微波解冻猪里脊肉过程的优化设计研究 Key words:

猪肉在我国是最重要的肉类之一,而为了储存更长时间,通常采用冷冻的方式保存。因此,在进一步加工之前就需要经过解冻这一过程,传统的解冻方式耗时长,严重制约了生产效率。微波加热作为一种常用的加热方式,与传统加热方式相比,具有加热速度快、省时节能等突出优点。本文利用家用变频微波炉对冷冻猪里脊肉块进行解冻处理,对解冻程序进行了优化设计,并与微波炉自带的解冻程序进行了对比研究,对肉汁渗出率、色泽以及质构特性进行分析。结果表明：两种优化程序的解冻效果要优于微波炉自的解冻程序,样品能基本解冻完全,肉汁渗出率较低,能较好维持鲜肉的颜色,经过优化后的微波解冻猪里脊肉温差更小,质构特性更佳,同时也缩短了解冻时间。     

Endogenous Factors Affecting Oxidative Stability of Beef Loin, Pork Loin, and Chicken Breast and Thigh Meats

ABSTRACT:  The susceptibility of meats from different animal species (chicken breast [CB] and thigh [CT], pork [PL], and beef [BL]) to lipid oxidation was studied. The amounts of TBARS in raw PL, CB, and CT did not change during a 7-d storage period. TBARS values of raw BL, however, significantly increased during 7-d storage because of high heme iron content, high lipoxygenase-like activities, and low 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activities. Ferric ion reducing capacities (FRC) were detected in all raw meats, but their characteristics were different: storage-unstable in CB and CT and storage-stable in PL and BL. Ferric ion reducing capacities in raw CB and CT was higher than those of PL and BL, and could be related to their high oxidative stability. The TBARS values of cooked meat increased significantly with storage. The rates of TBARS increase in cooked CT and BL were significantly higher than those of cooked CB and PL after a 7-d storage. Nonheme iron content in cooked BL was higher than other meats and increased significantly after 7 d. Cooked BL had a higher amount of heat-stable FRC, which acted as a prooxidant in the presence of high free ionic irons, than other meats. Therefore, high heat-stable FRC and increased nonheme iron content in cooked BL were responsible for its high susceptibility to lipid oxidation. Despite relatively low nonheme iron and heat-stable FRC levels, cooked CT showed similar levels of TBARS to cooked BL after a 7-d storage because of its high PUFA content.     

Consumer Discrimination of Rancidity in Pork Loin Chops and Pork Sausages

ABSTRACT: To determine if consumers could discriminate samples differing in rancidity, 2 experiments were conducted with freezer-stored pork loin chops (M. longissimus dorsi ) and sausages made from pigs fed diets varying in fatty acid composition. Samples were categorized as "normal" and "rancid" using Principal Component Analysis of data from trained sensory panel evaluations. These samples were presented to 2 consumer panels (n = 206 and n = 213). Rancidity did influence consumer preference. Consumers were able to discriminate between "normal" and "rancid" sausage, and preferred "normal." No differences ( P > 0.05) in preference or flavor were detected between the chop groups.     

Effects of Weak Oscillating Magnetic Fields on the Freezing of Pork Loin

A number of novel freezing systems have been developed that claim to improve the quality of frozen foods by enhancing supercooling in the food prior to ice nucleation and consequently controlling ice crystal formation. One of these is the Cells Alive System (CAS) produced by ABI of Japan, which applies oscillating magnetic fields (OMF) during freezing. This study was carried out to investigate what effect applying OMF (0.04 to 0.53 mT) during freezing had on the freezing characteristics of pork loin samples when compared to freezing under the same conditions without OMF. Overall, the results of this study clearly indicate that freezing under the OMF conditions used in these experiments had no significant effect on the freezing characteristics of pork, in comparison with freezing under the same conditions without OMF.     

Macro and Micro Minerals from Selected Muscles of Pork

Ten individual muscles (Semimembranosus, Semitendinosus, Biceps femorus, Gluteus medius, Longissimusu muscle, Psoas major, Serratus ventralis, Supraspinatus, Infraspinatus, and Triceps brachii) from 10 pork carcasses were removed and analyzed for selected minerals. Individual muscles contained relatively large quantities (mg/100g) of K, Na, P and Mg with smaller amounts of Ca, Cu, Fe, Mn, and Zn but varied between muscles with differences of one- to twofold. Semimembranosus had lesser amounts of Ca, Cu, Fe, and Mn than any other muscle studied. In general, the mineral content of leg, loin, and shoulder were different. The shoulder muscles had a greater quantity of Fe and Zn present in their muscles than leg or loin.     

Characterization of the Residual Pink Color in Cooked Turkey Breast and Pork Loin

The residual redness was characterized in well cooked meat from turkey breast and pork loin. A simple method of scanning thin slices by transmission spectrophotometry was used to evaluate the meat pigments in situ. Absorption bands at 414, 520, and 550 nm of the spectra obtained from cooked meat led to the conclusion that residual pink color was caused by cytochrome c. The method was further modified to study the effect of air contact on meat color after cooking. Other pigments were spontaneously oxidized as soon as meat surface was exposed to air. The concentrations of hemoproteins in turkey and pork were determined and found to be related to cooked meat color.     

Effects of Internal Temperature and Thickness on Palatability of Pork Loin Chops

Three thicknesses (2.54, 1.90 and 1.27 cm) of pork chops were cutl alternately from 20 paired loins of similar quality. Chops were cooked on Farberware grills or in a convection oven to internal temperatures of 60, 70 and 80°C for sensory and objective evaluations. Juiciness, percent moisture and tenderness decreased and cooking losses increased (P < 0.05) as temperature increased for both cooking methods. Pork flavor intensity increased in oven- prepared chops, while no change was observed in grilled chops at each level of increased temperature. Thickness had no effect (P > 0.05) on tenderness, juiciness or total cooking loss of oven-prepared or grilled chops. The thickest chops received the highest (P < 0.05) pork flavor scores.     

水和盐对猪里脊肉糜介电特性的影响

应用网络分析仪和同轴探头技术,研究室温(25℃)下10～4500MHz 频段内0%～20% 的加水率和0%～4%的加盐率对新鲜猪里脊肉糜射频和微波介电特性的影响。研究结果表明,肉的相对介电常数随着频率的增大而减小;介质损耗因子在约2500MHz 时出现最小值。相同条件下肉的相对介电常数和介质损耗因子随加水率的增加而增大。整个频段内,介质损耗因子随加盐率的增加线性增加,当频率大于约200MHz 时,相对介电常数随含盐量的增加而减小。加水率和加盐率分别对相对介电常数和介质损耗因子有明显的影响,且其间的线性决定系数大于0.98。     

Effects of Endpoint Temperature on the Internal Color of Pork Loin Chops of Different Quality

ABSTRACT: The effects of 5 endpoint temperatures for cooked, internal color were determined for boneless pork longissimus muscle from 4 treatment groups: normal, normal-injected, PSE, and DFD. Visual and instrumental color, myoglobin denaturation, and acid phosphatase (ACP) of raw and cooked samples were evaluated. Visual internal color became (P < 0.05) less pink as endpoint temperature increased; however, DFD chops were more pink (P < 0.05) and PSE chops were less pink (P < 0.05) than other treatments at most endpoint temperatures. Cooked color was similar (P > 0.05) for chops from normal and normal-injected groups. Myoglobin denaturation increased as endpoint temperature increased. ACP activity in raw chops was not affected by treatment group and it was a good indicator of doneness at 71.1 °C.     

Biochemical Properties of Natural Actomyosin Extracted from Normal and Pale, Soft, and Exudative Pork Loin After Frozen Storage

ABSTRACT: The studies of natural actomyosin (NAM) extracted from normal and pale, soft, and exudative (PSE) pork longissimus muscle stored at -20°C for up to 6 mo, revealed that the surface hydrophobicity (S₀-ANS) of NAM from PSE pork was significantly ( P < 0.05) higher than that from normal pork indicating greater conformational changes in proteins from PSE meat that resulted in the exposure of hydrophobic aromatic amino acid residues on the surface. Also, the S₀-ANS of NAM was a function of storage time. The equations were as follows: S₀-ANS = 16.9 × storage mo + 123 for normal and S₀-ANS = 17.5 × storage mo + 164 for PSE. NAM from frozen normal pork had lower α-helical content than comparable fresh pork. With extended frozen storage, viscosity of NAM from PSE meat was lower than that from normal pork. The sulfhydryl and disulfide contents were unchanged. Electrophoresis revealed an extra 95 to 100 kDa band from PSE meat NAM, possibly from α-actinin or myosin degradation. Water-binding capacity (WBC) of normal and PSE meat decreased with increasing storage time; however, there were only minor changes in thaw loss. The decrease of WBC of pork meat partially can be explained by the increase of S₀-ANS observed for the NAM. These results suggest that proteins from PSE pork are more susceptible to denaturation and degradation in fresh meat and following frozen storage.     

Content of Zinc in Selected Muscles from Beef, Pork, and Lamb

Zinc concentration was measured in four muscles from beef, pork, and lamb: longissimus dorsi (LD), biceps femoris (BF), gluteus medius (GM), and triceps brachi (TB). Within a species, BF, GM, and LD had similar zinc concentrations but TB was significantly (P<0.01) higher in zinc. The means for the four muscles ranged from 39.8–53.5, 13.9–28.0, and 28.2–36.9 μg Zn/g wet weight for beef, pork, and lamb, respectively. The zinc concentration of muscle may relate to protein synthesis and the predominant type of energy metabolism occurring in the muscle. The mean zinc concentration of the four muscles between species was significantly (P< 0.01) different.     

Prevention of Pinking, Off-odor, and Lipid Oxidation in Irradiated Pork Loin Using Double Packaging

ABSTRACT: Lipid oxidation, color, volatiles, and sensory evaluation of double-packaged pork loin were determined to establish a modified packaging method that can improve the quality of irradiated pork loins. Vacuum-packaged irradiated samples produced dimethyl sulfide and dimethyl disulfide responsible for irradiation off-odor, whereas lipid oxidation was promoted under aerobic conditions. Exposing double-packaged irradiated pork to aerobic conditions for 1 to 3 d was effective in controlling both lipid oxidation and irradiation off-odor, regardless of packaging sequence. Sensory panels could distinguish the decrease in irradiation off-odor intensities by modifying the packaging method. However, carbon monoxide heme pigments, responsible for the increased redness by irradiation, were not effectively controlled by double packaging alone.     

Efficacy of Pork Loin as a Source of Zinc and Effect of Added Cysteine on Zinc Bioavailability

Based upon Zn uptake in chick tibia, Zn in raw and cooked pork loin was about 40% more bioavailable than that in ZnSO₄-H₂O. Neither roasting nor braising affected Zn bioavailability in the loin preparations. Adding 0.40% cysteine to diets containing ZnSO₄ improved Zn bioavailability by 73%. Pork loin is an excellent source of bioavailable Zn, and SH-containing compounds such as cysteine and glutathione that are present in meat may contribute to enhanced gut absorption of meat-source Zn.     

腐生葡萄球菌CGMCC 3475对发酵里脊猪肉脂质分解氧化及风味特性的影响

以腐生葡萄球菌(Staphylococcus Saprophyticus)CGMCC 3475为发酵剂发酵里脊猪肉,以不接菌的样品为对照,通过测定各发酵阶段(发酵30 d、50 d、70 d、90 d、110 d)的游离脂肪酸(FFA)、硫代巴比妥酸值(TBARS)、双烯值和羰基值等来研究腐生葡萄球菌对发酵里脊猪肉脂质分解氧化规律的影响。通过测定醛和酮等挥发性风味物质来研究腐生葡萄球菌对发酵里脊猪肉脂质的氧化产物对风味特性的影响。结果表明,接菌处理发酵里脊猪肉中的SFA、MUFS、PUFA的含量除发酵50天显著低于对照发酵里脊猪肉外(P<0.05),其余各个阶段这3种脂肪酸的含量都显著高于对照发酵里脊猪肉(P<0.05)。2个处理发酵脊猪肉中的SFA、PUFA的含量都在发酵90天达到最大值,而MUFA的含量在发酵过程中持续增加。TBARS值整体趋势都是减少的,只有在发酵70天的时候有所增加。羰基值从发酵30天到90天都是呈显著增加的(P<0.05),到发酵110天时有所降低。双烯值都是显著增加的(P<0.05),而且接菌处理发酵里脊猪肉的双烯值均显著高于对照处理发酵里脊猪肉(P<0.05)。发酵70天时,接菌处理发酵里脊猪肉检测出高达56.71%的酯类物质而检测出相比对照处理发酵里脊猪肉较少的直链醛和酮外,其余各个发酵阶段的直链醛和酮的含量均显著高于对照处理发酵里脊猪肉(P<0.05)。     

Effectiveness of Dipping with Phosphate, Lactate and Acetic Acid Solutions on the Quality and Shelf-life of Pork Loin Chop

Extending the shelf‐life of pork loin chops by dipping in 2% acetic acid (AA), 10% sodium lactate (SL), or 10% trisodium phosphate (TSP), compared to the undipped control (CONT), was demonstrated. TSP had the highest pH and water‐holding capacity. However, TSP had a dry and dark visual appearance on the loin chop surface, while AA was similar to pale, soft, and exudative (PSE) pork. CONT and SL had obvious putrid odor with TPC exceeding 10⁷ CFU/g at d 6 and d 9, respectively. Pork loin chops dipped in 10% sodium lactate solution resulted in better visual appearance and lower microbial counts, suggesting a possible extension of the shelf‐life to 6 d under refrigeration.     

Nutrient Content and Edible Yield of Selected Cuts of Cooked Pork

Analysis of lean-type pork cooked by standard methods showed that cooking to a final internal temperature of 77°C for fresh cuts, and 71°C for cured meats resulted in increased amounts of several essential nutrients. Edible yield was similar to that reported from earlier studies, while amounts of internal fat were somewhat lower. Levels of thiamin, riboflavin and niacin and of several minerals were found to be slightly higher than Handbook 8 values. Cobalamin and zinc from 100g of edible lean would provide approximately 10% and 20–35% of the respective recommended daily allowances. Iron contents were lower than previously reported for pork.     

猪肉品质的影响因素

近年来,猪肉的肉质问题已经成为人们关注的焦点。本文综述了遗传因素、营养因素、环境因素对猪肉品质的影响,并对猪肉市场的发展进行了展望。     

加工因素对东坡肉品质的影响

采用感官评定和物性测定仪TA-XT2 质地剖面分析(TPA)调味料配方和加工工艺对湖北传统名菜黄州东坡肉的影响。结果表明：酱油(P ＜ 0.05)和煨制时间(P ＜ 0.05)显著影响东坡肉的感官品质;煨制时间、黄酒、糖、盐与质构多项指标呈显著或极显著负相关;酱油、黄酒对肥肉的质构指标影响较小,煨制时间对肥肉的质构指标影响较大;盐和加水量对肉皮的质构指标影响较小,酱油、煨制时间对肉皮的质构指标影响较大,且酱油对肉皮弹性影响显著(P ＜ 0.05)。煨制时间、盐对瘦肉的质构指标影响较大。     

荣昌猪肉在不同烤制温度条件下的挥发性风味物质变化

为探明荣昌猪肉在不同烤制温度中的挥发性风味物质,采用偏最小二乘回归分析结果表明,在荣昌猪肉的烤制加工过程中吡嗪类化合物变化比较显著,对烤肉的整体风味贡献较大。同时蒸馏萃取和固相微萃取两种提取方法对风味化合物的提取效果差异显著。固相微萃取法提取的风味化合物更接近样本的真实风味。