Meat Processing

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chemical engineering in meat processing

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    MEAT PROCESSING

    INTRODUCTION

    Meat processing technologies were developed particularly in Europe and Asia. Burger patties, frankfurter-type sausages and cooked ham originated in Europe. Traditional Asian products are fermented type. All processed meat products have been in one way or another physically and/or chemically

    treated.

    Raw materials for meat processing are mainly derived from: Cattle Pigs Poultry

    Buffaloes Sheep Goats

    Gameanimals

    COMPOSITION OF MEAT

    The value of animal foods is essentially associated with their content of proteins. Protein is made up of about 20 aminoacids. Approximately 65% of the proteins in the animal body are skeleton muscle protein, about 30%

    connective tissue proteins (collagen, elastin) and the remaining 5% blood proteins and keratin

    (hairs, nails).

    MEAT CHARACTERISTICS

    Changes in pH:

    Immediately post-mortem the muscle contains a small amount of muscle specific carbohydrate,called glycogen

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    (about 1%), most of which is broken down to lactic acid in the muscle meat inthe first hours (up to 12 hours) after slaughtering.

    The build up of lactic acid in the muscle produces an increase in its acidity, as measured by the pH.

    The pH of normal muscle at slaughter is about 7.0 but this will decrease in meat. In a normal animal, the ultimate pH (expressed as pH24= 24 hours after slaughter) falls to around

    pH 5.8-5.4.

    The typical taste and flavour of meat is only achieved after sufficient drop in pH down to 5.8 to5.4.

    From theprocessingpoint of view, meat with pH 5.6-6.0 is better for products where good waterbinding is required (e.g. frankfurters, cooked ham), as meat with higher pH has a higher water

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    binding capacity. In products which lose water during fabrication and ripening (e.g. raw ham, dry

    fermented sausages), meat with a lower pH (5.65.2) is preferred as it has a lower water binding

    capacity.

    The pH is also important for the storage lifeof meat. The lower the pH, the less favourable conditions for the growth of harmful bacteria. Meat of animals, which had depleted their glycogen reserves before slaughtering (after stressful

    transport/handling in holding pens) will not have a sufficient fall in pH and will be highly prone tobacterial deterioration.

    PSE MEAT

    In stress susceptible animals pH may fall very quickly to pH 5.8 5.6 while the carcass is stillwarm.

    This condition is found most often in pork. It can be recognized in the meat as a pale colour, a soft, almost mushy texture and a very wet

    surface (pale, soft, exudative = PSE meat).

    PSE meat has lower binding properties and loses weight (water) rapidly during cooking resultingin a decrease in processing yields.

    DFD MEAT A reverse phenomenon may arise in animals which have not been fed for a period before

    slaughter, or which have been excessively fatigued during transportation and lairage.

    In these cases, most of the muscle glycogen has been used up at point of slaughter andpronounced acidity in the meat cannot occur.

    The muscle pH24 does not fall below pH 6.0. This produces dark, firm, dry (DFD) meat. The high pH cause the muscle proteins to retain most of their bound water, the muscle remain

    swollen and they absorb most of the light striking the meat surface, giving a dark appearance.

    DFD vs. PSE

    MEAT COLORING

    The red pigment that provides the characteristic colour of meat is called myoglobin. The maturity of the animal also influences pigment intensity, with older animals having darker

    pigmentation.

    The different myoglobin levels determine the curing capability of meat. As the red curing colour of meat results from a chemical reaction of myoglobin with the curing

    substance nitrite, the curing colour will be more intense where more muscle myoglobin is

    available.

    In buying meat, most consumers prefer bright red beef, however, aged beef with a darkerappearance is more likely superior in eating quality.

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    WATER HOLDING CAPACITY

    One of the most important factors of meat quality both from the consumer and processor pointof view.

    As the muscle tissue develops acidity (decrease of pH) the water holding capacity decreases. To obtain good yields during further processing including cooking, the water holding capacity

    needs to be at a high level.

    TENDERNESS

    Meat tenderness plays an important role, where entire pieces of meat are cooked, fried orbarbecued.

    Some types of meat, in particular beef, have to undergo a certain ripening or ageing periodbefore cooking and consumption in order to achieve the necessary tenderness.

    In the fabrication of many processed meat products the toughness or tenderness of the meatused is of minor importance.

    AGING

    To age meat means to keep it for a time under controlled temperature. This allows the naturally occuring enzymes within it to slowly break down and soften the muscle

    fibers, making the meat more tender and developing flavor.

    Fluctuations in temperature or humidity during meat aging can have detrimental effects on meatquality and result in a reduced storage life.

    Carcass Aging

    In this process, the carcass is stored or hung in the chiller, ideally at - 1.50C to + 20C and at 88%humidity.

    A carcass stored for 10 days may lose from 1% to 4% in weight. Lower temperatures and higher humidity can lessen weight loss.

    Vacuum Packed Aging

    Large cuts, usually primals, are packaged in moisture-proof, airtight material and stored chilled. This vacuum pack protects the meat from oxidation and evaporation during storage. The oxygen-free environment inhibits aerobic bacterial growth and provides better yields by

    preventing weight loss from evaporation.

    FLAVOUR

    The typical desirable taste and odor of meat is ,to a great extent, the result of the formation oflactic acid (resulting from glycogen breakdown in the muscle tissue) and organic compounds like

    aminoacids and di- and tripeptides broken down from the meat proteins.

    The meaty taste can be further enhanced by adding monosodium glutamate (MSG) (0.050.1%),which can reinforce the meat taste of certain products.

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    MEAT PROCESS TECHNOLOGY

    SOPs (Processes usually used)

    Raw materials preparation Cutting/chopping/comminuting (size

    reduction)

    Mixing/tumbling Salting/curing Utilization of spices/non-meat additives

    Stuffing/filling into casings or othercontainers

    Fermentation and drying Heat treatment Smoking

    Raw Materials PreparationMeat Preparation

    In order to produce the desired product, one must select the right kind of meat whether itspork, beef, lamb, veal or poultry.

    Meat cuts are also important because every cut can be processed to produce different products. In buying meat products, always check for quality seals.

    Meat Grades

    BEEF

    Grade Beef 1 (B1) Lean beef without visible fat and connective tissue

    Grade Buffalo 1 Lean buffalo meat without visible fat and connective tissue

    Grade Beef 2 (B2) Beef with less than 10% (visible) connective tissue and less than 10% fat

    Grade Beef 3 (B3) Beef trimmings with up to 20%(visible) connective tissue and 20%fat

    Difference between Beef and Buffalo Meat

    Colour: Buffalo meat has slightly darker red colour than beef, also processed meat productscontaining buffalo meat have a darker and more intensive red curing colour.

    Taste: Buffalo meat has a more pronounced meat flavour and taste. Texture: Buffalo meat cuts, upon ripening and aging, can be made sufficiently tender but remain

    with slightly stronger texture as compared to similar beef cuts.

    Fat content: Buffalo meat is usually leaner than beef and the colour of buffalo fat is white ascompared to the yellowish fat colour in beef.

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    Meat Cuts

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    Poultry Meat Cuts

    POULTRY GRADING

    Non-meat Ingredients

    SALT

    1.5 3.0% Salt is the main agent used in meat processing and it contributes to basic tastecharacteristics of the final product.

    In processed meat products it usually ranges from 1.5 to 2.2%. Apart from improving the taste, salt in combination with water assists in opening up the

    structure of proteins (solubilises myofibrillar proteins). These proteins gel upon heating and by

    entrapping moisture and fats give form, structure and firmness to the finished product.

    Salt used at the above levels also improves the water holding capacity of meat.WATER

    Water is the main component of meat (up to 80% in lean meat). Besides its natural presence, water is used in many processed meat products also as an

    ingredient. However, the assumption by some consumers that water is added to meat products only to

    increase product weight and manufacturers profits is incorrect.

    In fact, there are many types of meat products where the addition of water is needed fortechnical reasonsor to compensate for cooking losses.

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    The addition of water is essential during themanufacture of raw-cooked meat batters (meat

    loaves, frankfurter sausages etc).

    In this case water acts together with salt andphosphates to solubilize muscle proteins, thus

    creating a strong protein network structure holding