Microbial Indicators Of Food Safety And Quality Lecture Notes PDF

Chapter Five Microbial Indicators of Food Safety and Quality  Outlines  Objective  Microbial indicators of food safety and quality  Organisms associated with product quality  Microbial product as an indicator of food quality  Indicator of food safety  Limitation of Coliforms as indictor o...

Chapter Five Microbial Indicators of Food Safety and Quality  Outlines  Objective  Microbial indicators of food safety and quality  Organisms associated with product quality  Microbial product as an indicator of food quality  Indicator of food safety  Limitation of Coliforms as indictor of safety 12/03/2024 1  Objective  After completion of this chapter, students should be able to:  Describe the criteria of Indicator organism for food safety and quality,  Identify the organisms & their product associated with food quality  Describe the criteria for indicator of food safety  Differentiate the intestinal origin organism to be used as safety indicators  Recognize the lowest possible number of Coliforms to indicate quality food with their limitation 12/03/2024 2  Microbial Indicators of Food Safety and Quality  Indicator organism  Frequently necessary to conduct a microbiological examination of food to determine its quality.  May be necessary to estimate:  Product shelf-life,  Product safety from food borne pathogens,  Product suitability for human consumption or,  To confirm that it meets some established microbiological criterion. 12/03/2024 3  Criteria to be an indicator organism 1. They have to be present in most foods and detected (enumerated or isolated). 2. Their growth and number should have a direct negative correlation with quality of the product. 3. They should be easily detected and enumerated with proper identification within a short time, easily, and economically. 4. Should be enumerable in short period of time 5. Their growth should not be affected by other product flora. 12/03/2024 4  Criteria cont’d…  A good indicator organism should always be  Present when the pathogen may be present,  Present in relatively large numbers to facilitate its detection,  It should not proliferate in the environment being monitored,  Its survival should be similar to that of the pathogen, for which it is to be used as an indicator.  Escherichia coli is a natural component of the human gut flora.  Its presence in the environment, or in foods, generally implies some history of contamination of faecal origin. 12/03/2024 5 Organisms associated with product quality  The following table showed organism and metabolic products that is useful as indicator of product quality.  The most reliable indicator organism is product specific.  Organisms products  Acetobacter Fishes  Bacillus species Bread  Clostridium species Hard cheeses  Lactic acid bacteria Wines and Beers  Lactococcus lacti Raw Milk  Pseudomonas species Butter  Yeasts Fruit juices 12/03/2024 6 Microbial product as an indicator of food quality  Metabolites Foods products  Cadaverine and putrescine Vacuum packaged beef  Ethanol Apple juice  Diacetyl Frozen juice  Histamine Canned Tuna  Lactic acids Canned vegetables  Trimethylamine (TMA) Fishes  Volatile fatty acids Butter 12/03/2024 7  Indicator of Food Safety  Microbial indicators: are more often used to asses food safety and sanitation than quality.  A food safety indicators should have the following criteria:  Easily and rapidly detected  Have a history of constant association with the pathogen  Always present when the pathogens of concern present,  Absent from foods that are free of the pathogens, except in minimum numbers. 12/03/2024 8  Cont’d…  Escherichia coli was used as the first indicator organism with the following additional criteria:-  The bacteria specifically found only in the intestine,  Found in high number in faces,  They should resist the external environment,  Should be detected easily and even when they are found in small numbers. 12/03/2024 9  Cont’d…  Coliforms notably E.coli and Enterobacter aerogenes are used as:  Indicator organisms as they grow in the presence of bile salts unlike gram positive bacteria, i.e. selective isolation is possible from various sources,  They ferment lactose with acid and gas production that make presumptive determination. 12/03/2024 10  Detection and Enumeration  Various methods- direct count, broth culture methods etc.  Distribution of Coliforms  The intestinal tract of most warm blooded animals are the primary habitat of Escherichia coli ,  While Enterobacter aerogenes is mainly found in vegetation and occasionally in the intestine. It is also suspected in air, dust, hands, in many foods, but their number is insignificant from the point of Public health importance. 12/03/2024 11  Cont’d…  Coliform criteria and standards  The presence of large number of coliforms and E.coli in food is undesirable.  The basic questions regarding numbers are:  At what quantitative level do coliforms and E.coli indicate unsafe products? The lowest possible number is in a properly harvested, collected , handled and stored foods/ water. 12/03/2024 12  Cont’d…  The following criteria have been used in water, diary products and other foods:  Not more than 10/ml of pasteurized milk, milk products  Not over 10/ml of certified raw milk,  Not over 1/ml of certified pasteurized milk.  Not more than 10/ml for precooked or partially cooked frozen foods.  Not more than 100/ml for crab meats  Not more than 100 /ml for custard filled items. 12/03/2024 13  Limitation of Coliforms as indicator of safety  Coliform tests for diary products are not intended to indicate fecal contamination,  But do reflect overall diary farm and plant sanitation.  Some coliforms found in vegetation like Enterobacter, has no sanitary significance in vegetation,  But showed process problems  Poultry products are not good sanitary indicators,  As Salmonella species may exist. 12/03/2024 14  Cont’d…  Enterococci may be used as Quality and Safety indicators of water due to:  These species do not grow in water  Found in less number in human faces  Die slower than E.coli  Therefore, some authors suggests the simultaneous use of E.coli and Enterococcus as indicator organism particularly in water.  In frozen foods, Enterococcus is used better indicator of food sanitary quality, but not in fresh foods.  Bifidobacterium bifidium, used also as fecal pollution indicators of water. 12/03/2024 15  Summary  Microbial indicators are often used to assess food safety and sanitation than quality.  Previously intestinal originated bacteria was used as a safety indicator for food quality.  Criteria to be an indicator organism  Present in most foods and has to be detected.  Growth and number should have a direct negative correlation with product quality.  Easily detectable and enumerated in short period of time.  Growth should not be affected by other flora. 12/03/2024 16  Summary cont’d…  The most reliable indicator organism is product specific.  There are specific organisms and metabolic products which are used in indicator system.  Salmonella is a good indicator of poultry production.  Enterococci is used as a quality and safety indicator for water and frozen foods.  Limitation of coliforms as indicator or safety  Coliforms tests reflect overall quality of farm and plant sanitation  But not intended to indicate fecal contamination.  Coliform 12/03/2024 may not have sanitary significance in vegetation. 17  Chapter Six: Food Born Diseases  Outlines  Vibrio  Objective  Salmonella  Food borne illnesses  Shigella  Bacteria involved in food borne  Escherichia illnesses:  Yersinia enterocolitica  Clostridium  Plesiomonas shigelloids  Bacillus cereus  Mycotoxins  Listeria monocytogens  Summary  Staphylococcus aureus 12/03/2024 18  Objective  After the end of this chapter, students will be able to:  Differentiate food intoxication and food infection.  Describe microorganisms responsible for food borne illnesses.  List and analyze the factors that affect microorganisms of food borne illnesses.  Identify the original sources of microorganisms and the type of food stuffs which are highly vulnerable for microorganism of food borne illnesses. 12/03/2024 19  Food born illnesses  Food borne illness is estimated to affect 10% of the population annually.  Estimates of annual cost of treatment and work hours lost at more than $3 billion.  Among microbes mainly bacteria are involved in food borne illness.  When we discuss food borne illness, we must distinguish between food intoxication and food infection. 12/03/2024 20  Food born illnesses…  Food borne diseases can be divided into food infection and food poisoning. 1. Food poisoning: is caused by consuming foods that contain toxins.  These toxins can be produced by microorganisms;  Occur naturally in the food (for example, in certain mushrooms).  Affect the biological reactions taking place in the body.  At high concentrations, the effects are acute and take place a few hours after consumption. 12/03/2024 21  Food born illnesses…  Symptoms: nausea and vomiting.  The toxins can have various origins, but the two most well known bacterial toxins are produced by S aureus and Clo. botulinum.  Most of these toxins are resistant to heat, so they are not eliminated by cooking. 2. Food borne infection: is caused by infectious pathogens (microorganisms that cause infections) in the food.  Microorganisms multiply in the intestine.  Release toxins that invade and damage the epithelium cells. 12/03/2024 22  Food born illnesses…  The consequences are stomach ache and diarrhoea within some hours or several days after eating the contaminated food.  The bacteria causing most food infections are:  Salmonella, Campylobacter and E. coli.  Proper heating of food can prevent food borne infections.  Almost all non-spore forming bacteria are killed at temperatures >70 °C. 12/03/2024 23 Some general characteristics of food poisoning  Toxin is produced by a pathogen while growing in a food.  A toxin can be heat labile or heat stable.  Ingestion of a food containing active toxin, not viable microbial cells, is necessary for poisoning (except for infant botulism, in which viable spores need to be ingested).  Symptoms: generally occur quickly, as early as 30 min after ingestion. 12/03/2024 24 Some general characteristics of food poisoning  Symptoms differ with type of toxin;  Enterotoxins produce gastric symptoms,  Neurotoxins produce neurological symptoms.  Febrile symptom is not present. 12/03/2024 25  Bacteria involved in food born illnesses  C. botulinum : the strains are  Motile,  Gram positive rods  Occur as single cells or in small chains  Obligate anaerobes,  Form single terminal spores,  Sensitive to low pH (