Blast chilling and low voltage electrical stimulation influences on bison (Bison bison bison) meat quality

Conventional carcass chilling is a lengthy and energy expensive process. Blast chilling (BL) can reduce cooling time and associated shrink loss, although its application may compromise meat quality, particularly in lean carcasses or those with localized finish such as bison. Low voltage electrical stimulation (LVES) can reduce the risk of decreased meat quality by inducing rapid rigor onset prior to exposure of the musculature to extreme cold temperature. BL (−20°C, 3 m·s⁻¹ air velocity, 2 h) accelerated temperature decline of bison Longissimus lumborum (LL) and significantly reduced cooler shrink loss versus conventional chilling (CONV: 0–2°C, 24 h). While BL tended to produce darker meat, this effect was tempered by the application of LVES, and samples from the combined treatment were significantly lighter than CONV. BL resulted in reduced tenderness in the LL, as assessed by shear force measurement, in part due to significantly shorter sarcomere length in BL samples. Taste panelists, however, were unable to detect a significant or detrimental BL effect. Where LVES was incorporated, there was an improved tenderness response with ageing. The combined LVES/BL treatment of bison carcasses is recommended for rapid processing without compromising meat quality.     

Prevalence of Escherichia coli O157:H7 in the American bison (Bison bison)

Bison is becoming a popular meat source for consumers, but very little is known about the bison's status with respect to Escherichia coli O157:H7. We conducted a study to determine the prevalence and identify virulence genes and pulsed-field genetic types of E. coli O157:H7 in bison. Rectal contents and rectoanal mucosal swab (RAMS) samples were collected from a total of 342 bison at slaughter on seven different dates. Isolation of E. coli O157:H7 was by enrichment, immunomagnetic separation, and plating on selective medium, and identification was based on sorbitol fermentation reaction, indole production, and O157 agglutination test. An overall E. coli O157:H7 prevalence of 47.4% was observed. Fecal prevalence across sampling days ranged from 17 to 83%, with an average of 42.1%. The prevalence in the rectoanal mucosal region ranged from 2.2 to 50%, with an average of 19.9%. All E. coli O157:H7 isolates (n = 212) possessed eae, hlyA, fliC, and stx2 genes. The antiterminator Q gene, Q933, was present in 50.7% of fecal and 38% of RAMS isolates, and Q21 was present in 52.1% of fecal and 61.5% of RAMS isolates. The pulsed-field gel electrophoresis analysis of isolates revealed 11 types (> 95% Dice similarity) and 19 subtypes (100% Dice similarity). Two pulsed-field genetic types accounted for 76.4% of total isolates. Our study suggests that the prevalence of E. coli O157:H7 in rectal contents or on rectal mucosa of bison is variable, but relatively high overall and bison could serve as an important reservoir for human infection.     

The conditioning of wheat. The influence of conditioning temperature on flour yield,moisture content and colour

Two UK wheats of similar protein content but differing in hardness have been conditioned at temperatures of 4, 10.5, 19 and 28°C to a moisture content of 15.5%, using lying times in the range 2 to 24h. The milling performance of the wheats has been assessed in terms of flour yield, moisture content and grade colour figure (GCF). Flour yield was expressed as straight-run milling yield (SR) and also as total yield (TE) which included flour from the impact finishing of by-products. The use of a conditioning temperature of 28°C increased TE and SR for the hard wheat and TE for the soft wheat, but decreased SR for the latter. Both types showed a reduction in flour yield when a lying time of 2h was employed. The use of temperatures above or below 19°C led to improved GCF results. The combination of low temperatures and short lying times brought about reductions in flour moisture content but these reductions were shown to be only partially responsible for the accompanying decreases in flour yield.     

Effect of subcutaneous fat and high temperature conditioning on bovine meat tenderness

Effects of subcutaneous fat cover and high temperature conditioning on tenderness of meat were studied using 16 steer carcasses. Longissimus subcutaneous fat cover was completely removed from eight carcasses and the right and left sides were stored at either 0°C or 26°C. After 6 h at 26°C, the sides were transferred to the 0°C room; and after 24 h, all sides were transferred to a 1°C room for the duration of the experiment. Cold temperature and removal of fat cover reduced (P < 0·05) the longissimus muscle temperature at 6, 9 and 12 h post-mortem. The pH of the longissimus muscle was lower (P < 0·05) as the result of high temperature conditioning and fat cover 6, 9 and 12 h post-mortem. Consequently, conditions existed which would have been expected to promote cold shortening, yet high temperature conditioning and fat cover had no consistent effects on myofibrillar fragmentation index, sarcomere length or shear values.     

常压蒸煮工艺对包装扣肉品质的影响

采用感官评价、质构仪全质构分析和微生物测定等方法进行包装扣肉制品的口感、蒸煮异味、白油凝结现象和卫生状况的分析,评价常压蒸煮对包装扣肉品质的影响。结果表明:常压蒸煮下扣肉肥肉和瘦肉部分的硬度、胶黏性和咀嚼性指标数据值均随着热处理时间的延长而明显降低,在100℃90min的蒸煮条件下可获得较佳的扣肉口感;随着包装后二次杀菌时间的延长增加了包装扣肉的蒸煮异味和成品冷藏后出现的白油凝结现象;采用先100℃蒸煮60min,然后真空包装并进行100℃30min二次杀菌的加工工艺,可以获得具有原汁原味,无明显蒸煮异味和较少白油凝结的包装扣肉制品,达到我国熟肉制品的卫生要求。     

高温加工方式对肉品质的影响

以猪肉(红肉)、鸡鸭肉(白肉)为原料,以色泽、全质构(TPA)等为指标,研究高温加工方式(煎制、炸制、烤制)对常见红、白肉食用品质的影响。结果表明:3种加工工艺对3种肉样的色泽、剪切力、TPA影响均显著(P0.05)。经煎、炸、烤制工艺处理后,3种肉样L~*、b~*值均显著增大(P0.05),猪肉a~*值减小(P0.05),而鸡肉a~*值增大(P0.05);3种高温工艺处理后,猪肉、鸭肉剪切力值显著增大(P0.05),鸡肉剪切力变化均不显著(P0.05);煎、炸、烤3种工艺均能显著增大猪肉硬度(P0.05),对于白肉,除煎制2,3 min及炸制3min 3组外,肉样硬度均显著增大(P0.05);经3种高温工艺处理后,猪肉、鸡鸭肉弹性均显著增大(P0.05)。     

鱼肉调理制品配方优化及贮藏品质研究

目的开发草鱼调理制品最佳麻辣配方并研究其贮藏品质。方法以草鱼为主要原料,感官评价为主要判别依据,通过单因素和正交试验优化原味配方(料酒、姜粉、食盐、味精和白砂糖)的添加量,再利用单因素和正交试验优化麻辣调味料(花椒、辣椒和胡椒)的添加量,最后对产品在–18℃条件下的贮藏品质变化情况进行研究。结果产品最佳原味配方为料酒1.6%,姜粉0.2%,食盐1.5%,味精1.0%,白砂糖2.0%; 3种麻辣调味料的最适添加量为花椒0.3%,辣椒0.4%,胡椒0.3%;鱼肉调理制品在–18℃冻藏条件下品质保持良好,货架期至少可保持2个月,添加聚赖氨酸后产品的品质得到了更好地保持。结论本配方鱼肉调理制品麻辣鲜香且货架期长,为鱼肉调理制品的开发和贮藏保鲜提供了参考。     

Nutrient profiles in retail cuts of bison meat

The objectives were to determine the nutrient composition and variation in eight cuts of bison meat in bulls and heifers and identify nutrient relationships in the clod and sirloin by principal component analysis. The nutrients analyzed were: energy, protein, total fat, saturated fat, monounsaturated fat, polyunsaturated fat, transfat, cholesterol, vitamin A, Ca, Fe, Na and moisture. Differences were observed in fat components between cuts and bulls had higher (P < 0.05) amounts of total, saturated, monounsaturated and polyunsaturated fat in the blade compared to the other cuts. The sirloins had less (P < 0.05) cholesterol than all the other cuts in bulls and the clod in heifers. Fat varied more than protein and moisture in all cuts. Four principal components (PC) accounted for 63.9% of the total variation of the nutrient composition. Total, monounsaturated and saturated fats were in PC1 and cholesterol in PC2 showing that cholesterol is independent of other fats. If dietary alterations elicit changes in bison meat fatty acid profiles, it may be possible to reduce cholesterol independent of total, monounsaturated or saturated fat.     

The influence of exhaustion and electrical stimulation on the meat quality of young bulls: Part 1-Post-mortem pH and temperature

After designing a method of handling cattle so that they reproducibly developed DFD meat, pH and temperature in cattle developing DFD and normal meat, respectively were studied. The influence of low voltage stimulation on both groups was also investigated. Depending on final pH and other characteristics of the meat, the carcasses could be assigned to subgroups representing pronounced DFD, slight DFD and normal meat, with and without electrical stimulation. In normal and in pronounced DFD carcasses electrical stimulation speeded up the pH drop but did not affect the final state of the meat. In stressed animals the pH values are variable for the first few hours post mortem. This effect is enhanced by electrical stimulation which, in carcasses with slight DFD (from stressed but not exhausted animals), may produce extremely fast pH drop and PSE-like meat. There is no evidence that electrical stimulation would influence the incidence of DFD in cattle slaughtered under commercial conditions. In normal animals electrical stimulation raised the carcass temperature during the first few hours post mortem by approximately 2°C. Carcasses from stressed animals had a higher temperature, independent of stimulation.     

生猪宰前皮温、宰后肉温及pH值对肉品质量影响

生猪屠宰后,肉尸(胴体)会产生系列新陈代谢变化.这一过程和结果直接关系到肉品卫生安全质量.宰前皮肤温度与宰后肌肉温度及pH值变化,是影响猪肉品质的三个主要因素.宰前充分休息与饮水,宰后严格冷却工艺和屠宰修正工艺是提高肉品品质的重要措施.     

冻藏温度对鱿鱼品质的影响

以鱿鱼持水力(water holding capacity,WHC)、p H值、硫代巴比妥酸反应物(tiobarbituric acid reactive substances,TBARS)、甲醛(formaldehyde,FA)、盐溶性蛋白含量(salt soluble protein,SSP)、活性巯基含量、Ca2+-ATPase活性为指标,探讨了在不同冻藏温度下(-10、-20、-30和-40℃)鱿鱼的品质变化。实验结果表明:鱿鱼不同冻藏温度下p H值在6.4~7.0,各温度之间无显著差异(P0.05),不同冻藏温度对鱿鱼的p H没有显著影响(P0.05);WHC、FA和TBARS分别与冻藏时间有显著相关性(r=0.951、r=0.953和r=0.955),随着冻藏时间的延长,鱿鱼失水率、FA、TBARS均呈上升趋势,其中-10℃的TBARS增加量明显高于其他3组(P0.01),冻藏初期各组FA由2 mg/kg左右快速上升到4 mg/kg左右,随后甲醛含量仍然呈上升趋势,但上升速度减缓;鱿鱼SSP、活性巯基含量和Ca2+-ATPase活性随着冻藏时间的延长,均呈下降趋势,相同冻藏时间内,-10℃下降最多,依次为-20、-30、-40℃,鱿鱼蛋白质指标的变性速度在不同冻藏温度下的差异是显著的(P0.05)。冻藏温度越低,鱿鱼品质越好。     

Apoptosis during postmortem conditioning and its relationship to duck meat quality

The aim of this work was to examine the relationship of skeletal muscle apoptosis and postmortem development of meat quality. Colour, cooking loss, myofibril fragmentation index (MFI) and shear force of duck breast and thigh meat postmortem were measured, and changes of positive nuclei were assessed with Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphophate nick end-labelling method (TUNEL). Correlation analysis revealed that apoptosis were positively correlated with colour (L^∗, a^∗ and b^∗), cooking loss and MFI (P < 0.05), while it is negatively correlated with shear force (P < 0.05). Our results indicate the growing level of duck skeletal muscle cell apoptosis was associated with the postmortem development of meat quality traits such as meat colour, water holding capacity and tenderness.     

The calibration temperature of pH-glass electrodes: significance for meat quality classification

In this short communication we show important factors concerning pH measurements in pork. The purpose of the study was to investigate the effect of the calibration temperature of pH-buffer and of the pH-electrode on pH measured 1–120 min post mortem in pork, and to evaluate its significance for prediction of meat quality. The calibration temperature of pH-electrodes as well as the sample temperature is essential for pH measurements, as pH measurements are highly temperature-dependent. This is especially important when using pH measurement for prediction of meat quality or when different experiments are compared. We have used two calibration temperatures of 15 °C (normal) and 35 °C (modified) in the present investigation. Based on our findings, we therefore recommend a buffer and electrode temperature of 35 °C as a standard procedure for measuring pH early post mortem. As a minimum the pH should be presented along with the measuring and calibrating temperatures.     

The influence of dietary lipid source on quality characteristics of raw and processed chicken meat

The influence of dietary lipid source [animal fats (AF) and vegetable oils (VO)] on quality characteristics of raw chicken meat (breast, thigh and meat batter) and cooked breaded patties prepared using a conventional technology (CT; forming, battering, breading, frying and convection cooking) or innovative technology (IT; forming, pre-dusting, steam cooking, battering and frying) was evaluated. Overall, dietary lipid source did not influence the chemical composition of raw meat while it modified its colour (L*, a*, b*). With respect to AF, VO produced higher breast and thigh meat cooking losses as well as a lower moisture and higher protein content of cooked breaded patties. VO also determined an increase of polyunsaturated-to-saturated fatty acid ratio of both raw and processed meat. Despite the different fatty acid profiles, the oxidative status of lipids was not affected by dietary lipid source and was acceptable in both raw meat and cooked patties as indicated by peroxide and thiobarbituric acid reactive substance values. As for the processing technology, IT determined a higher moisture and lower lipid content of the cooked breaded patties. Moreover, lipolysis degree was slightly higher in the products coming from IT. Finally, patties from AF group were lighter and more yellow than products belonging to VO group whereas IT led to lighter, less red and more yellow patties in comparison to CT.     

P(y)-a parameter for meat quality

The P_y is a parameter which assesses the integrity of the cell membranes. It is a direct indicator for the volume fraction of cells surrounded by insulating cell membranes. The P_y has been shown to correlate well with meat quality parameters like the drip loss or pH. It is a useful parameter for the discrimination between normal suited meat and PSE meat. The measurement is instantaneous and nondestructive. Due to aging of meat, P_y depends on the time post mortem. It shows the highest significance between 4 and 24 h p.m.     

The bacterial quality of red meat and offal in Casablanca (Morocco)

The present study aimed to evaluate the bacteriological quality of beef (n = 52), lamb (n = 52) and beef offal (n = 52) marketed in Casablanca, Morocco. Meat and offal samples (n = 156), were collected randomly from butcheries, supermarkets, and slaughterhouses. Two sampling periods were considered, one during the hot season and the second one during the cold season. The samples were analyzed for the presence of the following bacteria: Escherichia coli, coagulase-positive Staphylococcus, Clostridium perfringens, Salmonella, and Listeria monocytogenes. Results indicated that counts of the aerobic plate count, and fecal coliforms were particularly high in all the samples analyzed. E. coli, coagulase-positive Staphylococcus and C. perfringens were detected in 37.8, 16, and 4.5% of the meat samples, respectively. Neither Salmonella nor L. monocytogenes were isolated from meat samples. Approximately 26.9% of beef, 34.6% of lamb and 28.8% of beef offal samples contained bacteria above the maximum limits established by the Moroccan regulatory standards for meat and meat products. Seasonality and the distribution location significantly (p < 0.05) affected bacterial populations: the hot season and butcheries appeared to be cases where the highest populations of bacteria in meat were observed. These high levels of microbiological contamination attest the poor hygienic quality of meat and offal, possibly due to uncontrolled processing, storage, and handling of these products.     

Bacteriological quality assurance (BQA) of mechanically deboned meat (MDM)

Adequacy of bacteriological quality assurance during the commercial production of mechanically deboned meat (MDM) was assessed. Lax standards of hygiene during production were observed, resulting in high numbers of Staphylococcus aureus, viz. 10⁴ to 10⁵ cfu g⁻¹, and severe contamination with Enterobacteriaceae: 10⁵ to 10⁶ cfu g⁻¹. These data indicate that measures of hygiene observed during boning of carcasses and during collection, storage and transport of bones or poultry parts should be markedly tightened, while conditions of refrigerated storage of raw materials and MDM should be improved. Use of bones of poor sensory quality (discoloration, abnormal smell) generally resulted in MDM of inferior bacteriological quality.

Phage typing, biotyping and assessment of enterotoxin production was carried out with 136 St. aureus cultures, isolates from mechanically deboned pork produced at one plant. Fifty-five per cent of the isolates was not typable, 28% was typable with human phages, 8% with bovine phages. The majority of the strains could not be explicitly assigned to any Meyer and/or Hájek and Mar álek types. Applying the simplified system of Devriese to eighteen strains isolated in our investigation, ten were found to belong to the poultry ecovar, one to the bovine ecovar, while seven strains were non-host specific. None of the isolates produced enterotoxins A–E.

Microbiological inspection of end products is recommended as part of an integrated quality assurance system. The following reference values for the final product (maximal colony counts to be expected under GMP conditions expressed as 95th percentile) were calculated: Pig MDM: log₁₀ mesophilic colony count 6·8 and log₁₀ cfu mesophilic Enterobacteriaceae g⁻¹ 4·8; Poultry MDM: log₁₀ mesophilic colony count 6·6 and log₁₀ cfu mesophilic Enterobacteriaceae g⁻¹ 4·7.     

The influence of breed,gender, and PSS (Halothane) genotype on meat quality,cooking loss,and palatability of pork

A total 851 swine of four breeds (Duroc, Hampshire, Landrace, and Yorkshire), three genders (barrows, gilts, and boars) and two PSS (halothane) genotypes (carriers and non-carriers of the halothane gene) were evaluated for meat quality, cooking, and palatability traits. Breed exerted a major influence on meat quality, cooking, and palatability traits. The most palatable meat was produced by Hampshires and the least desirable meat was produced by Yorkshires. Although juiciness was negatively correlated with cooking loss (r=−0.60), meat from Hampshires received the highest ratings for juiciness, despite sustaining the greatest cooking losses. Gender exerted minor influences on meat quality and palatability attributes, and no indication was obtained genders differed sufficiently in palatability to warrant discrimination based upon gender. Therefore, entire males can be utilized to capitalize on reported production advantages without influencing palatability, particularly if adequate means for screening boar taint are available for carcasses from heavier or more mature animals. Halothane genotype exerted substantial influence on meat quality traits and statistically significant but relatively minor influence on palatability traits. Carriers of the halothane gene produced meat which was of clearly inferior quality to the meat produced by non-carriers. Carriers of the halothane gene consistently produced a higher proportion of unacceptable chops than non-carriers, although differences were not statistically significant.     

Tenderisation of lamb meat: Effect of rapid postmortem temperature drop on muscle conditioning and aging

Lamb Longissimus dorsi muscles were excised from carcasses of 9-12 kg and 16-20 kg weight and brought to internal temperatures of either 0°C, 4°C, 10°C, 15°C, 20°C or 36°C within 3-4h post mortem. After rigor completion they were allowed to age at 4°C for 7 days. Sensory panel scores obtained on the first day of post-rigor aging showed that meat from heavier animals was tougher than that of lighter ones at any temperature. In all cases aging for 7 days had a marked tenderising effect which was similar at all studied temperatures, and greater in heavier animals. Tenderness was also dependent on the temperature at conditioning, as shortening caused by either high or low temperature resulted in meat toughening. The sole and surprising exception to this fact was, however, the high sensory scores obtained in 0°C experiments, even though shortening occurred as expected. In fact, a more intense proteolysis was evident in this case, which was already apparent on the first day of aging. The effect of a rapid drop of muscle temperature to 0°C on the fast and intense proteolysis, capable of even overcoming toughness due to cold shortening, was explained by the higher pH and the dramatic increase of the sarcoplasmic Ca(++) level induced early post mortem by chilling and which might result in the activation of calpain.