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PMVPH (round 2) > CS - meat preservation > Flashcards

CS - meat preservation Flashcards

1
Q

Why preserve meat?

A
  • delays spoilage
  • extends shelf lif
  • imprves taste and quality
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2
Q

Methods - preserving good

A
  • extreme heat/cold
  • deprivation of water
  • increased acidity etc
  • salting and pickling
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3
Q

Legal definition - meat

A 
edible parts (including blood) of domestic ungulates (bovine, ovine, caprine, porcine
species, domestic solipeds), lagomorphs, poultry and game.
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4
Q

Define fresh meat

A

‘meat that has not undergone any preserving process other than chilling,
freezing or quick-freezing, including meat that is vacuum-wrapped or wrapped in a controlled
atmosphere’.

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5
Q

Define meat products

A

: ‘processed products resulting from the processing of meat or from the further
processing of such processed products, so that the cut surface shows that the product no
longer has the characteristics of fresh meat’, for example bacon, ham or salami.

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6
Q

Define meat preparations

A

: ‘fresh meat, including meat that has been reduced to fragments, which
has had foodstuffs, seasonings or additives added to it or which has undergone processes
insufficient to modify the internal muscle fibre structure of the meat and thus to eliminate the
characteristics of fresh meat’, for example raw burgers, chicken nuggets or shish kebab.

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7
Q

Define minced meat

A

‘boned meat that has been minced into fragments and contains less than 1%
salt’. Minced meat is considered to be a meat preparation when it contains more than 1% salt.

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8
Q

What are the food ‘risk products’?

A

1) High risk products: raw meat, fish and dairy products, chilled products containing raw meat,
fish, dairy products, products with pH>4.6, infant formulas
2) Medium risk products: dried and frozen products containing fish, meat, egg, dairy products,
sandwiches and meat pies, fat based products (e.g. chocolate, margarine), spreads, mayonnaise
and dressings
3) Low risk products: acid products, unprocessed raw vegetables, jams, marmalade and
conserves, sugar-based confectionery, dried cereal products, edible oils and fats

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9
Q

Name 4 types of food microorganism

A
  • desirable
  • spoilage
  • indicator
  • pathogenic
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10
Q

Function - lactobacilli

A

convert carbohydrates into lactic acid

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11
Q

T/F: spoilage organisms cause illness

A

Illness normally does not occur unless large amounts of the spoiled food are ingested.
Spoiled food may also harbour pathogenic organisms, but spoilage usually discourages the
consumption of potentially dangerous food.

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12
Q

What are indicator organisms?

A

organisms that are generally non pathogenic but often associated
with pathogens. Their presence can give an indication of the presence of pathogens in food
stuff, particularly enterobacteria

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13
Q

4 phases of bacterial growth

A
  • lag
  • log
  • stationary
  • reduction (death)
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14
Q

What is the D-value?

A

e=decimal reduction time, the time

required at a certain temperature to reduce 90% of the organisms being studied.

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15
Q

Influences on shape of bacterial growth curve

A

temperature, nutrient supply and other growth factors

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16
Q

What determines the bacteria’s generation times?

A

Bacterial growth rates during the phase of exponential growth, under standard nutritional conditions

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17
Q

Intrinsic factors affecting survival/growth of microorganisms?

A
  • nutrient content
  • water activity
  • pH
  • redox potential
  • biological structures
  • natural inhibitors
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18
Q

T/F: pseudomonas grow on almost all kinds of food

A

True

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19
Q

What is Aw?

A

water availability. This is a measure of the partial vapour pressure of the
food compared to that of pure water (aW=1), i.e. it gives information about the amount of water that is
available in the food. Lies between 0 and 1. Depends on absolute amount of water and the structure of food.

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20
Q

T/F: This is a measure of the partial vapour pressure of the
food compared to that of pure water (aW=1), i.e. it gives information about the amount of water that is
available in the food.

A

True

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21
Q

At what Aw will microbial growth cease completely?

A

if Aw is

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22
Q

What is the pH of most food products of animal origin?

A

3.5-7 (most bacteria grow best in range 6-8 but there are exceptions)

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23
Q

What is Eh?

A

redox potential - the tendency of a compound to acquire or release electrons and thereby be reduce or oxidated. The more
positive the potential, the greater the product’s affinity for electrons and tendency to be reduced.

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24
Q

List some natural inhibitors of microorganism growth in food

A

lysozymes in meat or eggs, lactoferrin in milk or salicylic acid in
plants.

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25
Q

What is the most important factor to influence bacterial growth?

A

temperature

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26
Q

Freezing below what temperature or lower stops any microbial growth in food (bacteria, yeasts, mould)

A

10 degrees or lower

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27
Q

Effect of refrigerations

A

extends the lag and log phase which provokes a slower growth of Psychrophiles and Psychotrophs and inhibits growht of most pathogens (except Yersinia, Clostridium botulinum type E and listeria spp)

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28
Q

Define obligate aerobe

A

O2 required for energy production. they grow on food stored in air, O2 permeable wrap or in a modified atmosphere containing O2 (pseudomonas, Microcossu, Actinobacter)

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29
Q

Example - facultative anaerobes

A

E.coli, Salmonella

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30
Q

Example obligate anaerobe

A

Clostridium (if present can be lethal)

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31
Q

Example - microaerophile

A

Campylobacter

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32
Q

Superficial changes to meat with storage - 3

A
  • shrinkage
  • sweating
  • loss of bloom
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33
Q

Explain meat sweating

A

this is condensation of water vapour on meat from cold store to ordinary room temperature as refrigerated carcase lowers the temperature of the air to below dew point

34
Q

What is bloom?

A

the colour and general appearance of a carcase surface when viewed through the semitransparent layers of CT moist the collagen fibres swell and become opaque, the carcase looks dull and lifeless

35
Q

Describe meat pH post slaughter

A
  • lactic acid remains in mm (no circulation) causing pH to fall until the glycogen stored in mm is consumed
  • In PM phase, ph drops fro 7-7.2 to 5.3-6.8 depending on spp, mm type and stress during pre-slaughter period. If great lactic acid build up with high stress, pH falls too quickly after slaughter –> Pale Soft Exudate (PSE) meat. The opposite is if glycogen is depleted before slaighter, the pH does not drop quickly enough because there is less glycogen available and not enough lactic acid produced –> Dark, Firm and Dry (DFD) meat which is more susceptible to spoilage (higher pH).
36
Q

What is rigor mortis?

A
  • all stored glycogen consumed
  • actin and myosin bound as actomyosin complexes
  • fixes length of sarcomeres (thus mm length and texture of meat: relaxed –> tender meat, contracted –> tough)
37
Q

How is mm contraction reduced in the meat industry?

A

hang carcasses straight after slaighter by hip/peliv bone to stretch mm by gravity

38
Q

What is meat tenderness related to?

A
  • spp
  • breakdown of mm fibres
  • loosening of CTs
  • natural proteolytic enzymes (cathepsins and calpains) break down proteins –> weaken its structure
39
Q

T/F: meat can age w/o packaging for up to 14d depending on microbial status and storage temp.

A

true

40
Q

What do different colours of spoilage indicate?

A
  • green, brown or purple = microbial

- black, white and green may indicate moulds or freezer brun

41
Q

Cause of meat alteration

A
  • microbes
  • chemical
  • biological
  • physical
42
Q

T/F: yeats and moulds tend to grow faster than bacteria

A

False - bacteria tend to grow faster hence spoilage is most often attributed to them

43
Q

How many bacteria cause ‘off’ odours?

A

10^7 bacteria/cm^2

44
Q

How many bacteria cause visible slime formation?

A

10^8 bacteria/cm2

45
Q

List preservation methods

A
  • heating
  • chilling and freezing
  • drying, curing, smoking, fermentation
  • chemical preservation
  • irradiation
46
Q

List new preservation mthods

A
  • ultrahigh pressure
  • electroporation
  • high intensity light pulses
  • manothermosonication (combined ultrasound and pressure)
  • addition of bacteriolytic enzymes
47
Q

What heating temperature is needed to elimate pathogenic and spoilage bacteria?

A

> 60 degrees

48
Q

Aim - pasteurisation

A

reduce numbers of target pathogen by a theoretical factor of 10^7 –> appreciable margin of safety

49
Q

Outline food sterilisation

A
  • 115-138 degrees for varying periods of time
  • UHT milk is 145 degrees for 2-4 seconds. Even after this some organisms remain, generally thermophiles which don’t grow/ produce toxins/ spoil the product.
  • rapid and continuous cooling and protection from recontamination
50
Q

T/F: low pH foods need little heating to be rendered sterile

A

true

51
Q

Outline canning of meat

A

involves heat destruction of microorganisms, including the relatively heat-resistant
spores of some strains of Clostridium botulinum. When spoilage occurs, this is usually due to underprocessing,
contamination of the product through can leakage or pre-process growth of
microorganisms and/or toxin formation.
- curing agents are used where appropriate

52
Q

T/F: most food, especially meat, will undergo some refirgeration immediately after primary processing and before cutting/deboning

A

true

53
Q

What temperature do abattoirs hold meat post-slaughter?

A

for 48 hours until carcase is 7 degrees (red meat) or 4 degrees (white meat and offal)

54
Q

T/F: L. monocytogenes can grow at 2 degrees

A

true

55
Q

T/F: some salmonella spp can grow at 5 degrees

A

true

56
Q

T/F: campylobacter can grow at 7 degrees

A

True

57
Q

What temperature does blast freezing achieve?

A
  • 18 degrees (down to minus 40 degrees)
58
Q

What temperature does meat freeze?

A
  • 3 degres
59
Q

Effect of freezing on microorganisms

A
  • kills a proportion on the meat surface
  • ice prevents replication
  • slows organism metabolism
  • most bacterial spores and some vegetative cells (staph, enterococcus and micrococcus are resistant to freezing (highly)
60
Q

What happen if meat is cooled too rapidly below 10 degrees before pH of mm has fallen below 6?

A

mm fibres contract (cold shortening) and meat is tough (small carcases - lamb). only post-rigor meat should be frozn

61
Q

What is thaw rigor?

A

Another problem can arise during thawing of pre-rigor frozen meat when the muscle
contracts and exudes a substantial part of its weight as tissue fluids (thaw rigor)

62
Q

What does meat vacuuming do?

A
  • low permeability to atmospheric gases
  • extends shelf-life significantly
  • continued respiratory activity of meat tissues rapidly reduces the
    oxygen concentration below 1%, while the carbon dioxide accumulates.
  • absence of O2 can cause the loss of characteristic red colour of meat (once unpacked for sale and exposed to air with regain its red colour)
  • used for meat maturation: can age for up to 3 months
  • rapid spoilage if pH is unusually high (DFD meat) d/t H2S producing organisms
63
Q

Define MAP

A

= modified atmosphere packaging

  • extends shelf life
  • gas-impermeable film used in combination with specific gas mixtures
  • 3 main gases = O2, N2 and CO2
  • UK generally 60-85% O2 (enhances attractive red colour) and 15-40% Co2 (inbibits microbial growth of spoilage flora)
  • efficacy depends on quality of raw meat, gas mixture, storage temp, hygiene and packaging material
  • rarely poultry
64
Q

How to dehydrate meat

A
  • add salts and sugar (sequester water)

- won’t necessarily kill microorganisms but will inhibit growth

65
Q

Methods - meat drying

A
  • heated air
  • direct contact with heated surface
  • radiation
  • microwave
  • dielectric sourve
  • lyophilisation (accelerated freeze-drying)
66
Q

Define sublimation

A

converting ice under low pressure fro solid state directly to vapour by heat

67
Q

Define curing

A
  • preservation using salt (NaCL0 and sodium or potassium nitrite (-NO2) or nitrate (NO3) or mixutre of latter two salts
  • preserves by dehydration and osmotic pressure
  • adds flaour
  • salt conc of 1.5-5%
  • nitrates/nitrites develop mmeat colour, flavour, antioxidants and inhibit growth of spoilage organisms
  • revents growth of C.botulinum
  • mixture of NaCL and NO source changes myoglobin to the nitrosomyoglobin form
  • timely process (takes 1-2 weeks)
68
Q

Method - smoking

A
  • wood fire

- wood sawdust in generator

69
Q

Aim - smoking

A
  • flavour
  • preservation
  • intensifies colour
  • dries surface
  • deposits compounds with bactericidal or fungistatic effect (formaldehyde, phenols and ketones)
70
Q

T/F: smoke is sufficient at preserving food

A

false - doesn’t penetrate food thus often combined with drying or curing.

71
Q

Differentiate hot and cold smoking

A
  • hot smoking = when the product is to be partially or completely cooked
  • Cold smoking = an hours-days long process in which smoke is passed by food which is held at room temperatures to add colour and flavour to the product
72
Q

Outline sausage production

A
  • some produced in dry or semi-dry form without being smoken or heat processed, then eatedn without cooking
  • microbrial changes d/t those already present and those added as started cultures
  • ingredients: meat, fat, starter cultures, spices, curing agents
  • processed –> stuffed into casings –> care drying process –> flavour
  • during fermentation pH falls rapidly below 5 (lactobacilli and other lactic acid bacteria predominate)
73
Q

Main microbial processes in sausage making

A
  • nitrate –> nitrite through micrococci or staphylocci
  • carbohydrates –> lactic acid through lactobacilli
  • surface mould growth through penicillium spp (desirable but controlled)
74
Q

What does giving an additive an E number ean?

A
  • it has passed safety tests and has been approved for use in the EU
  • e.g. nitrate and nitrite
  • sulphur dioxide
75
Q

Outline food irradiation

A
  • a processing technique
  • uses ionising radiation to increase food stoarge life, reduce post-harvest food losses and eliminate food borne pathogens
  • gamma rays, x rays with eergies 5MeV, high energy electrons of 10 MeV
  • in UK, only gamma radiation (cobalt-60 or caesium-137)
76
Q

Chemical/biological effects of irradiation

A
  • kill bacteria
  • delay fruit ripening
  • help stop vegetables sprouting
  • organoleptic effects are minimal
  • in UK, legislation allows irradiation of 7 food types (fruit, veg, cereals, bulbs/tubers, spices/condiments, fish and shellfish and poultry
77
Q

Outline salmonella in primary production

A
  • A survey in 2013 found that 30.5% of 600 pigs tested at abattoir carried Salmonella spp. in the caecum.
  • The occurrence of the clinical disease is rare and the symptoms are often short lived (possible symptoms: diarrhoea, dehydration, septicaemia, mortality, abortion).
  • Diagnosis at the farm using faecal or environmental samples
  • Salmonella control options include farm hygiene and biosecurity, all-in/all-out, cleaning and disinfection, vermin control, sourcing salmonella free stock, reduction of stress, vaccination
78
Q

Outline salmonella in harvesting

A
  • New EU legislation requires abattoirs to identify farms where pigs show regular salmonella contamination.
  • Food Chain Information (FCI) sheets with improved detail now dictate the level of carcass inspection required.
  • Measures to promote safety include handling, management, stocking densities, and hygiene in transport and lairage, feed withdrawal times, logistic slaughter use of HACCP principles, carcass decontamination.
79
Q

Outline salmonella in processing

A
  • Curing includes the addition of a combination of salt, sugar and either nitrate or nitrite.
  • Salt lowers the water activity aw inhibits spoilage organisms.
  • Nitrite has antibacterial and antioxidant properties and enhances colour and flavour.
  • Massaging and tumbling help to distribute the salt and improve the water-holding capacity of the meat by reaction between the salt and the structural proteins – binding.
80
Q

Outline cooking, smoking and cooling

A
  • Fully cooked hams are thermally processed to temperatures up to 75°C for a defined time to eliminate nearly all salmonella in the product.
  • Smoking reduces the surface bacterial population and adds a physical barrier by dehydration, but is commonly used nowadays to add flavour.
  • Cooling prevents multiplication - the temperature range for growth of Salmonella spp. is 5.2–46.2°C.
81
Q

Outline packing and labelling

A
  • Modified atmosphere packaging (MAP) extends shelf life and prevents microbial growth by introducing a mixture of carbon dioxide and nitrogen into the pack.
  • The new EU regulation 1169/2011 details the labelling requirements for food products (e.g. name of the food, ingredients, details of the food business operator that markets the product, etc).
82
Q

Outline consumption with salmonella

A
  • Infection can cause diarrhoea, fever, vomiting, and abdominal cramps 12 to 72 hours; 4-7 days, most people recover without treatment.
  • Laboratories must notify public health authorities on the confirmation of Salmonella spp, as they are listed as notifiable organisms.
  • In a survey in 2008-2009, >38,600 salmonellosis cases were estimated for the UK.
  • Consumers contribute to food safety through kitchen hygiene and appropriate handling of products (e.g. maintain cold chain, prepare raw and cooked foods separately, wash hands)

PMVPH (round 2) (45 decks)

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