Meat, frozen
| Infobox on Meat, frozen | |
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| Example of Meat, frozen |  |
| Facts | |
| Origin | This table shows only a selection of the most important countries of origin and should not be thought of as exhaustive:
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| Stowage factor (in m3/t) |
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| Angle of repose | - |
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| Oil content |
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| Ventilation | Recommended ventilation conditions: circulating air, 6 circulations/hour without supply of fresh air in order to ensure uniform cooling of all parts of the cargo. |
| Risk factors | Frozen meat (especially pork) is prune to temperature variations and highly odor-sensitive and very rapidly absorbs foreign odors. |
Meat, frozen
Contents
Description
Deep frozen meat includes beef, veal, pork, lamb, venison and game.
Meat is marketed and transported in several forms:
- Frozen carcasses and primal cuts (sides, legs etc.)
- Frozen retail cuts
- Frozen mince including hamburgers
Frozen meat should have a core temperature of -18°C so that the activity of micro-organisms comes to a standstill and enzymatic degradation processes are largely suppressed. Temperature measurements must be performed and recorded at regular intervals.
The travel temperature must be maintained constantly as variations in temperature may result in re-crystallisation, resulting in growth of the ice crystals. Variations in temperature are associated with continual slight thawing and refreezing. Since small ice crystals have a higher vapour pressure than larger ones, they will melt more rapidly when the temperature rises, while on cooling the same effect means that the water is preferentially deposited as ice on the larger ice crystals. This consequently brings about growth of the ice crystals, as a result of which the rapidly frozen meat increasingly takes on the appearance of slowly frozen meat on storage. The large ice crystals rupture the cell walls, as a result of which, on thawing, cell fluids (drip) escape, giving rise to a distinct reduction in utility value.
It is essential to maintain the deep-freeze chain. Thawing damage occurs in the event of extended interruption of freezing, followed by warming and refreezing of the product. "Snow" forms within the plastic bags, especially around leaky container doors.
Freezing is used to minimise any physical, biochemical and microbiological changes affecting quality in storage. During freezing most of the water content of the meat, about 80%, solidifies into pure ice-crystals, accompanied by a separation of dissolved solids.
A product can be considered frozen when its centre has a temperature of -12°C or less.
To reach this temperature the product passes through the temperature range of maximum crystallisation (from -1°C to -5°C). The speed of freezing is a very important factor as frozen meat quality depends mainly on the size of the ice crystals formed: the lower the speed of freezing the larger the size of the crystals.
Slow freezing facilitates the separation of solution and the migration of water out of the muscle cells which is subsequently frozen, forming rather large crystals. Quick freezing conversely produces many small ice crystals, mainly formed within the muscle cells, and reduces water migration and separation of solution. It is obvious that the latter technology will preserve the meat closer to its original quality and, particularly during thawing, moisture loss will generally be lower.
Temperatures lower than specified are not generally harmful, but they should be maintained throughout all the transport operations as there is otherwise a risk of re-crystallization.
Meat itself is not a living organism but it is subject to endogenic enzymatic activity, or proteolysis, which causes muscle tissue to mature, become tender and develop a typical taste. This process is retarded by low temperatures. Due to its chemical composition which is rich in proteins, lipids and water, meat is a particularly favourable substrate for the growth of micro-organisms. The lipidic content also makes it very sensitive to oxidation. Following animal slaughter the evisceration and dressing operations inevitably produce microbial contamination in depth and especially on the surface, through contact with equipment, tools, hands and clothes, despite all precautions. Micro-organism growth is a temperature-dependent process. To avoid it, it is absolutely essential to reduce the temperature of the meat, especially on the surface, immediately after dressing. Cooling must therefore be carried out in the slaughterhouse itself. This operation is known primary chilling.
For optimum meat quality, meat should be held at 15°C to 16°C during the onset of rigor mortis. Temperatures which are too low can result in unfavourable conditions such as thaw rigor and cold shortening. Temperatures which are too high can result in heat rigor.
When meat is frozen before the onset of rigor mortis, a more severe form of rigor mortis will set in upon thawing the meat. This is called thaw rigor. When this occurs, severe muscle contractions will cause the length of the muscle to shrink 60 to 80 percent. The resulting meat is very tough and lacks juiciness. When meat is not frozen but is stored between 0°C and 15°C cold shortening develops, which is similar to but less severe than thaw rigor. Muscles which are not attached to the skeleton are the most severely affected but there will also be some undesirable effects in those, which are attached to the skeleton. Beef and lamb are particularly susceptible to this condition, but it occurs in other meats as well. Carcasses with lower fat content lose their heat more quickly and will be more severely affected than carcasses with higher fat content.
Electrical stimulation can be used to prevent cold shortening and is a widely used method to improve the tenderness of beef and lamb. It causes the carcass muscle to contract violently and hastens the conversion of muscle to meat. The pH level drops more quickly than usual and rigor mortis sets in more quickly than in non-stimulated carcasses. Electrical stimulation protects against cold shortening and may improve meat tenderness, colour and appearance. It also hastens the development of quality characteristics such as bright red muscle colour, muscle firmness and marbling.
Aging time of electrically stimulated beef is also reduced. Due to the enhanced quality of meat and reduced costs, electrical stimulation has become more widely practiced in recent years.
Muscle which is held at temperatures above the optimum temperature (above 15,5°C) will have severe shortening due to early onset of rigor mortis (i.e. heat rigor). This condition results in tough, less juicy meat.
After freezing, carcasses and quarters must be protected with plastic film, usually under cloth or jute fabric. Meat cuts are covered with plastic film, or vacuum-packed in plastic bags; they are placed inside cardboard boxes and usually frozen in these.
When meat cuts are pre-packaged without vacuum, air pockets must be avoided. A 20-mm space should be left in the upper part of the box to allow for expansion. Superficial fat should be eliminated before freezing to reduce the development of rancidity during storage.
Applications
Meat is a versatile source of nutrition, being boiled, fried/roasted, salted, smoked or processed into sausage.
Shipment/storage
Frozen meat is transported as quarters of beef, sides of pork or whole calf, sheep and lamb carcasses and is usually packaged as follows:
- Quarters of beef: in plastic bag and stockinet (protective covering made, for example, from linen).
- Sides of pork: in stockinet
- Sheep, whole carcass: in plastic bag and stockinet
- Boned portions: wrapped in film and then packaged in cartons
The protective coverings must be clean and dry. Blood-stained and frozen down coverings are a sure sign of noncompliance with the necessary cold chain (interim thawing).
As there is a certain degree of quality deterioration, even at very low temperatures, storage life is limited. The usual temperatures are in the range of -18°C to -25°C for periods of preservation of one year or more. However, each type of meat requires specific conditions.
The main problem with frozen storage is deterioration in organoleptic quality. There may be changes in meat texture, fat can become granular and crumble, and there can also be some discolouration of the meat. Fat modification induced by air oxygen produces rancidity and ancidity, and a disagreeable taste. Microbial enzymes also remain active, especially those that attack the fat. Water loss from proteins as described below can also have a significant effect.
Weight loss through water evaporation can occur. This can be seen as freezer burn, i.e. superficial desiccated areas which can occur even in packaged meats when the packaging film is loose and temperature fluctuates inside the chamber/container. Weight loss, which can be between 1% and 4% in unpacked meat, favours organoleptic deterioration. Meat surface can dry and become porous, encouraging rancidity and transfer of aromas. Weight loss, resulting in a mark down of products price is considered of great importance in high value frozen foods.
Storage temperatures of frozen meats and other animal products and cross tainting is negligible owing to the low temperatures and to the fact that most of the products are in adequately protective packages.
Meat absorbs odours from strong smelling food products such as apples, oranges, onions and fish. This rate is limited in frozen meat, compared with fresh and chilled and also depends on packaging.
After cooking, eating quality is judged partially by its appearance, but mainly by its tenderness, flavour and juiciness. If the frozen storage life is not exceeded, freezing and storage of meat has little (if any) effect on the main quality parameters. Drip is the only exception, as it is substantially increased by freezing. The quality of meat after thawing (especially its eating quality) is therefore determined before it is frozen. In the past, factors such as poor packaging and poor temperature control could result in freezer burn and rancid off-odours and flavours in frozen meat. Now, unless storage times are exceeded or temperature control abused, the quality of meat after frozen storage will be identical to that before freezing.
Tenderness is the most important eating characteristic of red meat. The two most important refrigeration factors controlling the texture of meat are the rate of chilling, and the length of time and the temperature during ageing. Both need to be carefully controlled to maximise eating quality.
Drip is a problem with red meat and is considerably increased by freezing. Although the potential for drip loss is predetermined to a large extent by breed and conditions before slaughter, the realisation of this potential is influenced by the temperature time history in the cold chain. Rapid cooling substantially reduces drip production.
Occasionally, meat is supplied which, after freezing, has been exposed to higher temperatures. Such incorrect storage results in depreciation. Such interim thawing can be recognized by the protective coverings having frozen onto the meat. Distortion of the pieces of meat and dark muscle tissue color are further indications of incorrect handling.
Due to an increased risk of decomposition, frozen meat must not exhibit the slightest trace of fresh blood. Frozen meat with spots of mold must also not be loaded. The duration of storage of various types of frozen meat depends upon temperature and relative humidity.
Holds/containers must be appropriately precooled prior to loading. They should be at a temperature of -18°C. Frozen meat should have a core temperature of -18°C so that the activity of microorganisms comes to a standstill and enzymatic degradation processes are largely suppressed. Temperature measurements must be performed and recorded at regular intervals.
The travel temperature must be maintained constantly as variations in temperature may result in recrystallization, resulting in growth of the ice crystals. Variations in temperature are associated with continual slight thawing and refreezing. Since small ice crystals have a higher vapor pressure than larger ones, they will melt more rapidly when the temperature rises, while on cooling the same effect means that the water is preferentially deposited as ice on the larger ice crystals. This consequently brings about growth of the ice crystals, as a result of which the rapidly frozen meat increasingly takes on the appearance of slowly frozen meat on storage. The large ice crystals rupture the cell walls, as a result of which, on thawing, cell fluids (drip) escape, giving rise to a distinct reduction in utility value.
It is essential to maintain the deep-freeze chain. Thawing damage occurs in the event of extended interruption of freezing, followed by warming and refreezing of the product. "Snow" forms within the plastic bags, especially around leaky container doors.
A dark red to black coloration due to transient thawing processes is irreversible, the color change being retained on subsequent refreezing. Temperatures lower than specified are not generally harmful, but they should be maintained throughout all the transport operations as there is otherwise a risk of recrystallization.
Relative humidity in the storage space should be kept at 95% in order to prevent the surface of the meat from drying out. Sublimation proceeds constantly at the surface of frozen meat, i.e. the moisture bound in solid form passes directly into the gaseous state. This drying process is an unwanted change because the shrinkage in mass impairs surface appearance. In extreme cases, surface drying may result in freezer burn, an effect which may be counteracted by plastic film packaging.
If moisture is observed on the meat, relative humidity should be maintained at 75% for short periods (mold growth threshold). Wet spots on transiently thawed frozen meat may subsequently be recognized from the "tide mark" they leave on drying. Care should thus be taken especially during loading and unloading in rain, fog and snow as there is a risk of discoloration and distortion of the meat and of surface spoilage due to microorganisms.
Quality and safety
The International Organization for Standardisation, ISO, is the worldwide federation of national standards bodies. ISO defines quality as "the totality of features and characteristics of a product or service that bear on its ability to satisfy stated or implied needs." The quality of meat and meat products depends on safe and hygienic practices. Outbreaks of meat-borne illnesses are reduced if appropriate practices are followed when handling, manufacturing, refrigerating and transporting meeat and meat products. Ensuring standards of quality and safety are high also minimizes the post-harvest losses."
"The meat industry must ensure that their meat handling, processing and transportation facilities meet requisite standards. Adequate training of both industry and control authority staff must be provided by support institutions, and channels for feedback from consumers established. Ensuring high standards for quality and safety is good economics, minimizing losses that result from spoilage, damage to trade and from illness among consumers."
Meat processing highly involves very strict controls and measurements in order to ensure that all processing stages have been carried out hygienically. Thus, all meat processing companies are highly recommended to join a certain type of food safety system. One of the certifications that are commonly known is the Hazard Analysis Critical Control Points (HACCP).
Hazard Analysis and Critical Control Points.
HACCP is a system which identifies hazards and implements measures for their control. It was first developed in 1960 by NASA to ensure food safety for the manned space program. The main objectives of NASA were to prevent food safety problems and control food borne diseases. HACCP has been widely used by food industry since the late 1970 and now it is internationally recognized as the best system for ensuring food safety.
"The Hazard Analysis and Critical Control Points (HACCP) system of assuring food safety and quality has now gained worldwide recognition as the most cost-effective and reliable system available. It is based on the identification of risks, minimizing those risks through the design and layout of the physical environment in which high standards of hygiene can be assured, sets measurable standards and establishes monitoring systems. HACCP also establishes procedures for verifying that the system is working effectively. HACCP is a sufficiently flexible system to be successfully applied at all critical stages -- from harvesting of fish to reaching the consumer. For such a system to work successfully, all stakeholders must cooperate which entails increasing the national capacity for introducing and maintaining HACCP measures. The system's control authority needs to design and implement the system, ensuring that monitoring and corrective measures are put in place."
HACCP is endorsed by the:
- FAO (Food and Agriculture Organization)
- Codex Alimentarius (a commission of the United Nations)
- FDA (US Food and Drug Administration)
- European Union
- WHO (World Health Organization)
There are seven basic principles:
- Principle 1: Conduct a hazard analysis.
- Principle 2: After assessing all the processing steps, the Critical control point (CCP) is controlled. CCP are points which determine and control significant hazards in a food manufacturing process.
- Principle 3: Set up critical limits in order to ensure that the hazard identified is being controlled effectively.
- Principle 4: Establish a system so as to monitor the CCP.
- Principle 5: Establish corrective actions where the critical limit has not been met. Appropriate actions need to be taken which can be on a short or long-term basis. All records must be sustained accurately.
- Principle 6: Establish authentication procedures so as to confirm if the principles imposed by HACCP documents are being respected effectively and all records are being taken.
- Principle 7: Analyze if the HACCP plan are working effectively.
Additional information on frozen meat
Whilst meat is carried at -18°C, temperature variation can also occur. Severe variation results in blood loss and therefore the presence of heavy amounts of blood-ice can indicate a problem. Such variation results in discolouration of the product. Prolonged periods at high temperature can result in mould formulation and the onset of decomposition so attention should be paid to any foreign odours which may be detected. With further regard to temperature it should be stressed that the maximum temperature at which frozen meat will be permitted entry into the European Community is -12°C.
Whilst containerization has largely removed the problem of tainting, such problems do still occur. Such taints should they occur can be removed by ozone treatment. However, care should be taken that this treatment is acceptable in the country of receipt.
Offal is usually shipped hard frozen and includes tails, hearts, livers, kidneys etc.
Risk factors
- Thawing / Microbiological spoilage
- Odor
- Contamination
- Mechanical influences
- Shrinkage/Shortage