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49 Cards in this Set
- Front
- Back
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Considerations of food microorganisms |
Spoilage of food by nonpathogenic microorganisms Methods of food preservation Use of microorganisms in food production Foodborne diseases-causing microorganisms |
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Food spoilage |
Any change in the appearance, smell, or taste of a food product that makes it unacceptable to the consumer Food not necessarily unsafe but unpalatable |
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Foods contain organic materials therefore |
They are suitable as microbial media |
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Perishable |
Meat, eggs, milk, fruit, veg |
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Semiperishable |
potatoes, nuts, apples |
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Stable or nonperishable |
sugar, rice, flour, dry beans |
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Water activity |
Measure of available water V of air in equilibrium with substance or solution/ V of pure water Organisms have a min water activity in which they can survive Gram - are less tolerant |
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Fruits and Veg |
Pectin-hydrolysis-methanol, uronic acids Sugars-ferment-CO2, organic acids, alcohol Pseudomonas, corynebacterium Soft rot, loss of structure, souring, acidification |
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Fresh meat, poultry, seafood |
Proteins-proteolysis, deamination-amino acid, peptides, amines, H2S, ammonia, indole Carbohydrates-hydrolysis, fermentation- CO2, organic acid, alcohol Campylobacter, Escherichia, Listeria, Pseudomonas, salmonella, candida, sporotichium Bitter, bad odor, slimy, souring, acidification |
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Milk |
Lactose-hydrolysis, fermentation-lactic acid, CO2 Protein(casein)-proteolysis, deamination-amino acids, peptides, amines, H2S, ammonia, indol Stroptococcus, Pseudomonas, proteus Souring, clumping, bitter, sour, foul odor, slime |
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Bacterial growth in batch culture |
Food is analogous to flask of growth medium Last doublings exponential become visible Rate affected by temp, O2, pH, Aw, nutritive value of food, natural antimicrobial substances, makeup of foods microbial community Lag phase determined by contaminats and growth |
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Food preservation aim |
To extend lag phase indefinitely To slow growth Lag, Exponential, stationary, death |
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Phases important in spoilage |
Lag Exponential |
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Food Preservation - temp Cold storage |
Refrigeration - 5 degrees Freeze -20 to -80 Microbial growth slows, not stops Psychrotolerant microorganisms thrive Freezing extends shelf life but freeze thaw alters foods physical structure which makes it more susceptible |
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Food preservation - tep Heat processing |
Cooking- reduces microbial load, avoid reinoculation Canning- heat and sealing, food is stable indefinitely |
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Pasturization |
designed to reduce microbial load, kill pathogens LTH- low temperature hold 63deg 30 min HTST- high temp short time 72deg 30sec |
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Aseptic food processing |
Juice boxes, milk products Europe- flash heat milk products 133deg and aseptic packaging |
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Flash pasteurization |
Continuous flow system Small volume of raw milk spends specified short amount of time flowing through heated metal plates enters cooling unit to prevent heat denaturation or nutrients |
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Increase of acidity of food Pickling |
Add acidulant Vinegar addition to cucumbers, peppers, meat, fish Entails other additions such as salt, sugar, spice |
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Increase acidity of food Encourage fermentation |
Nutural/added inoculum
Lactic acid bacteria- lactococcus, lactobacillus, leuconostoc -milk - yogurt, cheese, sour cream -cabbage- sauerkraut Acetic acid bacteria Propionic acid bacteria -flavor and holes in swiss cheese |
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Decrease water activity of food |
Drying -sunlight, oven smoking -fish, meat, fruit Lyophilization -freeze drying -camping rations Addition of sugar - fruit, jam, jellies, preserves Addition of salt- meat, fish, sausage, ham |
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Chemical preservation of food |
Salt, sugar - not considered chemical GRAS- generally recognized as safe |
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Sodium, calcium propionate Sodium benzoate Sorbic acid Sulfur dioxide, sulfites, bisulfites Formaldehyde, food smoking Ethylene and propylene oxides Sodium nitrate |
Bread Carbonated beverages, fruit, pickles, margarine Citrus, cheese, pickles, salads Dried fruit, veg, wine Meat fish Spices, dried fruits, nuts Smoked ham, bacon |
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Irradiation |
60CO or 137Cs sources Food does not become radioactive Physiochemical damage may occur Potatoes, onions, spices, dehyrated seasonings, wheat flour, hamburger, poulty Reduction in microbial load, limit contamination Sterilization -NASA, hospital diets |
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Modified atmosphere packaging (MAP) |
Use of impermeable films, evaculation, elevation of CO2 content Altered atmosphere around packaged meat may shift potential for growth of microbial community |
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Strategies of effective food preservation |
often employ multiple hurdles pH, temp, Aw... |
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Food fermentations |
Pickles, sausages, yogurt, cheese homolactic fermentation: Glucose --> lactic acid |
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Use of microorganisms in food production |
Beverage alcohol : ethanolic fermentation: glucose --> ethanol + CO2 Yeast - sacharomyces cerevisiae Vinegar production |
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Food additives Solvents Enzymes Biofules Agrochemicals Whole foods Fine chemicals |
Amino acids, organic acids, fatty acids, vitamins Acetone, butanol, ethanol Protease, amylase, cellulose, lipase Ethanol, methane, hydrogen Feed additives, biopesticides Bakers yeast, crop inoculants Antibiotics, nucleic acids, enzymes |
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Biotransformation (biocatalysis) |
Cortisone production First step is difficult to accomplish via chemical reaction Rhizopus nigricans is a fungus that catalyzes progesterone --> 11a-hydroxyprogesterone Then becomes hydro cortisone and then cortisone |
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Primary metabolite |
One that is formed during the growth phase of the microorganism eg. ethanol prodcued by fermenting Saccharomyces cerevisiae |
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Secondary metabolite |
One that is formed near end of growth phase, near/in stationary phase eg. penicillin produced by penicillium chrysogenum NOT ESSENTIAL FOR GROWTH, REPRODUCTION |
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Making vinegar |
Requires alcohol and acetic acid bacteria (acetobacter, gluconobacter) Strict aerobes, do not oxidize their growth substrate completely |
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Acetic acid bacteria's energy metabolism |
Partial ethanol oxidation ethanol - acetaldehyde - acetic acid |
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Vinegar generator |
aeration is important, fluid recirculated until desired acetic acid produced Operates continuously with lifetime of 5-30yrs Other materials will contribute to flavour Circles around bioflim of acetic acid bacteria wood chips |
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Vitamin syntheses Cobalamin |
vitamin B12 Natural synthesis is exclusively by microorganisms B12 deficiencey can lead to pernicious anemia in humans |
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Vitamin syntheses Riboflavin |
Vitamin B2 Needed for flavin synthesis Fad Fmn coenzymes that participate in oxidation-reduction reactions Ashbya gossypii fungus |
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Amino acid type |
Lglutamate- flavour enhancer meat tenderizer Glycine- flavour, organicsyntheses (sweet) Aspartame- low calorie sweetener (gum, drinks) L-lysine-nutritive additive (bread, feed) |
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Amino acid production |
Use overproducing strain of bacteria Brevibacterium flavum Control of synthesis is circumvented (mutants) Aspartate-asparylPO4-diaminopimelate-lysine Feedback inhibition is stopped Aspartokinase continues producing |
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Production of enzymes |
Often exploit extracellular enzymes - exoenzymes Specificity of enzymes catalytic reaction useful in bioconservations (Lamino acid production) Extermophile enzymes -extremozymes remain functional under harsh conditions |
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Production of enzymes Detergents Taq polymerase Invertase |
Amylases, proteases, lipases, reductases from Bacillus licheniformis Thermostable DNA polymerase from Thermus aquaticus used in polymerase chain reaction Sucrose digesting enzyme (caramilk) |
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Glucose isomerase
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High fructose sweetener from corn, wheat, patato starch Industrial enzyme is Streptomyces Production of soft drinks Converts glucose into fructose |
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Immobilization |
of soluble enzymes allows large scale reactions under continuous conditions * expensive enzymes can be reused by immobilizing them to beads or membranes |
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Scale up |
Lab flask - lab scale fermentor - pilor plant scale Oxygen transfer, mixing, aeration, temperature control, sterilization protocols, bioengineers all become more complex and difficult |
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Downstream processing Yeast biomass |
Collect cells, wash cells, dewater cells, achieve desired consistency, package, store |
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Compressed yeast cakes |
Dewatering-compressing-packaging-cold storage |
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Active dry yeast |
dewatering-exruding-gentle drying-packaging-coldstorage |
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Nutritional dry yeast |
pasturizing-drum drying- grinding-packaging- dry storage |
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Processing of cellular products may entail |
Removal of biomass from culture medium concentration and purification of product from spend medium Harvesting and fractionation of biomass to recover desired product, separation from cellular debris, concentration and purification |
