*Anand TS, Hamna Vahab, Ipseeta Nanda, Lalrohlui and S. Talukder
Meat quality is the most concerned aspect of today’s nonvegetarian consumers. Domestically and internationally the safety of meat and meat products has attract the attention from consumers and government bodies. Many a serious food poisoning incidents attributable to the consumption of contaminated and inferior quality meat and meat products has further raised the need for systems governing meat production which properly and effectively control the hazards which can compromise meat safety. Many controlling measures and practices are there to assure the meat safety. These approaches are associated deeply with the pre and post slaughter care and handling practices of food animals and has a crucial role in the assurance of meat quality. The major stages in the pre slaughter handling that affect meat quality include transportation, lairage, fasting, pre-slaughter sugar feeding, ante-mortem inspection etc. Whereas, in the post slaughter handling portion the major approaches include, post mortem inspection, proper packaging, refrigeration, maintenance of cold chain, suitable transportation etc.
Pre-slaughter handling of animals and the related aspects to assure meat quality
Pre-slaughter handling mainly involves all the activities that take place in the farm, during the stages of transportation, marketing of the animal and at the slaughter plant.
Deterioration of health and weight of the animal is mainly subjected to poor handling conditions before slaughter. During this stage all kinds of stresses may occur like physical (higher ambient temperature, sudden acceleration of the vehicles, noises and overcrowding etc.) and physiological (mixing of different unfamiliar animals, breaking of social grouping or some unfamiliar smell, environment etc.) (Warriss, 2000).
Sometimes the animal may suffer from tiredness, starvation, bruises, injuries, deprivation of food and water and stress while loading and unloading from the vehicles. Higher levels of these stresses will cause poor meat quality apart from cruelty and being inhumane (Lowrie, 2006). Genotype, transportation, lairage time, season of the year, environmental conditions are the other factors apart from stress will affect the quality of meat(Kuchenmeister, 2005)
The conditions namely pale, soft, exudative (PSE) pork and dark, firm, dry (DFD) beef occurs due to preslaughter stresses. Due to these pre slaughter stresses there will be alteration in the onset of rigor mortis and fall in the muscle pH. This will affect the eating quality and appearance of the meat (Collins and Huey, 2014).
- Transportation of animals
Transportation is the process that starts with loading of animals in transporting vehicle and end with unloading of them. These have to be done only in a quite environment in gentle manner. Careful process of loading and unloading is necessary (Adzitey and Nurul, 2011). Animals are exposed to various conditions like cold, heat, humidity, overcrowding and noises during transportation. Other factors like over speeding, sudden stops of vehicle, rapid acceleration and very long journey time without breaks and inappropriate feeding will deteriorate meat quality (Adzitey, 2011)
Cleaning and disinfection of vehicle, provision of anti-slippery floors, adequate lighting inside the vehicle and avoidance of overcrowding are important during animal transport. For journeys more than 65 km, a qualified attendant must accompany (Collins and Huey, 2014).
Lairage is the place where animals are temporarily held before slaughter. It provides the animals with some rest and recovery from transportation stress. Animals are observed for any possible injuries or infections. Adequate amount of feed and water must be provided if the animals are kept very long period before slaughter.Also, animals may suffer from bruises and injuries by overcrowding and fighting. Lairage can also act as a source of infection by different pathogenic bacteria. Therefore excessively longer holding time in the lairage must be avoided (Warriss, 2003).
- Pre-slaughter fasting
There is a practice of withholding food from animals prior to slaughter seen among the butchers throughout the world. They assume that the fasted animals will bleed better and easy to dress and have a brighter appearance. But there is no scientific evidence in this. Also, the hungry animal will not be easily settled down (Collins and Huey, 2014).
It is not advisable to slaughter the animal in full stomach due to the chance of accidental contamination of carcass due to rupture or incision on the gastro intestinal tract (Guise et al., 1995).
- Pre-slaughter sugar supplement
According to the findings of Collins and Huey (2014), there is a chance of 25% reduction in the liver weight of cattle that are detained for 2 days in the lairage. The stress of the cattle was reduced by administration of molasses in drinking water in Chicago. It has been shown that the sugar feeding will restores rapidly the carbohydrate reservoir in the muscles and liver allowing the proper development of normal acidity in the muscle and preventing the loss of weight of liver. Under present day abattoir conditions, it is doubtful that the pre-slaughter sugar feeding is practical or economic.
- Ante mortem inspection
Ante-mortem inspection is done to ensure only clean, healthy and stress-free animals are only presented for slaughter. On the day of arrival at the slaughter house or before beginning of the daily slaughter, the animal must undergo ante-mortem inspection. If the animal is stayed in the lairage for overnight, then the inspection has to be repeated (Collins and Huey, 2014).The inspector must determine these conditions like whether the animals is suspected for any communicable disease to man and other animals, whether they show any signs of ageneralized conditions which makes it unfit for human consumption, whether they are tired, injured or over excited and whether they are clean enough to enter the slaughter (Collins and Huey,2014). According to Collins and Huey (2014), there are pre-defined decision categories of ante mortem inspection. They are as follows,
- Healthy animal without any abnormalities will proceed to normal slaughter.
- Condemned animals like dead, moribund, excessive dirty or emaciated showing signs of septicemia should not enter the abattoir. This result in meat being unfit for human consumption.
- Animals having a localized infection or suspected for a generalized condition are slaughtered but requires a special and detailed post-mortem inspection. They are slaughtered at different time in a specialized area. Animals suspected for the administration of illegal drugs or growth promoters will require special attention.
- Some animals are segregated for slaughter under special conditions like excessive dirty stock at a slow line speed.
- Delayed slaughter for excessive fatigued or excessively excited animals. Such animals require medical attention.
3. Post-slaughter care and handling of animals and related aspects to assure meat quality
- Post mortem inspection
There should be thorough and systematic inspection of any abnormal conditions in the head, lymph nodes, lungs, heart, liver, esophagus, stomach, intestine, kidney, spleen, uterus, udder and testes. The final judgment must be based on the evidences noticed by palpation, smell, incision, ante-mortem signs noticed and the laboratory test results of suspected samples (Collins and Huey, 2014).
Packaging of a product protects it from deteriorative agents like discoloration, off flavor and off odor, nutrient losses, microbial contaminations and other factors (Zhou, G. H et al., 2010). Vacuum packaging, atmospheric and active packaging are the 3 types of packaging used now a days (Gazalli et al., 2013). The modified atmospheric packaging (MAP) is the removal or replacement of the surrounding atmosphere of the meat and sealing it with vapour-barrier material (McMillin et al.,1998; McMillin et al., 2008). For meat packaging the modified atmospheric packaging utilizes sealed high barrier packaging material from which the air is removed and replaced with another mixture of gases. Most commonly used gas for this purpose is 10% Carbon dioxide, which will inhibit the growth of microbes in refrigerated meat. Other than that 20-50% oxygen containing gas mixture is used for fresh meat to convert the myoglobin into an oxygenated form having cherry red which will be more attractive (Collins and Huey, 2014).
High oxygen modified atmospheric packaging is the widely used method in western countries for beef packaging. The gas mixture used contains 80% oxygen and 20% carbon dioxide (Lagerstedt et al., 2011). The high oxygen content will give rise to a stable bright red colour that will be appealing to the buyers (Carpenter et al., 2001). Torngren et al. (2003) demonstrated that the high oxygen modified atmospheric packaging will increase the toughness of meat.
Vacuum packaging is mainly used to pack large and whole meat cuts for ageing period before they are before cutting into pieces for consumer packaging. Vacuum packaging produces more tender meat. It is easy to handle and store and have a long shelf life will prevent the need for short term frozen storage (Jenkins et al., 1991).
The active packaging system utilizes the incorporation of specific compounds into packaging systems which will improve the quality and shelf life. It is the incorporation of some specific compounds in to the packaging system that interact with the internal content to maintain the shelf life of the products. The intelligent or smart packaging system senses the food particles and provides information about the status of internal environment of food to the processor, retailor or consumer (Kerry et al., 2006).
Active packaging techniques includes moisture control, oxygen permeable films, oxygen scavengers, oxygen generators, carbon dioxide controllers, odor controllers, flavor enhancers, ethylene removal substances, antimicrobial agents and microwave susceptors (Brody et al., 2008).
- Refrigeration of meat by chilling and freezing
The purpose of refrigeration is to reduce the temperature of the meat such that the microbial growth is either reduced (chilling) of arrested (freezing) (James and James, 2009).
The freshly slaughtered animals have wet and warm surfaces which provide a good substate for growth of micro-organisms. Immediate chilling of milk after slaughter will reduce the surface temperature of carcass into a value under which microbial growth is minimized. Combining a high standard of hygiene and packaging with a temperature of −1 to +0.5°C during storage, transport and display can routinely extend shelf life to 12 weeks. While freezing there is a chance of increase in drip from meat and this will make the meat less attractive. However, the drip will not influence the eating quality of meat after cooking (Collins and Huey, 2014)
The following criteria are adopted for proper chilling and freezing,
- The design of refrigeration space must consider the following aspects like tenderness, possible spoilage, weight loss, size of individual units, space requirement, rail height and floor and wall surfaces.
- Regular checking of temperature.
- Overloading of carcass must be avoided and the carcass must not touch each other.
- Minimal number of opening and closing of doors.
- Adequate amount of air flow is required around the carcass.
- Carcass of different species must not put together in the same refrigeration area.
- Carcass must not be chilled below 10°C in less than I hour to avoid cold shortening.
Chilling is used for short term storage of meat. It does not affect flavor, appearance or nutritional value of meat. Meat is maintained at about 1°C in the dark. Because the light may accelerate the oxidation of fats and produce rancidity. The chilling site must be kept always dry to prevent formation of molds on meat. Rapid lowering of carcass temperature within 1 hour of slaughter and avoid freezing is called fast chilling. These meats will be said to have a good keeping quality due to lower air temperature usually below −3°C initially and have very low microorganisms on the surface of meat. Very low temperature and higher air speed may cause cold shortening of muscles. Pig carcass has to be chilled quickly inorder to prevent spoilage and they are very less susceptible to cold shortening. There was an estimation done by Meat Research Institute in Britain on beef carcass stores in chilling room will loss 0.1% per day, while lamb carcass may loss 0.05% in a relative humidity of 90%. Due to the larger surface area, smaller items will loss more compared to larger items. A relative humidity of 90% is most suited for commercial chilling and retail purpose. In order to minimize the carcass weight loss during chilling, initially a higher air circulation speed is necessary to lower the carcass temperature and carcass surface water vapor pressure quickly. After the carcass temperature have sufficiently lowered, then slower air circulation rates are most suited (Collins and Huey, 2014). From 1990, a number of alternative chilling procedures have developed. This includes spraying the carcass with cold water. Such procedures reduced the evaporative losses and avoided cold shortening (Brown et al., 1993; Jones et al., 1993). Currently the European Union is taking interest in development of commercial procedure for fast chilling that is reducing the temperature of carcass to –1 °C within 5 hours of post mortem. This was proved to ensure tenderness of meat (Joseph, 1996).
Lower temperatures are now considered as satisfactory due to the reduced deterioration of meat. Temperature no higher than −18°C, even −30°C are using now a days for freezing of meat. The freezing point of meat is in between −1 and −1.5°C. While slow freezing of meat larger extracellular ice crystals is formed between the temperature of −0.5 and −4°C. This temperature zone is called as zone of maximum ice formation. The ice crystals grow continuously while stored in this temperature. It has been postulated that the ice crystals formed will be intracellular if fast freezing is done to a temperature lower than −4°C. The presence of a watery, bloodstained fluid which will escape from frozen meat when it is thawed and it consists mainly of water, together with salts, protein and damaged blood corpuscles is termed as weeping. The latter are responsible for the pink coloration of the fluid and are readily recognizable on microscopical examination. Weeping is an undesirable feature and is caused partly by the rupture of the muscle cells and tissues by crystals of ice and partly by irreversible changes in the muscle plasm. The presence of watery, blood-stained fluid which escapes from frozen meat when thawed is termed as weeping. It mainly contains water, salt, protein and damaged blood cells. The blood cells are responsible for the pink coloration of the fluid and recognizable under microscopical examination. Weeping is an undesirable change caused by damage of muscle cells by ice crystals formed and by irreversible changes in the sarcoplasm. (Collins and Huey, 2014)
- Maintenance of cold chain
As per the European Union legislation, the maintenance of the cold chain is considered as one of the main principles on food hygiene (Regulation (EC) 2004). There should not be any interruption to the cold chain at any time of meat distribution chain (EFSA, 2016).
Cold chain in slaughterhouse
The most common technology to chill meat before transportation are air chilling, immersion chilling, spray chilling and vacuum chilling (Nychas et al., 2008).
Cold chain in meat distribution
The vehicle used for transportation must be provided with a good refrigeration system in order to maintain the required temperature at all times during distribution process (Nychas et al., 2008).
Cold chain in meat retail
Maintenance of cold chain at retailers during display has an important role in prevention of microbial spoilage and maintenance of freshness and safety of meat. The size, capacity of chilling chamber, size of cabinets, initial temperature of the incoming meat, surrounding temperature, ventilation and lighting are the possible weak points at the retailer and all have to be addressed for proper quality (Nychas et al., 2008).
- Transport of refrigerated meat
Meat can be transported by road in properly insulated and refrigerated vehicles or insulated or non-insulated or non-refrigerated vehicles. Among this only insulated type will be considered as adequate. The other modes especially non-insulated types are inadequate particularly for chilled meat.
The well-designed refrigerated road vehicles should maintain the following criteria like high standard of insulation, good internal lining, air tight door, watertight flooring, rigid construction, an effective refrigeration unit, properly spaced overhead rails and a temperature indication in the driving cabinet. In addition to these criteria, the vehicle should be economical, light weight and noiseless. The internal temperature is maintenance is influenced by the difference between inner and outer temperature, insulation of the vehicles, number of times the doors opened and closed, loading temperature of the cargo, efficiency and rating of the refrigeration system, respiration rate of the product etc. If the vehicle left standing in the summer times with doors wide open will attracts heat and undesirable arthropods.
The vehicle used for transport of meat should be equipped with a good refrigeration system which is operated constantly during the process of transportation in order to maintain proper temperature of the product. There may be chances of undesirable heat infiltration due to hot weather, inadequate insulation and air leakage. The optimum conditions of transport must be attained by avoiding all these. The weakest link in the distribution chain is the transport period from the product purchase to the domestic refrigerator of the consumer. A consumer survey conducted in Greece reveals that about one third of the consumers’ needs more than 20 minutes to carry food from point of purchase to the domestic freezer, with a 5 percent exceeds 45 minutes. In the summer months with an ambient temperature exceeding 32 °C will lead to significant amount of heating up of food that will end up in a potential microbial growth (Koutsoumanis et al., 2005)
As far as the meat quality is concerned, pre and post slaughter care and handling have a major role in it. Each of the above-mentioned steps have to be under taken with at most care. There should be a proper transportation system provided that is stress free to the animals. We must ensure a good lairage facility, pre-slaughter fasting and proper ante-mortem inspection. After the slaughter process, a thorough post-mortem inspection must be there. There must be a propre packaging system, refrigeration system and transport facilities for the meat. Also, there should be a perfect maintenance system of cold chain in the slaughterhouse, during the distribution process and at the retailers. Even a small mistake in any one of the above-mentioned steps will cause severe deterioration in the meat quality.
*Division of Livestock Products Technology, ICAR-IVRI, Izatnagar, Bareilly, UP-243122
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