Lecture notes
Summary Quality of Animal Products
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This document contains class notes from all lectures of the course Quality of Animal Products, and a summary of recommended key articles for each topic.
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QUALITY OF ANIMAL PRODUCTSMEAT QUALITY
Meat consumption
World meat production total 335.2 million tonnes, of which 130.5 million are poultry meat (increased in
last years), followed by pork meat (decreased in last years), bovine meat and ovine meat. From 1961 to
2018, the largest increase in production occurred in Asia, and especially poultry meat.
Global meat consumption (kg carcass/capita/year) 43.4 in 2019, especially in developed countries. Meat
consumption also increased in the last decades, especially in Asia and Southern Europe.
- Largest sheep consumer Australia
- Largest poultry consumer Israel
- Largest pork consumer Korea
- Largest beef/veal consumer Argentina
Meat consumption (kg/capita) in NL mainly pork, then poultry and beef. In total, around 76 kg
carcass/person.
NB: there is a difference between the carcass weight consumed, the weight purchased by people and
restaurants, and the weight that is actually consumed, because some weight is lost as fluids, bones,
leftovers (avanzi) and parts that are used for pet food and not human consumption. Therefore, the actual
consumption in the NL is 36.8 kg/capita (about 48% of the carcass weight (76 kg/capita)).
Distribution channels in the NL in 2012, 59% of meat is sold by supermarkets, 35% by
catering/restaurants and only 4% by butchers.
Factors that determine meat consumption:
- Religion. Jews and Muslims cannot eat pig and also have rules on how to slaughter animals and
process meat. Hindus are largely vegetarian and do not eat cow meat anyway. Consumption of
poultry is not prohibited by any of the major religions.
- Vegetarianism/veganism/flexitarianism. Flexitarians are mainly vegetarian but occasionally eat
meat or fish.
- Income. In general, if people have more money they will eat more meat. This is why developing
countries tend to not eat much meat, but eat more fish (protein of the poor).
Meat quality
Meat quality is defined by the compositional quality (lean to fat ratio), nutritional quality and palatability
factors such as appearance, smell, firmness, tenderness, flavours.
Another definition:
- Quality characteristics scientifically measurable or objective quality aspects
- Quality attributes quality aspects that are perceived as important by consumers, so it is a
subjective type of quality.
Quality aspects related to meat:
- Carcass quality (slaughter quality) determined by:
o Quality of the carcass: weight and length, conformation, %meat, %fat, %bone.
o Carcass grading/classification: based on the %meat you give a score to the carcass
(SEUROP system). The S class has >60% of carcass meat, while the P class has <40%.
, o Methods to estimate %meat: in pig carcasses, via backfat and muscle depth (CGM); in live
pigs mainly via ultrasonic backfat measurement.
CGM measures between the 3rd and 4th rib from the posterior, and 6 cm from the
dorsal midline, in the left carcass side.
Cattle classified with visual carcass grading (SEUROP) and based on weight.
Veal calves grading is similar to cattle and also based on meat color (from 1-
white to 13-dark pink)
Sheep/goat live weight or carcass weight + visual grading
Broilers payment per kg of live weight for batches of animals
o NB: farmers usually get paid based on carcass weight and quality.
o Myostatin gene is responsible for the double muscling in cattle (e.g. Belgian Blue).
- Technological quality of meat refers to the quality of muscle tissue in terms of size/shape of
muscles, pH, glycogen content, water-holding capacity (related to cooking loss (acquetta)),
connective tissue and fat content (fat covering and inter-/intra-muscular fat), and firmness.
o Muscle anatomy skeletal muscles are made of multiple muscle fibres. Each muscle fibre
is made of sarcomeres with filaments made of myosin filaments and actin filaments. These
filaments move past each other to generate contractions.
o Chemical composition of adult mammalian muscle 75% water, 19% protein, 2.5% fat
and 1.2% carbohydrates.
o pH in pigs post mortem after death, the pH in muscles tends to decline because
carbohydrates in muscles are broken down anaerobically (because there is no more O2
available) and this generates lactic acid.
Pale-Soft-Exudative PSE undesirable meat in which pH declines too fast. This
meat loses a lot of water. It occurs because there was an acute stress right before
slaughter it increases stress hormones, body temperature goes up and also
metabolism goes up.
Dark-Firm-Dry DFD also undesirable in
which pH does not decline much. This
meat does not lose much water. It occurs
because of a chronic stress earlier before
slaughter e.g. during transport; this causes
glycogen (glucose store) to be metabolised
so animals are tired before slaughter, so it
cannot be broken down later and pH does not decrease much.
RN effect researchers found low yields of cured cooked hams, caused by higher
level of glycogen in muscles. This effect is heritable and mainly occurs in the
Hampshire pig breed. The RN- is the dominant allele responsible for low yields,
while the recessive rn+ is responsible for normal yields.
An intermediate type of mead is the best.
- Sensory quality of meat includes shape and fat covering, color, amount of drip/cooking loss
(acquetta), marbling (amount of intra-muscular fat, very desirable), taste/smell, juiciness,
tenderness, texture, pH at 45min and 24h post mortem.
, o Role of sarcomeres after death, sarcomeres shorten and become less flexible because of
rigor mortis; the cooling process of carcasses affects rigor. Extra shortening (more rigor)
occurs because:
Cold shortening freshly slaughtered meat is exposed to rapid cooling.
Thaw rigor if pre-rigor muscles are frozen and thawed after
(thaw=disgelo). Thaw rigor can be removed by freezing meat after it has
gone into full rigor.
Heat shortening if the carcass is kept at too high temperature before
rigor
Extra rigor results in more water drip.
Rigor mortis results in tender or tough meat depending on the conditions of
cooling.
Sarcomere shortening/rigor can be prevented via mechanical stretching of
carcasses or electrical stimulation. Electrical stimulation causes fast contractions
and relaxation of muscles, so it stimulates use of ATP and glycogen.
After maturation, meat becomes usually tender again.
o Intramuscular fat (IMF) the Japanese cattle breed Wagyu is famous for its high IMF
content, and it is highly desirable because it seems to contain more linoleic acids so it might
have a good effect on health.
- Nutritional and healthiness characteristics consumption of red meat and especially processed
meat is associated with a higher risk of stroke, diabetes and lung cancer.
o Nutritional characteristics include energy and protein content, vitamin, digestibility and
biological value of proteins.
o Healthiness depends on the amount of fat, fatty acid composition (saturated or
unsaturated), cholesterol, possible allergens.
- Hygienic characteristics and safety
o Hygiene is mostly related to particles or dirt in the meat that may contain harmful
microbes. Contamination can occur in the slaughter houses, during transport, in fridge,
kitchen. Contaminated meat might be unsafe (Salmonella, Campylobacter) but it often
influences mostly shelf life or appearance.
o Safety of meat from healthy animals is related to the presence of unnatural components,
e.g. residues from feed (additives) or medicines/hormones, or particles like needles, knife
tips or packing material.
- Production (emotional) quality of meat it refers to the environmental impact of producing
meat, welfare of animals, intensity of production, safety for consumer, prices. It is also related to
cultural differences, as in some countries people eat animals that are not considered meat animals
in other countries, e.g. dog, whale, guinea pig.
- Quality of fat the main fat deposits in animals are subcutaneous fat, internal fat, intramuscular
and intermuscular. Fat is important for processing, shelf life and tase. In particular, quality of fat
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