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BI 2020
Microbiology: P7 Food Microbiology
| Question | Answer |
|---|---|
| What two factors of mantaining food quality is microbial growth essential for? | in production and preservation |
| What are factors that are naturally present in food (do not change) | Intrinsic factors |
| What are the environmental conditions are we are able to control? | Extrinsic factors |
| Define Food Spoilage | Undesirable biochemical changes in the food |
| In what conditions do microbes multiply most rapidly in? | Moist, nutritionally rich, pH neutral foods |
| What are some intrinsic factors about food? | Water availability, pH, nutrients, biological barriers, and antimicrobial chemicals |
| What does aw represent? | Water activity aw is used to designate the amount of water available |
| at what aw does bacteria require to grow? | aw >= 0.90 |
| At which aw does fungi require to grow? | >= 0.80 |
| Which microbes prefer a low pH? | Lactic acid bacteria and Fungi/mold |
| Which bacteria are used in the fermentation process of food production? | Lactic acid bacteria |
| What causes the spoilage of more acidic foods? | Fungi (not bacteria) |
| Rinds, shells, and other outer covering that protect foods from microbial invasion is an example of a... | biological barrier |
| What exists naturally in some foods that inhibit the growth of organisms responsible for spoilage? | Antimicrobial chemcials |
| T or F: the extent of microbial growth is largely dependent on the storage of food | true |
| T or F: warm, oxygen rich environments inhibit the growth of most microbes | False |
| What are two extrinsic factors? | Storage temperature and atmosphere |
| How do low storage temperatures impact microbial growth? | At low--enzymatic action is very slow or nonexistant. Below freezing--Water crystallizes and is unavailable halting microbial growth (since cells are over 70% water) ---survive |
| How do hot temperatures impact microbial growth. | They will die off |
| How does the atmosphere impact microbial growth? | Prescence or abscence of Oxygen affects types of microbial population |
| What are microorganisms that cannot grow under anaerobic conditions (no oxygen) | obligate aerobes |
| What are microorganisms that cannot grow under aerobic conditions (oxygen) | obligate anaerobes |
| Lactic Acid bacteria aids in the production of which foods? | Yogurt, pickles, sharp cheeses, and some sausages |
| what is homofermentative L.A. bacteria? | Bacteria that only produce lactic acid |
| what is heterofermentative L.A. bacteria? | Bacteria that produce lactic acid plus other volatile compounds and small amounts of alcohol |
| why does swiss cheese have holes? | lactic acid can be fermented to propanoic acid and CO2 (gas creates air pockets) |
| T or F: production of fermented mile products rely on naturally occuring lactic acid bacteria | False. Starter cultures are needed. |
| What are different strains of starter cultures good for? | selecting strains |
| What happens to milk during the production of acid? | Coagulates and curdles, which sours the flavor |
| What does pasteurization do? | Increases the temperature to kill off most things, and if needed for cheese production, it is introduced back in |
| how are cheeses classified based on water content? | hard or soft |
| why is cottage cheese easy to make? | whey (liquid waste) is not drained away |
| What is the major part of cheese production made from - solid or liquid and what is it called | curd (solid) whey (liquid) is drained |
| What is ripening or curing of cheeses? | Further microbial processing |
| What is the name of the enzyme that is added to fermenting milk to hasten protein coagulation | rennin |
| what is the product of pasteurized milk that is concentrated slightly and then inoculated with starter culture | Yogurt! |
| What is the name of the bacteria that grow rapidly at higher temperatures | thermophiles |
| What does controlled incubation due for Yogurt prodcution> | ensures proper levels of acid and flavor compounds |
| what happens to a cell in a hypotonic solution? | water rushes into the cell |
| what happens to a cell in a hypertonic solution? | water rushes out of the cell (shrinks) |
| In what kinds of food production are hypertonic solutions applied? | Pickling |
| T or F: some yeasts ferment sugars to produce ethanol and CO2 | true |
| what is the product of alcoholic fermentation of naturally occuring sugars in juices of fruits | wine |
| What parts of grapes are using in red wines? | ENTIRE GRAPE (red grapes) |
| What parts of grapes are used in whtie wines? | Grape JUICE |
| What is the difference between carbonated and noncarbonated wines? | Carbonated wines add CO2 back into the wine and non carbonated have all CO2 escape during aging |
| what is the difference between dry and sweet wines? | Dry wines have no residual sugar whereas sweet wines contain residual sugar |
| What is added to inhibit the growth of natural microbial populations? (WINE) | Sulfur Dioxide |
| What do natural microbes usually do in alcohol process? | convert alcohol to acetic acid |
| What is added to initate the fermentation process? | yeast |
| What happens to the wine after fermentation process completes? | wine is siphoned many times to separate juice from sediment |
| What alcohol is the result of the breakdown of starches into simple sugars? | Beer. |
| T or F: Yeast contain enzymes to convert grains to alcohol | False. Malted barley contains enzymes |
| T or F: mashing is the addition of malt, starch, sugars, and other adjuncts soaking in warm water | true: the enzymes in malt act on starches converting it to fermentable sugars |
| what is wort? | remaining liquid in beer production when spent grains are removed(after mashing) |
| what is the substance that is added that gives beer its distinct bitter taste and also has natural antimicrobial substances? | Hops |
| Why is the hops/wort mixture boiled? (beer) | extract flavor of hops, concentrate wort, and inactivates enzymes and precipitates proteins |
| Why is wort centrifuged? (beer) | to remove solids |
| T or F: the fermentation process of distilled spirits is exactly the same as for beer | false. Distilled spirits do not boil the wort |
| what does the fermentation of molasses produced? | Rum |
| what does the fermentation of aged barley produce? | Scotch whiskey |
| what does the fermentation of the agave plant produce? | Tequilla |
| Does the production of vinegar require an aerobic or anearobic environment? | Aerobic -- the bacteria are obligate aerobes |
| Why does bread rise? | CO2 produced by the fermentation of sugars by bakers yeast |
| What is responsible for the characteristic flavor of sour dough bread? | Lactic acid produced by bacteria |
| Generally, why is spoiled food considered unsafe? | Existence of spoilage organisms indicate foodborne pathogens might be present |
| What kind of microorganisms can multiply in the refrigerator? | Psychrophilic organisms |
| What kind of organisms can survive cooking and in some canning processes? | endospore-forming |
| What types of microorganisms can spoil foods at extreme pH or low moisture environments? | Fungi! |
| That is an illness resulting from consumption of an exotoxin produced by organism? | food intoxication |
Created by:
savelae