Topic 3

Question 1

Animal carcasses

Answer 1

The carcass is those portions remaining after removal of blood, head, hide, feet, digestive tract, intestines, bladder, and all other organs.
The main components of the carcass are – muscular tissue and fatty tissue, tendons, other connective tissue.
Carcasses: Pigs – 75% of live weight, cattle – 55% of live weight, sheep 50% live weight.
Muscular tissue: pigs 36.6% of weight, cattle 49 to 68% of weight, sheep 46 to 65% of weight.

Question 2

Conversion of muscle to meat – slaughtering

Answer 2

First step in the process. Mechanical chain system.
Preslaughter handling of livestock - stressed animals bleed poorly, dark appearance, exhausts animals reserve of glycogen: pH remains high and meat will have a tough texture
Stunning - cattle using a captive pistol, sheep lambs and pigs are stunned electrically.
Sticking- main blood vessels severed
Skinning/ de-hairing – Hair loosened by hot water
Evisceration – viscera the animal are removed, large internal organs of liver heart kidneys and the GIT.
Inspection
Washing and grading, electrical stimulation, cutting and boning.
Refridgeration

Question 3

Rigor mortis

Answer 3

Characterised by – a loss of elasticity and flexibility of the muscle which causes the muscles become stiff.

Question 4

Events that occur after slaughtering of animals that initiate onset of rigor mortis

Answer 4

1. Depletion of oxygen supply to the muscle: glycolysis switches to anaerobic pathways with the resultant accumulation of lactic acid in the muscle, lactic acid lowers the pH of the muscle from original value of 7.0 to approximately 5.5.
2. Bio synthesis of glycogen is halted, degradation of ATP continues. As ATP supply is exhausted the actin and myosin filaments lock together.

Question 5

Factors determining the ultimate pH of meat

Answer 5

Breed –
Types of cats –
Preslaughter and conditions of the animal – less glycogen reserve means less lactic acid produced, high ultimate pH.
Temperatures at which the carcass is held – The higher the storage temperature, the faster the pH decreases.

Question 6

Resolution of rigor

Answer 6

Proteolysis – Hydrolytic degradation of protein produces peptides and amino acids, many of which are flavour agents.
Degradation of ATP – ATP is converted to ADP and then AMP, AMP is the animated IMP. IMP is a strong flavour enhancer.
Increasing the pH of the meat
Increase in the amount of free fluids with in the muscles
Decreases in finding strength between actin and myosin
Degradation of lipids

Question 7

Post-mortem quality problems of meat

Answer 7

Dark, firm, dry meat – caused by a high ultimate pH.
Pale, soft, exudative – characterised by soft, mushy texture, a poor water water holding capacity, and a pale colour. Caused by unusually fast rate of pH decline, and unusually low ultimate pH.
Fiery fat and splotched lean cuts – short-term violence excitement in cattle causes blood to fill the capillaries in fat and muscle.
Cold shortening – carcass is chilled too rapidly or if the temperature of the carcass is reduced to low 10 to 15°C while is still in pre-rigor condition. Five fold increase in toughness.
Thaw-rigor – Carcass is frozen pre-rigor. Upon thawing, muscle contracts due to high levels of ATP and calcium.
Heat ring – Quality defect in beef carcasses that have a thin layer of external fat.

Question 8

Electrical stimulation

Answer 8

Improves – tenderness of meat, meat texture and firmness, colour of lean cuts, overall quality of the carcass, reduces incidence of cold shortening and heat ring problems, facilitates more thorough bleeding of the carcass, makes hide pulling process easier.
Biochemically – acceleration of post-mortem anaerobic glycolysis, Swift drop in the pH below 6.0, accelerates onset of rigor mortis, allows carcass to be chilled immediately.

Question 9

Conditions that make meat highly favourable for microbial growth

Answer 9

Hi moisture content (60 to 70%) and water activity.
Rich in nitrogenous nutrients
Adequate supply of fermentable carbohydrates e.g. glucose and glycogen
Adequate supply of minerals vitamins and other microbial growth factors
Favourable pH, > 5.5

Question 10

Spoilage organisms in meat

Answer 10

Pseudomonas spp. – Causes putrefactive spoilage, strictly a aerobic, inhibited by 20% carbon dioxide. Putrefaction odours, slime formation.
Enterobacteriaceae – Facultative anaerobic, resistant to carbon dioxide, growth reduced or halted at refrigeration temperatures.
Lactic acid bacteria – spoilage by souring, resistant carbon dioxide.
Aeromonas spp & Alteromona hydrophila – Produce hydrogen sulphide, major cause of greening of meats with high pH.
Brochothrix therospacta – Dairy like odours, reduced by high levels of carbon dioxide greater than 40%.

Question 11

Pathogenic organisms in meat.

Answer 11

Clostridium botulinum – causes a food borne intoxication called botulism, neutroparalytic disease. Unable to grow PH value less than 4.6 or water activity lower than 0.93.
Salmonella – microorganisms must be alive to cause the disease, primary reserve is the intestinal track of vertebrates, cannot grow at temperatures less than 5°C, pH less than 4.0, or water activity less than water 0.93. Not heat resistant.
Staphylococcus aureus – Intoxication, large number needed, entrotoxin very heat resistant, tolerant to dry conditions, water activity as low as 0.83. Temperature range 6 to 46°C, ph 4.2 to 9.3.

Question 12

What is oxidative rancidity in meats

Answer 12

Quality deterioration that gives an unpleasant odour. In meat is the result of autoxidation of lipids in meat. Unsaturated fatty acid’s of lipids are gradually oxidised in the presence of oxygen into hydroperoxides, then to aldehydes, ketones, acids. Meat with higher concentrations of unsaturated fatty acid is more susceptible to autoxidation.
Rate of the reaction is positively related to the concentration of oxygen.
Pro oxidative compounds – heme containing compounds.
Common antioxidants including citric acid, ascorbic acid, and BHA.

Question 13

Factors influencing oxidative rancidity

Answer 13

Fat content of the meat
Degree of unsaturation of fatty acid’s
Concentration of oxygen in the environment
Presence and concentration of pro and antioxidants
Temperature of storage
Pre-storage holding temperature and time

Question 14

The freezing curves of meat

Answer 14

Solutes such as sodium, potassium, calcium, phosphate, amino acids lower the freezing point of water. Meat does not freeze at 0°C, but -2°C.
Rapid decline in temperature, continues beyond freezing point due to lack of ice nuclei (supercooling). Point A, ice nuclei start to form, water starts to freeze. Latent heat of water is released, raises temperature. B – C, water is transformed into ice, ice reduces amount of water in meat, increases the concentration of solutes, decreases the freezing point. Past C – freezing point becomes steeper.

Question 15

Quick freezing versus slow freezing

Answer 15

Rate the freezing influences – size and distribution of ice crystals, loss of meat juice juice through dripping (drip loss).
Effects of quick freezing – ice crystals are smaller and more uniformly distributed, translocation of water is insignificant, drip loss of meat juices upon thawing is low.
Slow freezing – ice crystals in the extra cellular spaces, imbalance in solute concentration, water translocation.

Question 16

Changes in meat quality during frozen storage

Answer 16

Oxidative rancidity of leopards – no safe temperature, acceptable temperature -18°C retard the reaction.
Freezer Burn – sublimation of ice on meat surface during frozen storage. Opaque, desiccated area. Factors include air velocity in the freezer, rate of freezing, storage temperature, condition of meat before freezing.

Question 17

Meat curing ingredients

Answer 17

Salt – antimicrobial agents, flavouring agent, concentrations of 2 to 4%.
Sugar – flavour, reacts with amino groups of protein.
Nitrite – antimicrobial agents, stabilises colour, flavour, retards oxidative rancidity.
Alkaline phosphates – increase water binding capacity, prevent shrinkage, retard development of oxidative rancidity, chelate ions of heavy metals.
Sodium ascorbate and erythrobate – Accelerate development of colour, stabilise colour, reduces curing time. Antioxidant, retards oxidative rancidity, protects from colour fading.

Question 18

Pigments and colour of fresh meat

Answer 18

Two heme pigments –
myoglobin – Predominant pigment in the muscle, serves as storage for oxygen.10% in living animals, 95% of iron after bleeding. Composed of a globin protein and heme moiety.
haemoglobin – Red pigment in animal blood, responsible for transporting oxygen.

Question 19

Methods of meat curing

Answer 19

Dry salt cure – meats are rubbed with and packed in salt.
Conventional dry curing – use of salt, nitrate, sugar. Used for specially products.
Main advantages – regarded as high-quality, wide very variation in curing temperatures, less prone to microbial spoilage.
Main disadvantage – labour intensive, slow, large space needed.
Pickle cure – salt in the water, concentration of salt is called brine strength, usually 60 to 70°. Narrow temperature range of 1 to 4°C.
Pump curing – pickle is pumped into cuts by means of needles. Includes artery pumping, single needle pumping, multiple needle pumping.

Question 20

Smoking of meat

Answer 20

To develop flavour, compounds of smoke a major contributor.
Smoking preserves meat by –Reducing number of surface bacteria.
Inhibiting microbial growth. Decreasing moisture content and water activity.
Aid in colour development.
Retard lipid oxidation, increases shelf life.

Question 21

Composition of smoke

Answer 21

Two phases – solid phase: floating ash and tar. Volatile phase: Non-condensable air, combustion gases, condensable volatile compounds. Includes –
Phenols – 20, prevent oxidative rancidity, contribute to microbial, inhibit microbial growth.
Organic acids – lower pH of meat surface, coagulation of surface proteins, essential in development of outside covering.
Carbonyls – More than 20, distributed in vapour phase, contribute to flavour and aroma.
Alcohols – carrier for other volatile compounds in smoke.
Hydrocarbons – carcinogens.
Combustion gases contribution unclear.

Question 22

Types of smokehouses

Answer 22

Natural air circulation
Forced air – Uniform air movement, distribution, better temperature control.
Continuous

Question 23

Liquid smoke

Answer 23

A solution of the condensable fraction of natural wood smoke. Manufactured by pyrolysis of hardwood sawdust. Dissolved in water in absorption tower.
Liquid smoke can be applied by – dipping or drenching, spraying, atomising, vaporising, including directly in formula.
Advantages – more reproducible, easier to control, products more uniform, faster, capital investment is less, carcinogen is removed, less gaseous pollution.

Question 24

Classification of sausages

Answer 24

Fresh – from fresh but I’m Q would meet. Must be cooked.
Uncooked smoked - sausages fresh but smoked, must be cooked.
Cooked sausages – fully cooked, cured and smoked during processing, refrigerated.
Dry and semidry sausages – fermented meat products, addition of lactic acid starter culture.
Specialty meats – lunch meats.

Question 25

Sausage Manufacturing processes

Answer 25

Particle size reduction – grinding, chopping, flaking
Mixing or blending
Emulsifying
Stuffing
Linking and tying
Smoking and cooking
Chilling
Peeling
Packaging

Question 26

Sausage emulsion

Answer 26

Two phases – dispersed phase of fat droplets, continuous phase of water, dissolved proteins, other dissolved ingredients.
Factors leading to unstable emotions –
Over chopping – Surface area of fat globules too large to be covered with protein, some fat particles will be exposed to aqueous phase.
Heat breakdown – Product heated too fast or at too high a temperature. Protein coat denatures.
Short Meat – Ratio of collagen to Meyerson too high. Collagen vines water, fat globules covered, collagen shrinks during heating, converts to gelatin, drains from fat surface, that particles on coated. Equals fat at top, pocket of gelatin at bottom.

Question 27

Sausage casings

Answer 27

Function – determine size and shape of sausages, processing mould, containers for handling and shipping, display units.
Types:
Animal casings – from GIT of sheep, cattle, pigs. Usually edible, expensive, less uniform, easy to break.
Regenerated collagen casings – from the corium layer of beef hides. Extruded, more uniform in size and strength, less costly.
Cloth casings – made from cotton bags. Not common, certain types of fresh sausages, smoked, specialty products, good strings.
Cellulose casings – Manufactured from material from cotton seeds. Extruded, widely used, strong, uniform, clean, cheap.