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Quality of meat
Most important aspect of the sensory quality of meat is the colour. A pink, bright red or deep red colour is wanted.
Responsible for the colour of meat are:
- the quantity of colour pigments in the meat:
- myoglobin is most responsible for the color
- hemoglobin is less responsible
- oxidative reactions to the colour pigments:
- iron ions from the colour pigments can oxidate
- 30-50% oxidation gives a red colour (myoglobin -> oxymyoglobin)
- more then 50% oxidation gives a brown colour (oxymyoglobin -> metmyoglobin)
- reactions of the pigments with gases:
- mixtures of gases can influence the reactions in a positive, but also negative, way
- packages who provide oxygen to diffuse trough the package give the myoglobin constantly enough oxygen, the colour will stay red
- structural property of the muscle proteins:
- at a pH lower than 5 little metmyoglobin is formed
- the solubility of oxygen decreases at higher temperatures, result is less oxymyoglobin
A second very imports aspect is the texture of the meat. The texture of the meat is defined by the slaughtering process and the further preparation of the meat. If the animal are stressful just before slaughtering, the pH is decreasing to fast after slaughtering. This results in PSE-meat (Pale, Soft and Exudative). PSE-meat occur less often lately, because of good selection there are less stressful animals (especially pigs).
By means of longtime hunger or weariness, there can not be produced enough lactic acid and the
pH does not decrease enough after slaughtering. This results in DFD-meat (Dark, Firm and Dry). DFD-meat can still be used for the production of cooked sausages.
Further preparation of the meat has influence on the binding tissues and the preparation should be different for every cut, due to another compilation of the meat.
Other aspects of the sensory quality of meat is the form of the cut, the content of visible fat and the present meat flavours.
Meat is the most important source of protein, one third of the daily needed protein is provided by meat. The ratio of amino acids in meat represents the ratio of amino acids in a human body.
Meat does not contain much carbohydrates. Only 0,2 – 1% is carbohydrate in the form of glycogen. Nevertheless is this small amount responsible for the brown colour and specific flavours in smell- and taste during cooking.
The fat content of meat is specific to the type of meat. The compilation of animal fat is less proper than vegetable fat. Animal fat has a high amount of cholesterol, which is being related to cardiac and vein diseases.
Most important minerals that meat contains are iron, zinc, chromium and selenium. The iron in meat is easily being taken in into the human body, because it occurs as a complex in hemoglobin.
The biggest source of vitamin B12 is meat, vitamin B12 is needed for the fabrication of red blood cells.
The hygienic aspects of meat can be divided into two groups, microorganisms and residues. Contamination due to microorganisms can exist of spoilage microorganism or pathogens. The spoilage microorganisms (on meat mostly Pseudomonas, Acinetobacter and Alcaligenes) affect the colour, smell and taste of the product. The pathogens which can occur on meat are Salmonella, Campylobacter, Yersinia, Shigella en Enteropathogene E.coli.
Residues who contaminate the meat consist of:
- animal treatment, like antibiotics, hormones, thyreostatica en tranquillizers
- environmental contaminants, like pesticides, herbicides, fungicides en heavy metals
- processing instruments, like disinfectants en packaging
The technological processing ability of the meat depends on the cut which is being used and the product wanted. Of influence are the water binding properties, the quality and quantity of protein, the quality and quantity of fat, the quantity of binding tissues and strings, toughness, structure and pH-value.