Term
| what is the temperature for milk to be kept at |
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Definition
| kept refrigerated at 4C until delivered to the factory |
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Term
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Definition
not the same as sterilisation
- heating of every particle of milk to a specific temp for a specific time
for public health and improved keeping quality- to destroy bacteria harmful to humans and to destroy enzymes that may spoil the milk.
min temp and time based on requirement for most heat resistant pathogen found in milk- Coxiella burnetti ( Q fever) . |
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Term
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Definition
1. Vat pasteurisation ( BATCH)
2. High temperature short Time ( HTST) |
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Term
| Temperature and time for Vat pasteurisation |
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Definition
63C for not less than 30 min
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Term
| Temperature and time for high temperature short time |
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Definition
| 72C for not less than 15 sec. |
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Term
| Vat pasteurisation ( BATCH) |
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Definition
- uses a vat pasteuriser- jacketed vat surrounded by either circulating water, steam or heating coils of water.
- used highly for the ice cream industry, as well as in processing of cheese, yogurt, buttermilk |
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Term
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Definition
- saves time and energy compared to the vat method
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Term
| methods for checking milk following pasteurisation |
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Definition
-raw milk contains enzyme alkaline phosphatase which is destroyed by pasteurisation- so can test for this
- peroxidase- but denatured at 78C and thus HTST milk is usually peroxidase positive
- plate counts and coliform numbers usally indicates poor plant hygiene
Bitty cream- caused by bacillus cereus and usually indicates problems with disinfection of the plant
pasteurised milk must therefore be phosphatase negative, peroxidase positive, with a low plate count test and low colofirm test |
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Term
| Sterilisation ( UHT milk) |
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Definition
complete elimination of micro organisms
subjecting to temperatures above 100C and packaging in air tight containers. ultra high temperature.
- high quality product, reduced cost |
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Term
| Factors that affect the survival and growth of micro organisms in milk |
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Definition
- nutrient content- high nutrients, good environment for organisms
- moisture content
- PH- 6.6
- available oxygen
- biological structure- no barriers to the spreading of microorganisms
- antimicrobial constituents
- temperature :
psychotrophs, mesophiles, thermophiles |
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Term
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Definition
| optimum growth temperature 20-30C, capable of growing at temp less than 7C. |
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Term
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Definition
| growth temp at 30-40C, do not grow at refrigeration temp. |
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Term
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Definition
| growth between 55 and 65C |
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Term
| Two main groups of bacteria present in raw milk |
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Definition
1. Lactic acid bacteria
2. coliforms |
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Term
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Definition
ferment lactose to lactic acid.
also used as starter cultures |
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Term
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Definition
| indicator organisms, can cause rapid spoilage of milk because they are able to ferment lactose with the production of acid and gas, and are able to degrade milk proteins. killed by HTST treatment . therefore their prescence is indicative of contamination |
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Term
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Definition
microorganisms used in the production of cultured dairy products
two groups:
simple or defined:single strain or more than on in which the number is known
, mixed or compound: more than one strain each providing its own specific characteristics
- one concern is bacteriophages which are viruses that attack bacteria |
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Term
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Definition
deteriorating taste, color, texture
- usually psychotrophic microorganisms- but are destroyed by pasteurisation , but some organisms can survive pasteurisation and grow at fridge temperatures
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Term
| Pathogenic microorganisms |
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Definition
the following are still a concern:
Bacillus Cereus
Listeria Monocytogenes
Yersinia enterocolitica
Salmonella spp.
E. Coli
Campylobacter jejuni |
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Term
| Antibiotic residue in milk |
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Definition
Reasons for test failures:
human error- incorrect withholding time, incorrect cow ID
equipment fault: mechanical failure, contamination of equipment
off label use of antimicrobial products : change of duration of treatment, change of frequency of treatment |
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Term
| testing of antibiotic residue in milk |
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Definition
Delvotest SP
- microbial inhibition test using Baciullus , used to detect a wide range of ABs
- if bulk milk tank fails an inhibitory substance test, then milk is usually re -tested to confirm the failure.
- may only pay farmer 1ppl for contaminated milk |
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