Food & Beverages

I. All foods have Microorganisms on their surface. II. Microorganisms take food for metabolism and turns it into acids, alcohols, & gas. III. Sometimes desirable – pleasant tastes & textures. IV. Fermentation – foods altered by the careful controlled growth of microorganisms A. Desirable – sour cream & blue cheese. B. Undesirable – Spoilage, sour milk, molded bread does not change the quality of food but may lead to illness

V. Factors Influencing the growth of organisms on foods A. Availability of Water (aW) 1. Bacteria - .9 or higher for growth 2. Fungi – lower aW B. Low pH Most are inhibited by acidic conditions. C. Temperature Low temperatures slow down enzymatic activities. D. Intrinsic factors 1. Nutrients 2. Coverings 3. Antimicrobials

VI. Production of foods & beverages A. 6000 BC Sumerians & Babylonians B. 4000 BC Egyptians – bread & beer C. Milk 1. Sterile from cow but handling leads to contamination. 2. Lactic Acid – Sour 3. Yogurts a Pasteurize to eliminate undesirable spoilage. b. Inoculated with Streptococcus thermophiles or Lactobacillus bulgaricus. c. Incubated at 40C. d. Produces lactic acid, pH drops causing coagulation of milk protein which changes texture. e. Conditions are controlled so only certain bacteria can grow. f. ½ million pounds of yogurt is sold in US, yearly

4. Cheese a. 8,000 yrs ago – Asia b. Steps 1. Milk inoculated with starter culture (Lactic Acid bacteria). 2. Incubated until fermentation of milk sugars 3. RENIN (enzyme) is added to coagulate milk proteins (CURD). 4. Solids (CURD) is separated from liquid (WHEY). 5. CURD – cottage cheese, WHEY - Cheese

c. Types of cheeses 1. Brie – White fungus, Pencillium caseisolon 2. Limburger – Bacteria, Brevibacterium linen 3. Swiss – Bacteria, Propionibacterium sp. a. Produces propionic acid & CO2. 4. Cheeses differ in water content a. very hard, semi, soft

D. Pickled Vegetables & Olives 1. Made with Lactic Acid bacteria E. Sauerkraut 1. Cabbage is shredded & layered with salt. 2. Salt dries out cabbage to prevent unwanted bacteria growth. 3. Permits desirable bacterial growth (Lactobacillus plantarian) in 2- 4 weeks. 4. Lower pH levels results in tangy taste

F. Soy Sauce 1. soy bean & Fungus Aspergillus oryzae. 2. Mix salt, soy bean, & wheat = Koji 3. Let sit for 3 days 4. Carbohydrates are broken down to produce fermentable sugars. 5. Mixed with 18% NaCl & bacterium (Pediococcous soyae & saccharomyces rouxi) for 8 – 12 months. 6. Liquid is drained for soy sauce

G. Breads – Bakers Yeast 1. Leavened Bread. 2. Mixture of flour, sugar, milk, water, yeasts (Saccharomyces cerevisiae), butter or oil. 3. Yeasts ferments carbohydrates from sugar to ethanol & Co2. 4. Produces ethanol gas which is burned off in baking. 5. CO2 causes bread to rise.

H. Alcohols 1. From fruits. 2. 10 million yeast cells on grapes. 3. Fruit sits for days at room temperature and begins to bubble as juices ferment. 4. Weeks – mixture alcohol

a. Crush selected grapes – solids & juices – Must. 5. Wine a. Crush selected grapes – solids & juices – Must. b. Red wine 1. Red grapes 2. Entire grape c. White – Only juice from red grapes d. Rose – red for a day then only juices ferments. e. S. cerevisicae for growth. f. Fermentation, controlled temperature for days to weeks. g. Sugar Ethyl alcohol & CO2. Less than 14% alcohol

a. Fermentation of sugars from grain by Saccharamyces. 6. Beer a. Fermentation of sugars from grain by Saccharamyces. b. Malting – starch to sugars 1. Malt (germinating grain) is soaked in water to yield an extracting enzyme (wort) – sugars & nutrients for yeast growth. c. Wort is boiled to destroy enzyme & most microorganisms. d. Hops are added for flavor & inhibited unwanted bacterial growth. e. Brewers’ Yeast 3.4% - 6% alcohol. f. Sits in vats to settle out solids including yeast & microorganims & flavoring. g. Bottom Fermentation S carlsbergensis – 6 – 12 C 8-14 days (American beer). h. Top Fermentation S cereviside – 14-23 C 5 – 7 days, carried to top by CO2. Stouts.

7. Distilled Spirits a. Similar to beer except wort not boiled. b. Degradation continues during fermentation. c. Alcohol is separated by distillation. d. Rum – sugar cane or molasses. e. Scotch whiskey – barley & aged in oak or cherry barrels. 8. Vinegar a. Product of oxidation of ethyl alcohol by acetic acid bacteria. b. 4% acetic acid.

VI. Food Spoilage A. Growth of unwanted microorganisms on or in food that produces an undesirable change. B. Characteristics of food determines the type of microorganism present. C. Bacteria commonly involved in food spoilage 1. Gram Negative a. Pseudomones sp. Wide range of food & temp. b. Erwinia sp. Degrade fruits & vegetables. c. Acetobacteria sp. ethyl alcohol to acetic acid d. Alcaligenes sp. degrade cottage cheese

2. Gram positive a. Streptococcus, Leuconstoc & Lactobacillus – sour milk b. Bacillus & Clostridium – survive cooking. c. B. coagulans & Strearothermophils = sour spoilage of some can foods. D. Fungus 1. Rhizopus sp. = bread mold 2. Aspergillus – peanut & grains

VII. Food Borne illness A. Interotoxication 1. Hours 2. Consumption of a toxin produced by a microorganism growing on a food product. ex. Staphylococcus aureus – ham, pasteries, salads nausea & vomiting. B. Botulism 1. Neurotoxin by Clostidium botulinea (Gram positive) 2. Errors in canning with endospore contamination. ex canned food – bulging C. Colonization - Salmonella & E. Coli 1. Infection after ingestion in the small intestines by a living organisms. 2. Up to 24 hrs to feel effects resulting in diherrhea 3. Prevention a. Thoroughly cook food. b. Wash cutting board to prevent cross contamination.

IX. Food Preservation A. Drying – Salting B. High Temperatures – Cooking C. Low Temperatures – Freezing D. Irradaition – Radiation E. Sugar – Lactic Acid F. Smoked – replaces aW G. Pasteurization 1. High temp – short time 2. Low temp – long time 3. Ultra high