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61 Cards in this Set
- Front
- Back
What is food spoilage? |
Deterioration in quality of food (colour, odour, texture, flavour) making it aesthetically unpleasant or unsafe |
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What causes food spoilage? |
Microbial growth and/or chemical changes eg. enzyme activity |
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What is food quality? |
Aesthetics: colour, odour, flavour, texture |
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What does safety of a spoiled food product depend on? |
Whether pathogens are present initially and how they behave in product during/after shelf life |
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What is the significance of food spoilage? |
Global problem |
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What 7 costs are associated with food spoilage? |
Production, processing, distribution, storage, retailing, disposal, environmental cost |
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How much food is discarded? |
~25-30% |
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What are the 2 major types of food spoilage organisms? |
Psychrophilic and mesophilic |
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What temp do psychrophiles like? |
=7*C
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What are the 2 main psychrophiles involved in food spoilage? |
Listeria monocytogenes, Aeromonas hydrophila |
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What temp do mesophiles like? |
>/= 8*C = 45*C |
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What type of microorganisms are mesophiles? |
zoonotic |
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What is the main mesophile involved in food spoilage? |
Staphylococcus aureus |
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What temp do thermophiles like? |
>/= 46*C |
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What causes variation of the dominant species in meat? |
meat composition, storage and packaging conditions (eg. gas permeable vs vacuum packed) |
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How do food spoilage bacteria proliferate? |
binary fission |
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What influences replication time? |
composition and storage conditions |
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What 5 intrinsic factors affect microbial growth? |
pH, moisture content, nutritional profiles, antimicrobial constituents and biological structures |
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What unit is used to measure moisture content? |
Aw water availability |
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What nutrients are intrinsic factors affecting microbial growth? |
carb and protein profiles |
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What antimicrobial constituents are found in milk and eggs? |
Lactoferrin (milk), Lysozyme (milk and eggs) |
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What 4 extrinsic factors affect microbial growth? |
Storage temp, relative humidity, presence comp and conc of gases, presence and activity of other microorganisms |
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What 3 gases affect microbial growth? |
O2, CO2 and N2 (ratio) |
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What does LAB produce? |
bacteriocin |
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Which microorganism in food spoilage is a poor competitor? |
S. aureus |
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What are the 4 stages of bacterial growth? |
Lag phase, exponential phase, stationary phase, death phase |
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What makes lean meat susceptible to spoiling? |
high Aw |
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What protects meat? |
pH goes from 7 to 5.5-5.8, inhibiting growth |
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What are the 5 results of spoilage of meat? |
Putrefaction, rancidity, odours, slimes, discolouration |
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What type of meat fat is especially susceptible to spoilage? |
Abdominal and surface fat |
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What type of meat fat is less susceptible to spoilage? |
intramuscular marbling |
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What 4 prevention technologies are used to prevent microbial growth on meat? |
hygiene, cold line controls, chilling, freezing |
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What does freezing do? |
Freezes water, lowers Aw, Increases osmotic stress |
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What does freezing physically damage? |
cells |
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What does chilling do? |
Prevents microbial growth and enzyme activity |
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What temp should red meat be chilled at? |
= 7*C 24hrs PM, = 4*C thereafter |
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What temp should poultry be chilled at? |
= 4*C ~2hrs PM |
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What are the 4 methods of preservation used on meat? |
Curing, drying, smoking, fermentation |
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What 3 ways is salt added to meat during curing? |
rubbing, immersing in brine, injecting brine |
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What does addition of salt result in? |
Decreased Aw |
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What do nitriles do? |
Colour and inhibit clostridia |
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What 2 things are added to meat for curing? |
salt and nitriles |
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What does drying of meat cause? |
Decreased Aw, increased osmotic stress |
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What is smoking? |
Wood chip buring |
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What 3 things does smoking produce? |
Phenols, aldehydes and furans |
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What does smoking time depend on? |
Smoke temp |
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What does fermentation cause? |
LAB, decreased pH, increased lactic acid |
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What are the 4 packaging technologies? |
gas composition, gas permeable packaging, vacuum packaging, modified atmosphere packaging (MAP) |
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What concentrations of gases are used in MAP? |
60-70% CO2 / 10-15% O2 / 15-30% N2 |
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What is the shelf life of fresh meat? |
7-10 days at -1 - 1*C |
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What is the shelf life of vacuum packed meat? |
>70 days at -1 - 1*C |
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What is the shelf life of MAP red meat at 60% CO2? |
Up to 70 days at -1 - 1*C |
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What is the shelf life of MAP poultry at 60% CO2? |
Up to 25 days at -1 - 1*C |
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What chemicals are used to preserve foods? 4 |
nitrates in bacon and ham, sulphites in beverages, sorbates in cheeses and beverages, salt in cured meats |
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What is an example of a natural food 'additive' used for preservation? |
Bacteriocins (nisin) produced by LAB |
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What are the 5 main pathogens in raw milk? |
L. mono, M. bovis, Campy, Salmonella, E. coli |
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What pathogen of raw milk is capable of growth a refrigeration temp? |
Pseudomonas |
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What is curdling? |
Protein precipitation and souring lactic acid, rancidity |
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Which microorganisms survive pasteurisation? |
Thermodurics |
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What are the 8 steps in yogurt production? |
Pasteurise, homogenise, pre-heat 40-46*C, add starter cultures, incubate 40-46*C for 4-5 hours, stir and cool 5*C, add fruit/flavours/colours, filling/packing |
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What pH is yogurt? |
~4.3 |