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59 Cards in this Set
- Front
- Back
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Rinderpest; 'Cattle Plague' (Morbillivirus)
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affects cloven-footed animals, 100% mortality due to starvation; welfare implications
UK epidemic 1865 - Veterinary profession recognised, State Veterinary Service created GLOBAL ERADICATION PROGRAMME - officially free status achieved 2011 |
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John Gamgee (1831-1894)
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supported the idea of VETERINARY INSPECTIONS, as well as first diagnosing Rinderpest epidemic and developing refrigeration
MI for TB, parasites, abscesses etc |
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New slaughterhouse rules due to the EVOLUTION of hazards....
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Less TB
More contamination with mass production New agents; BSE - removal of specified material |
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POLITICS and MONEY issues affecting slaughterhouse rules;
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global trade
cost of production fear of epidemics jobs |
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the origin of HAZARDS linked with foods of animal origin
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animal disease; zoonotic pathogens and metabolic disorders (toxins)
human origin; residues (antibiotics, pesticides, chemicals, dioxins), microbiological contaminants, physical contaminants environmental heavy metals etc |
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When do hazards arise?
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Lifetime of animal; disease, feed/supplements, drugs, environmental exposure
Further processing; slaughter, milking, raw meat processing, cooking/curing, storage |
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Slaughter
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causing death of the animal by bleeding
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Killing
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causing death by a process other than slaughter
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Meat
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skeletal muscle with naturally included/attached tissue
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Offals
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fresh meat other than the carcase; whether or not naturally connected to the carcase
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Wild Game
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wild land mammals and wild birds which are hunted
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What does the presence of the health mark indicate?
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When it was applied, official controls had been carried out in accordance with the respective EUROPEAN REGULATIONS
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WHO definition of Veterinary Public Health
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"the sum of all contributions to the physical, mental and social well-being of humans through an understanding and application of veterinary science"
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Methods of meat preservation;
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irradiation, modified atmosphere, preservatives, packaging/canning, freezing, curing, salting, fermenting, cooking, drying, smoking
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the principle of food microbiology applies to
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the different factors that affect microbial growth; can be intrinsic (physicochemical properties), extrinsic (storage environment) or implicit
*all can be modified by processing factors |
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Common food spoilage microorganisms
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Pseudomonas, Brochotrix, Proteus, Clostridia, Bacili
Penicillium, Aspergillus |
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Common food poisoning organisms
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Salmonella, Campylobacter, Listeria, E.coli plus viruses/fungi/toxins
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Phases of bacterial growth..
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1. Lag phase
2. Exponential growth phase 3. Stationary phase 4. Death phase |
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Intrinsic factors that affect food microbiology;
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Nutrients (may favour particular organisms)
pH, buffering capacity redox potential water activity antimicrobial factors present |
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High SUGAR content increases risk of....
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fungal growth
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pH definition
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negative logarithm of the hydrogen ion capacity
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why does pH affect microorganisms?
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transmembrane transport of nutrients
ATP synthesis stability of enzymes growth and metabolism |
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Preferred pH of different microorganisms;
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6.0 - 8.0; Bacteria
5.0 - 6.0; Lactobacilli 4.5 - 6.0; Yeasts 3.5 - 4.0; Filamentous Fungi |
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pH of food commodities
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5.6; muscle
6.2 - 6.5; fish 6.4 - 6.6; milk 9.2; egg white |
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Bacterial pH limits
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4.5/6.0 - 8.0/9.0; most bacteria
3.0/4.0 - 5.0/9.0; aciduric bacteria 5.0 - 11.0; alkali tolerant bacteria 'vibrio' 2.0/5.0 - 7.0/11.0; moulds and yeasts |
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Definition of Redox potential;
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the tendency of a medium to accept or donate electrons to oxidise or reduce
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Microorganisms favoured by particular redox potentials...
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obligate aerobes - HIGH redox, +100-500
obligate anaerobes - LOW/negative redox - though also depends on the presence of oxygen and the ability of the microorganism to destroy superoxides |
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Redox potentials of different food commodities;
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-200 E(mV); meat at pH 5.6
+225 E(mV); minced meat at pH 5.9 -20 to -150 E(mV); cooked sausages +383 E(mV); lemon at pH 2.2 |
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Definition of Water Activity
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the ratio of water vapour pressure of a food to that of pure water at the same temperature
(may be affected by the relative humidity of the atmosphere |
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methods to reduce water activity in foodstuffs
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drying, freezing, addition of solutes (NaCl,sugar) or altering microstructure
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water activities of common foodstuffs
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0.98 - 1.00; fresh veg, meat, eggs, milk
0.96-0.93; cured meat <0.60; honey |
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minimum water activity levels tolerated by different microorganisms;
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0.90; most bacteria
0.88; most yeasts 0.80; most moulds 0.75; halophilic bacteria (grows in higher salt) 0.65; xerophilic bacteria (grow in dry food) 0.61; osmophilic yeasts (grow in high conc. of ionised substanced) |
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Antimicrobial factors present in foodstuffs
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OVOTRANSFERRIN (egg-white protein)
lactoferrin, lysosyme (milk proteins) egg shell/cuticle factors introduced during processing; rind, packaging, preservatives |
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Relative Humidity and Food
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affects aW; outer surface of food, e.g.
white spots - Sporotrichum canis black spots - Cladosporidium herbarum; imported chilled carcases, with decomposition green-blueish mould - Penicillium |
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Which gases are used in modified atmosphere packaging?
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Carbon Dioxide, Nitrogen
affects pH as produces carbonic acid with water and so reduces surface contamination |
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High temperature affects
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membrane integrity
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Low temperatures affect
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nutrient availibility
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'Thermophiles'
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range: 40 - 90 degrees
optimum: 55 - 75 degrees e.g. Clostridium botulinum in canned foods |
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'Mesophiles'*
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range: 5 - 47 degrees
optimum: 30 - 40 degrees *important in food production e.g. Staph aureus, E. coli, Salmonella, Shigella in foods at ambient temperature |
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'Psychrophiles'
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range: -5 to 20 degrees
optimum: 12 - 15 degrees e.g. Thamnidium elegans may be present in frozen foods/in chiller or freezer units |
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'Psychotrophs'*
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range: -5 to 30 degrees
optimum: 25 - 30 degrees *important in food production |
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'Thermotroph'
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range: 10 - 50 degrees
optimum: 42 - 46 degrees NB. poultry body temp?! |
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"Thermo-tolerant"
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includes spores of bacteria, and fungi
may be found in pasteurised foods |
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Principles of effective freezing:
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-12 degrees required to prevent microbiological growth (some fungi/yeasts grow at -10)
slow freeing promotes bacterial survival rapid freezing; water crystallisation; bacterial death |
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Implicit factors related to food microbiology
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Growth Rate: bacteria>mould
Mutualism: Streptcoccus thermophilus growth helps Lactobacillus grow at pH 5.5 Antagonism: Lactic fermentation restricts bacterial growth of pathogenic strains Physiological status, strain diversity, adaptation |
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How does salting/curing work?
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2-6% Salt with Nitrites <200mg/kg
e.g. by injection/dry curing salt reduces aW and interacts with cell components transporting electrons N-nitrosamines generated are carcinogenic red/pink colour as nitrosomyoglobin when cooked turns to nitrosylhaemochrome |
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Definition of Fermentation
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phase of intensive growth and metabolism of lactic acid bacteria - accompanied by rapid fall of pH
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Natural Fermentation Process
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The aerobic, gram-negative flora in chilled meat e.g. Pseudomonas
gradually replaced (2-3 days) by gram-positive facultative anaerobes/microaerophiles Micrococcus, Staph, Lactobacillus acid-tolerant gram-negatives may persist E. coli O157, Salmonella Insufficient pH drop allows gram-positive pathogens to grow |
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Effects of starter cultures on Fermentation
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Same process, but faster
Starter organisms have to be competitive to have an effect with existing flora |
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Why does fermentation help preserve food?
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pH control and antagonism
cheeses, yoghurt, salami. fermented sausage aW also a factor may also be pasteurised afterwards |
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Smoking is the effect of....
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"aerobic/anaerobic pyrolysis of woods, their polysaccharides; cellulose, hemi-cellulose, lignin"
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Smoking process:
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Starts at 170 degrees, up to 270 in endothermic; above this, intensively exothermic
cold smoking: 30 degrees warm smoking: 40 - 60 degrees hot smoking: 70 - 80 degrees hardwood smoke or liquid (injected) drying+phenols/formaldehyde+temperature |
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Drying - the removal of water - is achieved by:
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keeping product suspended in air
lyophilisation; frozen, exposed to v. low pressure (5-6mbar) at 20 - 40 degrees |
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Food groups based on aW values:
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High moisture (0.9-1.0):
at pH 5.2, >0.95 refrigerated at 5 degrees, 0.91-0.95 refrigerated at 10 degrees Intermediate moisture (0.6-0.9): can be stored without refrigerating Low moisture (<0.6): self stable |
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Pasteurisation (water or steam @ <100 degrees)
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normally destroys all psychrophiles and mesophiles
vegetative cells of thermophiles, plus spores, may survive products stored with refrigeration |
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Boiling (water at 100 degrees, centre of product reaches 80-90 degrees)
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kills all vegetative microorganisms, spores may survive
products refrigerated |
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commercial 'sterilisation' (>100 degrees, e.g. pressurised steam autoclaves at 105-130)
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all vegetative forms killed
spores destroyed/injured and unable to germinate 'botulinum-treated' (121 degrees, 20mins) stored for years with no refrigeration |
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Vacuum-packed foods
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3 month shelf life
needs to have low bacterial level initially; hygienic handling, pH <5.8*, and stored below 2 degrees to prevent Clostridium botulinum growth * green sulphomyoglobin present if pH not low enough |
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Modified Atmosphere Packaging; selected cases in impermeable plastic pack
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Red Meat: 60-80% oxygen (oxymyoglobin - red) with 20-40% carbon dioxide, to have bacteriostatic/fungiostatic effect
Cured Meat/Poultry: 75-80% nitrogen plus carbon dioxide |
