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Flashcards in Chap14 Deck (35)
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1
Q

Most common microorganisms in food

A

Lactic acid bacteria: Gram+, aerotolerant anaerobes, rods or cocci. Reduces food spoilage and imporves storage quality (ph down)
Homofermentative: fermentation yields primarily lactic acid(pickles, sauerkraut)
Heterofermentative: fermentation yields lactic acid and variety of flavorful compounds (salami, milk).
Yeasts: alcoholic beverages, saccharomyces strains

2
Q

Sauerkraut

A

Cabbage is shredded and salted (2,2-2,8% NaCl, restricts growth of spoilage). Microorganisms are naturally present on cabbage: Leuconostoc mesenteroides (lactic acid, flavor, killed when acidity reaches 0,7-1%), lactobacillus plantarum (lactic acid only, increases acidity to 1,6-1,8%)

3
Q

Pickles

A

Use natural flora OR kill natural flora and use pure culture of pediococcus cerevisiae and lactobacillus plantarum (used for salami, bologna as well)

4
Q

Salami

A

Pork or beef. Mixed with salt, sugar, spices, yeast, sometimes a starter lactic acid (lactobacillus plantarum). Mixture is added to casing and allowed to cure (preservation done by salt and drying). Warm (25C) and humid (95%) conditions for 1-3 days. Transfer to cool (12-18C) and humid (70-80%) and dry for 6-10weeks.

5
Q

Milk products (general)

A

Naturally contains lactic acid bacteria, but are removed by pasteurization and added back.
Yogurt: Streptococcus thermophilus (produces acids that help growth of lactobacillus) and lactobacillus bulgaris (lactic acid bacteria) at 42C. Acid denatures casein = thickening. Other organisms can be added (BL, bifido)
Cheese: Hundreds of microorganisms. Raw milk cheese may contain pathogens: curdling( l.a bacteria precipitate the proteins=curd) and ripening (l.a bacteria and others create flavor)

6
Q

Cheese curdling

A

Lactose fermenters promote development of curd (precipitates) and whey (supernatant). Rennin (enzyme) can be added to cleave casein = curd formation. Whey drained off for whey powder or treated like sewage bcuz high BOD. Curd is heated and solidifies. Salt may be added for flavor, extraction of water, growth of spoilage organisms. Packaging, pressing, brining, ripening can be added.

7
Q

Cheese ripening

A

SOME OF THE RIPENING IS DUE TO LACTIC ACID BACTERIA, RENNIN OR OTHER ENZYME PRESENT.
Cheddar, swiss, gouda: wrapped cheesecloth. Cheddar (lactic acid bacteria ONLY). Longer ripening =higher acidity and sharpness. Swiss: propionibacteria for propionic and acetic acid (flavor) and CO2 (bubbles) 3-12months.
Oka: pressed curd is brined surface washed frequently, Geotrichum.
Blue/roquefort: mold penicilum roqueforti, spores from mold are mixed with milk or curd, small holes are drilled in the curd before wrapping(where mold grows and produces spores) 3-6months.
Camember,brie: unwrapped, mold(penicilium) and bacteria (brevibacterium) spread on the surface. Ripening in curing room (humid!), 1-5months. Proteases are responsible for softening, good sanitary practices for that cheese!

8
Q

Wine

A

Crushed grapes. Metabisulfite is added to kill wild yeasts. Sugar and organic acid may be added depending on final product. S.cerevisae and S.ellipsoideux are resistant and tolerant to 12-14% alcohol. Dry wine: all sugar is fermented. Sweet wine: some sugar is left or added.

9
Q

Vinegar

A

Acetic acid bacteria oxidize ethanol to acetic acid. AEROBIC = not fermentation. Ethanol -> acetaldehyde -> acetic acid. Acetobacter: used in all commercial applications, very efficient but in the absence of ethanol, it will oxidize acetic acid to CO2 and H2O - some ethanol must remain to prevent this.

10
Q

Key factors of brewing

A

Water, malt, hops, yeasts, conditions of fermentation (T, time)

11
Q

First step in brewing

A

Malting: because grains have starch that cannot be digested by yeasts, we germinate grains so they produce amylase. Then, they are dried and crushed = MALT. Malt is soaked (65C for 1-2h)= mashing (amylase degrade starch into glucose, maltose). Mash is filtered.

12
Q

Second step in brewing

A

(BOIL) Hops is added to the wort. Wort is boiled (1-2h, near sterilization). Hops gives flavor and bitterness, antimicrobial properties, prevents lactic acid bacteria. Filtered if commercial beer. Cooled to 20C.

13
Q

Last step in brewing

A

Fermentation. Yeast is added: lager(Saccharomyces carlsbergensis, bottom yeast 6-12C). Ale(Saccharomyces cerevisisae (top yeasts, carried up by CO2 during fermentation, 14-23C). Polishing: filtration, carbonation, pasteurization. Light beers: yeasts manipulated genetically so they can use all the sugars in the wort.

14
Q

Distilled alcoholic beverages

A

Similar to beer making process but no hops, different grains are used. Vodka: wheat rye potatoes. Gin: grains, starchy product+juniper oil. Rum: sugar cane (molasses). Brandy/cognac: wine. Whiskies: malt brews (scotch), wort is not boiled mixed fermentation of yeasts and resident lactic acid bacteria (water, resident lactic acid bacteria, barley, shape of still, ageing in wood cask). Alcohol is distilled. Aged, diluted with water. Flavor ingredients added.

15
Q

Kombucha

A

Any tea but black is better. Normal tea preparation + remove bags + add sugar + add mother or scoby = bacteria and yeast (acetobacter + saccharom.) + let ferment 7-10 days + add flavourings.

16
Q

Food spoilage

A

Food spoilage: unacceptable to customer, but not necessarily a food hazard. 10-20%(N.america) not suitable for consumption because of spoilage, 50% in dev.countries.
Type of microorganism(Molds, yeasts, bacteria), growth, moisture, T, pH, oxygen, chemical composition + physical state, surfaces/insides

17
Q

Moisture content

A

All need water. Availability of water= Aw, qualitative. Moisture content = takes into account bound water, quantitative. Solutes dissolved in water decrease availability of water to microorganisms. Fresh food Aw>0.95. Maple syrup high, cereals low. 0.9-1 everything. 0.8-0.9 only molds or staphyloccocus aureus (above 0.83). Below 0.8= xerophiles (dry environment, low osmolarity), osmophiles (high osmolarity, high sugar), halophiles (high salinity).

18
Q

Temperature for food spoilage

A

4,5-60 is dangerous. Psychrotrophs are able to grow at low temp, Psychrophiles grow best at low temp. Below 4,5C, only yersinia enterocolitica, listeria, clostrodium boti. Freeze/thaw is risky

19
Q

pH for food spoilage

A

Most foods are neutral or acidic.
B: Bacteria can grow at 5. Lactic acid grow a 4.
M and Y: many can grow, main source of spoilage.

20
Q

Oxygen for food spoilage

A

Required for molds and many yeasts and bacteria. Vacuum, canning, modified atmo are good ways. Some can still grow without (anaerobic) = swelling CO2 dont buy

21
Q

Composition - food spoilage

A

Meat: high in proteins/fat= require proteases and lipases = bacteria and molds. When anaerobic= bacteria.
Vegetables: high in starch, cellulose, pectin. Fruits: sugars, pectin. Require saccharase, cellulase, pectinase (bacteria, yeasts, molds)

22
Q

Food borne illnesses

A

Poisoning/intoxication: microbial toxins in food, symptoms appear quickly.
Infection: organisms multiply, symptoms take longer. Invasion or toxins

23
Q

Food-borne disease

A

Room temp, 12h or more between prep and consumption, infected person handling, inadequate reheating, improper hot holding, contaminated raw, foods from unsafe sources, improper cleaning of equipment, cross contamination (raw to cooked), inadequate cooking.

24
Q

Botulism

A

Food poisoning, caused by clostrodium botulinum. 10% mortality, flaccid paralysis, respiratory or cardiac failure. Difficulty swallowing breathing, double vision, paralysis. 1-2 days. Anaerobes that produces spores: insufficient heat to kill spores, processed food that are not reheated (non-acid canned veggies, sliced meats), spores germinate and toxin is produced (destructed by 80C 10 mins, properly cooked destroys toxin not the organism)

25
Q

Most common food poisoning

A

Most common = staphylococcal (40%). Enterotoxin (SE) produced by some strains of staphylococcus aureus. Toxin is relatively heat-stable (30mins at 100C, 16h at 60C). 20-30% humans are colonized by S.aureus, it is easily transferred to food where it can grow and produce the toxin. Symptoms (1-6h): nausea, vomiting, diarrhea. Associated with food prepared in large quantites and then left at room T. Halotolerant. Keep cold food cold and hot food hot. Adequate sanitation/hygiene.

26
Q

Salmonella Enterica

A

Infection, Salmonella enterica grow in intestinal tract (salmonellosis): 2 injectisome systems. Enteritidis and typhimurium. Invasion and destruction of intestinal epithelium = Can break through bloodstream and be deadly, but most people recover (4-7days) without treatment. 105-108 organisms are required (often multiply on food before being eaten). Cooking kills it but can be contamined back aften( cross-contamination).

27
Q

Ecoli O157 H7

A

Fecal coliform: does not grow at 44,5C!!. Espace detection by standard fecal coliform methods. Enterohemorraghic E.coli (EHEC) effective dose is lower than 100 microorganisms. Cooking kills the organism. Food infection that attaches to intestinal mucosa and produces Abexotoxin shiga like that inhibits protein synthesis. Damages underlying tissues and causes diarrhea (hemorrhagic colitis). Toxin travels through bloodstream and destroys cells in kidney and causes hemolytic uremic syndrome (HUS) renal failure and death

28
Q

Food processing and preservation

A

Delay decomposition by microorganisms (spoilage), destroys pathogens or inhibits their growth, prevents self-decomposition by enzymes.
Refrigeration, freezing, heating(pasteurization), canning, reducing water availability, irridiation, chemicals

29
Q

Freezing and refrigerating

A

Inhibit growth of microorganisms, -20C the water availability reaches 0.82 where most microorganisms can’t grow. Will resume growth after. Freeze/thaw affects quality of food (ice crystals) and microorganisms can grow between

30
Q

Cereulide

A

Cereulide: Toxin produced by B.cereus (spore-forming). Attacks mitochondria, membrane potential and oxidative phosphorylation = apoptosis. Emetic agent (vomiting). Liver and pancreas mostly (bcells)

31
Q

Pasteurization

A

Reduce number of microorganisms and eliminate pathogens. Dairy, liquid egg, alcoholic, juices. 3 methods for milk:LTLT: 30mins, 62.8C, bad taste (ice cream, cheese)
HTST: 15 sec, 71.7C (drinking milk)
UHT: 2sec, 141C (long shelf life at room temp, virtually sterile.
T and Time affected by fat, sugar, protein
LTLT HTST: equally safe.

32
Q

Canning

A

No microorganisms can enter, heat to kill most or all microorganisms, anaerobic conditions. Temperature: 100C for acidic, 121 for low acid food. 12D process: T and time of exposure must be sufficient to kill 1012 spores of clostrodium botulinum. Must have balance between safety, nutritive, taste.

33
Q

Reduce water availability

A

Prevents microorganisms from growing. Drying: meat, fish, fruits, milk (powdered): sundried, hot air, freeze drying (lyophilization, little lost of quality, expensive). OR Adding salt of sugar to increases osmotic strength of surrounding solution. Don’t necessarily kill, but inhibits growth.

34
Q

Irridiadtion

A

Reduce contamination of fresh products byh pathogens and spoilage organisms. Dosage can be adjusted to kill all microorganisms (radappertization), specific (radicidation), overall contamination (radurization). Possible radioactive contamination, carcinogenic compounds, altered nutritive value, off-flavor?

35
Q

Chemicals and other treatments

A

Control growth of microorganisms (usually selected). Chemicals generally recognized as safe (GRAS): nitrite (prevents c.botu), sulfites (wine, prevents wild yeasts), nisin (bacteriocin produced lactococcus lactis, in cheese, effective agains many gram+ lactic acid bacteria like monocytogenes, aureus, cereus, botulinum). Bacteriophage preparation (FDA approved bacteriophages to prevents listeria)