The effect of pre-slaughter showering and post-slaughter rapid chilling on meat quality in intact pork sides

Thirty pairs of Landrace or Large White pigs were used to determine the effects of pre- and post-slaughter cooling treatments on pork quality and yield. One animal from each pair was showered in cold water and after slaughter one side from each carcass was rapidly chilled and the other side was conventionally chilled. Two experiments were carried out in winter: they examined different times of exposure to cooling treatments; a further experiment was carried out in summer time. Showering caused a reduction in the temperature of the deep loin at 40 min post mortem (P < 0·01). Rapid chilling caused a further reduction in carcass temperature and the rate of pH fall was lower (P < 0·05) in the rapidly chilled sides. There was a strong indication that showering in the winter time lowered drip loss in slices of Longissimus dorsi muscle (P = 0·077) whereas showering in the summer time was not effective. Shower water temperature may have been important in this regard. Showering did not lower drip loss in intact pork legs. Rapid chilling was not effective in lowering drip loss in either slices of Longissimus dorsi or intact pork legs. Rapid chilling at -20°C for 3 h without an air blast lowered evaporative chill losses in sides of pork by 27-29% (P < 0·1) compared to normal chilling. Reduced treatments gave reduced effects. Neither treatment had any significant effect on cooking loss or toughness in broiled slices of pork Longissimus dorsi muscle.     

Influence of Different Chilling Conditions on Hot-Boned Pork

The objective of this study was to determine whether cold shortening affects porcine muscles with the intention of evaluating optimum chilling conditions for hot-boned pork. Fast chilling of the porcine M. longissimus below 10°C increased purge with little effect on toughness. The fast fall of pH induced by electrical stimulation at prevailing body temperatures has been associated with PSE characteristics. Rapid chilling may reduce or prevent this effect. Electrical stimulated/cold-boned loin segments exhibited higher levels of purge than those which were electrical stimulated/hot-boned and chilled rapidly. Cooking losses were not effected by hot-boning or electrical stimulation.     

Effect of different electrical stimulation and chilling treatments on pork quality

The effect of different chilling and electrical stimulation (ES) treatments on the carcass and eating quality of pork has been examined. Preliminary trials (Study I), with a variety of ES treatments, indicated that, on the basis of pH fall, drip loss and tenderness, the most effective was that using 700 V peak at 12·5 Hz for 90 s applied at 20 min post-slaughter. These ES parameters were used throughout the main study (II) using 80 pigs, one side of which was stimulated and the other not, before being chilled rapidly (10°C in deep loin within 2–3 h of slaughter) or conventionally (10°C in deep loin within 5 h of slaughter).

Changes in pH and temperature during chilling were observed and, after chilling, quality assessments on LD and Sm muscles included drip loss, muscle opacity and instrumental toughness at 3 days post-slaughter.

Electrical stimulation, 20 min post-slaughter, improved tenderness of the LD and, to a lesser extent, the Sm of rapidly chilled pig sides. This advantage was gained without producing PSE pork. In fact, drip loss from the LD was consistently less from the sides which had been stimulated.     

Effect of cooling rate upon processing characteristics of pork meat of different glycolysis type during post mortem ageing

Rapid chilling was applied to porcine longissimus dorsi muscles at 1 h post mortem in order to observe its effect on the quality of canned products prepared from those of different pH₁ values.

The muscle from one side of each animal was removed from the carcase 50 minutes post mortem and divided into two longitudinal strips. One was chilled immediately to 13–15°C (1 h post mortem): the other after a further hour (2 h post mortem) acted as control. After the centre temperature had reached 10°C the muscles were stored in a refrigerator at 3–5°C.

Compared with the control samples (chilled at 2 h p.m.), rapid chilling from 1 h p.m. caused an improvement in the water-holding capacity and the texture of pork meat, which had higher pH₁ values and was processed at 2, 4 and 48 h p.m. There was minimum brine retention and texture score if samples—both rapidly chilled and control—were processed at 24 h p.m.

Although brine retention of PSE pork meat could not be increased even by rapid chilling, the texture of heat treated PSE pork showed an improvement during storage, which was more pronounced after ageing for 48 h, if PSE samples were chilled at 1 h p.m.     

Cryogenic chilling of pork carcasses: Effects on muscle quality, bacterial populations and palatability

Two experiments were conducted to determine the effects of cryogenic chilling on the carcass shrinkage, meat quality, bacterial condition and palatibility of pork. In experiment I, pork sides were chilled at 1°C (n = 20), or immersed in liquid nitrogen (LN) for 1 or 3 min prior to placement in a 1°C cooler. Muscle temperature in the loin was significantly lower at 2 and 6 h post mortem in treated compared to control sides, and loin muscle pH was higher (P < 0·05) at 6 h post mortem in sides immersed for 3 min in LN. Carcass side shrinkage was reduced from 29·3 g kg(-1) in control sides to 20·9 and 13·5 g kg(-1) in sides dipped in LN for 1 and 3 min. Chilling treatment had no significant effect on the survival of mesophilic bacteria on carcass sides, on meat colour, drip loss, protein solubility or sarcomere length, but sides dipped for 1 min in LN has a higher muscle shear value than control sides. In experiment II, carcass sides from halothane positive (H+) and negative (H-) pigs were conventionally chilled (n = 49), immersed in LN for 3 min (n = 23), or electrically stimulated and chilled in LN for 3 min (n = 26). Similar results for temperature, pH, colour, protein solubility and drip loss in loin muscle were found to those in experiment I. Laboratory taste panel results showed that chilling treatment had no effect on palatability. Genotype produced meaningful differences in most palatability attributes with H+ pigs having less tender, less juicy and less desirable flavour than pork from H- pigs. Laboratory studies with inoculated fresh muscle slices showed that a 3 min immersion in LN resulted in a 10-fold reduction in the aerobic spoilage pseudomonads, but effects upon other spoilage bacteria and potential human pathogens were less pronounced. It was concluded that cryogenic chilling using LN reduced carcass shrinkage during cooling, but had no consistent effects on meat quality, palatability or bacterial numbers on the carcass. In contrast, genotype had a significant effect on most pork quality and palatability attributes.     

Effects of Packaging and Processing Procedures on the Quality and Shelf Life of Fresh Pork Loins

Thirty crossbred hogs were slaughtered and the longissimus muscle from the left side was removed and divided into two equal sections within 20 min postmortem (HP) and those from the right side were removed and divided 24 hr postmortem(CP). One-half of the muscle from each side was wrapped in parchment paper (PP) and the other half was vacuum packaged (VP) and loin sections were assigned to storage intervals of 0, 7, 14, 21, or 28 days. At the end of each storage period, loins were evaluated for moisture loss, bacterial levels, off-odor, sensory properties and retail case display. VP and HP treatments had reduced moisture loss (P<0.05). Off-odor scores were higher (P<0.05) for PP wrapped loins on day 14. Few palatability differences were observed with packaging and processing treatments. Vacuum packaging had positive effects on the storage and retail display characteristics of fresh pork.     

The influence of controlled atmosphere and vacuum packaging upon chilled pork keeping quality

A total of 48 pork loin section (1 kg) with normal inherent muscle quality were utilized to evaluate and compare the effects of a vacuum packaging system and a CO(2) controlled atmosphere packaging system on keeping quality of chilled pork stored at -1·5°C. Results indicated based upon appearance CO(2) packaged porl loin had a storage life of greated than 15 weeks and vacuum packaged pork loid had a storage life of slightly over 12 weeks. However, off-flavor development coinciding with lactic acid bacteria reaching maximum numbers presently restricts the actual storage life of pork loin stored at -1·5°C to 9 weeks in both packaging treatments. Therefore, if microbial contamination on the commercial product can be reduced significantly to prevent spoilage organisms, including lactics, from rapidly growing to maximum numbers, storage life of pork loin at -1·5°C can be extended sufficiently to accomodate all domestic and export applications using either vacuum or CO(2) packaging.     

The influence of storage and display conditions on the retail properties and case-life of display-ready pork loin roasts

A total of 216 pork loin subsections were utilized to investigate the effects of storage atmosphere (100% N(2); 100% CO(2); or 70% O(2) and 30% CO(2)), storage temperature (-1.5, 2 or 5 °C) and duration of chilled storage (≤28 days) and subsequent aerobic display (≤30 hr) on the retail properties and storage life of display-ready pork cuts. Composite results clearly emphasize the importance of subzero storage to the retail properties, and storage life of pork for all the types of storage atmosphere utilized. However, in the present study, controlled atmospheres of 70% O(2) and 30% CO(2) possessed the greatest preservative properties for masterpacked display-ready pork loin subsections (roasts) during chilled storage for up to 24 days, based upon visual and olfactory criteria. A decrease in retail appearance, attributable to a progressive increase in surface discoloration during both chilled storage and subsequent, aerobic display, resulted in a increase in the incidence of unacceptable packages, during both chilled storage and subsequent, aerobic display, which restricted chilled storage life to 20 days or less. Storage time consistently exerted the greatest influence on retail properties and generally accounted for 80% or more of the variation in most attributes evaluated. In addition, off-odors developed progressively during both chilled storage and subsequent, aerobic display, which further restricted chilled storage life to 12 days. Consequently, based upon previous cited results, for distribution of display-ready pork cuts to be successful, the hygienic quality of the commercial product must be improved.     

Improving pork quality by electricalstimulation or pelvic suspension ofcarcasses

This investigation compared the separate and combined effects on meat quality of electrical stimulation (ES) and pelvic suspension of pig carcasses chilled rapidly or conventionally. Sides from 80 pigs, 80–90 kg live weight, were allocated to one of four treatments followed by either conventional chilling (1°C for 24 h) or rapid chilling (-20°C for 2–3 h, before 1°C until 24 h post-slaughter). The four treatments were: Achilles suspended, with and without high voltage ES, and pelvic suspended, with and without ES.

The quality attributes: pH, colour and opacity, drip loss, instrumental and sensory texture were measured in M. longissimus thoracis et lumborum, at 10 days post-slaughter. Rapid chilling reduced the evaporative weight loss by 0·5% There were no significant effects of treatment on colour or opacity, although ES samples were slightly paler. Drip loss was also slightly greater with ES, particularly when combined with pelvic suspension, but in no case was the meat classified as PSE. Instrumental measurements of 'texture showed improved tenderness from both ES and pelvic suspension, even after 10 days ageing. The improvement was less pronounced when ES and pelvic suspension were combined Taste panelling confirmed that samples treated by ES or pelvic suspension, separately or combined, were significantly more tender than samples from non-ES, Achilles hung sides. ES and pelvic suspension were equally effective in improving the tenderness of pork loin. Pelvic suspension did not suffer the disadvantage of increased drip loss that occurred with ES in this study.     

Antioxidant activity of Carob fruit extracts in cooked pork meat systems during chilled and frozen storage

The purpose of this study was to evaluate the effect of adding condensed tannins in the form of non-purified (Liposterine^®) or purified (Exxenterol^®) extracts obtained from Carob fruit to prevent lipid cooked pork meat systems from oxidising during chilling and frozen storage. The antioxidant activity of these extracts was compared with that of α-tocopherol. Meat lipid alteration was evaluated as thiobarbituric acid reactive substances content (TBARS) and polar material-related triglyceride compounds followed by high-performance size-exclusion chromatography (HPSEC). TBARS levels were lower (P < 0.05) in samples containing Liposterine (LM), Exxenterol (EM), and α-tocopherol (TM) than in control sample (CM) under chilled storage. TBARS formation was similar (P > 0.05) for LM and EM but lower (P < 0.05) than for TM. Polar material increased several times in all samples, but significantly less in TM and EM than in LM. Thermal oxidation compounds determined by HPSEC were lower (P < 0.05) in EM than in LM or TM. The changes in polar material were proportionally smaller after six months frozen storage than after chilled storage, with Exxenterol displaying the highest antioxidant protection. Therefore Carob fruit extracts can be successfully used to reduce fat alteration in cooked pork meat at chilled and frozen temperatures.     

肌肽对猪肉的氧化抑制和保鲜作用

肌肽是一种具有抗氧化等功能的天然的二肽,本试验比较了肌肽对猪肉匀浆的抗氧化作用,同时比较了不同保鲜剂对冷鲜肉保藏期的延长作用。实验发现,1mmol/L肌肽标准液对猪肉匀浆中丙二醛的形成量就能起到显著的抑制作用(P<0.05),此时对体系中脂类氧化的抑制率即达到12%,5mmol/L肌肽对体系中脂类氧化的抑制率达15%,20mmol/L肌肽对体系中脂类氧化的抑制率达47%,表明不同浓度的肌肽均能对猪肉匀浆中脂类氧化起显著的抑制作用,其中随浓度的增加效果增强。与BHT和α-生育酚相比,肌肽对TBARS的抑制能力较高。肌肽可以延长冷鲜肉的保存时间,添加了肌肽的冷鲜肉保藏时间由不添加保鲜剂的9天增加到15天,其效果要优于抗坏血酸,肌肽牛肉预煮液也可以延长冷鲜肉的贮藏时间。     

Effects of micro-perforated film on the quality and shelf life improvements of pork loins during chilled storage

The effects of micro-perforated film (MPF) packaging method on the quality and shelf life of pork loin during chilled storage were investigated, compared with non-packaging (control) and non-perforated film (PPF) packaging. Loins were removed from five hogs after slaughter and chilling, and each loin was portioned into four parts. These samples (40 sections) were allocated to each of five intervals (0, 1, 4, 7 and 14 days) to minimize variation among treatments and stored for 14 days under 55±10% relative humidity and 0±1?°C. Total aerobic counts of control sample were significantly lower than those from MPF or PPF loins after 14 days of storage. At 14 days, the counts of Pseudomonas and Enterobacteriaceae in the samples from MPF were significantly lower than those from PPF. At 7 days, 'L' value for the control and 'a' value for PPF were significantly lower, and ΔE values for the control were significantly higher than other samples. During storage time, percentage weight loss was the most in the control samples with MPF following and PPF the least. Accordingly, water contents decreased highest in the control samples followed by those from MPF and PPF. TBA values increased with storage time, however no significant differences were observed among treatments. Sensory evaluation analyses showed that MPF samples were generally better evaluated in all parameters over the storage time. Therefore, it has been concluded that MPF could be used as an effective packaging technology since it extends the shelf life of fresh meat by controlling the microbial growth and evaporation at a moderate level.     

Spray chilling of deer carcasses—Effects on carcass weight,meat moisture content,purge and microbiological quality

Twenty red deer carcasses were included in the study. Two treatments were applied to the carcasses; control (air chilling) and spray chilling (n = 10 for each treatment). Carcass weight and temperature change were registered during over-night chilling. Meat moisture content was measured in the shoulder, loin, flap and leg before and after the chilling treatments; purge, cooking loss and tenderness were measured in loin samples stored at −1.5 °C for 3 and 9 weeks. Microbiological status was assessed on swabs taken at the lumbar end of the loin before and after the chilling treatments. Spray chilling reduced carcass weight loss significantly; air chilled and spray chilled carcasses lost 1 kg and less than 0.01 kg, respectively. No effects of spray chilling on tenderness, purge and cooking loss were found. Bacterial levels were low in general even after 9 weeks of vacuum packaged chilled storage.     

THE SHEAR FORCE OF VERY-RAPIDLY CHILLED LAMB 1: THE EFFECT OF CARCASS SPLITTING

The effect on tenderness of splitting lamb carcasses longitudinally under very-rapid chilling conditions was investigated. Whole (unsplit) and split carcasses were chilled in very-rapid chilling conditions (−20C for 3.5 h followed by chilling at 4C for 20.5 h) and conventional chilling conditions (4C for 24 h), giving a total of four treatments. Loin (M. longissimus thoracis et lumborum) shear force was measured at f and S days postmortem by Warner-Bratiler shear force measurement. By 5 days postmortem, split carcasses were not different (P>0.05) in shear force to unsplit carcasses when conventionally chilled but differences (P<0.05) were present between unsplit and split carcasses when very-rapidly chilled (57.7 N vs 41.5 N, respectively).     

冷却猪肉新鲜度的色差快速分析评价方法

为了得到冷却猪肉新鲜度的变化规律,本研究以冷却猪肉里脊部分为研究对象,进行球蛋白沉淀实验、感官评价、pH值、水分含量、肉浸液以及肌肉表面颜色值测定。结果表明：球蛋白沉淀实验、pH值能够较好地反应肉品新鲜度的变化,色差分析符合一定的规律：肌肉表面色差测定中,20℃条件下,a*变化与贮藏时间显著相关(P＜0.05),L*变化显著(P＜0.05);4℃条件下,b*、C变化与贮藏时间极显著相关(P＜0.01),L*值与pH值极显著相关(P＜0.01);对于肉浸液,L*、b*、C、ΔE*均发生显著性变化(P＜0.05),20℃条件下L*、b*、C、ΔE*与贮藏时间和pH值显著相关(P＜0.05),而4℃条件下,L*、C、ΔE*与贮藏时间显著相关(P＜0.05),L*、a*、b*、C、ΔE*值与pH值极显著相关(P＜0.01);冷链过程中,当L*高于48.73、a*高于4.72、b*高于9.18时可认定冷却肉为新鲜肉。     

X射线辐照对冷鲜猪肉品质和货架期的影响

为研究X射线辐照对冷鲜猪肉品质的影响。该实验用0.1~1.0 kGy梯度的辐照剂量对纯培养细菌、冷鲜猪肉进行处理,评估不同辐照剂量和贮藏时间下微生物、理化指标和感官特性的变化。结果表明：微生物菌落数随辐照剂量的增加而减少。纯培养大肠杆菌和单核细胞增生李斯特氏菌的D10值分别为0.177 kGy和0.180 kGy。0.6 kGy X射线辐照处理时,纯培养细菌菌落数显著（p<0.05）减少3.0 log值以上;人工接种细菌菌落数显著（p<0.05）减少2.0 log值以上。1.0 kGy辐照处理冷鲜猪肉,固有微生物菌落数显著（p<0.05）减少2.0 log值以上;货架期从原来的4 d延长到9 d;贮藏前期感官评分无显著（p>0.05）差异,后期感官评分下降缓慢;与对照相比TVB-N和pH值的上升速率在贮藏期内显著降低（p<0.05）;辐照后冷鲜猪肉TBA值有所增加,但在贮藏中对照组TBA值上升速率大于辐照组。综合考虑,1.0 kGy X射线辐照处理冷鲜猪肉,在保证冷鲜猪肉符合国家食品安全标准规定的同时将货架期延长了 4~5 d,为冷鲜猪肉的辐照保鲜技术提供科学依据。     

The effects of different chilling methods on meat quality and calpain activity of pork muscle longissimus dorsi

The objective of this study was to investigate the effects of conventional chilling (0 to 4 °C), rapid chilling (RC, -20 °C for 30 min, followed by 0 to 4 °C), and short-duration chilling (0 to 4 °C for 30 min, followed by 25 °C) on meat quality and calpain activity of pork muscle longissimus dorsi (LD). The muscle quality characteristics pH, color, cooking loss, pressing loss and tenderness, and calpain activities were measured 0-, 3-, 12-, and 24-h postmortem. Results show that the RC resulted in a faster temperature decline of the muscle, and prevented the meat pH and Commission Internationale de l'Eclairage L* value from declining during postmortem aging. RC also reduced meat cooking loss and pressing loss compared with the other two chilling methods. However, the chilling methods did not significantly affect meat shear force. During the first 24-h postmortem, there was not a noticeable change in the activity of m-calpain. But μ-calpain activity decreased regardless of chilling method. In the rapidly chilled carcasses, μ-calpain activity remained the same 3- and 12-h postmortem. However, in the short-duration chilled and conventionally chilled carcasses, the activity was visibly reduced. At 24-h postmortem, no clear zones on the gel were observed in all three treatments. PRACTICAL APPLICATION: Conventional and RC methods are commonly used for pork in commercial practice nowadays. Compared with conventional chilling, the effect of RC on quality parameters of pork varies. In recent years, short-duration chilling (SC) is widely used in many Chinese pig slaughtering facilities. However, few researchers have studied the effect of SD on pork quality. Therefore, the present study investigated the effect of different chilling methods on functionalities or quality of chilled pork meat.     

ULTRA-RAPID CHILLING: CHILLING RATE EFFECTS ON THE APPEARANCE OF LAMB CARCASSES AND TENDERNESS OF LAMB CHOPS

The effects of different chilling rates on the visual attributes of lamb carcasses and the tenderness of lamb chops were investigated. Carcasses (n=72) were chilled at -20C, -10C, -4C or + 4C. After chilling all carcasses were stored at +4C for up to 8 days. Samples were taken at 2, 6 and 9 days postmortem for sarcomere length, Warner-Bratzler shear force and sensory analysis. Carcasses were visually appraised at 2, 6 and 9 days postmortem for fat color, flank color, visible vein color, wetness and overall acceptability. Carcasses chilled at -20C had significantly higher Warner-Bratzler shear force values than the other chilling treatments at 2 and 6 days but not at 9 days postmortem. No difference (P> 0.05) was found in Warner-Bratzler shear force or sensory tenderness between any of the treatments by 9 days postmortem. Carcasses did not differ (P>0.05) in fat color, flank color or overall acceptability at any stage postmortem. Carcasses chilled at -20C had slightly darker (P< 0.05) vein color at 2 days postmortem but this was not evident by 6 days postmortem. Carcasses that were chilled at -20C had significantly lower evaporative weight losses than carcasses in any of the other treatments. Rapid chilling did not adversely affect the tenderness of lamb chops or appearance of lamb carcasses at 9 days postmortem compared with conventional chilling.     

Hot Pork Processing, Brine Chilling and Mechanical Portioning as a Fresh Pork Processing System

Rapid chilling was investigated as a link between hot pork processing and mechanical portioning. Loins from market weight hogs (n = 40) were removed (pre- or post-rigor) and were assigned to one of two chilling treatments (brine chilling or blast freezing). Loins were chilled until crust frozen, then tempered, pressed and cleaved. Ultimate pH, cooking yields, taste panel ratings and Warner-Bratzler shear force values (WBS) were obtained. Pre-rigor chops had significantly higher WBS values and lower (less tender) taste panel ratings than post-rigor chops. Generally, pre-rigor chops were juicier but less tender. There were no major differences between rapid chilling treatments nor in ultimate pH or cooking data. Less severe chilling techniques are needed to make this processing system feasible.     

Spray chilling of deer carcasses—Effects on carcass weight,meat moisture content,purge and microbiological quality

Twenty red deer carcasses were included in the study. Two treatments were applied to the carcasses; control (air chilling) and spray chilling (n = 10 for each treatment). Carcass weight and temperature change were registered during over-night chilling. Meat moisture content was measured in the shoulder, loin, flap and leg before and after the chilling treatments; purge, cooking loss and tenderness were measured in loin samples stored at −1.5 °C for 3 and 9 weeks. Microbiological status was assessed on swabs taken at the lumbar end of the loin before and after the chilling treatments. Spray chilling reduced carcass weight loss significantly; air chilled and spray chilled carcasses lost 1 kg and less than 0.01 kg, respectively. No effects of spray chilling on tenderness, purge and cooking loss were found. Bacterial levels were low in general even after 9 weeks of vacuum packaged chilled storage.