Food quality

Microbial growth has impact on?

Safety (mathmatically and HACCP) and spoilage (experimentally)

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Microbial food spoilage depends on?

Types and number of microorganisms present, enviromental conditions and the chemical characteristcs of the food

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Types and kinds of microorganisms depend on....

Extent of contamination, previous opportunities for growth and pre-treatments the food may have recieved

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Microorganisms and spoilage link with f poisoining

Changed so unpleasant, not food poisoining but may be present and have a natural reaction to taste, spoilt food is not of the nature or substance demanded by the consumers

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Spoilage symptoms result from...

transformations caused by microbial enzymes

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Carbohydrates

Alchohols, keytones, Co2, H20, hydrocarbons and aldehydes

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Peptides and Amino Acids

Co2, nitrates, acids, amines, ammonia, thiols, sulphides and oximes

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Fats and Oils

Volifile fatty acids, glycerol, alchohols, hydrocarbons, C02 and H20

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Pshycotripic

Refrigeration, moulds and yeasts, spore formers, common species: flavobacterium, broncothrix and psuedomonas: odour slime and colour - able to grow 7c or below.. The influence of bacteria in the shelf life of pasteurized milk depend packging after pa

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Thermoduric spoilage

Streptococcus, Baccilus, Clostridum, flavour colour etc. Microbacterium, putritive spoilage clostridium and flat sour spoilage - Baccilus,he sources of contamination are poorly cleaned and sanitized utensils and equipment on farm and processing plant

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Acid

Lactobacillus, Acetobacter, Streptoccus, Leuconostoc, Prediococcus - acid, sour taste and vingegar (high acid or carbohydrate rich foods and dairy products)

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Lipolytic Spoilage

Fats high fats common species involved, development of rancid flavours and odours

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Proteolytic spoilage

high protein food, bacillus, clostridium, psuedomonas and proteus, rotten smells

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Yeasts and moulds

Yeasts: Fermentation of sugars, production of alcohol, Co2 and H20, fruity alchohol, visable growth, mouldty earth - occurs in food where bacteria is unable to grow

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protocoll for shelf life

Storing at several temps and humidities, 20, 25 and 30, samples taken, macerated in a sterile system, serially dilated and put onto medium suitable for growth of selected microorganisms- then innubased and enumerated

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Considerations

Montioring, prioritising, which pathogen to monitor depnds on many intrinsic and extrinsic properties.

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Issues shelf life

Slow- product may have to be released - factory and trials should be taken place to give an indiction microbial spoilage flora change in product compositon and processing may affect spoilage flora

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resistant microorganisms

Acetic acid tolerant bacteria, sorbate resistant yests, osmophilic yeasts - hence challenge testing is used

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What is MCT

determining the ability of a food to support the growth of spoilage micorganism or pathogens

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MCT plays an important role

validation of processes intended to deliver some degree of lethality against a target organisms or group of target organism, also useful in determining shelf life of certain refridgerated and ambient stored priducts

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Defintion MCT

Microbiological challenge testing is very useful for food products that may sustain the growth of pathogenic organisms that are stored under regrigerated tempertures, elevated temperature or at ambiet temperaturee and are volunerable to the growth

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MCT is useful to determine

Product safety, estbalish product shelf life and aid in product reformulation

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When considering a MCT a numner of factors may be considered

1. Selection of pathogens, 2. level of challenge inoculum 3. Innoculation preporation and method of inoculation 4. the duration of the study 5. forumation factors and storage 6. Sample analysis - interpreation (pass/fail) critical in time/temp contro

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Limitations of MCT?

time comunising, expensive, requires skill, requires appropriate facilites and results are only valid for the specific product

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Other issues of MCT?

RTE - High risk - guidlines and microbiological specifications to interpret results

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Examples humidities?

40% 60% and 80%

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Food packaging and transfer of

Moisture and atmosphere

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Arobic plate

Usually 35c for 48 hours many organisms not declared in inculation

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Organisms grow between

0-55

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Water activity greater than

0.6

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Specific of challenge testing

The number of organisms added to the food is generally significantly higher than what would normally be found as a result of contamination during processing. The inoculation levels used are generally greater than 10 per gram, offering easy observatio

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Pathogens used

Commonly used pathogens are Salmonella, Listeria monocytogenes, Staphylococcus aureus, Bacillus cereus, Clostridium perfringens, Yersinia enterocolitica, Clostridium botulinum, and Escherichia coli. If the pathogens do not grow,

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if pathogens do not grow...

If the pathogens do not grow, the food is considered stable with respect to the ability of the food system to inhibit their growth.

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Other definitons of shelf life

Period during which food product maintains its microbiogical safety and suitability at a specific storage temperatrue and where appropriate, specififed storage and handling conditions

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Shelf life relies on....

Process control, HACCP management procedures , prerequiste controls

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innoculum level of

102 and 103 cells/g higher may be appropraite in other products

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Salmonella (pathogen) found in?

salad and sources

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MAP risk for?

Clostridium botulinum

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Before challenge strains should be tested

for mutual antagonism and possible of a surrogate strian

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vegtative cells

18h 24hours regriative

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Why its important to test past shelf life?

becuase substanitial injury may occur,5-7 data points over shelf life to be representative, if shelf life is months no less than once a week- all should start with 'zero time' testing analysis of product straight after innoculation

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Challenge representative tempartures of?

shelf life, which held and distibuted,

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Tolerable growth for B.cillus

>106 CFU/g hazadous toxins at high levles

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Botulinium

>105 CFU/g for illness

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Food quality

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