It’s structure and nutritional value Meat It’s structure and nutritional value

What is meat? Simply defined it’s the flesh of animals used as food. To be more precise it refers to the muscle, connective tissue and fat. Offal may also be referred to as meat. The flesh after an animal dies is not considered as meat as it has to undertake biochemical changes so that the meat is the correct colour, texture and cookability.

Muscle structure The muscle tissue contains protein, water, vitamins and minerals. It is the protein in the meat which coagulates during cooking to set. The muscle tissue of meat and poultry is made up of thin muscle fibres. These fibres are held together in bundles by connective tissues. There are two types of connective tissue: Collagen, this holds the bundles of muscle fibres together. Elastin, binds the muscle together or to a bone. The muscle of animals which converts to meat is striated or voluntary muscle. It consists of long cylindrical cells. The muscle fibres are held together in bundles by connective tissues, the smaller the bundles the more tender the meat. Each individual muscle fibre is surrounded by a sheath the sarcolemma. The fibre is divided into myofibrils which are surrounded by fluid. The myofibrils are made of two different proteins myosin (which are thicker) and actin which are thinner. These two proteins are responsible for the contraction of muscle and for rigor mortis. https://www.youtube.com/watch?v=_9WL8x-pLMg Rigor mortis is the contraction after death

Conversion of muscle to form meat If meat is cooked while still in its rigor mortis state it will be tougher and of darker colour. It is however tender. Before an animal is slaughtered it may become stressed, loose weight or become infected with disease. This can cause moisture loss in the muscle which can cause stringy/ tough meat. This also reduces glycogen in the muscle. Copy the paragraph on page 113 starting with “ATP is replenished after contraction….

What is rigor mortis? If meat is cooked while still in its rigor mortis state it will be tougher and of darker colour. It is however tender.

Where in the spec? Content What students need to learn Subject content Resources 1. Meat and fish Storage and handling of meat To be able to describe/ explain the correct storage and handling conditions for meat after slaughter STF pages 114-115 Meat and preservation – canning Focussing on the quality and safety issue of heat penetration during the canning process and the resulting effect on the quality of meat STF pages 116-118 Meat preservation – freezing The effect of the rate of freezing on the meat quality. Different methods of freezing meat Freezing STF pages 205 - 207

Storage and handling of meat Game animals need a much longer period of conditioning due to their tougher meat structure. They are “hung” at room temperature Meat must be stored at a chilled temperature to slow the enzyme changes and minimise microbial growth. 50C or less is the best Storage and handling of meat Adding 10% carbon dioxide to a chill store will extend storage life but can cause darkening of meat. Miccroorganisms rapidly contaminate the previously sterile muscles of animals after slaughter. This is the main cause of putrefraction

Meat preservation - Canning When meat is sealed in a can and heat processed in order to sterilise the product the manufacturer is faced with the problem that heat penetration is slow and the process takes too long. This can affect the quality of the meat and its eating quality. If they reduced the production time it would improve the organoleptic quality but could present possible risks of………?

Meat preservation - freezing LO – The effect of the rate of freezing on the meat quality . What are the different methods of freezing meat? AS RECAP If foods to be frozen are placed in a cold store a very poor quality product is produced. However the quality of most frozen foods by controlling the process be equal to that of the fresh food material. Freezing preserves by two principles 1. the low temperatures inhibit microbial growth often causing the death of some organisms and retards the action of enzymes or chemicals. 2. The production of ice during freezing causes water to be withdrawn from the food. This dehydration effect also prevents microbial growth. The thermal arrest period is the time it takes the food to pass through the part of the cycle where water is frozen into ice. To produce high quality foods you need this period to be as short as possible. It will depend on the size of the product. Something like a side of beef could take up to 36 hours to pass through this period. Freezing meat Meat does not have such an obvious structure compared to plants but have different types of tissue. Water can be withdrawn and on thawing can produce a pool of water around the product known as drip

Freezing methods Immersion freezing – one of the first methods. It is slow with little control. Brine are prepared from salt and ice. Food is immersed into this. Modern methods use refrigerants which are sprayed onto the food. It is not a very popular method. Plate freezing – has only been replaced in the last few years for some products. Food is prepared in the normal way and packed into a flat container. Usually a cardboard based container often with a polythene or wax lining. The box is placed between flat hollow refrigerated metal plates. They are adjusted to press tightly against the pack. This is a contact method, any air gaps will slow the heat transfer from the product which makes the process slower. They may be horizontal or vertical. The main disadvantage is that they cannot easily freeze irregular shaped materials. Blast freezing – a large cabinet in which a fan is introduced to move the air over the product. Stationary air acts as in insulator but moving air readily takes up heat and looses it again quickly. Ideally the air should be -25C or lower. It is a batch system. Main disadvantages include only being able to small batches at a time. Cryogenic freezer – very cold liquefied gases such as nitrogen and carbon dioxide. Freezing is so rapid that some products can suffer thermal shock which is the sudden contraction caused by the rapid lowering of temperature. The gas is sprayed onto the food whilst it is on a conveyor belt in a tunnel .The gas is removed by fans. This is not so good for larger items as too much nitrogen would be used. CO2 is more effective than the nitrogen because the gas can be recovered and reused. It produces rapid freezing rates as it produces a snow once released and is on contact with the food. It also helps to preserve food product.

Exam questions – you have 10 minutes Give the ideal commercial storage conditions for storing fresh meat after slaughter. (2 marks) Name 3 nutrients meat contributes to the diet ( 3 marks) Explain what’s happens to meat during ageing or conditioning. (5 marks)