Survey of Microorganisms in Food PDF

SURVEY OF MICROORGANI SMS IN FOOD Sources of microorganisms in food Internal tissues of healthy plant (fruits and vegetables) and animals (meat) are essentially sterile. Yet raw and processed foods contain different types of microorganisms Microorganisms get into foods from sources to whic...

SURVEY OF MICROORGANI SMS IN FOOD Sources of microorganisms in food Internal tissues of healthy plant (fruits and vegetables) and animals (meat) are essentially sterile. Yet raw and processed foods contain different types of microorganisms Microorganisms get into foods from sources to which food comes into contact from the time of production until the time of consumption  Natural sources of plant origin:–  surface of the fruits,  surface of the vegetables  surface of the grains and  the pores in some tubers (radishes and onions, lettuce)  Natural sources of animal origin :–  Skin  Hair  Feathers  gastrointestinal tract  respiratory tract and  milk ducts in udders of milk  Natural microflora exist in ecological balance with their hosts and their types and levels vary greatly with the type of plants and animals  Food can be contaminated with different types of microorganisms coming from outside sources such as:  Air  Soil  Sewage  Water  Humans  food ingredients  Equipment  package and  insects  Microbial types and their levels from these sources getting into foods vary widely and depend upon the degree of sanitation used during the handling of foods. Sources of microorganisms in food is important in order to:  Develop methods to control access of some microorganisms in the food  To develop processing methods to kill them in foods  To determine the microbiological quality of foods  To set up microbiological standards and specifications of foods and food ingredients. Types of Microorganism in Different Sources For Food Contamination 1. Plants (Fruits and Vegetables)  Plants harbor microorganisms on the surface, type and level vary with the soil condition, type of fertilizers and water used and air quality Common plant surface microbes include: Mould Yeasts lactic acid bacteria Pseudomonas Micrococcus Erwinia Clostridium Enterobacter untreated sewage. Microbial numbers can greatly increase as a result of: Diseases of the plants Damage of the surface before, during and after harvest, Long delays between harvesting and washing Unfavorable storage and transport 2. Animals, Birds, Fish and Shellfish Carry many types of microorganisms in the: Digestive tract Respiratory tract Skin Hooves Carriers can carry pathogens such as: Salmonella spp. Pathogenic Escherichia coli Campylobacter jejuni Yersinia enterocolitica Listeria monocytogenes  Laying birds – suspect of carrying Salmonella enteritidis in ovaries and contaminating yolk during ovulation Poor husbandry resulting in fecal contamination on the body surface (skin, hair, feathers and udder) and supplying contaminated water and feed (contaminated with Salmonellae) can also change their normal microbial flora.  Milk – contaminated with fecal materials on the udder surface Egg shells – contaminated with fecal material Meat- contaminated with the intestinal contents during slaughtering Enteric pathogens from fecal materials include: Salmonella spp Pathogenic E. coli Shigellae Enteric viruses Protozoa Helminths Other common organisms are:  Staphylococcus aureus  Micrococcus spp  moulds and yeasts.  Prevention Effective husbandry Testing animals and birds for pathogens and culling the carriers will be important in reducing incidence in foods Using good quality water during slaughter, de-feathering, removing digestive and respiratory organs Proper sanitation during processing to keep the microbial quantity at desirable  Proper cleaning of udder prior to milking Immediate cooling of milk after milking Fish and marine products should be harvested from non-polluted and recommended water. Carcasses should be stored in proper temperatures to prevent further contamination and microbial growth. 3. Air Microorganisms are present in dust in air Do not grow in dust but are transient and variable depending upon the environment Their level is controlled by the degree of humid, size and level of dust particles, temperature and air velocity and resistance of microorganisms to drying Dry air with low dust content and higher temperature has a low microbial level.  Spores of Bacillus spp., Clostridium spp., and mold Microbial contamination in the air can be reduced by:  removing the potential sources  controlling dust particles in the air via  using filtered air  using positive air pressure  reducing the humidity level and  Soil contains several varieties of microorganisms Can multiply in soil, their numbers can be very high Moulds, yeasts and bacteria genera (Enterobacter, Pseudomonas, Proteus, Micrococcus, Enterococcus, Bacillus and  Soil contaminated with fecal materials can be source of enteric pathogenic bacteria Sediments where fish and marine foods are harvested can also be a source of microorganisms in those foods Prevention - removal of soil and sediments and avoiding soil contamination  sewage when used as fertilizer in crops can contaminate food with microorganisms such as enteropathogenic bacteria and virsus major concern with organically grown foods and many imported fruits and vegetables where untreated sewage may be used as fertilizers Prevention – not to use sewage as fertilizers, or should be efficiently treated to kill the pathogens. 6. Water ♣ used to produce, process and in some cases store foods ♣ used for irrigation of crops, drinking by food animals ♣ raising fishery and marine products ♣ washing foods, processing (pasteurization, canning and cooling of heated foods) ♣ washing and sanitation of equipment, ♣ water is used as an ingredient in many processed foods thus can greatly influence the microbial quality of foods ♣ wastewater can be recycled for irrigation ♣ chlorine-treated potable water should be used in processing, washing, sanitation and as an ingredient ♣ although potable water does not contain coliforms and pathogens, it can contain other bacteria capable of causing food spoilage (including Pseudomonas, Alcaligenes and Flavobacterium) ♣ improperly treated water can contain pathogen and spoilage microorganisms ♦ between production and consumption, foods come in contact with different people handling the foods ♦ not only the people working in a food processing plant, but those handling foods at restaurants, catering services, retail stores and at home. ♦ Source of pathogenic microorganisms in food that later cause foodborne disease aesthetic sense and personal hygiene, dirty clothes and hair can be a major sources of microbial contamination in foods ♦ Pathogens such as Staphylococcus aureus, Salmonella spp. Shigella spp. Pathogenic E. Coli and hepatitis A can be human sources. 8. Food Ingredients ♥ prepared or fabricated foods many ingredients or additives are included in different quantities ♥ can be a source of both spoilage and pathogenic microorganisms ♥ various spices can possess very high populations of mold and bacterial spores ♥ starch, sugar and flour can have spores ♥ prevention: ingredients should be produced under sanitary conditions and given antimicrobial treatments. Setting up acceptable microbial specifications for the ingredients will be important in reducing microorganisms in foods from this source ♠ wide variety of equipment is used in harvesting, transportation, processing and storage of foods ♠ microorganisms from air, raw foods, water and personnel can get into the equipment and contaminate foods ♠ depending on environment and time, microbes can multiply from low initial population to reach high level and period of time, microorganisms present initially can multiply and act as a continuous source of contamination in the product ♠ small parts, inaccessible sections and certain materials may not be efficiently cleaned and sanitized therefore can serve as sources of both pathogenic and spoilage microorganisms in food knives, spoons due to improper cleaning can be source of cross-contamination ♠ Salmonella, Listeria, Escherichia, Enterococcus, Micrococcus, Pseudomonas, Lactobacillus, Listeria and yeasts and moulds can get into food from equipment ♠ Proper cleaning and sanitation of equipment at prescribed intervals are important used in food. Since they are used in the products ready for consumption and in some cases without further heating, proper microbiological standards (or specifications) for packaging materials are necessary.