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Week 2

by: Molly Gersbach

Week 2 Micr 407

Molly Gersbach

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week 2 notes
Food and Dairy Microbiology
Xiuping Jiang
Class Notes
Microbiology, food and dairy, food, dairy, Biology, micro, Bio
25 ?




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This 7 page Class Notes was uploaded by Molly Gersbach on Wednesday January 20, 2016. The Class Notes belongs to Micr 407 at Clemson University taught by Xiuping Jiang in Spring 2016. Since its upload, it has received 36 views. For similar materials see Food and Dairy Microbiology in Microbiology at Clemson University.


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Date Created: 01/20/16
a. Impact of microbes in food i. Fermentation and food production: 22 billion gallons of beer, 2.2 million tons of cheese, 90 million ponds of pickles ii. Foodborned illnesses: 48 million cases, 3,000 death, 128,000 hospitalizations iii. Spoilage loss: 1/3 of world’s food supply b. Food Regulatory System i. USDA 1. FSIS: meat, poultry, and egg products a. 15% food imported b. 85% seafood imported c. 60% fruits/veg imported 2. APHIS: protecting against plant and animal pests and diseases ii. FDA 1. Fresh produce, seafood, imported food iii. EPA 1. Controls pesticide usage iv. Department of commerce 1. National marine fisheries service c. Food Safety-related Acts i. 1906: Federal Meat Inspection Act ii. 1957: Poultry Products Inspection Act iii. 1997: Pathogen Reduction: Hazard Analysis and Critical Control Point Final Rule (PR/HACCP) 1. Requires food industry to make sure standard sanitization policies, and HACCP ahead of time. Required 10 e. Coli tests iv. 2011: Food Safety Modernization Act (FSMA) v. “inspection acts” – instilled mandatory inspections of meat processing industries based on appearance/smell/etc d. Sources of Microbes in Food i. Classification of foods 1. Stable/Nonperishable: sugar, flour a. Sometimes these will go bad if too moist of environment, but in general at room temperature and dry conditions they are nonperishable. 2. Semi perishable foods: a. Potatoes, nutmeats (coconut, shredded pecans) b. Nutmeats can be oxidized because of high fat content c. Potatoes sprout 3. Perishable foods: a. Meats, milk, fish b. Usually high in water c. Even if you use some kind of preservation method, they will still have a shelf life ii. Sources of microbes in food 1. Plant sources: surfaces of fruits, veggies, crops; pores of some tubers, e.g. radish and onions a. High number of microbes found on surface of plants nad areas close to soil 2. Animal sources: a. Skin, hair, feathers, gastrointestinal, milk ducts/teats b. Outside of the animal associated with microbes –skin, fur, etc c. GI tract also mostly associated with microbes 3. Environmental sources: a. Air, water, soil, manure, equipment, insects, rodents, food handlers, etc. iii. Plant microorganisms 1. Most common: molds, yeasts, lactic acid bacteria, Pseudomonas, Alcaligines, Micrococcus, Erwinia (contributes to soft rot), Bacillus, Clostridium, Enterobacter (GI tract) 2. Type and numbers are affected by: a. Presence of plant diseases b. Surface damage c. Delay between harvesting and washing: important b/c you have cut surface by harvesting which allows unfavorable microbes to get in d. Unfavorable storage e. Transportation conditions 3. Because of their high nutrient content, plants can support growth of various microorganisms iv. Animal microorganisms 1. In healthy animals: a. Internal tissues are sterile b. Digestive tract has commensal bacteria and pathogenic bacteria: i. Salmonella spp.: very powerful, cause diarrhea and gasteroenteritis ii. pathogenic E. coli: ground beef, apple cider, fresh produce iii. Campylobacter jejuni: raw chicken iv. Yersinia enterocolitica: affects GI tract v. Listeria monocytogenes: 1:4 people who get sick will die c. Animal hides/feathers: i. If you clean animal very well before slaughtering, you can reduce number of microorganisms in the carcass significantly. d. Lymph nodes: i. Immune defense system of animals ii. Particles (including microbes/pathogens) are embedded in fat tissue of animals iii. If you don’t take these nodes out before processing, you risk contamination. 2. Sea animals: a. Fish: microbes are in scales, gills, and digestive tract b. Shellfish: in digestive tract i. These animals are filter feeders, which concentrates the microbial content – more dangerous for human consumption c. Types of microbes affected by water quality, feeding habits, seasons i. Off shore fish/sea animals, microbial quality is much better because water is cleaner ii. Bottom feeders have more contamination than surface feeder iii. Water temp increases, more microbial growth d. Major Pathogens: i. Vibrio parahaemolyticus: causes liver damage, paralysis ii. V. vulnificus iii. V. cholerae iv. Listeria monocytogenes: more in processing environment than the fish itself or the water. v. External sources of microbial contamination 1. Air: dust particles containing bacterial endospores, e.g., Bacillus spp., fungal spores, Micrococcus spp., Sarcina spp., yeasts a. Not visible to naked eye but they are there – meaning they must be very lightweight. Spores are common because they are dehydrated so therefore very light 2. Soil: molds, yeasts, bacteria, many types; great variations in species and total numbers 3. Sewage: used as a fertilizer for some crops – can lead to contamination enteropathogenic bacteria and viruses a. Common in developing countries to use human waste. b. In developed countries, waste is treated before use as fertilizer 4. Water: used for production, processing, storage (ice), washing equipment, food handling facilities – may contain species of Pseudomonas, Alcaligenes and Flavobacterium a. Water is recycled because it is in high demand b. Listed bacteria are common and spore- producing 5. Humans: during processing, restaurants, retail stores, and homes; Staphylococcus aureus, Salmonella spp., pathogenic E. coli, Hepatitis A a. Humans are carriers of many pathogens b. Importance for sick food service employees to stay home 6. Food ingredients: may introduce spoilage and pathogenic microorganisms, e.g., spices; molds, bacterial spores a. Ex) large outbreak in sausage because of a spice used in cooking b. Microbes found in spices/herbs are those that can tolerate extremely dry environments 7. Equipment: microbes introduced from equipment during harvesting, transportation, processing, and storage e. Microbial Classification i. Eukaryote: 1. Has a membrane-bound nucleus 2. Mold, fungus, and yeast ii. Prokaryote: 1. Nucleoid 2. Thick/thin cell wall 3. Gram +/Gram – 4. Gram staining process 5. Some are motile – have flagella 6. Bacillus, spirillus, spherical iii. Mold 1. Multicellular, many spores produce at the end 2. Pizza crust – ascorbic/propionic acid added as preservatives to dry and stabilize it. Relies on moisture free packaging 3. Important mold genera in foods: a. Aspergillus: spoilage of grains, jams, cured hams, nuts, fruits, vegetables; some produce mycotoxins i. A. oryzae: sake production ii. A. niger: produce many enzymes; including beta-galactosidase 1. Mold usually grows very slowly and then once you can see it, it grows very quickly b. Alternaria: brown to black rots of stone fruits (peach, plums); some produce mycotoxins c. Geotrichum: “dairy mold” spoilage of dairy products d. Mucor: spoilage of vegetables; used in some fermentation; source of enzymes. i. White/greenish hair looking ii. Use to make Chinese cheese e. Penicillium: rot of fruit and vegetables; spoilage of grains, bread, meats; some species produce mycotoxins; some used in food production i. Spores called “conidia” on penicillium, gives blue cheese its blue color f. Rhizopus: spoilage of fruits and vegetables; common black mold found on bread i. Also spoils lamb meat iv. Yeast 1. Single-cellular 2. Yeast is roughly 5-8 micrometer in diameter (slightly bigger than bacteria) 3. Can grow in a wide range of pH 4. 55-65% sucrose (grows well in grape because they have a high sucrose content) 5. Cream to red color 6. Important yeast genera in foods a. Saccharomyces: spoilage of some foods; used for production of bread, wine and beer i. Good in foods with higher sugar content like juices b. Pichia: spoilage of beer, wine, and foods preserved in brine; some used in fermentation of food i. Arabic yeast c. Kombucha tea: a product of the fermentation of black and/or green tea and a mushroom-shaped culture of yeast and bacteria d. Rhodotorula: causing discoloration of meats, fish, and sauerkraut i. Pink/red color ii. Grows in psychotropic environments (cold) – like refrigeration e. Candida: spoilage of food of high acidity, high salt, high sugar content; forming pellicle on liquid surface; causing rancidity of butter and dairy products i. In gut ii. In clinical setting: causes yeast infection v. Prokaryotes 1. Acinetobacter: G-, rods, widely distributed in soil, many food, esp. refrigerated fresh products a. psychrophile 2. Aeromonas: G-, rods, associated with aquatic products/environment, intestines of fish a. psychrophile 3. Alcaligenes: G-, rods, widely distributed in nature and decayed material, raw milk, poultry products, fecal matter 4. Alteromonas: G-, rods, marine and coastal water, seafoods 5. Arcobacter: G-, s-shaped rods, poultry, raw milk, shellfish, cattle, swine, water a. Used to be in same family as campylobacter but not anymore because they can tolerate more environments 6. Bacillus: G+, sporeforming rods, aerobes, soil, dust, water, fresh & processed foods 7. Brochothrix: G+, nonsporeforming rods, processed meat a. Very similar to listeria monocytogenes


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