This series of articles will

Transcription

1 1 Introdction This series of articles will address some of the practical isses of processing poltry and how to prevent carcass downgrading and problems. Chicken is a versatile and healthy meat and the indstry has been very sccessfl at adapting to meet the changing demands of consmers for variety, versatility, convenience, qality and vale. Poltry prodcts can be divided into three broad categories; whole bird, fresh portions, and frther processed prodcts (for example vale added and convenience foods). Prodcts in these categories have different tolerances in terms of carcass finish, downgrading, and. Carcass downgrading can be cased by a mltitde of factors inclding disease, contamination and physical trama or damage. The severity ranges from major problems leading to whole bird condemnation to minor trimming of wing tips or skin. This series of articles will deal only with problems cased by the physical interactions between the bird and its environment and the handling of the carcass and meat. The incidence of downgrades will vary between companies; the key is for individal processing plants to nderstand what happens in their own plant. Monitoring downgrades will enable a processor to qickly identify and deal with any deviation from the normal sitation. Meat qality here refers to the attribtes of the meat sch as drip loss, cook loss, textre, tenderness, flavor, jiciness, and appearance. Problems with cook and drip loss can reslt in a loss of yield and having to re-pack precooked prodcts. Poor textre, jiciness, tenderness and flavor will affect consmer satisfaction and whether they prchase a prodct again. Variability in appearance, sch as color, strongly inflences consmer selection at point of prchase. In addition, fat content can affect the shelf-life of a prodct and can case problems complying with labelling of prodcts. The perceived importance of will depend on the reqirements of specific prodcts. Meat qality is inflenced by complex interactions of a whole range of factors inclding genetics, management, ntrition, environmental conditions, preslaghter stress, and postmortem handling of the meat. Many of the factors that affect the carcass qality and meat qality also have implications for bird welfare, highlighting the importance of monitoring welfare and optimising conditions at all stages from farm throgh to processing. For more details on these topics sbseqent articles in this series will cover: lunderstanding and measring. lon the farm factors inflencing carcass and. ltransport and the slaghter plant key considerations. lstnning birds at the processing plant methods and potential problems. lpost-mortem handling of carcasses and meat. lshelf-life. lkey points in preventing downgrade and problems.

2 2 Poltry prodcts have expanded rapidly into frther processed and convenience foods. Meat qality characteristics sch as drip loss, cook loss, textre, flavor and appearance inflence processing ability and properties of these prodcts, which affect consmer satisfaction. Meat qality is affected by management, environmental conditions, pre-slaghter stress, and post-mortem handling of the meat. Many of these factors will be discssed in sbseqent articles. First it is important to nderstand post-mortem mscle metabolism and its effect on. After slaghter, glycogen is converted to energy via glycolysis, with an accmlation of lactic acid casing a drop in mscle ph. The rate and extent of drop in ph, combined with mscle temperatre, affect. These are determined by glycogen content at slaghter and the rate of glycolysis. Stress stimlates glycogen breakdown and inflences post-mortem mscle metabolism. Short, acte stress increases mscle temperatre and accelerates metabolism, casing a rapid drop to low ph, implicated in the development of pale meat with poor water retention. Conversely, prolonged stress depletes mscle Measring glycogen so ph remains high, leading to darker meat, with poor shelf-life. The simplest measrements to take on-line as an indication of are ph and color. Initial ph (to allow an indication of the rate of drop) shold be measred immediately after slaghter, as soon as there is access to the birds and before final ph is reached. The timing of measrement of initial ph mst be consistent bt this is less critical for final ph, provided that ph has reached an end-point. Final ph and color (for example lightness/reflectance - L*, green/redness - a*, ble/ yellowness - b*) are often measred at deboning. Color and ph give a qick indication of variation in meat qality and can be sed to investigate the effects of management, processing and seasonal factors. Color measrements may also be sed to grade meat on-line. However, first it is necessary to establish the qality criteria reqired for a prodct by establishing the relationship between ph, color and qality aspects of the meat (for example drip loss, toghness and textre). With this information meat cold then be sorted for specific prodcts. For advice on measring meat qality please contact Dr Joanne Gatcliffe. Measrements of color, sing a Minolta chromameter, and ph, sing a meat probe, as indicators of.

3 3 Key inflences on the farm Transferring birds from the farm to the processing plant is the time when birds are at the greatest risk from physical damage and stress; leading to downgrading or problems. In order to avoid these, good welfare and a consistency in how the birds are treated shold be planned and achieved. On the farm and loading: l Environmental conditions The farm manager shold aim to provide optimal, consistent conditions (air qality, temperatre and hmidity) and avoid long, chronic stress or short acte stress (for example heat stress), both of which can inflence. l Stocking density High stocking density can redce performance and niformity of the flock. In addition, competition between the birds increases the risk of physical damage (scratching, brising, wing fractres etc) and stress. l Ntrition Good ntrition promotes healthy, balanced growth with good skeletal and msclar development. Uniform, healthy birds are better able to cope with any additional stressors. Also, fat in the diet has a direct effect on the meat, prodct qality and shelf-life. Ntritional spplements (for example vitamin E) can help protect against mscle damage and oxidation of the meat. Shelflife will be covered in a later article. l Feed withdrawal (FW) Removal of feed on the farm redces faecal contamination in the processing plant. The FW programme implemented needs to be consistent between flocks and it is important to keep good records for each hose on a farm. The calclation of FW time shold inclde transport and holding time at the processing plant. For broilers a FW of 4-8 hors is sfficient and for trkeys 8-10 hors. Water shold always be available to the birds. Prolonged FW (>12h) increases gt fragility (higher risk of contamination) and in extreme cases energy reserves are depleted, which cold have a detrimental effect on. Intermittent feeding, cased by removal and retrn of feed between loads, can be very stressfl for the birds, especially if depoplation of a hose occrs over a long time. This type of stress can slow down digestive transit and increase the risk of faecal contamination and in extreme cases may affect. l Depoplation It is important to minimise stress dring catching and loading. Exposre to lod noises, bright lights, large changes in temperatre etc, are major stressors and can case panic leading to physical damage. Any eqipment sed shold be in good repair and personnel mst be trained in appropriate bird handling and identifying birds that are not fit for transport. l Transport crates Transport crates need to be in good repair and designed to avoid damage to the birds dring loading and in transit. It is important that stocking density is optimal for the welfare of the birds; encoraging the birds to sit dring transport with spport from other birds withot overcrowding. It can not be over emphasised that good welfare is vital to prodce good qality prodcts. The next article in this series will cover transport and the slaghter plant.

4 4 Key transport considerations Transportation to the slaghter plant presents a range of potential stressors. It is in the interests of the company/processor to manage and control these stresses to ensre birds arrive in good condition. Transport: l Loading. The birds ability to cope with stress is affected by health, physical condition and handling. If birds are badly handled dring catching and loading they will be less able to deal with the additional stress of transport. l Crate density. Bird weight and environmental conditions inflence the optimal nmber of birds per crate. There shold be enogh birds to prevent excessive movement dring transport (can case physical damage), whilst avoiding overcrowding as this redces the birds ability to thermoreglate. l Environmental temperatres and ventilation. Birds are ssceptible to heat and cold stress and the conditions experienced can vary de to location on the trck. Poor air circlation can lead to hotspots in some locations, whilst birds located on the oter edges can sffer hypothermia de to wetting and air velocity. Trcks with forced ventilation (operates when the trck is moving) may experience problems with heat stress dring traffic hold-ps or delays at the slaghter plant. Climate controlled vehicles offer the best soltion, providing good conditions and redcing variation. l Transport time. The length of the jorney can have a major impact on condition of the birds at slaghter. Birds experience vibration, noise, motion and thermal stresses dring transport and the longer the transport time the greater the impact is likely to be on the birds physical condition at slaghter. Slaghter Plant: l Holding area/lairage. It is good practice to have a short period of rest and recovery when the birds arrive, provided conditions are condcive to recovery. Lairage shold be designed to minimise noise, light, and temperatre extremes, be well ventilated and provide protection from the elements (wind, rain, sn). In hot climates water misting systems can be sefl to cool the birds. However, care shold be taken to avoid high hmidity, as this can be lethal to the birds by redcing the effectiveness of heat loss throgh panting and evaporation. Birds recover qickly from stress nder the right conditions. A prolonged holding time may increase stress and fatige, particlarly in adverse conditions. l Unloading and shackling. Live handling is a period of extreme stress for the birds. Carefl handling, dimmed lights or ble lighting, and low noise levels will help to keep the birds calm. Systems for controlled atmosphere stnning (CAS) redce stress by removing the need to hang live birds on the shackles. Getting the birds to the slaghter line is a crcial step with many potential stressors. Every factor needs to be considered and careflly managed to ensre the birds arrive in optimal condition. The next article in this series will review systems for stnning and killing the birds and the potential impact on carcase and.

5 5 Pre-slaghter stn/kill has improved the welfare of poltry. This article will discss electrical water-bath and gas stn/kill systems. Stnning by any method mst kill the bird or stn ntil death throgh blood loss. The most common gas systems stn/kill birds in transport containers. Exposing to gas ntil dead is preferable de to the short recovery time. There are three commonly sed gas mixtres: l Inert gas/mixtre (for example argon, nitrogen) in air with maximm 2% oxygen by volme (anoxia). l Inert gas/mixtre pls carbon dioxide (<30%) and oxygen (<2%). l Two-stage: 40% CO2 + 30% O2 + 30% N2 followed by 80% CO2 in air. Advantages of gas stn/kill: l Not hanging live birds improved welfare. l Delay in neck ctting is not a welfare problem. l Improved carcase and meat qality. l No affect on blood loss provided neck-ct is within three mintes of exposre. l Anoxia accelerates rigor development and matration of meat, enabling earlier deboning. Electrical stn/kill systems commonly se constant-voltage, mlti-bird water-baths. Crrent mst be sfficient to indce immediate loss of consciosness. It is not possible to control actal crrent to each bird de to individal variation in resistance, hence the effectiveness of the stn varies. Inadeqate stn can affect neck-ct accracy, especially with atomated systems, with implications for welfare, bleedot, and carcase qality. Condctivity can be improved by wetting the shackle; Stnning birds at processing adding salt (0.1%) to the waterbath; sbmerging birds to the base of their wings; and ensring constant connection between the earth and shackle lines. Water-bath length and line speed determine how long the birds receive the crrent and depth and dration of stn. The live electrode mst extend the entire length of the water-bath to apply crrent for the fll time the birds are sbmerged. Pre-stn shocks entering the water-bath are a welfare isse and affect carcase qality. Control by: l No overflow of water at the entry. l Electrically isolating the entry ramp. l Minimising flapping. Flapping increases the risk of haemorrhages, wing breaks, dislocations, and red wing tips and can reslt in an inadeqate stn. Redce by: l Carefl handling. l Low light intensity, ble or UV lights in the live area. l Avoid lod noises; jolts, dips, or sharp trns in the shackle line. l Breast comforters. l Correct shackle size. l Time to settle on the shackle before stnning. Low freqency crrents (50/60 Hz) provide the most effective stn/kill bt are associated with greater incidence of downgrades (broken bones, brised wing joints, red wing tips etc). Higher freqencies redce downgrades bt also the depth and dration of stn, making it harder to achieve an adeqate stn. The inflence of crrent, waveform, freqency and dration on the effectiveness of stn is complex and reqires expert advice to ensre correct bird welfare. All individals involved in the slaghter of poltry mst ensre they comply with all legislation and reglations.

6 6 Events post-mortem are as important for carcase and as live bird handling and killing. An effective neck-ct and sfficient bleed-ot time (typically 90s) will redce carcase defects and meat discoloration de to blood retention. The most effective neck-ct, to achieve a good bleed-ot and rapid death by exsangination, is to sever both carotid arteries and jglar veins in the neck. Blood loss of less than 2% bodyweight has been implicated in engorged veins and darkening of breast meat. Hot water scalding assists feather removal, with temperatre and dwell time affecting ease of plcking and carcase appearance. The ideal scald will depend on carcase size and final prodct reqirements. For example, a soft scald (typically 50-5 C, mins) leaves the cticle intact making it the preferred method for airchilled, whole, fresh, dry carcases, whereas a medim to hard scald (58-60 C, mins) improves plcking bt removes the cticle, reslting in nsightly barking of the skin (browning) if air-chilled. This method wold be nacceptable for fresh, dry carcases bt is sitable for water-chilled, fresh wet or frozen (packed), whole birds or meat. Problems with scalding, sch as line stoppages, incorrect temperatre, and ineffective mixing of the water (temperatre gradients) can case barking and srface discoloration of the breast meat (white cooked appearance 1-2mm deep). Plcking machinery has improved the efficiency of the process and redced labor reqired, however, the severity of plcking can have implications for carcase qality. Post-mortem handling of meat Uniformity of the birds and the correct settings for the size of bird will redce the incidence of skin tears, bone breakages, rptred veins (blood stains nder skin) and improve feather removal. Several chilling systems are available. The most common are water-immersion, water-spray (often referred to as evaporative air chilling), and air-chill. The aim is to remove heat from the carcases qickly and efficiently (typically to a max. 4 C after hors for a 1.5-2kg carcase). Rapid chilling alleviates potential problems sch as pale, exdative meat. This can reslt from a combination of high mscle temperatre and low ph (denatred mscle proteins leading to increased drip loss and pale meat) so by chilling the carcases rapidly the risk is minimised. When carcases are sed for ctting then hot-boning is ideal from an economic/efficiency perspective, as the birds can be processed in-line, redcing time, labor and storage reqirements. However, hot-boning can reslt in nacceptably togh meat so normal practice is to take carcases off-line and age for at least 6-8 hors. Many commercial plants now tilise techniqes that accelerate the rigor process, redcing the matration time and improving tenderness. For example, electro-stimlation plses electricity throgh the carcases to advance the rigor process and is reported to achieve matration in-line in three hors (or the eqivalent of for hors matration off-line). Other techniqes inclde control atmosphere stnning and matration chilling (two-phase air-chill designed to promote enzyme activity to break down proteins).

7 7 Shelf-life covers the risk to hman health (pathogenic micro-organisms) and acceptability (spoilage). Micro-organisms casing foodborne illnesses (salmonella, campylobacter) may be present prior to slaghter and cross-contamination of carcases may occr. Steps to redce bacterial load and inhibit microbial growth can improve prodct safety and shelf-life. Many chemical and physical treatments can be effective (chlorine; organic acids; hydrogen peroxide; TSP; carcase rinses; hot dips; steam; irradiation; electron accelerators; electromagnetic waves; modified atmosphere packaging (MAP)). Application of these techniqes is dependant on local legislation and consmer acceptance. Spoilage relates to npleasant odors, rancidity, deterioration of color, and srface slime. Spoilage is de to micro-organisms and chemical changes in the meat, inflenced by environmental factors (temperatre, hmidity, oxygen, light). Spoilage bacteria are not present at slaghter; they are derived from the environment and can mltiply at low temperatres on fresh meat. Chemical spoilage de to oxidation of lipids (fat) cases changes in flavor and odor and is responsible for the development of rancidity. The color of meat is determined by the concentration and chemical state of myoglobin (Oxymyoglobin red, Myoglobin prple/red, Metmyoglobin brown discoloration). Over time meat discolors permanently de to the accmlation of metmyoglobin. Discoloration can be a problem in dark poltry meat (thigh) when small pieces in a pack trn brown, redcing the Shelf-life of poltry meat perceived shelf-life. The prodcts of lipid oxidation (free radicals) trigger oxidation of oxy- and myoglobin to metmyoglobin. The rate of discoloration is highly variable and inflenced by many factors. Common cases of redced shelf-life: l Temperatre abse in the spply chain. Chilling qickly and storing at low temperatres inhibits growth of pathogenic micro-organisms and delays lipid oxidation and meat discoloration. Storing close to 0 C compared to 3 or 4 C gives additional benefits. l Low antioxidant content in diet/meat. Antioxidant spplementation (vitamin E) in the diet can be highly beneficial for shelf-life. l High fat content of diet/ meat. Fat in the diet is related to fat content in the meat. High fat content promotes lipid oxidation. l High proportion of nsatrated fat in diet/meat. Unsatrated fats are more ssceptible to oxidation. The fatty acid composition of lipid in poltry is directly affected by dietary fatty acids and is a major determinant of flavor and shelf-life. l Packaging falts poor qality materials, falty seals, incorrect gas mixtre, meat contacting film. Exclding oxygen by vacm packing or MAP in CO2 increases shelf-life by redcing oxidation. MAP with 60-70% O2 and 30-40% CO2 can have a beneficial effect on shelf-life and appearance as high O2 promotes oxygenation of myoglobin to oxymyoglobin, which gives a more appealing color and is more stable against oxidation to metmyoglobin. l The rate and extent of oxidation can also be inflenced by pre-slaghter stress and postmortem events (early ph and temperatre profile).

8 8 Prevent carcase downgrades This series of eight articles has addressed many of the practical isses concerned with prodcing and processing poltry, in terms of minimising economic loss de to downgrading and prodcing good qality prodcts. The cases of qality isses are mlti-factorial and can occr at any stage of prodction on the farm; catching and loading; transport; stnning and killing; and dring post-mortem handling of the meat. The key to identifying and solving problems lies in a good nderstanding of the processes the bird goes throgh from farm to processing and a knowledge of the normal level for downgrades and. Large variations exist between companies de to differences in prodction systems; breeds; slaghter age and weight; processing methods; inspection criteria; and how data is recorded. It is important to monitor the sitation at the processing plant in order to qickly identify problems and associated economic loss and to go on to investigate cases. To achieve this it is helpfl to consider the following steps: l Define the downgrade/ qality criteria. l Measre and record the incidence at the processing plant. l Estimate the economic loss to the processing plant. l Determine importance for the welfare of the birds. Based on this information, make a decision regarding legal reqirements and the economic benefits of redcing the incidence of damage. Previos articles in this series dealt with some of the areas commonly associated with carcase downgrading and meat qality problems: l Live bird: the farm environment; stocking density; ntrition; feed withdrawal; catching and loading; transport; nloading and shackling; stnning and killing. l Processing: bleed-ot; scalding; plcking; chilling; deboning; packaging and storage. Prevention is always the best option to minimise losses and maximise profits. Good bird welfare is directly related to good prodct qality. Continos assessment and monitoring of all the areas covered above, particlarly where there is close interaction between the bird and operational staff, shold help to prevent qality and welfare isses arising. As an indstry we have an ethical and legal obligation to maintain the highest standards of bird welfare in all areas of prodction, from the genetics of the birds, to the rearing, handling and processing. It is the responsibility of the breeding companies to ensre that fitness traits pertinent to the welfare of the birds (for example leg strength, walking ability, conformation and fitness) are inclded in a balanced selection programme. The indstry as a whole mst be transparent in all areas of prodction to nrtre consmer confidence. Each company has a responsibility to ensre that all stock persons, catching teams, and slaghter plant personnel (involved in live bird handling) are flly trained, well eqipped and aware of the importance of welfare reglations and company codes of practice relating to management and handling of live birds.