Effects of exogenous porcine somatotropin (pST) administration on pork meat quality

Two experiments were conducted on Large White pigs in order to assess the effect of porcine somatotropin (pST) administration upon meat quality criteria. No clear trend was observed concerning pH1 or pH2 measurements in Longissimus dorsi (LD), Adductor femoris (AF) and Semi spinalis (SS) muscles or drip loss in LD. Cooking loss in LD was not affected by pST treatment. Intramuscular lipid content was decreased by pST in LD and AF. Only non-polar lipids were affected by pST, whereas polar lipid content was similar in control and pST treated pigs. Percentage polyunsaturated fatty acids was significantly increased by pST in backfat and LD lipids, whereas no clear trend was observed concerning fatty acid composition of AF lipids.     

Effects of growth rate, sex and slaughter weight on fat characteristics of pork bellies

A total of 119 Duroc × (Landrace × Yorkshire) commercial pigs were used to investigate the effect of growth rate (fast vs slow), sex (barrows vs gilts) and slaughter liveweight (107, 115 and 125 kg) on the fat characteristics of bellies. Backfat thickness increased with weight (P < 0.01). Fat firmness score was only affected by sex (P < 0.05), with gilts showing softer bellies than barrows. Fat from gilts and slow growing pigs showed a lower proportion of saturated fatty acids (SFA; P < 0.001 and P < 0.01, respectively), a higher proportion of linoleic fatty acid (C18:2 n-6; P < 0.01), a higher proportion of total polyunsaturated fatty acids (PUFA; P < 0.001 and P < 0.01, respectively), and an increased iodine value (P < 0.001). Consequently, the fat from these bellies had higher PUFA:SFA ratios (P < 0.001) and n-6:n-3 ratios (P < 0.01 and P < 0.001, respectively) than that from the bellies of barrows and fast growing pigs. The belly fat from barrows and fast growing pigs had higher stearic fatty acid (C18:0; P < 0.01) and SFA proportions (P < 0.001 and P < 0.01, respectively) than that from gilts and slow growing pigs. The belly fat from gilts and slow growing pigs would better meet the health requirements of consumers, but it is more prone to rancidity during storage leading to a potentially reduced bacon shelf-life.     

The interaction between ractopamine supplementation, porcine somatotropin and moisture infusion on pork quality

Ninety six crossbred pigs were used in a 4×2×2 experiment to determine the influence of management strategy, moisture infusion and ageing on pork quality. The treatments were i) management strategy (MS) during the last 28days pre-slaughter (Control: conventional diet; Ractopamine (Rac): porcine somatotropin (pST); and combined (Rac+pST): Rac for 28days and pST for the final 14days), ii) moisture infusion (MI) (0% and 10%) and iii) ageing period (24h and 7days). L* was decreased by pST and Rac+pST, followed by Rac and then the Control MS. Shear force was increased by Rac and Rac+pST but not by either pST or the Control MS. MI decreased L* and shear force while ageing for 7days increased L* and yellowness, and decreased drip loss and WB shear force. MI or ageing for 7days improved sensory pork quality. The results from this experiment indicated that as expected MI and ageing can be used to improve pork quality.     

添加猪瘦肉对牛肉丸品质的影响

针对牛肉丸口感欠佳的问题,在传统肉丸加工的基础上,通过添加猪瘦肉,改善牛肉丸口感。研究了猪瘦肉不同添加量对牛肉丸保水性、蒸煮损失率、乳化性、乳化稳定性、凝胶特性及感官的影响。结果表明,当牛肉与猪肉的质量比为8∶2和7∶3时,肉糜的失水率及蒸煮损失率较低,乳化能力及乳化稳定性最佳;同时肉丸感官评分最高,且质构适宜。因此牛肉丸中添加适量猪瘦肉可以使产品更爽口,味道更鲜美。     

Effects of exogenous porcine somatotropin on the development of fat cells and fatty acid composition in backfat of live finishing pigs

The effects of long-term application of recombinant porcine somatotropin (pST) to Landrace pigs on the development of backfat thickness, fat cells and fatty acid composition were investigated from about the 116th to the 186th day of life. Biopsy samples from the backfat of 56 castrates were taken at the beginning of treatment and after 5 and 10 weeks. The daily injection of 2 or 4 mg of pST induced a considerable decrease in backfat growth compared to untreated controls. This was attributed to a decreased size (about 18–20%) and number (about 13–25%) of fat cells. The higher dose of 4 mg pST/day induced a greater restriction of fat growth. This was obviously based on differences in fat cell number. Furthermore, pST treatment delayed the normal decrease of unsaturated fatty acids (C 18:2; C 18:3) during the period of growth examined. Therefore, the percentages of unsaturated fatty acids increased, indicating changes in fat cell metabolism of pST treated pigs.     

Effects of pork collagen on thermal and viscoelastic properties of purified porcine myofibrillar protein gels

The objectives of this study were to examine the thermal, water-binding and viscoelastic properties of mixed protein systems containing purified myofibrils from porcine semimembranosus (MP) and pork collagen (PC) during gelation and subsequent cooling. MP:PC mixtures (100:0, 90:10, 80:20, 70:30, 60:40, 50:50) normalized to 4% protein were evaluated. No significant differences in thermal characteristics of these mixtures could be detected using differential scanning calorimetry. A primary peak was observed near 66?°C. Using small-strain oscillatory testing, the rheological properties during gelling and cooling were quantified. Storage modulus (G') increased upon heating for all treatments, but the rate of gel firming and the G' value at 85?°C were significantly lower (P<0.05) as PC was added to the mixed protein system. Upon cooling, gels revealed a significantly lower (P<0.05) rate of gel firming and significantly lower (P<0.05) G' value at 5?°C in samples with 20% inclusion of PC and higher. Addition of PC yielded a significant linear (R(2)=0.65; P<0.01) increase in the water-holding capacity (WHC) of the gels, indicating that the matrix formed in MP:PC gels had a greater ability to entrap water than that of the control MP gels. The inclusion of 10% PC resulted in gels with significantly higher (P<0.05) WHC and similar firmness when compared with gels comprised of MP as the only protein source.     

Effects of administration of bovine somatotropin on milk yield and composition

Thirty-two Holstein cows were assigned to four treatment groups in a continuous lactation trial to evaluate effects of daily subcutaneous injections of 0 (A), 5.15 (B), 10.3 (C), and 20.6 mg (D) of recombinantly derived bovine somatotropin monomer. Responses were milk yield and composition, component yields, net energy intake, body weight, and somatic cell counts. Treatments began in fall, 28 to 35 d postpartum, and continued for 266 d. Base ration was corn silage and concentrate. Least squares means of milk and constituent yields and gross efficiency of milk production differed among treatments, but percentage fat and protein, energy intake, body weights, and somatic cell counts did not. Least squares means of 3.5% FCM were 21.3 (A), 25.0 (B), 26.2 (C), and 28.5 kg/d (D); fat and protein yields showed similar response to treatment. Milk yields adjusted for pretreatment yields were 21.1 (A), 25.5 (B), 26.5 (C), and 29.3 kg/d (D). Orthogonal contrasts showed lower milk and constituent yields and net energy intake for control (A) than for hormone-injected cows (B, C, D), but no differences were detected between treatments B, C, and D. Gross efficiency of production (3.5% FCM/feed net energy intake) was greater for hormone-injected cows.     

Effects of processing parameters on immersion vacuum cooling time and physico-chemical properties of pork hams

The effects of agitation (1002 rpm), different pressure reduction rates (60 and 100 mbar/min), as well as employing cold water with different initial temperatures (IWT: 7 and 20 °C) on immersion vacuum cooling (IVC) of cooked pork hams were experimentally investigated. Final pork ham core temperature, cooling time, cooling loss, texture properties, colour and chemical composition were evaluated. The application for the first time of agitation during IVC substantially reduced the cooling time (47.39%) to 4.6 °C, compared to IVC without agitation. For the different pressure drop rates, there was a trend that shorter IVC cooling times were achieved with lower cooling rate, although results were not statistically significant (P > 0.05). For both IWTs tested, the same trend was observed: shorter cooling time and lower cooling loss were obtained under lower linear pressure drop rate of 60 mbar/min (not statistically significant, P > 0.05). Compared to the reference cooling method (air blast cooling), IVC achieved higher cooling rates and better meat quality.     

Influence of dietary oils and protein level on pork quality. 2. Effects on properties of fat and processing characteristics of bacon and frankfurter-style sausages

Palm kernel oil (PKO) and palm oil (PO) are used in tropical countries as cheaper substitutes for conventional feed sources such as soya bean oil (SBO) but little is known about their effects on meat quality. This study, therefore, evaluated the effects of these three dietary oils on the fatty acid composition (FA) of pork fat and the qualities of belly bacon and frankfurter sausage. The 3×2 factorial design also included high and low dietary protein. Total cooking loss, water loss and fat losses were determined in frankfurter sausages at chopping temperatures from 2 to 24°C. PKO resulted in a poor P:S ratio (0.34) and a relatively hard fat (slip point 32.8°C), but resulted in bacon with a higher tensile cohesive force and more high quality slices, judged subjectively. PO had a fatty acid composition closer to the SBO control, a better P:S ratio than PKO (0.48) and softer fat. There was a trend for total cooking losses and fat losses to be higher in PKO compared with PO and SBO at all chopping temperatures, suggesting that the firmest, most saturated fat (PKO) was least suitable for frankfurter production. The low protein diet increased the concentration of saturated fatty acids and increased fat firmness but its effect on fatty acid composition and other properties were less marked than those of oil type.     

Modelling the yield and texture of comminuted pork products using color and temperature. Effect of fat/lean ratio and starch

Practices to control the processing of finely comminuted meat products are proposed. The objective was to test the practical value of both temperature and light reflection measurements made during emulsification as potential indicators of cooking losses and resulting gel texture in pork sausages emulsified within a wide range of temperatures and starch and fat levels. Prior to cooking, pork batters were chopped for different times to ensure final emulsion temperatures ranging from 5 to 50°C. The effects of the fat/lean ratio (0.25 and 0.67) and starch addition (0.8 and 3.2% w:w) on temperature and optical reflection were also investigated. The chopping increased the temperature and decreased the light reflection of fresh meat emulsion. There was no relevant loss of emulsifying capacity at emulsion temperature below 30°C and lightness values over 70 CIE units. The losses and textural parameters of cooked emulsions could be predicted by means of non-linear regression equations based on the temperature and color of the raw emulsion. The determination coefficients obtained ranged from 0.89 to 0.99. The prediction models needed to be fitted to each batter formulation, especially in the presence of reduced levels of gelation agents (meat protein and starch). Lightness was a better predictor than chromaticity, since it decreased constantly with chopping in the range of final emulsion temperatures studied (5-50°C). This confirms previous studies that lightness could be used for monitoring emulsion stability in meat batters.     

Effects of RN genotype and silage feed on fat content and fatty acid composition of fresh and cooked pork loin

This study aimed to establish effects of RN genotype and feed (red clover silage) on intra muscular fat content (IMF) and fatty acid composition (FA) of fresh and cooked pork loin (M. longissimus dorsi). Raw loins from silage-fed pigs compared with those from conventionally fed pigs had lower IMF, lower relative levels (rel.%) of saturated (SAFA) and monounsaturated (MUFA) fatty acids, and higher rel.% of polyunsaturated fatty acids (PUFA, ω6, ω3). Cooked loins, from silage-fed pigs compared with those of conventionally fed pigs, had higher rel.% of ω3, and lower ω6/ω3 ratios. IMF and cooking influenced FA concentrations in a pork portion. The differences in concentrations of SAFA, MUFA, PUFA and ω6 between raw loins of silage-fed pigs and conventionally fed pigs did not remain in cooked loins. The ω6/ω3 ratio, however, remained low, and thus more beneficial in loins from silage-fed pigs after cooking.     

不同盐浓度下磷脂含量对猪肉糜凝胶特性的影响

探究不同盐浓度(质量分数1. 5%～3. 5%)下磷脂含量(质量分数0. 2%～0. 6%)对猪肉糜凝胶特性的影响。以猪里脊肉为原料,在不同盐浓度下研究不同磷脂含量对肉糜的蒸煮得率、保水性、质构、色差、体外消化率的影响。在同等盐浓度下0. 4%磷脂含量肉糜凝胶有最高的蒸煮得率、保水性和弹性以及较低的硬度和咀嚼性,且有最高的体外消化率;相对于0. 2%磷脂含量组,0. 4%～0. 6%磷脂含量组肉糜在高盐浓度(3. 5%)下,蒸煮得率、保水性、硬度、弹性以及G'值等指标并未出现明显下降;(硫代巴比妥酸反应物,TBARS)和蛋白质氧化分析结果显示,磷脂的添加可以抑制肌原纤维蛋白氧化,但体系中脂肪氧化程度增加。0. 4%的磷脂含量肉糜凝胶特性最优;磷脂与蛋白质结合后抑制了蛋白质的氧化。实验结果可为不同磷脂含量的肉类加工适性提供理论参考。     

不同处理条件对猪肉匀浆物凝胶特性的影响

采用二次通用旋转实验设计,研究pH、NaCl浓度和加热温度对猪后腿肉匀浆物的蛋白质浓度及其热诱导凝胶特性的影响。结果表明,匀浆物的蛋白质浓度随着pH和NaCl浓度的增大而增大。pH和NaCl浓度对凝胶脱水率、保水性和凝胶强度的影响存在明显的交互作用,随着pH和NaCl浓度的升高凝胶的脱水率降低,随着加热温度的升高凝胶的脱水率增加。在一定范围内,凝胶的保水性与pH、NaCl浓度和加热温度呈正相关。在不同加热温度下,pH和NaCl浓度对凝胶强度的影响趋势基本一致。进行整体优化计算得到猪后腿肉匀浆物形成凝胶的最佳条件是:pH为6.33、NaCl浓度为0.67mol/L、加热温度为75℃。     

Effects of catechin on the phenolic content and antioxidant properties of low‐fat cheese

The effect of (+)‐catechin on total phenolic content (TPC) and antioxidant properties in low‐fat hard cheese were examined over a 90‐day ripening period at 8 °C. Antioxidant activity (AA) in cheese was measured by ferric reducing antioxidant power, oxygen radical absorbance capacity (ORAC) and 2,2‐diphenyl‐1‐picrylhydrazyl assays and compared with TPC. Catechin retention coefficients in cheese curds were in the range of 0.63–0.75 and decreased the pH of cheese without affecting protein, fat or moisture content. Both TPC and AA increased during the 90‐day ripening period. Oxygen radical absorbance capacity was the most suitable technique for evaluating AA in cheese due to the high correlation with TPC and suitability in both lipophilic and hydrophilic systems.     

Effects of chemical interesterification on solid fat content and slip melting point of fat/oil blends

Fat/oil blends, formulated by mixing fully hydrogenated palm oil stearin or palm oil stearin with vegetable oils (canola oil and cottonseed oil) in different ratios from 30:70 to 70:30 (w/w %), were subjected to chemical interesterification reactions on a laboratory scale. Fatty acid (FA) composition, iodine value, slip melting point (SMP) and solid fat content (SFC) of the starting blends were analysed and compared with those of the interesterified blends. SMPs of interesterified blends were decreased compared to starting blends because of extensive rearrangement of FAs among triacylglycerols. These changes in SMP were reflected in the SFCs of the blends after the interesterification. SFCs of the interesterified blends also decreased with respect to the starting blends, and the interesterified products were softer than starting blends. These interesterified blends can be used as an alternative to partial hydrogenation to produce a plastic fat phase that is suitable for the manufacture of margarines, shortenings and confectionary fats.     

微波处理对卤制猪肉货架期及其品质的影响

以卤制猪肉贮藏过程中水溶性氮(water soluble nitrogen,WSN)、pH值、硫代巴比妥酸(thiobarbituric acid,TBA)、挥发性盐基氮(total volatile basic nitrogen,TVB-N)、菌落总数和感官评价为指标,与高温高压处理作对比,研究不同微波处理时间(微波时间为10、15、20、25 s,微波功率800 W)对卤制猪肉(3 cm×3 cm×0.5 cm)货架期及其品质的影响。结果表明,微波处理和高温高压处理均能有效抑制卤制猪肉pH值、TBA值、TVB-N含量和菌落总数上升,其中高温高压处理组、微波20 s和25 s处理组效果较好,其货架期均在30 d以上。微波20 s和25 s处理组还能较好地抑制卤制猪肉WSN含量上升,而高温高压处理组的WSN含量较高,说明高温高压处理组卤制猪肉蛋白质降解情况较严重。微波20 s处理组感官品质保持最好,而高温高压处理组感官品质保持最差。经综合评定,微波20 s处理能有效延长卤制猪肉货架期的同时最大限度保持其品质。     

Prediction of lean meat content in pork carcasses using the Hennessy Grading Probe and the Fat-O-Meater in Argentina

Rapid evolution of pork production in Argentina requires new calibrations for predicting carcass lean meat percentage with the Fat-O-Meater (FOM) and Hennessy Grading Probe (HGP), first adopted in 1995. The second objective was to unify the lean percentage units with those applied by the European Union. Carcasses of 59 gilts and 56 barrows from different environments and breeds were tested. Carcass weights were from 65 to 117kg, and lean content was from 38% to 62%. Predicting lean content by multiple regression equations, the coefficients of determination R(2) were 0.801 and 0.794 for the FOM and HGP equations, and the residual standard deviations (RSD) were 2.40% and 2.45%, respectively. Both instruments had the same precision and were accurate enough to be adopted in national carcass grading classification. Hot carcass weight was not selected as a significant variable. The same prediction equations could be used for gilts and barrows. Quadratic terms did not improve predictions.     

微波间歇处理对卤制猪肉保鲜效果的影响

以贮藏过程中水分含量、pH值、挥发性盐基氮(total volatile basic nitrogen,TVB-N)、硫代巴比妥酸(thiobarbituric acid,TBA)、菌落总数以及感官评定为指标,研究微波功率密度为16 W/g,微波间歇比(微波工作期间微波打开时间与关闭时间的比值)为20 s-on/60 s-off时,不同微波间歇次数(0、1、2)对卤制猪肉保鲜效果的影响。结果表明,微波间歇次数越多对卤制猪肉贮藏过程中TVB-N含量和菌落总数上升的抑制效果越好,但卤制猪肉感官品质越差。同时,微波间歇次数过多,卤制猪肉TBA值、pH值会明显增大,水分含量会明显降低。基于所有评价指标,微波间歇1次处理能较好地抑制微生物生长的同时品质保持较好。     

Contribution of lean,fat, muscle color and degree of doneness to pork and beef species flavor

Flavor is an important contributor to consumer acceptability of meat, our objective was to characterize the impact of species-specific fat/lean sources, fat level, degree of doneness and muscle color are on pork and beef flavor. Three separate experiments were conducted. Patties were formulated differently for each experiment in order to evaluate the desired variables. Experiment. 1: Flavor from combination patties (same species lean/fat or combination of species lean/fat) was not impacted by degree of doneness (66 °C vs. 71 °C). Beef flavor was highest in samples made with beef lean, regardless of species fat type. Pork flavor was highest in samples made with pork lean and had higher flavor intensity scores. Experiment. 2: Beef flavor was not increased in all-beef patties formulated with higher fat levels. Pork patties formulated with higher fat content increased pork flavor. Experiment. 3: All-beef and all-pork patties formulated with light or dark lean did not impact flavor in either species.     

Effect of a prolonged-release formulation of N-methionyl bovine somatotropin (sometribove) on milk fat.

Nine Holstein cows were injected bi-weekly with a prolonged-release formulation of N-methionyl bST, and 9 cows were injected with excipient. Intramuscular injections began at 60 +/- 3 d postpartum and continued at 14-d intervals for the full lactation. Administration of bST increased production of milk, total fat, and all milk fat components measured. Average fatty acid composition of milk fat was not influenced by bST treatment. Stage of lactation had a large influence on production and percentage of individual fatty acids in milk fat from both bST-treated and control cows. The stage of lactation impact on the fatty acid composition of milk fat reflected changes in the relative contributions of body fat mobilization and de novo synthesis of milk fat components in response to changes in energy balance. Initiation of bST treatment caused some transient changes in milk fatty acid composition that were related to energy balance. These changes were small compared with the normal changes because of stage of lactation in all cows. Phospholipid and cholesterol content of milk also changed with stage of lactation but were not influenced by bST treatment. Melting properties of milk fat were influenced greatly by stage of lactation. Bovine somatotropin did not cause any changes in composition or physical properties of milk fat that were outside the range of normal variation.