121 terms

Prescott's Microbiology Chapter 40

This flashcard set reviews chapter 40 of Prescott's Microbiology
What is a nutrient-rich, excellent environment for the growth of microorganisms?
Food spoilage
What results from growth of microbes in food?
Intrinsic and Extrinsic Factors
What are the two factors that influence growth of microorganisms in/on food?
Intrinsic Factor
What are food-related factors such as moisture, pH, water activity and availability and available nutrients that influence microbial growth?
Extrinsic Factor
What is an environmental factor such as temperature, humidity, and atmosphere (gases present) that influences microbial growth in food.?
Food spoilage involves predictable succession of what?
Spoilage processes
Different foods undergo different types of what?
Depending on the type of microorganism, what are sometimes produced?
Food Composition
What is a critical intrinsic factor that influences microbial growth?
What is the anaerobic decomposition of organic matter, especially protein, by microorganisms, resulting in production of foul-smelling matter?
Yeasts and molds
The pH of a food is critical because a low pH favors the growth of what?
In neutral or alkaline pH foods (meats), what microorganisms are more dominant?
Protein or fat rich food will promote growth of what?
Colonize foods
The presence and availability of water also affect the ability of microbes to do what?
Water availability
What is measured in terms of aw - ratio of relative humidity of the air over a test solution compared with that of distilled water.
What kind of microbes grow best in or on media of high solute concentration?
What are microbes that prefer a low aw environment and may not grow under high aw conditions?
Oxidation-reduction potential and the physical structure of a food
What two other factors affect food spoilage?
Ground Meats
What kind of meat will the microbes will be mixed and spread throughout the product?
Under intrinsic factors, Carbohydrate rich food exhibit fungal
growth initially, then what kind of growth?
What can grow on grains and corn in moist conditions?
What disease is caused by toxins due contamination by Claviceps purpurea?
More microbe activity
Higher relative humidity equals what?
Modified atmosphere packaging (MAP)
What process involves the addition of gases such as nitrogen and carbon dioxide to packaged foods in order to inhibit the growth of spoilage organisms? It is nearly impervious to
oxygen, increasing shelf life
1. Acid production by Lactococcus lactis
2. Additional acid production by more acid tolerant organisms like Lactobacillus
3. Yeast and molds become dominant and degrade the lactic acid making the environment more basic.
4. Protein-digesting bacteria become active, resulting in a putrid odor and bitter flavor. Milk becomes clear.
What are the steps of the spoilage of milk?
Antimicrobial compounds
What compounds do some foods naturally contain?
What do eggs contain that has an antimicrobial effect?
Sage and rosemary
Give two examples of spices with antimicrobial properties?
What is any of a group of toxic compounds produced by certain fungus/molds, especially Aspergillus flavus, that contaminate stored food supplies such as animal feed and peanuts.It can intercalate into DNA, causing frameshift
mutations. Can be carcinogenic, cause liver disease?
What is a family of toxins produced by mold belonging to the genus Fusarium. They primarily affect corn and are known to be carcinogenic and hepato- and nephrotoxic in animals. They disrupt synthesis and metabolism of sphingolipids?
What are methods to reduce or eliminate populations of spoilage and disease-causing microbes?
1. Removal of microorganisms (Filtration)
2. Low temperature
3. High temperature
4. Reduced water availability
5. Chemical based preservation
6. Radiation
7. Microbial product-based inhibition
What are the seven basic methods of food preservation?
What type of food preservation would you use to remove microbes from liquids (water, wine, beer, juices, soft drinks)?
Low temperature
What type of food preservation works by retarding microbial growth in the refrigerator at 5 degrees C?
Does storing food in a refrigerator stop the growth of microorganisms?
Will refrigeration at -10 degrees C keep all bacteria from growing?
What microorganism can grow well at -10 degrees C?
Canning and pasteurization
What are two methods of food preservation that use high temperatures?
What high temperature food preservation method heats the food in special containers called retorts at about 115°C for 25 - 100 minutes, then the cans are cooled as quickly as possible with cold water?
1. Spoilage before canning
2. Underprocessing during canning
3. Leakage of contaminated water through can seams during cooling.
What are the reasons for canned foods getting spoiled?
What high temperature food preservation method involves heating the food to a temperature that kills disease-causing microbes and substantially reduces the levels of spoilage organisms?
Will pasteurization sterilize beverages?
Lengths of time
Different pasteurization procedures heat for
different whats?
Low temperature holding pasteurization (LTH)
What kind of pasteurization is used for processing milk, beers, and fruit juices; Temperatures are maintained at 62.8°C for 30 minutes?
Concerning pasteurization: shorter heating times result in improved what?
High-temperature, short-time (HTST)
What kind of pasteurization uses a temperature at 71°C for 15 seconds?
Ultra-high temperature (UHT - really high, really short)
What kind of pasteurization uses a temperature at 141°C for 2 seconds?
Dehydration (Reduced water availability)
What method of food preservation removes water as a means for eliminating microbial growth?
What method of dehydration produces freeze-dried foods and is commonly used to eliminate bacterial growth? food preservation occurs as a result of freewater loss and an increase in solute concentration.
Chemical based preservation
What method of food preservation involves chemical agents can be used to preserved foods. They are regulated by US FDA and includes simple organic acids, sulfite, ethylene oxide, sodium nitrite and ethyl formate?
Chemical agents "generally recognized as safe" by the US FDA
What does "GRAS" means"
1. Damaging the microbial plasma membrane
2. Denaturing various cell proteins.
Give two ways that chemical based preservatives work?
The pH of the food
What impacts the effectiveness of chemical preservative?
1. Ultraviolet radiation (UV)
2. Gamma radiation
3. Radappertization
4. Electron beams
What are three methods of radiation food preservation?
Ultraviolet radiation
What method of radiation food preservation is used to control populations of microbes on surfaces of lab and food-handling equipment, but it does not penetrate food?
Gamma radiation
What method of radiation food preservation is a major method for radiation sterilization of food from a cobalt-60 source, has excellent penetration power, but it must be used on moist foods?
What method of radiation food preservation uses ionizing radiation (gamma radiation) to extend shelf life or sterilize meat, seafoods, fruits, and vegetables kills microbes in moist foods by producing peroxides from water?
Electron beams
What method of radiation food preservation electrically generates electrons, so it can be turned on only when needed. It does not generate radioactive waste, but also does not penetrate foods as deeply as gamma radiation?
Does radiation of foods make them radioactive?
What are bactericidal proteins active against closely related bacteria, which binds to specific sites on the cell, and often affect cell membrane integrity and function?
1. Some dissipate proton motive force of
susceptible bacteria
2. Some form pores in plasma membranes
3. Some inhibit protein or RNA synthesis
How do bacteriocins work?
What is the only currently approved bacteriocin that is made by Lactococcus lactis, a small hydrophobic protein
non-toxic to humans. It affects gram+ bacteria and is used in low acid foods to improve inactivation of Clostridium botulinum during canning process or to inhibit germination of any surviving spores?
1. food-borne infections
2. food intoxications
What are the two primary types of food-related diseases?
Food-Borne infections
What gastrointestinal illness is caused by ingestion of microorganisms, followed by their growth within the host?
Symptoms arise from tissue invasion and/or toxin production
Raw foods (e.g., sprouts, raspberries, and seafood)
What are important sources of food-borne infections?
1. Salmonella
2. Campylobacter jejuni
3. Listeria monocytogenes
4. E. coli
What are the top bacteria that cause food-borne infections?
What bacteria causes gastroenteritis from the ingestion of contaminated meats, poultry or eggs?
Campylobacter jejuni
What bacteria is the leading cause of acute bacterial gastroenteritis in humans and is transmitted by uncooked or poorly cooked poultry products or raw milk?
Listeria monocytogenes
What bacteria is most harmful to pregnant women, the young and old. It is responsible for the largest meat recall in U.S. At risk people should not eat soft cheeses, refrigerated smoked meats, deli meats and undercooked hot dogs?
E. coli
What is this important food-borne disease organism?Enteropathogenic, enteroinvasive, enterotoxigenic types can cause diarrhea. One type is thought to have acquired enterohemorrhagic genes from Shigella, including genes for the shiga-like toxin; spread by fecal-oral route;
1. Viruses
2. Protozoan pathogens
3. Prions
What are other causes of food-borne infections?
Viral contamination
What is the cause of food-borne disease based on the transmission by waters or by lack of hygiene in food preparation and direct contamination by food processors and handlers. It recently occurred on cruise ships. It is more prevalent than bacterial food-borne infections and harder to diagnose?
An uncooked state
Other concerns with food-borne illnesses involves foods that are transported and consumed in what state?
1. sprouts
2. shellfish and finfish
3. raspberries
Name some foods that cause concern about food-borne infections?
Food-Borne Intoxications
What type of food-borne disease involves the ingestion of toxins in foods in which microbes have grown. It produces symptoms shortly after food is consumed because of growth of the disease-causing microbe is not required. It can be associated with microbial cells or can be released from cells?
1. Staphylococcal food poisoning
2. Botulism
3. Clostridium perfringens food
4. Bacillus cereus food
Name some bacteria that cause food-borne intoxications?
1. Molecular techniques
2. Culture based techniques
What are the two main methods for the detection of food-borne pathogens?
1. Trying to figure out how to enrich for the desire microorganism
2. Some organisms do not grow well in the laboratory
3. It requires time - days to weeks for positive identification of pathogens
4. Identification complicated by low numbers of pathogens compared with background microflora
5. The varied chemical and physical composition of foods can make isolation difficult.
What are some reasons that culture based techniques do not work well for the detection of food-borne pathogens?
1. to detect the presence of a single, specific pathogen
2. to detect viruses that cannot be grown conveniently
3. to identify slow-growing or nonculturable pathogens
Molecular Techniques are used for what three purposes?
What technique performs DNA "fingerprinting" by pulsed-field gel electrophoresis (PFGE) on disease-causing bacteria isolated from humans and from suspected food using standardized equipment and methods?
What is an active surveillance network that follows nine major food-borne diseases. Can rapidly find causes of food caused outbreaks?
What is a major way of preserving foods?
1. lactic
2. propionic
3. ethanolic
What are the major fermentations used in food microbiology?
1. lactic acid bacteria
2. mesophilic bacteria
3. probiotic lactic acid bacteria
4. yeasts and molds
Fermentations are carried out by what?
Lactic Acid bacteria
What kind of bacteria creates the majority of fermented milk products?
Lactobacillus, Lactococcus, Streptococcus
Name some lactic acid bacteria?
Mesophilic fermentations
What kind of fermentation inoculates milk with starter culture (Lactobacillus), incubates it at 20-30°C, then cools it; lactic acid bacteria is then used to enhance the aroma and acid production. It is used to make buttermilk and sour cream?
If you ferment skim milk, what do you get?
Sour cream
If you ferment cream, what do you get?
Thermophilic fermentation
What kind of fermentation is carried out at 45°C. Yogurt production: milk is pasteurized, cooled, inoculated with Lactobacillus and Streptococcus salvarius ssp.?
What is the addition of microbes to the diet in order to provide health benefits beyond basic nutritive value?
1. Lactobacillus acidophilus fermented milk
2. Bifidobacteria fermented milk
What are two kinds of probiotic foods?
Acidophilus milk
What are produced by using Lactobacillus acidophilus. It may modify microflora in lower intestine, thus improving health?
What are irregular, nonsporing, gram+ rods, club shaped or forked nonmotile, anaerobic bacteria that ferment lactose and other sugars to acetic and lactic acids. They mprove lactose tolerance, antitumorigenic activity and reduce serum cholesterol levels.
Yeast-Lactic Fermentation
What kind of fermentation is this?
It makes Kefir - A product with an ethanol concentration of up to 2%. It is foamy and frothy due to active carbon dioxide production; Kefir grains are coagulated lumps of casein that contain yeasts, lactic acid bacteria and acetic acid bacteria.
Inoculate milk with it. The grains are recovered after fermentation
Mold-Lactic Fermentation
What kind of fermentation is this?
It results in a unique Finnish fermented milk called Viili. Milk is placed in a cup and inoculated with a mixture of the fungus Geotrichium candidum and lactic acid bacteria. The cream rises to the surface. Fungus forms a velvety layer across the top of the final product.
What is one of the oldest human foods; developed over 8,000 years ago. It has 2,000 varieties with 20 general types?
Texture or hardness
What are two ways to classify cheeses?
1. soft cheeses - cottage, cream, Brie
2. semisoft cheeses - Muenster, Limberger, blue)
3. hard cheeses - cheddar, Colby, Swiss
4. very hard cheeses - Parmesan
What are the four basic kinds of cheeses?
1. All cheese results from a lactic acid fermentation of milk, which results in coagulation of milk proteins and formation of a curd.
2. After curd is formed, it is heated and presses to remove the watery part of the milk (whey), salted, and then ripened.
Give the basic steps in cheese making?
What is an enzyme from calf stomachs that promotes curd formation?
Lactococcus lactis
What is used as a starter of many cheeses (Gouda and cheddar)?
What is sometimes added to enhance the cheese (Roquefort and blue cheese are examples)?
Country-cured hams, summer sausage, salami, bologna, fish sauces, tuna
What products are the result of fermentation of meat?
Alcoholic beverages
What is produced by cereals and other starchy materials are mixed with water and incubated. Then, the clear liquid is fermented with simple sugars and other compounds?
What step in alcohol production happens when cereals and other starchy material are mixed with water and incubated?
What is a clear liquid containing fermentable sugars and other simple molecules that came from the mashing step (alcoholic beverages)?
What is the science of wine production?
All grape juices are what color?
To make red wine, the grape skins are allowed to remain in contact with the must before fermentation to release their skin coloring components.
How do you make red wine?
Sulfur dioxide fumigant and yeast,
Fresh must is treated with what before the wine is then fermented?
What wine making process removes sediments from the wine?
Beers and ales
What products are made in this fermentation process?
1. It uses cereal grains like barley, wheat and rice
2. Barley grains are germinated to produce a malt
3. The malt is mixed with water and the desired grains and put in a mash tun or cask to hydrolyse the starch to carbohydrates
4. Mash is heated with hops; inhibits spoilage and adds flavor;
5. The wort is pitched or inoculated with yeast
What kind of beer do you get when freshly fermented (green) beers are aged?
Distilled Spirits
What product is product by this method?
1. It is produced by an extension of beer production.
2. Fermented liquid is boiled; so it has a higher alcohol content than beer
4. Sour mash is inoculated with a homolactic bacteria;
What is one of the most ancient of human foods. Yeast growth is carried out under aerobic conditions; It releases CO2 and minimum alcohol accumulation?
Alpha- and beta-amylases present in dough release maltose and sucrose from starch. The yeast is added; and makes CO2 which makes the bread rise.
What are the steps for fermentation of bread:?
1. sufu - fermented tofu
2. tempeh - soybean mash fermented by Rhizopus
3. Sauerkraut - sour cabbage
4. Pickles
5. Silage
What are some other fermented foods?
What is grass, chopped corn, and other fresh animal feeds, if stored under moist anoxic conditions undergo a lactic-type mixed fermentation?
1. Mushrooms
2. Cyanobacterium Spirulina
3. Prebiotics
Name some microorganisms that are used as food?
What are oligosaccharide polymers which are not processed until they reach the large intestine?