Spray chilling of lamb carcasses

Two spray-chilling treatments were developed to improve appearance and reduce weight loss during lamb chilling. Rates of cooling and weight loss and meat quality were compared to conventionally chilled carcasses.

The first treatment was an intermittent spray during the first 3 h of chilling. The second consisted of only two sprays at 2 h and 10 h post mortem. The conventional control was a two-stage process, with air at 10°C and 1 m/s up to 10 h post mortem, followed by air at 0°C and 1 m/s for a further 14 h.

Both treatments significantly reduced weight loss at 24 h post mortem compared to conventional, from 2·20% to 0·86% and 1·20%, respectively. During a further 4 days storage, the savings were maintained, with weight losses being 3·97%, 2·97% and 3·19%, respectively.

There were small (<1 h) but significantly reductions in the cooling times of spray-chilled loins and legs, attributed to sustained evaporative cooling of the continually wetted surfaces.

No effects on texture or drip loss and only slight effects on surface lean and fat colour were found. Variation in texture between animals within treatments was far greater than between treatments and could not be accounted for by variations in cooling rates.     

The ultra-rapid chilling of lamb carcasses

Experiments were carried out on the effects of chilling lamb carcasses very rapidly in a pre-rigor condition. The chilling regime which was finally used was to cool the carcasses at an ambient temperature of -20°C and an air speed of 1·5 m/s for 3·5 h. Examination of striploins from carcasses subjected to this chilling regime showed that, after 7 day's storage, the meat was as tender as that from carcasses which had been conventionally chilled at 4°C for 24 h There were significant reductions in weight loss as a result of ultra rapid chilling, compared to conventionally chilled carcasses. The reductions obtained after 24 h varied between 0·8 and 0·9%, depending on whether the carcasses were washed or unwashed.     

Hot water surface pasteurisation of lamb carcasses: microbial effects and cost-benefit considerations

Although hot water pasteurisation of carcasses is accepted as a general intervention in USA, this is not the case in Europe. The aims of this study were (i) to evaluate the microbiological effects of hot water pasteurisation of lamb carcasses, both after slaughtering and dressing and following subsequent chilling and storage; (ii) to discuss hot water pasteurisation from a public health and cost-benefit perspective; (iii) to discuss the benefits of hot water pasteurisation compared with use of separate meat processing streams for high-risk carcasses; (iv) to evaluate the use of recycled hot water in a hygienic context and in relation to EU regulations; and (v) to consider the technological and sensory aspects of hot water pasteurisation of lamb carcasses. Samples were collected from 420 naturally contaminated lamb carcasses, with 50% of the carcasses (n = 210) subject to hot water pasteurisation at 82 °C for 8 s immediately after slaughter. Surface swab samples from 4500 cm² areas on carcasses were collected at slaughter, after chilling for 24 h, and after chilling for five days. The microbial analyses included Escherichia coli, Enterobacteriaceae, Bacillus cereus, Clostridium perfringens and aerobic plate count (APC). A resuscitation step using Tryptone Soya Agar was included in the microbiological analyses. Hot water pasteurisation significantly reduced the levels of E. coli, Enterobacteriaceae, B. cereus and APC (all P < 0.001). E. coli colony forming unit (CFU) reduction was 99.5%, corresponding to a reduction of 1.85 log CFU per carcass. E. coli was isolated from 66% of control carcasses and from 26% of pasteurised carcasses. After 24 h storage, the reduction in E. coli was increased to 2.02 log, and after five days E. coli could not be isolated from the pasteurised carcasses. These results suggest that surface pasteurisation could be an important and efficient procedure (critical control point) for reducing generic E. coli and thereby shiga toxin-producing E. coli on carcasses, and thus the risk for disease among consumers. The recycled water had acceptable physical and chemical parameters and no spore-forming bacteria were detected. Although some carcass discolouration was observed, after 24 h the colour was acceptable. Our data provide relevant input for some of the data gaps regarding hot water pasteurisation and indicate that replacing the expensive system of separate processing of high-risk carcasses with hot water surface pasteurisation should be considered as a serious option.     

Microbial contamination occurring on lamb carcasses processed in the United States

Lamb carcasses (n = 5,042) were sampled from six major lamb packing facilities in the United States over 3 days during each of two visits (fall or winter, October through February; spring, March through June) in order to develop a microbiological baseline for the incidence (presence or absence) of Salmonella spp. and for populations of Escherichia coli after 24 h of chilling following slaughter. Samples also were analyzed for aerobic plate counts (APC) and total coliform counts (TCC). Additionally, incidence (presence or absence) of Campylobacter jejuni/coli on lamb carcasses (n = 2,226) was, determined during the slaughtering process and in the cooler. All samples were obtained by sponge-sampling the muscle-adipose tissue surface of the flank, breast, and leg of lamb carcasses (100 cm2 per site; 300 cm2 total). Incidence of Salmonella spp. in samples collected from chilled carcasses was 1.5% for both seasons combined, with 1.9% and 1.2% of fall or winter and spring samples being positive, respectively. Mean (log CFU/cm2) APC, TCC, and E. coli counts (ECC) on chilled lamb carcasses across both seasons were 4.42, 1.18, and 0.70, respectively. APC were lower (P < 0.05) in samples collected in the spring versus fall or winter, while TCC were higher in samples collected in the spring. There was no difference (P > 0.05) between ECC from samples collected in the spring versus winter. Only 7 out of 2,226 total samples (0.3%) tested positive for C. jejuni/coli, across all sampling sites. These results should be useful to the lamb industry and regulatory authorities as new regulatory requirements for meat inspection become effective.     

Characteristics of lamb carcasses of contrasting subjective muscularity

In order to compare characteristics of lamb carcasses with superior muscularity (the European E class) with carcasses that did not fit the E specification, 114 E carcasses were individually matched for weight and fatness class with 114 Non-E carcasses. The carcasses (mean WEIGHT = 17 kg) were processed under commercial conditions into six trimmed, boneless cuts of the leg and saddle (inside, outside, knuckle, rump, striploin and tenderloin) and two bone-in cuts (hind-shank and 7-rib rack). After adjustment for carcass weight, fatness (as assessed by fat depth C and tissue depth GR) and sex, the E-class group, relative to the Non-E group, had a 4.3% higher yield of leg and saddle cuts, a 14.2% higher leg muscularity index calculated from the weights of trimmed boneless cuts around the femur and femur length, a 13.6% higher muscle to bone ratio in the femur region, an 8.2% greater ‘eye’-muscle depth (B), and a 3.7% greater ‘eye’-muscle width (A) (all P < 0.001). All boneless cuts except the knuckle were heavier for the E group. Carcasses of female lambs had legs with higher muscle to bone ratios and a higher yield from the leg plus saddle (both P < 0.01), but the muscularity index was similar between sexes. It is concluded that although lamb carcasses subjectively selected as having higher muscularity will yield slightly more meat, this difference will be small compared with the greater muscle depth relative to bone length. The importance consumers attach to carcass or cut shape over and above any association with meat yield needs to be assessed.     

Use of electronic probes for classifying lamb carcasses

Three commercially available electronic lamb carcass grading probes (Hennessy Grading Probe, AUS-Meat Sheep Probe, Swedish FTC Lamb Probe) and one developmental probe (Ruakura GR lamb probe) were assessed for accuracy and suitability for use on-line on the lamb dressing chain for objectively classifying lamb carcasses. GR is the total tissue thickness over the 12th rib taken at a distance 11 cm from the mid-line, used to define fatness in lamb carcass grading in New Zealand. Probe measurements were compared with manually measured GR (sometimes used at present) and Toland probe measurements (total tissue depth between the ribs) for accuracy of predicting both GR on the right side of the carcass and also carcass water (indicating muscle) and fat content. Probes were tested on six occasions, each having approximately 50 lambs. All probes combined with carcass weight accounted for over 70% of the variation (R(2)) of GR right, with GR left accounting for 92% of the variation of GR right. Inclusion of a quadratic probe term was not quite as useful as inclusion of carcass weight for predicting GR right. The three commercial electronic probes individually when combined with carcass weight could account for 36-49% of the variation in the percentage of water and fat in the carcass, with the manual GR probe (right) on the chilled carcass accounting for 55% of the variation in water and 58% of the variation in fat percentages. Chilled carcass measurements are expected to give better results than readings on hot carcasses. The use of a quadratic probe coefficient instead of carcass weight with the probe readings gave similar accuracy of prediction of carcass composition. There was little difference between the two sides in the accuracy of prediction. Small differences were found between regressions relating probe readings to GR and composition for the different probing occasions. The electronic probe results from this trial are consistent with overseas results where probes are in use for objectively grading the carcasses of meat animals.     

Electrical stimulation of rabbit and lamb carcasses.

Electrical stimulation of rabbit and lamb carcasses at voltages of 250 V, pulsed at 15 Hz, resulted in a rapid immediate fall of pH and a sustained rate of fall 2–3 times greater than normal. The ATP level falls in step with the pH; at about pH 6.2, 50% of it has disappeared and at pH 5.7, more than 90%. In lamb carcasses rigor onset in the major muscles of fore-, hind-limbs and back occurs 4–5 h earlier than the normal 5–7 h and rigor is complete at least 4 h earlier. As a result, it is safe to cool or freeze stimulated lamb carcasses within 3 h of slaughter, compared with the need to delay at least 10 h with normal carcasses to ensure that cold- or thaw-contracture will not occur with subsequent toughening of the meat.     

不同温度热水处理对鲜切皇冠梨生理生化的影响

采用40、45、50℃三种不同温度热处理梨果实,然后进行切分,研究其在10℃贮藏过程中的生理生化变化.热处理明显抑制鲜切梨果实PPO、POD 活性,降低呼吸强度和乙烯生成量,保持鲜切梨果实的颜色、硬度和较高的CAT活性,延缓其生理生化变化,保持鲜切梨果实的品质,延长其货架期.     

Development of a quality classification system for lamb carcasses

A total of 1660 commercial lambs, with slaughter weights ≥ 32kg and having no more than two permanent incisors, were selected on the basis of age, weight, gender, and fatness to be representative of the Canadian market lamb population and utilized to develop a quality classification system for lamb carcasses. Based upon the findings obtained, lamb should be defined as carcasses from ovines weighing 32 kg live or more and with no more than two permanent incisors. Mutton should be defined as carcasses from ovines with more than two permanent incisors or carcasses from ovines that have lost their third temporary incisor. Milk-fed lamb should be defined as carcasses from ovines weighing less than 32kg live. Consequently, classification recommendations arising from the present study apply only to carcasses from ovines defined as lamb, according to the previous definitions. Thus, lamb carcasses so defined can be effectively segregated into three quality groups based upon expected consumer acceptance, utilizing simple, subjective evaluations of the breakjoints and ribs, as follows: Group 1 possessing very red and moist breakjoints and round, red ribs, Group 2 possessing slightly red to red breakjoints and oval shaped ribs, which are either slightly red or have traces of red colour, and Group 3 possessing white, dry breakjoints and flat, white ribs. Classification of lamb carcasses on this basis will allow compensation to producers based upon carcass merit, reflecting consumer acceptance. Although availability and consumer demand will ultimately determine price premiums and/or discounts, based upon present findings, Group 1 should contain 9% or less of the lamb carcasses being marketed and should receive a premium to compensate for a higher degree of consumer acceptance. Group 2 should contain 75% or more of the lamb carcasses being marketed and should receive prevailing market value. Group 3 should contain 15% or less of the lamb carcasses being marketed and should receive a discount to compensate for a lower degree of consumer acceptance.     

Effect of chilling applied to suckling lamb carcasses on hygienic,physicochemical and sensory meat quality

The effect of post mortem temperature treatment on suckling lamb carcass and meat quality was study. Conventional (2 °C for 24 h), ultra-rapid (− 20 °C for 3.5 h, 2 °C until 24 h) and slow chillings (12 °C for 7 h, 2 °C until 24 h) were compared. Total viable counts (TVC), weight losses, and pH and temperature falls were recorded on carcasses. Meat colour, water holding capacity (WHC), Warner-Bratzler shear force, sarcomere length and sensory analysis were evaluated in M. longissimus. Ultra-rapid treatment reduced TVC and weight losses. The pH decline was faster in slow chilled carcasses than in faster chilled carcasses. No significant differences were found for colour and WHC. Slow treatment carcasses showed significantly lower shear force and higher sarcomere length. In the sensory analysis, tasters also rated the early post mortem slow-treated meat as more tender, less fibrous and chewy. Therefore, delay chilling in suckling lamb carcasses made it possible to obtain meat with better organoleptic characteristics, without affecting weight loss or hygienic quality.     

Effect of chilling applied to suckling lamb carcasses on hygienic, physicochemical and sensory meat quality

The effect of post mortem temperature treatment on suckling lamb carcass and meat quality was study. Conventional (2°C for 24h), ultra-rapid (-20°C for 3.5h, 2°C until 24h) and slow chillings (12°C for 7h, 2°C until 24h) were compared. Total viable counts (TVC), weight losses, and pH and temperature falls were recorded on carcasses. Meat colour, water holding capacity (WHC), Warner-Bratzler shear force, sarcomere length and sensory analysis were evaluated in M. longissimus. Ultra-rapid treatment reduced TVC and weight losses. The pH decline was faster in slow chilled carcasses than in faster chilled carcasses. No significant differences were found for colour and WHC. Slow treatment carcasses showed significantly lower shear force and higher sarcomere length. In the sensory analysis, tasters also rated the early post mortem slow-treated meat as more tender, less fibrous and chewy. Therefore, delay chilling in suckling lamb carcasses made it possible to obtain meat with better organoleptic characteristics, without affecting weight loss or hygienic quality.     

Blanching of potato with superheated steam and hot water spray

A heating system using superheated steam (SHS) and a spray of hot water microdroplets (WMD) has been developed to prevent drying of food material during SHS heating. Blanching of potato was examined with the new system (SHS + WMD), SHS, and hot water. In SHS + WMD heating, a mixture of SHS at 115 °C, 2.46 kg/h flow rate and hot water at 0.54 kg/h was used. In SHS heating, the flow rate and temperature of the SHS were 3.0 kg/h and 115 °C. The temperature of the hot water was approximately 100 °C. Potato tissue processed with hot water became soft and brittle, and its brightness and chromatic quality decreased due to absorption of water and dissolution of solid content to the water. In contrast, these quality changes were prevented in SHS + WMD and SHS heating. Heat transfer by SHS was enhanced by the presence of WMD, presumably because the water layer formed on the potato by condensation of SHS was stirred and its thermal resistance was decreased by collisions of WMD with the potato. The mass of potato processed with SHS + WMD was almost constant during the heating, while the relative mass of potato processed with SHS decreased to 96.7% with 16 min of heating.     

Effect of water immersion on the microtopography of the skin of chicken carcasses

Water-immersion cleaning and chilling of poultry carcasses caused the skin to swell and exposed deep channels and crevices in the skin surface as a result of water uptake. These changes were demonstrated by electron microscopy and were shown to be dependent on the time of immersion and the temperature of the water. Addition of sodium chloride to the immersion medium and manipulation of the medium pH did not markedly affect or prevent these changes. The implications of these changes for microbial contamination during water-immersion chilling are discussed.     

Effects of shearing and fleece cleanliness on microbiological contamination of lamb carcasses

The meat industry in Norway has developed national guidelines for Good Hygiene Practices for slaughtering and skinning, based on categorisation of animals. These include shearing sheep and lambs in the abattoirs immediately before slaughter. The aim of this study was to investigate microbiological carcass contamination associated with: (i) different shearing regimes; (ii) fleece cleanliness; and (iii) the slaughter process. In addition, the efficacy of the national guidelines in reducing microbial contamination was evaluated. A total of 280 swab samples were collected from the brisket areas (100 cm(2)) of 140 naturally contaminated lamb carcasses in a commercial abattoir. Half the samples were collected at skinning of brisket areas at the start of the slaughter-line and half of them were collected at the end of slaughter-line, just before chilling. The lambs were divided into four groups (n=35) according to the duration of the period between shearing and slaughter: (i) 0 days (shorn at the abattoir immediately before slaughter); (ii) three days; (iii) seven days; and (iv) not shorn. Mean log colony forming units (CFU) per 100 cm(2) at skinning were 5.78 and 6.95 for aerobic plate count (APC) (P<0.05), 1.65 and 2.78 for Escherichia coli (P<0.05) for shorn and unshorn lambs, respectively. For shorn lambs, divided according to the period between shearing and slaughter, the mean log CFU per 100 cm(2) were 5.45, 5.75, 6.12 (APC) and 1.77, 1.46, 1.71 (E. coli) for the 0-days, 3-days and 7-days groups, respectively (P<0.05 for the difference between 0- and 7-days groups in APC results). A four-category scale (0-3) was used for assessing fleece cleanliness before skinning. Visually clean lambs (score '0') had lower levels of APC on the carcass surfaces than those categorised as dirty (score '2-3') (P<0.05). The carcasses at the end of the slaughter-line had lower levels of APC than they had at skinning. However, the statistical significant reduction of E. coli on carcass surfaces at skinning point for shorn lambs, were impaired and no longer significantly different from the unshorn group at the end of the slaughter-line. The increased E. coli level at the end of the slaughter-line might be explained by weaknesses related to slaughter hygiene in particular suboptimal evisceration in the abattoir which was used as a basis for our trial, and thus the national guidelines concerning shearing had not the fully intended effect on reducing microbial carcass contamination.     

Low voltage electrical stimulation of lamb carcasses: effects on meat quality

The effects of an early post mortem low voltage electrical stimulation (28 V, 60 Hz) on biochemical changes and on final tenderness in muscles Longissimus thoracis et lumborum and Semimembranosus from lamb carcasses were studied. It was shown that electrical stimulation accelerated the glycolytic process resulting in a significant fall in pH during the first 6 h post mortem in both muscles examined and in a significant reduction in adenosine triphosphate (ATP) content in muscle Longissimus thoracis et lumborum. The effect of electrical stimulation on tenderness was recorded by measuring shear force values 2 and 7 days post mortem. Tenderness was significantly improved by electrical stimulation for the Longissimus thoracis et lumborum both at 2 and at 7 days post mortem, while for Semimembranosus electrical stimulation significantly increased tenderness just at 7 days post mortem.     

家庭滚筒洗衣机洗涤温度对机织物外观平整性的影响

家庭滚筒洗衣机洗涤衣物时,水、洗涤温度的共同作用对织物外观平整性影响显著,合适的温度设定有助于洗衣机的参数优化。文中选取5种常见白色普通整理的机织物,在滚筒洗衣机温度分别为室温20、30、45、60、75 ℃条件下洗涤,测试其洗后外观平整度、洗涤前后弯曲刚度及剪切刚度等指标。研究发现,洗涤温度较低时,机织物外观平整度较好;洗涤温度增大时,机织物平整度降低,洗后弯曲刚度及剪切刚度减小。纯棉织物20℃与75℃洗后的平整度最大差值为1.6级;涤纶织物20℃与75℃洗后的平整度最大差值为3.8级,洗涤温度对涤纶织物平整度的影响较棉织物大。研究成果可为机织物家庭滚筒洗涤温度的设置提供依据。     

Mineral composition of lamb carcasses from the United States and New Zealand

The mineral composition-iron (Fe), zinc (Zn), copper (Cu), calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), fluoride (F), and phosphorus (P) (New Zealand lamb only)-of lean tissue from lamb retail cuts was studied. Twenty-four US lamb carcasses of different ages (5 to 11 months), geographical regions (Texas, Colorado and Montana) and USDA quality grades (Prime and Choice) and 27 New Zealand lamb carcasses from three weight groups (11 to 12·5 kg, 13 to 14·5 kg, and 16·5 to 18 kg), age rangining from 7 to 8 months, were selected for use in this study. Mineral concentrations were influenced more by retail cut and age than by quality grade or weigth group. Foreshank and shoulder cuts from both the US and New Zealand group consistently had the highest (P < 0·05) Zn content among the cuts. The K content of the muscle in US lambs increased as age increased, while the level of Ca and Zn in New Zealand lambs decreased as carcass weight increased. Except for Ca, the mineral concentrations of the lean tissue from US lambs were higher than the New Zealand lambs, although the differences were not always significant. US lambs had approximately 20%, 30% and 37% more Fe, Zn and Mg, respectively, but 27% less Ca than lean tissue from the New Zealand lambs.     

Composition and sensory evaluation of lamb carcasses used for the traditional Mexican lamb dish, "barbacoa"

The objective of this study was to determine the differences in carcass characteristics and sensory attributes of "barbacoa" (a traditional Mexican lamb dish), both of imported (New Zealand) and domestic lambs in Mexico. A total of 28 carcasses from Pelibuey, Pelibuey×Suffolk and imported lambs were used. Carcass composition was determined by dissection of primal cuts from the left half of each carcass. The "barbacoa" from each ovine group was prepared separately in order to perform a consumer sensory evaluation for aroma, taste and tenderness. Results showed that imported lambs had larger carcasses, greater fatness and had better conformation than national lambs. There was no difference between groups in terms of lean tissue percentage (muscle+others) or in total carcass fat. The sensory attributes of the "barbacoa" did not differ among breeds. Pelibuey lambs (rustic, prolific and adaptable to the wide variety of Mexican climates) show competitive production performance in relation to specialized breeds.     

Importance of airborne contamination during dressing of beef and lamb carcasses

Carcasses along slaughter lines were exposed to normal slaughterhouse air or ultraclean air provided from a unit fitted with a HEPA filter. In cattle slaughterhouses, aerobic viable counts were measured by sponging the brisket at the end of the line to determine whether the slaughterhouse air had led to contamination of the carcasses. Furthermore, a replica cattle carcass with settle plates attached was exposed to similar conditions. The greatest contamination of the plates occurred at the hide puller (P < 0.01). The use of ultraclean air reduced the deposition of organisms onto settle plates (P < 0.01). The airborne route contributed to contamination in cattle slaughterhouses, but other vectors were more important. Further study of contamination of the brisket, at the time that it was first exposed, showed that knives transfer contamination from the hide. The use of ultraclean air at this position showed that the airborne route was a contributor to contamination (P < 0.1), but it was not the greatest vector. In lamb slaughterhouses, the highest counts on settle plates were found at the fleece puller (P < 0.05). The highest counts on the lamb carcasses were found on the brisket exposed from the start of the line to just after the fleece puller (P < 0.05). There was no clear relationship between the measured counts and the concentration of organisms in the air, indicating that the airborne route in lamb slaughterhouses contributes less to carcass contamination than do the surface contacts.