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Microbio Lecture 24
Food Microbiology
| Question | Answer | |
|---|---|---|
| 3 categories for classification of spoiled food | perishable, semi-perishable, nonperishable | hi |
| intrinsic factors related to food spoilage | food composition, pH, water activity, physical structure, presence of natural antimicrobial substances | |
| natural antimicrobial agents | 1. aldehydes and phenols --> cinnamon and cloves 2. allicin: antimicrobial sulfur compound in garlic 3. benzoic acid: cranberries 4. lysozyme: egg whites 5. polyphenols: catechins found in unfermented green tea | |
| what happens when egg spoils? | Proteus infection = spoilage of eggs. metabolic byproduct: H2S | |
| what does lysozyme do? | cuts bond between NAG and NAM so it breaks peptidoglycan | |
| what are the names of microorganisms that can survive and grow at lower temperatures? | psychrotrophic, psychrophiles | |
| extrinsic factors | 1. temperature 2. humidity 3. atmosphere | |
| what is pseudomonas? | an obligate aerobe. if oxygen is present , microorgs can grow. | |
| describe shrink wrap phenomenon. | if there is an air pocket, oxygen diffusion may occur | |
| describe atmospheric factor | 1) shrink wrap 2) oxygen allows for increased microbe growth on surface 3) CO2 inhibits most microbes and reduces spoilage | |
| prevention of food spoilage methods | 1) industrial canning 2) pasteurization 3) lycophilization 4) gamma irradiation | |
| what is a chemical agent of food preservation? | sodium nitrite | |
| What are the pros/cons of the chemical agent of food preservation? | 1. inhibits Clostridium botulinum growth decomposes to nitric acid which reacts with heme pigments to keep meat red 2. nitrites react with amines to forms carcinogenic nitrosamines (mutated DNA) | |
| example of a food antibiotic | nisin is a basteriocin, produced by Lactococcus lactis it inhibits peptidoglycan synthesis and targets gram positive bacteria like Clostridium botulinum | |
| origin of yogurt | Streptococcus thermophilus Lactobacillus bulgaricus | |
| origin of cheese | Streptococcus, Lactococcus, Lactobacillus | |
| sauerkraut, kimchi, pickles origin | lactic acid bacteria (Streptococcus, Lactococcus, Lactobacillus. Sauerkraut is made by Leuconostoc mesenteroides) | |
| origin of Soy sauce | Aspergillus oryzae, Pediococcus soyae, Lactobacillus, Saccharomyces rouxil | |
| origin of wine | Saccharomyces cerevisiae | |
| beer brewing steps | 1. wet barley. 2. starch is broken down into maltose and other sugars by enzymes 3. remove water and dry barley. 4. crush product into malt 5. add water to mashing kettle, so more enzymes break down more sugars. | |
| beer brewing steps part II starting from _ _ _ _ liquid | 6. if you remove solids, the remaining liquid is wort 7. add hops (plant) for flavoring 8. cook to extract flavor and kill microbes 9. remove hops and add yeast 10. ferment, pasteurize and filter wort and yeast. | |
| what do you add if you want ale? lager? | ale = top fermenting yeast (S. cerevisiae) lager = bottom fermenting yeast (Sacc. carlsbergensis) | |
| what makes swiss cheese? | Propriobacterium shermanii | |
| what makes roquefort cheese? | Penicillium roqueforti | |
| how do you make cheese? | 1. Streptococcus/Lactobacillus ferments lactose in pasteurized milk to make acid 2. acid + rennin enzyme coagulates milk proteins (casein) 3. whey = liquid and curd = coagulated protein | |
| koji | the fungus covered mixture of roasted soybeans and wheat | |
| moromi | koji + salt soln | |
| what produces acid when making soy sauce? | Pediococcus soyae and Lactobacillus | |
| what produces small amounts of alcohol? | Saccharomyces rouxii, by fermenting available glucose |
Created by:
syeonie
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