MMG301 1st Edition Lecture 37Outline of Last Lecture I. Vector transmitted microbial diseasesII. Soil borne microbial diseasesOutline of Current Lecture II. Food preservationIII. Foodborne microbial diseasesIV. Waterborne microbial diseasesCurrent Lecture-Spoilage is usually caused by microorganisms that normally colonize various foods:-different foods will contain different populations of microbes -Contamination of foods can result from pathogens that accidentally enter food products-Fecal matter contaminates meat processing-If animal intestines contained pathogenic E. coli, meat will potentially cause disease-Animal feces contaminates an agricultural field – produce could contain pathogenic bacteria-Refrigeration: -Lower temperatures = slower growth of microbes-Some microbes are psychrotolerant and can grow at refrigerator temps-Freezing can prevent growth, but damages certain foods-Acidity:-Acidic pH (less than 5) inhibits growth of most pathogens-can also add salt to the food (pickling)These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.-Drying: -Reducing water content (water activity) inhibits growth-Partial or complete drying can be used for long-term preservation-Salt: -NaCl of >7.5% inhibits most bacteria-Chemical preservatives: -Sodium benzoate, sodium nitrate, sodium nitrite, sorbic acid, sodium proprionate; act as growth inhibitors and are GRAS [generally recognized as safe] by the FDA-Radiation: -Ionizing radiation kills microbes (remember decimal reduction time?)-Can be used for a wide variety of foods: uncooked meats, produce, prepared meals, etc.-Irradiation will reduce, but may not eliminate microbes-Controversial because of possible breakdown of nutrients and generation of toxic compounds-Heat: -Pasteurization – short-term heating to reduce microbes in food without significant reduction in quality-Canning – heating in a sealed container; often complete sterility is not achieved (heat exposure damages some types of food)-Ultra high pressure processing:-“Cold Pasteurization” – most, but not all bacteria are killed-Spores are not killed-Also called “Pascalization”-Requires 50,000-100,000 pounds/sq. inch-Food infection:-Infection arising from ingestion of a pathogen-Disease occurs when organism grows after ingestion-Many pathogens causing food infection also cause waterborne diseases-Food poisoning: -Ingestion of preformed microbial toxins-Microbes that produced the toxins do not need to invade the host-Disease is due to the action of the ingested toxin-Staphylococcus aureus:-Commonly found on all humans, especially skin-Found on many common foods-Some strains produce heat-stable toxins-Some strains produce enterotoxins; nausea, vomiting, diarrhea in 1-6 hr-Clostridium perfringens: -Most prevalent food poisoning in US; 248,000 cases/yr-Spores germinate and grow in intestines – produce toxins-Clostridium botulinum:-Strict anaerobe commonly found in soil-Spores from soil contaminate in food-Canned foods that are undercooked or in low acid can contain live spores-After germination in can, botulism toxin is
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