in their optimum, minimum and maximum temperature for growth. 7  Molds and yeasts grow well at ordinary, refrigerator and freezing temperature and do not grow well above 35-37°C. Most bacteria grow best at ordinary temperature (mesophiles), some (thermophiles) grow well at high temperature and other (psychrophiles) at chilling temperature. 2- Relative humidity of environment (R.H) When foods with low aw values are placed in environment of high R.H, the foods pick up moisture from the air and thereby increase its surface water, leading to surface spoilage. On the other hand, if the R.H. is lower than the aw of the food, the latter will lose moisture to the atmosphere and thereby become undesirable. By altering the gaseous atmosphere, however, it is to retard surface spoilage without lowering the R.H. 3- Presence and concentration of gases in the environment The storage of food in atmosphere containing up to 10% Co2 is referred to as “controlled atmosphere” or CO2 storage. Carbon dioxide has been shown to retard fungal rotting of fruits. Ozone also may be added to food storage environment as preservatives. However, ozone should not be used on high lipid-content foods, as it may increases the rancidity due to its oxidizing action. Food poisoning The term food poisoning describes a state in which the victim suffers an acute attack of abdominal pain and diarrhea sometimes accompanied by vomiting and lasting usually 1-2 days, but sometimes a week or more. The onset is usually sudden and may start as early as 2 hours and up to 40 or more hours after eating the contaminated food. Types of food poisoning 1-Food itself may be poisonous; some plants, fungi, and shellfish. 2- Allergic or sensitivity reactions to certain foods. 3-Microorganisms, most commonly bacteria or the poisons they form, present in food or drink, some of which survive the heat of cooking. 4- Chemical contamination may occur during food preparation. Acid foods can dissolve metal from containers or utensils. Bacterial food poisoning 1-Food borne intoxication due to the presence of toxins produced by the bacteria in the foodstuff. 2-Food borne infections due to the activity, within the gastrointestinal system of victim, of large numbers of bacterial cells. These are the most important types of bacteria causing food poisoning 1- Salmonella  Organisms of the salmonella group cause food poisoning by infection; that is, by invasion of the body. 8   They reach food directly or indirectly from animal excreta at time of slaughter, from human excreta, or water polluted by sewage; also in the kitchen they may be transferred from raw to cooked foods by hands, surfaces, utensils, and other  Illness is more likely to occur when the organisms are ingested in large numbers; a chance contamination of the food by a small number of bacilli may not be harmful.  When they are allowed to multiply in the food, that is, if the lightly contaminated food stands for some hours in a warm room, then sufficient numbers of bacteria will develop to produce symptoms in the consumer.  The onset of illness occurs usually within 8 to 36 hours of eating the food, although the incubation period may be longer.  The symptoms are characterized by fever, headache and general aching of the limbs, as well as diarrhea, and vomiting. The duration of illness is from 1 to 7 days (longer than that caused by the toxin of Staphylococcus). 2- Staphylococcus Staphylococcal food poisoning follows the consumption of food heavily contaminated with certain types of Staphylococcus auieus which produce a poisonous or toxic substance in the food. The skin and nose frequently harbour staphylococci, and cooked foods such as meat and poultry intended to be eaten cold, and prepared foods such as custards, trifles and creams also, are readily contaminated by hands. Since the toxin is formed by the organism in food before it is eaten and not after it has entered the body, the incubation period may be as short as 2 hours but in general it is 4 to 6 hours. There is a rapid onset of symptoms characterized by severe vomiting, diarrhea, abdominal pain, and cramps, sometimes followed by collapse. Recovery is rapid. Whereas the staphylococcus itself is fairly readily destroyed by the heat of pasteurization and normal cooking procedures, the toxin is more resistant to heat: it is destroyed gradually during boiling for at least 30 minutes. It may remain active after light cooking. 3- Clostridium perfringens C.perfringens is a common organism frequently found in excreta from humans and animals, and in raw meats and poultry and other foods, including dehydrated products. It can survive heat and dehydration by means of the spores which remain dormant in food, soil, and dust. Illness occurs after eating food grossly contaminated with C.perfingens which has multiplied from spores which have survived cooking; they are activated to germinate by the heat. Multiplication takes place during long slow cooling and warm storage in the kitchen or canteen of cooked meat, poultry, fish, stews, pies, and gravies. The spores vary in their ability to withstand heat. Some strains of C.perfringens can survive hours of boiling; others only a few minutes. 9  Symptoms occur from 8 to 22 hours after consuming the contaminated foods; they include abdominal pain, diarrhea and nausea, but rarely vomiting; they may continue for 12 to 48 hours. The symptoms result from the activities of a large dose of organisms which produce an enterotoxin in the intestine; an effective amount of toxin is not formed in the food before it is eaten. 4- Clostridium botulinum  The toxin of C.botulinum, another anaerobic spore-bearing bacillus, is a highly poisonous substance produced as the organism grows in food. It affects the nervous system, causing an often fatal illness.  Outbreaks and cases of botulism rarely occur and depend on the feeding habits of the population  The spores are resistant to heat, and survive boiling and higher temperatures.  The toxin is sensitive to heat, and in pure form it is destroyed by boiling. Nevertheless, it may be protected when mixed with protein and other material in food.  The toxin is lethal in very small does and gives rise to symptoms quite different from those of the organisms just described. The incubation period varies from 24 hours or less to 96 hours (usually 18-36).  The first signs of illness are lassitude, fatigue, headache, and dizziness. Diarrhea may be present at first but later the patient is obstinately constipated. The central nervous system becomes affected and there is disturbance of vision; later, speech becomes difficult and there is paralysis of the throat muscles.  The intoxication reaches its maximum within 24 hours to 8 days.  Death often occurs by paralysis of the respiratory centers. If after 8 days, the patient survives, convalescence is slow.  Life may be saved by giving antitoxin as soon as possible. 5- Bacillus cereus  B.cereus is a common aerobic sporing organism. The spores are often found in cereals and other foods.  Some spores will survive cooking and subsequently germinate into bacilli which under long warm storage conditions in cooked food grow and produce toxin.  A wide variety of foods have been associated with outbreaks, particularly corn flour sauce, and boiled and fried rice  The incubation period varies from 1 to 16 hours.  The onset of symptoms may be sudden with acute vomiting and some diarrhea; the incubation and symptom may closely resemble those of staphylococcal enterotoxin food poisoning. They may also resemble those of C. perfringens food poisoning. There is a serological typing scheme for B. cereus. Certain serotypes appear to be more responsible for outbreaks than others. 6- Escherichia coli 10   Although a normal inhabitant of the intestinal flora of man and animals, many strains are enteropathogenic and give rise to acute diarrhoeal enteritis in infants. Certain serotypes cause diarrhoea in adults also. Esch. Coli is considered to be responsible for a proportion of incidents described as “traveller’s diarrhoea”.  Infection of infants is acquired by direct spread in maternity units also by contaminated feeds  Infection in adults are initiated by large doses of entero-pathogenic Esch.coli in foods.  The organisms may enter kitchens in many raw foods and readily pass to cooked foods by the usual means of hands, surface, containers, and other equipment; they may be water-borne also. Human excreta may also play a part in direct spread during epidemics.  The incubation period is 12 hours to 3 days.  The symptoms may be those of diarrheal food poisoning or dysentery-like with more prolonged diarrhea and blood and mucus in the stool. 7- Vibro parahaemolyticus  Vibrio parahaemolyticus occurs in warm coastal waters and various sea foods and it may pass from raw to cooked foods.  It is a common cause of food poisoning in Japan and is reported from other countries also.  The incubation period is approximately 15 hours and the illness includes profuse diarrhea and vomiting which may last five or more days. 8-Campylobacter  Wild birds are the primary sources of Campylobacter spp. And probably spread it to domestic animals. Wild birds also may directly contaminate water supplies.  Transmission of Campylobacter spp. to human may be by director indirect means. The later primarily involves food products where foods are cross contaminated or undercooked. Some direct acquisition of the disease may occur when persons working in abattoir or poultry processing facilities come in direct contact with the organism during evisceration operation or other meat handling procedures.  Most campylobacter outbreaks have been caused by raw or un-pasteurized milk or contaminated water, as well as the consumption of raw or undercooked meat or poultry, recontamination after cooking can occur.  Campylobacter constitute a part of normal gastrointestinal and genitourinary flora of animals, particularly sheep and cattle. Chicken, wild birds and domestic animals such as dogs may also carry the organism and probably play a significant role in transmission to humans.  Campylobacter jejuni has the broadest animal reservoir, which includes poultry, dog, cat, sheep and cattle. C.coli is found primarily in swine, C.fetus is isolated from sheep and cattle and C.laridis from deagulls.  Campylobacter typically begins 1-7 days after ingestion of the contaminated food with lower right abdominal pain, which may be severe enough to mimic acute appendicitis. The abdominal pain is followed by diarrheal stools that usually contain blood and pus, fever is commonly present. Other organisms, such as certain streptococci, proteus and those in the providence group sometimes suspected to cause food poisoning when reaching abnormal number in food. 11 Prevention of food poisoning 1-prevent spread of contamination in the kitchen: 1) Separation of raw and cooked food to avoid cross- contamination; 2) Care on part of food handler; 3) Cleanliness of kitchen environment. 2-Prevent bacteria already in food from growing and spreading: 1) Cold storage facilities must be adequate and efficiently maintained. 2) Avoid long storage in warmth (close time gaps between preparation and serving). 3) Provide facilities for rapid cooling in the retail store and in the kitchen. 3- Cook to destroy most bacteria (but not spores), with particular attention to: 1) Careful preparation and adequate cooking; 2) Serve at once. If not: 1. Keep hot; or 2. Cool rapidly and store cold; 3. Avoid recontamination. Food preservation Food for human consumption may be divided into eight main groups, of plant or animal origin. From plants origin From animals origin Cereals and cereal products Meat and meat products Sugar and sugar products Poultry and eggs Vegetables and vegetables products Fish and other seafood Fruits and fruit products Milk and milk product  Others as spices, flavoring material, minerals (as NaCl) vitamins...etc.  Most kinds of food are readily decomposed by microorganisms unless special methods are used for their preservation. Methods of food preservation 1- Asepsis, or keeping out microorganisms. 2- Removal of microorganisms. 3- Maintenance of anaerobic conditions. 4- Use of high temperatures. 5- Use of low temperatures. 6- Drying. 7- Use of chemical preservatives. 8- Mechanical destruction of microorganisms, e.g., by grinding, high pressure…etc. 9- Irradiation. 12 10- Combination of two or more of the above methods. Principle of food preservation 1- Prevention or delay of microbial decomposition 1. By keeping out microorganisms (a sepsis). 2. By removal of microorganisms. (filtration). 3. By hindering the growth and activity of microorganisms (low temp.) 2- Prevention or delay of self decomposition of the food  By destruction or in activation of food enzymes (blanching).  By prevention or delay of purely chemical reactions (prevention of oxidation using an antioxidants). 3- Prevention of damage because of insects, animals, mechanical causes…etc The methods used to control the activities of the microorganisms, usually are effective against enzymatic activity in the food or chemical reactions. Asepsis In nature there are numerous examples of asepsis, or keeping out microorganisms, as a preservative factor. The healthy inner tissues of plants and animals usually are free from microorganisms, and if any are present they are unlikely to initiate spoilage. If there is protective covering about the food, microbial decomposition is delayed or prevented (e.g. shells of nuts, sin of fruits and vegetables, shells of eggs…etc). It is only when the protective covering has been damaged or decomposition has spread from the outer surface that the inner tissues are subjected to decomposition by microorganisms. In the food industries an increasing amount of attention is being given to the prevention of the contamination of foods, from the raw material to the finished product. The food technologist is concerned with the "load" of organisms present. The kinds are important in that they may include dangerous spoilage organisms, those desirable in food fermentation, or even pathogenic (disease- producing) microorganisms. The numbers of microorganisms are important because the more spoilage organisms there are present, the more likely will be the spoilage of the food and the more difficult its preservation. The "load" may be the result of contamination, or the growth of organisms, and in many cases of both. Some examples of aseptic methods in food industry:  Proper handling of food to prevent contamination of the final product from raw materials.  Prevention of contamination, mainly from, equipments.  Packaging of food is a widely used application of asepsis. Removal of microorganism 13  It is not very effective in food preservation, but under special conditions may be helpful. 1) Filtration is only a successful method for removal of organisms from clear fluids as fruit juices, beer, soft drinks, wine and water. The liquids are forced to pass by –ve or +ve pressure. 2) Centrifugation or sedimentation are not very effective. 3) Washing can be helpful or harmful:  Washing of fruits and vegetables to remove soil organisms that might be resistant to heat processing during their canning.  Washing of equipments coming into contact with food.  Washing is dangerous if the water adds spoilage organisms or increases the moisture so that growth of spoilage organisms is encouraged. 4) Trimming away of spoiled portions of food may be helpful in food preservation. Although large numbers of spoilage organisms are removed, heavy contamination of the remaining food may take place. Maintenance of anaerobic conditions A preservative factor in sealed, packaged foods may be anaerobic conditions in the container. A complete fill, evacuation of the unfilled space, or the replacement of the air by carbon dioxide or by an inert gas (as nitrogen) will bring about anaerobic conditions. Production of CO2 during fermentation and accumulation at the surface will serve to make conditions anaerobic there and prevent the growth of aerobes. Some aerobic spore-formers are resistant to heat and may survive in canned food but be unable to germinate or grow in the absence of oxygen. Use of high temperatures  The killing of microorganisms by heat is supposed to be due to coagulation of the proteins and especially to the inactivation of enzymes necessary for metabolism.  The heat treatment necessary to kill organisms or their spores varies with the kind of organism, its state, and the environment during heating.  Depending upon the heat-treatment employed, only part of the vegetative cells, most or all of the cells, part of the bacterial spores, or all of them may be killed.  The heat-treatment selected will depend upon the kinds of organisms to be killed, other preservative methods to be employed, and the effect of heat on the food. Heat-treatment employed in processing foods The various degrees of heating used on foods might be classified as (1) pasteurization, (2) heating at about 100C, and (3) heating above 100C. 1- Pasteurization 14  Pasteurization is a heat-treatment that kills part but not all the micro-organisms present and usually involves the application of temperatures below 100C. The heating may be by means of steam, hot water, dry heat, or electric currents. Pasteurization is used 1. When more vigorous heat-treatments would harm the quality o the product, as with market milk; 2. When one aim to kill pathogens, as with market milk; 3. When the main spoilage organisms are not very heat-resistant, like yeasts in fruit juices; 4. When any surviving spoilage organisms will be taken care of by additional preservative methods to be employed, as is done in the chilling of market milk; and 5. When competing organisms are to be killed, allowing a desired fermentation, usually by added starter organisms, as in cheese making. Preservative methods used to supplement pasteurization: 1. Refrigeration, e.g., of milk; 2. Keeping out microorganisms, usually by packaging the product in a sealed container; 3. Maintenance of anaerobic conditions in sealed containers; 4. Addition of high concentration of sugar, as in sweetened condensed milk; and 5. Presence or addition of chemical preservatives, as the organic acids on pickles. Times and temperatures used in the pasteurization process depend upon the method employed and the product treated. Examples  Milk is heated at 61.7C for 30 min in the holding method (low-temperature-long-time) and at 71.7C for 15 sec in the high-temperature-short-time method.  Ice-cream mix is heated at 71.1C for 30 min or at 82.2C for 16 to 20 sec.  Dried fruits usually are pasteurized in the package at 65.6 to 85C for 30 to 90 min, the treatment varying with the kind of fruit and the size of the package. 2- Heating at about 100C Formerly, home canners processed all foods for varying lengths of time at 100C or less. This treatment was sufficient to kill everything but bacterial spores in the food and often was sufficient to preserve even low and medium acid foods. 3- Heating above 100C Temperatures above 100C usually are obtained by means of steam under pressure in steam-pressure sterilizes or retorts. Canning Is defined as the preservation of foods in sealed containers and usually implies heat-treatment as the principal factor in the prevention of spoilage. Most canning is in "tin-cans", which are made of tin-coated steel, or in glass containers. The canning procedure 15  Raw food for canning should be freshly harvested, properly prepared, inspected, graded if desired, and thoroughly washed before introduction into the can. Many vegetable foods are blanched or scalded briefly by hot water or steam before packaging. The blanching washes the food further, sets the color, softens the tissues to aid packing, help form the vacuum, and kill some microorganisms. Brine consisting of salt solution or salt plus sugar, is added to some canned vegetables, and before sealing, usually by the heating of the "head space", or unfilled part of the container, but often by mechanical means. The heat process The canner aims for complete sterilization of most foods but does not always attain it. Instead of killing all microorganisms in the food he may kill all that could spoil the food under normal conditions of storage and he may leave some that are unable to grow, making the can of food "commercially sterile". The heat processes necessary for the preservation of canned foods depend upon the heat resistance of the spoilage organisms present and heat penetration into the food in the can. The factors that determine the time required to bring the center of the container of food up to the sterilizing temperature are: (1) The material of which the container is made; (2) The size and shape of the container; (3) Initial temperature of the food (practically no difference); (4) Retort temperature; (5) Consistency of can contents and size and shape of pieces; and (6) Rotation and agitation. The cooling process Following the application of heat the containers of food are cooled as rapidly as is practicable. Use of low temperatures Low temperatures are used to retard chemical reactions and action of food enzymes and to slow down or stop growth and activity of microorganisms in food. The lower the temperature, the slower will be chemical reactions, enzyme action, and microbial growth; and a low enough temperature will prevent the growth of any microorganism. Lethal effect of freezing and subfreezing temperatures The lethal effect, supposedly due to the denaturation and flocculation of cell proteins, depends upon the following factors: 1. The kind of microorganism and its state. Resistance to freezing temperatures varies with the kind of organism, its phase of growth, and whether it is in the vegetative or spore state. 16  2. The temperature during freezing and storage. It was reported that bacteria die most rapidly in the range –1 to -5C. The quicker the freezing process, the more rapidly the temperature of the food would pass through this critical zone and the less would be the killing. Slow freezing permits some growth of bacteria before the food becomes frozen. Although a greater percentage of organisms are killed by slow freezing than fast, the greater total number of organisms present at freezing with the slow method may result in a greater number of surviving organisms than was in the original unfrozen food. 3. The time of storage in the frozen conditions. The numbers of viable microorganisms decrease with lengthened time of storage. Death supposedly is due to starvation. 4. The kind of food. Sugar, salt, proteins, colloids, fat may be protective, while high moisture and low pH may hasten killing. 5. Alternative freezing and thawing is supposed to hasten the killing of microorganisms, but apparently does not do so in all instances. Temperatures employed in low-temperature storage  Common, or cellar, storage.  Chilling.  Cold storage or freezing. 1- Common, or cellar, storage The temperature usually is not much below that of the outside air, and seldom is lower than 15C. Humidity is controlled to prevent loss of weight or spoilage. Root corps, potatoes, cabbage, celery, apples and similar foods can be stored for limited period. 2- Chilling It is the storage at temperatures not far above freezing. It may be used as the main preservative method for food or for temporary preservation until some other preservative process is applied. Enzymatic and microbial changes in the foods are not prevented but are slowed down considerably. Factors to be considered in connection with chilling storage include the temperature of chilling, the relative humidity, air velocity and composition of the atmosphere in the storeroom, and the possible use of ultraviolet rays or other radiations. 2.1. Temperature Although most foods will keep best at a temperature just above their freezing point, they are not necessarily stored at this low temperature because of greater cost. Temperature of ordinary icebox varies from 4.4 to 12.8C while mechanical refrigerator from 0.0 to 10.0C. 2.2. Relative humidity  It varies with the other factors. 17   The presence of low relative humidity results in loss of moisture and hence of weight, in the wilting and softening of vegetables, and in the shrinkage of fruits.  High relative humidity favors the growth of spoilage microorganisms. The highest humidity, near saturation, is required for most bacterial growth on the surface of foods; less moisture is needed by yeasts, about 90 to 92%, and still by molds, which can grow in a relative humidity of 85-90%.  Ventilation to maintain uniform relative humidity, throughout the room is needed in removing odors, and in preventing the development of stale odors and flavors. 2.3. Composition of storage atmosphere The presence of optimal concentration of CO2 or O3, (1) a food will remain unspoiled for a longer period; or (2) a higher relative humidity can be maintained without harm; or (3) a higher storage temperature can be used without shortening the keeping time of the food. 2.4. Irradiation The use of ultraviolet irradiation permits the use of a higher humidity or storage temperature. 3- Freezing 3.1. Selection and preparation of foods for freezing Fruits and vegetables are selected on the basis of their suitability for freezing and their maturity, and are washed, trimmed, cut, or pretreated as desired. Most vegetables are blanched and fruits may be packed in a syrup. Meats and seafood are selected for quality and are handled so as to minimize enzymatic and microbial changes in them. Most foods are packaged before freezing, but some foods are frozen in small pieces, e.g., strawberries, may be frozen before packaging. The blanching of vegetables is done with hot water or steam to accomplish the following: (1) inactivation of most of the plant enzymes which otherwise might cause toughness, change in color, mustiness, loss in flavor, softening, and loss of nutritive value; (2) reduction (99%) in the numbers of microorganisms on the food; (3) enhancement of the green color of vegetables; (4) the wilting of leafy vegetables like spinach, making them pack better; (5) the displacement of air entrapped in the tissues. 3.2. Freezing of foods The rate of freezing of foods depends upon the method employed, the temperature, size and shape of package, kind of food…etc. There are three methods of freezing, slow freezing 93 to 72 hours), quick freezing (30 min) and sharp freezing. The advantages claimed for quick freezing over slow freezing are that (1) small ice crystals are formed; and hence less mechanical destruction of intact cells of the food; (2) there is a shorter period of solidification and therefore less time for diffusion of soluble materials and for separation of ice; (3) there is prompt prevention of microbial growth; (4) there is more rapid slowing of enzyme action. 3.3. Storage During storage chemical and enzymatic reaction proceed slowly. The unfrozen concentrated solution of sugars, salts…etc, may ooze from the package as a viscous material called the metacryotic liquid. 18 Vegetative cells of microorganisms are unable to take food and, in time, will die of starvation. 3.4. Thawing When the ice crystals melt, the liquid either is absorbed back into the tissue cells or leaks out from the food. It is termed drip or bleeding in case of meat and leakage in case of fruits and vegetables. Drying Drying usually is accomplished by the removal of water, but any method that reduces the amount of available moisture in a food is a form of drying. Thus, for example, dried fish may be heavily salted so that moisture is drawn out from the flesh and tied up by the solute and hence is unavailable to microorganisms. Sugar may be added as in sweetened condensed milk, to reduce the amount of available moisture. Moisture may be removed from foods by any of a number of methods. A sun-died food has had moisture removed by exposure to sun's rays without any artificially produced heat and without controlled temperatures, relative humidities, or air velocities. A dehydrated or desiccated food has been dried by artificially produced heat under controlled conditions of temperature, relative humidity, and air flow. Condensed usually infers that moisture has been removed from a liquid food, and evaporated may have a similar meaning or may be used synonymously with the term dehydrated. Methods of Drying: 1- Sun Drying: Sun drying is limited to favorable climates and to certain fruits such as raisins, prunes, figs, apricots, nectarines, pears, and peaches. 2- Drying by Mechanical Driers: Most methods of artificial drying involve the passage of heated air with controlled relative humidity over the food to be dried or the passage of the food through such air. A number of devices are used for controlled air circulation and for the refuse of air in some processes. The simplest dried is the evaporation or kiln, where the natural draft from the rinsing of heated air brings about the drying of the food. Forced- draft drying systems employ currents of heated air that move across the food, usually in tunnels. An alternative method is to move food on convey or belts or on trays in carts through the heated air. Liquid foods, such as milk, juices and soups may be evaporated by the use of comparatively low temperatures and a vacuum in a vacuum pans or similar device; drums dried by passage over a heated drum, with or without vacuum; or spray-dried by spraying the liquid into a current of dry, heated air. 3-Drying During Smoking: Most of the preservatives effect of the smoking of foods is due to the drying of food during the process. 19 4- Other Methods: Electronic heating has been suggested for the removal of still more moisture from a food already fairly well dried.Recently the removal of moisture by freezing under vacuum (lyophilization) has received an increasing amount of attention. Factors in the control of Drying: The proper control of dehydration includes the following factors: 1- The temperature employed, which will vary with the food and the method of drying. 2- The relative humidity of the air. This, too, is varied with the food, method of drying, and also with the stage of drying. It usually is higher at the start of drying than later. 3- The velocity of the air. 4- The time of drying. Improper control of these factors may cause casehardening due to more rapid evaporation of moisture from the surface than diffusion from interior, with a resulting hard, horny, impenetrable surface film that hinders further drying. Preservation by Preservatives Definition Preservatives are chemical agents which serve to retard, hinder or mask undesirable changes in food Purpose of use (I) Main Purpose (II) Others Inhibition of growth and activity of 1)Antioxidants:hinder oxidation MO.s by interfering with their: of unsaturated fats. 1-cell membrane 2) Neutralizers of acidity 2-enzyme activity 3) Stabilizers to prevent physical 3-genetic mechanisms changes 4) Coating or wrappers The ideal preservative (Not found) One that would be harmless to the consumer, effective in its preservative action, and would not cover inferiority of the food or add undesirable colour, odour or taste. Food preservatives may be divided into: 1. Added preservatives. 2. Developed preservatives. Added Preservatives They are added to inhibit or kill microorganisms and may be classified according to : 20  1. Chemical composition. 2. Mode of action. 3. Specificity 4. Effectiveness 5- Legality. e.g. Sugar is effective because of its physical action. Sodium benzoate is effective because of its chemical action. Sodium chloride is effective because of both actions. Added preservatives may be divided into: Inorganic Organic 1-Inorganic acids, their salts. 1-Organic acid their salts. 2-Alkalies and alkaline salts. 3-Sugar 3-Metals 4-Alcohols 4-Hallogens 5-Antibiotics 5-Peroxides 6-Wood smoke 6-Gases 7-Species, other condiments Inorganic Preservatives 1- Inorganic acid, their salts 1.1. Sodium chloride - It is used in brines and curing solutions or is applied directly to the food - It is added to slow down or prevent the growth of microorganisms or to permit an acid fermentation depending on the added concentration. - It has the following effect: 1. Increase osmotic pressure and hence plasmolysis of cells, the concentration of the salt necessary to inhibit the growth or harm the cell varying with the organism. 2. Drowing out and tying up moisture resulting in dehydration of the food and the microorganisms. 3. It ionizes to yield the chlorine ion which is harmfull to microorganisms. 4. It reduses the solubility of oxygen in the moisture. 5. It sensitizes the cell against CO2. 6. It Interferes with the action of proteolytic enzymes. N.B: The effectiveness of NaCl varies directely with its concentration and the tempreture. 1.2. Hypochlorites Usually as Na or Ca salts which yield hypochlorous acid,a powerfull oxidixing agent, and are effective germicidal agents. 21 Mode of action: microorganisms are harmed by: a- Oxidation. b- Direct chlorination of cell proteins. Their effectiveness is reduced by presence of organic matter in large amounts. Uses  Treatment of water used in food plants for drinking, processing, cooling, cleaning.  Incorporated in ice for icing fish in transit.  Added to water used for washing the exterior of fruits, vegetables. 1.3. Nitrites and nitrates Effect on meat colour  The effect of nitrites and nitrates on meat colour is produced by niric oxide (NO); which is a decomposition product of nitrite.  It reacts with the myoglobin-the pigment that acts as a vehicle for O2 storage in the muscle- to form nitrosomyoglobin.  Nitrosomyoglobin has the characteristic red color of meat, which when cooked gives the desired pink color of meat (nitrosohemochrome).  Nitrates have no direct influence on color except as a reservoir from which nitrite can be produced by reduction. Effect on meat flavor  The principle curing agents that affect flavor are salt, sugar, smoke and nitrites.  Nitrite ion may be expected to react with other meat components giving products with complex aroma, which might contribute to the cured flavor.  At least100 p.p.m of nitrite in the cured meat is essential to produce a full development of typical cured flavor. Effect on microorganisms Nitrites  It inhibits the growth of a number of food poisoning and spoilage microorganisms.  The presence of nitrite as curing salt in the medium has an effect on the growth of staphylococcus aureus and the production of enterotoxin B.  It prevents the growth of Clostridium botulinum.  Increasing the level of added nitrites reduced the number of cans in which the toxin was produced.  The action of nitrites increases with falling pH value at the acidic medium. Nitrates  Nitrates raise the oxidation-reduction potential and therefore are more favorable to aerobic than anaerobic organisms, so the antimicrobial action of nitrates is directed exclusively towards anaerobic bacteria.  The antimicrobial action of nitrates derives much more from the nitrite produced from the nitrates in food. Sources of nitrites and nitrates  Nitrites may be derived from nitrates during the storage of vegetables (as lettuce and spinach) by bacterial reduction.  In drinking water reduction of nitrates to nitrites was observed. 22  Nitrites and nitrates are also synthesized endogenously by nitrifying bacteria in the human body.  Nitrites and nitrates in food as additives. Toxicology of nitrites and nitrates  Nitrite causes the formation of methemoglobin that is not able to transport O2 to the lungs and tissues and causes O2 deprivation.(more in children).  It causes the formation of N-Nitroso compounds as nitroso-amines and nitroso-amides,both in the product and in the digestive tract through ingestion of the salts.  Nitrates reduce the rate of iodine uptake by the thyroid gland.  Nitrates are responsible for vitamin A deficiency ( that can be considered as a direct toxicity to nitrates).  The health risk from exposure to nitrates depends on the presence or absence of conditions suitable to their reduction to nitrites. Young infants constitute the most vulnerable group due to: 1. Lower acidity in their stomach allows the growth of certain microbes that contain enzymes capable of reducing nitrates to nitrites. 2. Erethrocytes during childhood may be more susceptible to conversion to methemoglobin by the action of nitrites. 3. The enzyme system capable of reducing methemoglobin to hemoglobin is deficient in young infants. 4. The fluid intake of the young infant is higher than that of adult in relation to the body weight. Detoxification of nitrites and nitrates  Alpha tocopherol is used as a part of meat curing to inhibit N-nitroso compounds formation.  A combination of tocopherol and ascobate has a significant reduction of nitrosamines formation.  Soya products inhibit the formation of N-Nitroso amines (most probably the unsaturated fatty acids present). 1.4.- Sulfur dioxide (Sulfurous acid) and sulfites Uses 1- Applied chiefly to dried fruits. 2- Used for limited number of foods such as: molasses, wines, fruit juices. Action  Mainly conservation of colour and not the inhibition of microoganisms.  Also mold are affected more readily than yeast and bacteria.  SO2 is effective because of free hydrogen ions released in solution. Sources a- Metabisulfite is source of SO2 in canning powder. b-Liquid SO2 used in wine manufacture to inhibit competing microorganisms and hence favour the growth of wine yeast. 1-5- Boric acid and borates  Forbidden in USA, but still used in some countries. 23 Examples for its use: 1- Dusting powdered boric acid on meat surface. 2- Washing vegetables and fruits (borax ). 3- Adulteration of milk by adding boric acid. 1-6- Fluorides  Harmful to health, and their use is forbidden.  The tolerance of fluorides in food is 2 ppm (FDA). 2-Alkalies and alkaline salts - Used chiefly as cleansing agent or detergent. -NaOH solution as antiseptic, detergent in milking machine. -Example for alkaline salts: - Na carbonate - Tri-Na-phosphate - Na metasilicate - Polyphosphatase. -Effective antiseptic due to liberation of OH group in solution. 3-Metals  Heavy metals exert an antiseptic or germicidal effect on microorganisms ( oligodynamic action) as a result of direct combination of the metal with cell protien.  Silver is only metal that is recommended for use in food such as: vinegar, drinking water , fruit juice.  Silver ions released in water from silver electrode by a weak current and according to silver concentration. Microorganisms may be inhibited or destroyed (catadyn process). 4-Hallogens Uses  Chlorinated water used for drinking water, r washing foods and equipments.  Iodine impregnated papers for wrapping fruits.  Iodophors (combination of iodine+nonionic wetting agent+acid)for sanitation of dairy utensils. Action Hallogens kill microorganisms by oxidation or by combination to cell protein. 5-Peroxides (hydrogen peroxide) Action  Used as a preservative for milk in tropical or subtropical areas.  It is used in concentration less than 0.05%.  It reduces the total bacterial count, thus improve the keeping quality: - Coliform bacteria is very sensitive to H2O2. - Spores of aerobic bacteria are resistant.  Use of H2O2 is not intended as a substitute for pasteurization. 24 Effect of H2O2 1-At 0.05% or lower no undesirable taste heat At higher level oxidized taste  no taste processed 2- Ascorbic acid is affected. 3-Sugar and butter fat are not affected. 4- Milk proteins are softened by H2O2 which give the cheese made from it a medium firm elastic body. Detection of H2O2 in milk 2 cc milk + 2 cc HCl 1% + 2 cc KI 10% mix then add hot starch solution blue colour indicates the presence of H2O2 HCl + KI KCl + HI 2HI + H2O2 I2 + 2H2O 6-Gases CO2: Most often used in combination with chilling. N2: Used as an inert gas. O3: Used in gas storage but not for high fat content food to avoid occurrence of oxidative rancidity. Organic Preservatives 1- Organic acids and their salts 1-1-Benzoic acid and benzoates Usually used as the sodium salt. It is more active against yeasts and bacteria than against molds. It’s optimal pH for microbial activity 2.5-4.0. Used in carbonated beverages, fruit juices, pickles. Permitted levels are 0.2-0.3%, but only 0.02-0.03% is required to prevent undesirable microbial growth. Benzoate does not accumulate in the human body but is detoxified by conjugating with glycine to form hippuric acid which is excrected. It was stated that 66-95% is detoxified by this mechanism and the remainder may have been detoxified by conjugation with glycuronic acid. 1-2-Parabens (Methyl and propyl esters)  Are most commonly used in the USA at concentration of 0.1% or less.  Are most active against molds and yeasts and less effective against bacteria.  Are active at pH 7 or more as well as at lower pH values.  Used in soft drinks, beer, creams, backed goods flavor extract, fruit products, jams, jellies olives, pickles and syrups.  Benzoic acid is found naturally in prunes, cranberries, plums, cinnamon. 25 1-3-Propionic acid and propionates  Are active against mold and bacteria but inactive against yeasts.  Optimal pH is 5.0.  Are most commonly used to prevent mold growth in bread and other baked products.  Calcium propionate is usually preferred in bread products, where yeast is used to enriched content “sodium and potassium salts are employed in cakes and chemically leavened products, since Ca can alter the action of leavening agents.  Used in cheese: - Dipping the cuts of natural cheese. - Addition to process cheese.  Also treatment of wrappers to protect butter from mold spoilage.  Used with malt extract – syrup – blanched apple, figs to prevent mold spoilage.  Used as antifungal agents in artificially sweetened jams, jellies. 1-4- Salicylic, salicylates Comparable to benzoic in effectiveness but are more harmful to consumer. 1-5- Acetic acid derivative Not approved by FDA. E.x. - Dehydroacetic acid: used to impregnate wrappers for cheese to inhibit mold growth. - Monochloroacetic acid. 1-6- Sorbic acid, sorbate  White crystalline powder slightly soluble in water (0.016%), however soluble in oil.  The sorbates (K & Na) are soluble in water (> 50%).  Sorbates inhibit growth of yeast and molds but has a small effect against bacteria.  Their range of optimum effectiveness extends up to pH 6.5 (higher than benzoate and propionate), their effectiveness increase with increasing acidity (lower pH).  Sorbates are four times as effective as propionates.  Sorbates are three times as effective as benzoate.  Sorbic acid is generally effective at concentration of 3000 ppm (max. permitted limit) with pH below 6.5.  However, some mold can grow in the presence of at least 5300 ppm sorbic acid and then can degrade the acid to form 1,3 pentadienes, which imparts a hydrocarbon like odor to the substrate. This is due to high initial mold population; hence, sorbates will not adequately preserve cheese that was produced under unsanitary condition.  Yeasts and lactic acid bacteria did not utilize sorbic acid. However, species of Clostridium utilize the compound as a carbon source.  Since sorbic acid has been used largely as an antifungal agent, little attention has been given to its effect on bacteria. Some evidence suggests that bacteria such as Salmonellae, Staphylococci, Streptococcus thermophiles, Lactobacillus bulgaricus and Escherichia coli are inhibited or inactivated depending on the concentration of the acid and the environmental conditions. 26  (i.e: sorbic acid & sorbates have selective inhibition depending on concentration and pH). Uses of sorbic acid and sorbates  Baked goods: Sorbates cannot be added directly to yeast raised goods, since they affect yeast.  Beverages and fruit juices: Sorbates can be used alone or in combination with benzoate. They are less likely to alter the flavor. Benzoate 0.05% -- 0.1% Sorbates 0.025% -- 0.1%, in combination at lower levels.  Wines: they are effective in the inhibition of yeast during storage. A concentration of 0.04- 0.05% reduces the use of So2 by 25%.  Meat products: 1. Sorbates are only used in dry sausage by dipping the casings of stuffed dry sausage in 2.5% potassium sorbate solution to prevent mold growth on the surface during the drying period. 2. A combination of sorbate (0.2%) with decreased level of nitrites (40-80 ppm) acted synergistically and extended the time necessary for toxin to be produced in the products under abuse conditions. However, the products were responsible in some allergic reactions of certain individual’s conduction sensory evaluation. Toxicity  Sorbates are less toxic than benzoate.  LD50 for sorbic acid is 10 g/kg body weight.  LD50 for Nacl is 5 g/kg body weight.  Sorbates have the higher acceptable daily intake (ADI), which is 25mg/kg B.W.  Sorbates are metabolized by the organism in a way similar to the naturally occurring fatty acids (unlike benzoate). 2-Formaldehehyde - Not permitted in food.  Uses  Used for treatment of walls, shelves, floor as it is very effective against mold, bacteria, viruses.  Action  Combine with free amino group of the proteins of cell protoplasm. 3-Sugars  Action Tie up moisture, provide unfavourable conditions for organisms growth.  Used for: 27  Sweetened condensed milk  Jellies  Candies  Fruits in syrup N.B. Lable on package should regard its addition, concentration. 4-Alcohols  Action Coagulate cell proteins  Uses:  Preserving flavoring extract, vanilla, lemon extracts.  Alcohol in beer, wine is not great enough to prevent their spoilage by microorganisms but limits the types of organisms able to grow.  Liquors, distilled liquors.  Glycerol is antiseptic in high concentration (dehydrating effect).  Propylene glycol used as a mold inhibitor and as spray to kill air-borne microorganisms. N.B. methyl alcohol is poisonous, should not added to food. 5-Antibiotics Mainly used for proteinaceous food like meat, fish, poultry.  Methods of using: 1-Long term feeding of antibiotic as a part of ration for animals. 2-Concentrated course feeding before slaughtered. 3-Injection into living animals before slaughtering. 4-Perfusing whole Caracas with antibiotic by injection. 5-Applied to surface of fished products as sausage.  Public health hazards of antibiotic use:  Antibiotic sensitization (anphylactic shock).  Antibiotic resistant strains to therapeutic treatment.  Non significant food spoilage bacteria become resistant and causing food spoilage.  Change of normal balance of human intestinal flora.  Fermented food production which depend on useful bacteria is affected also (lactic acid bacteria). 6-Wood Smoke Operation carried out by suspending of food directly over the wood or by producing smoke in one chamber and blowing it through fans into another containing food. Purpose of use 1- Improving flavor, color, tenderizing action. 2- Aid into preservations. *Smoke is mixture of gases among which are: phenol, cresol, acetaldehyde, formaldehyde. Factors contributing in keeping quality of smoked products: 1- Heat produced by smoke (60°C). 2- Surface dehydration. 3- Bactericidal constituents of smoke mainly phenol, formaldehyde. N.B. Smoked foods are more susceptible to mold growth than bacterial spoilage. 28 7-Spices and other condiments  Oils of spices are more inhibitory than ground spices.  Inhibitory effect differs with kind of species and microorganisms in food. E.x. Mustard oil effective against sacchromyces. Cinnamon, cloves potent against most bacteria Developed preservatives Food fermentations serve in: 1. To produce new and desired flavors and physical characteristics and hence a different food product. 2. To aid in the preservation of food.  The preservatives produced in food by microbial action are, for the most part, acids (chiefly lactic) and alcohol.  The preservative effect of these substances nearly always is supplemented by one or more other preservative agents, such as low temperature, heat, anaerobic conditions, sodium chloride, sugar or added acids. Food Sanitation in the Areas of Preparation, Storage and Serving Some of the means by which foods stuffs can be protected from gross contaminated will be obvious, but others may not be quite so clear. The immediate application of methods to raise standards of hygiene are sometimes thought to be impractical , yet they should be discussed in the light of plants for future establishment designed for the preparation and service of food and for training of food handlers. 1. Personal hygiene of the food handlers Most outbreaks of food borne diseases are traceable to sick or infected persons or carriers. Thus it is the food handler’s responsibility to take scrupulous care that personal bacteria are not added to food. Personal hygiene can break the chain of infection through the following ways: The hands  The hands should be washed with hot water and soap and preferably rinsed in running water after using the WC, immediately before, during and after food preparation, after handling raw meat or poultry, and after using handkerchief. Hands, however, are not completely sterile after washing.  Hand washing should not be done in kitchen sinks.  Wash basins should be in or adjacent to a toilet and in the kitchen preparation area. They should be supplied with hot and cold water, a soap dispenser, nail brush and individual method of hand drying. Hand cream with added disinfectant should be available.  Cuts and abrasions should be covered with non-porous dressing and a fingerstall or glove if necessary. 29  Persons with septic lesions should not work or handle food until the infection is completely healed.  Nails should be kept short, unvarnished and very clean. Habits  There are certain bad habits which should be avoided by the food handler. Take care not to touch the nose, hair or face.  Avoid sneezing and coughing near food.  Maintain a high standard of body cleanliness.  Smoking must be prohibited in premises where there is uncovered food.  No tasting of food by sampling with finger.  Spoons used for testing should be immediately washed in hot water.  Do not lick your fingers when serving food or separating sheets of paper. Cleanliness Cleanliness is one of the best protections against disease.  Hair should be clean and well covered with cloth, net or paper caps.  Paper handkerchiefs should be available and after use disposed of in a box or cellophane bag kept in a convenient place.  Wearing clean overall and aprons are essential.  These protective clothing should be light coloured, washable and changed regularly and frequently.  The provision of shower-baths in charging rooms will encourage a high standard of personal cleanliness.  Toilets facilities should be available.  Pedal-operated flushes and tapes, and easily cleaned metals fittings should be used wherever possible. Health Because of the great hazards of transmission of disease by coughing, sneezing or by contamination, persons ill with ,or suspected of being carrier of, typhoid, paratyphoid, tuberculosis, or any other communicable diseases should not be allowed to handle food. Likewise persons with colds, sore throats, diarrhea, vomiting, nausea, abdominal pain, sores or skin infections such as boils, should be kept away from foods. Such persons should be examined and released by a health officer or physician before being permitted to return to work with food. 2. Purchasing During purchasing the standards of hygiene maintained by the supplier should be noted, such as  Cold and chilled storage,  Separation of raw and cooked foods,  Handling of unwrapped raw and cooked foods,  Cleanliness of premises and equipment, and  Suitable equipment. 30 Perishable foods such as raw and cooked meat and poultry, milk, cream, and fish should be bought in quantities sufficient for one day only unless there is ample refrigerated space. Meat and fish should not be refrigerated for more than three days. Non-perishable foods such as dry goods, preserves, and canned foods should be bought in reasonable quantities. Avoid over-stocking: there is danger from vermin and deterioration where storage facilities are poor. These products should be stored in a dry, well ventilated storeroom. 3. Storage Storage of perishable foods: Deep freeze storage (-18°C) keeps food safe for many months and even years, but domestic refrigeration (1-4°C) can keep food palatable for a limited number of days only. Storage of non-perishable food-storeroom and larder: 1) Keep cool, well ventilated, and dry ; 2) Proof against vermin and flies. 3) Surfaces of shelves, walls, and floors should be easy to clean. 4) Arrange packs in an orderly manner: a- Food should be put 18 inches (450mm) from floor unless in mobile metal bins; b- Stock are rotated – dated on delivery. Vegetables Keep in cool storage, preferably screened from the kitchen to keep soil bacteria away from food preparation and cooking areas. Rooms with extractor fans and adequate intake of air through filter pads to give moving air currents should be available. 4. Food preparation, cooking and serving Cooking techniques: Heat penetrates slowly and is lost slowly in traditional cooking methods; with microwaves heat penetration is rapid but not necessarily uniform. Infrared rays are used for browning only. Cooking does not always destroy bacterial spores or even bacteria, particularly in rolled and stuffed joints, poultry, large meat pies, and sausages. 1) Avoid partial cooking 2) Cool cooked food rapidly and refrigerate within one and a half hours. Cooling can be speeded up by:  Provision of rapid cooling of leftover.  Breaking up bulk and placing in shallow containers in a moving current of air.  Limiting the size of joints to not more than 6 Ib (2.7 Kg) 3) Avoid reheating food. If it is essential the food must be re-boiled or re-cooked thoroughly in all parts 4) Keep hot food hot and serve quickly. 31  5) Safe cooking methods including; pressure cooking, grilling, frying and roasting of small or thin points. Less safe methods includes; boiling, stewing, braising and roasting of large bulky and rolled joints. Kitchen equipment: Ease of cleaning is an important factor in selecting all surfaces, equipment, and utensils.  Keep surfaces, equipment, and utensils clean in good repair; they should not be old or worn.  Slicing machines, mincing machines, and can openers require frequent and through cleaning; they must be easy to dismantle and reassemble. In-plant cleaning may be necessary for fixed parts of equipment.  Use separate boards for raw meat, cooked meat, and vegetables.  Choose appropriate materials for ease of cleaning; for example, synthetic and/or natural rubber hardened with plastic fibers, high molecular weight, medium-density polyethylene, or phenolic fiber laminates.  For cleaning use hot water and an anionic or non-ionic detergent combined with or followed by a disinfecting agent such as hypochlorite.  Avoid cloth; use disposable paper instead. Serving: 1) Avoid exposure of susceptible foods in warm atmosphere. Keep cold food cold, below 5 oC or 10 oC (41 oF ). 2) Avoid warm storage of cooked food. Keep hot food hot above 63 oC (145 oF ). 3) Keep displayed food cold and under cover. 4) Minimize handling of cooked foods; use suitable kitchen tools. 5) Use new clean paper for wrapping and covering food. 6) Keep animals and insects out of the kitchen. 5. Washing-up: Efficient washing-up is necessary to clean and remove bacteria from all dining room and kitchen equipment. 1) Good layout of washing-up area. 2) Correct temperature of wash and rinse water. 3) A good detergent suited to the type of water 4) Orderly methods of work in rinsing, stacking, racking, and storage. When the hot rinse is at the right temperature, dishes in racks will air-dry in 30 to 40 seconds. Dish Cloths and tea towels harbour bacteria and require daily disinfection, preferably by heat. They can contaminate hands, equipment, and cutlery. Disposable paper should be used in place of dish cloths and tea towels. Covered storage should be provided. 6. Waste Disposal 32  Food scraps on floors and surfaces encourage bacteria growth and attract vermin. Waste can be collected: 1) In pedal-operated bins which can be emptied regularly and washed out. 2) In paper or plastic bags on pedal-operated stands. Bags can be sealed and put into dustbins, incinerated, or collected by the local council. 7. Vermin and fly control Rats, mice, fly, Cockroaches, and ants are the most common pests Control: 1) Do not provide a breeding ground such as uncovered refuse bins. 2) Use fly-proof windows. 3) Cover food. 4) Seal off crevices. 5) Presence of close-fitting lids to prevent access to food. 6) Use of suitable pesticide. 7) Care must be taken to prevent pesticides reaching food, preparation surfaces and equipment. 8. Premises The layout of a kitchen must be planned with the principles of hygiene in mind, with regard to the sources of food-poisoning bacteria (human, raw foods, environment) and also the importance of hot and cold storage. 1) Floor must be durable non-slip and easily cleaned. Equipments are raised or mobile. 2) Walls must be smooth and easily cleaned. 3) Ceiling must be smooth and easily cleaned. 4) Illumination must be good. Shadows should be avoided. 5) Good ventilation to avoid rise in temperature and humidity. 6) Toilets must not be open into food-preparation area. 7) Outer cloths must not be kept in kitchen. 8) Use of good preparation surfaces (polymers-not wood). 9) Use of separate boards for raw meat, cooked meat and vegetables. 10) Facilities for cold storage. 33