卤猪肉加工过程中游离脂肪酸、游离氨基酸及核苷酸变化分析

利用气相色谱质谱联用和高效液相色谱法检测分析了卤猪肉加工过程中游离脂肪酸、游离氨基酸及核苷酸的变化。结果表明,在加工过程中,总游离脂肪酸有效峰面积呈下降趋势,饱和脂肪酸也呈现下降的变化趋势,不饱和脂肪酸含量先增加后减少,在高温煮制1 h时达到最大值。总游离氨基酸的含量在卤猪肉加工过程中变化明显,在原料肉中总游离氨基酸含量为244.39 mg/100 g,其它样品中含量都显著(p0.05)高于原料肉,在二次煮制完成后达到最大值,为349.32 mg/100 g。谷氨酸在成品中的含量达到119.02mg/100 g,占总游离氨基酸的34.12%。呈味核苷酸检测结果显示,在加工过程中5'-IMP和5'-GMP的含量呈现下降趋势。由于加热导致核苷酸热降解,其降解产物肌苷的含量呈现上升趋势,在成品中检测到其含量显著(p0.05)高于原料肉中的含量。本研究结果为改进卤猪肉的生产工艺、提高产品品质提供了理论参考。     

Infectivity of Toxoplasma gondii in mutton following curing, smoking, freezing or microwave cooking.

To investigate the effects of curing with sodium chloride and sucrose, low temperature smoking, freezing at -20 degrees C, and cooking in a microwave oven, respectively, on the infectivity of Toxoplasma gondii encysted in mutton, meat from three experimentally and one naturally infected sheep was used. Samples of meat prepared accordingly as well as untreated, raw meat from each animal were assayed by mouse inoculation. Infective T. gondii was isolated from untreated samples from all animals used, but in no case from cured, smoked or frozen meat. However, in two of four steaks processed in a microwave oven, according to a standard household recipe, the parasite remained infective, possibly due to uneven heating of the meat.     

不同烹调方式对羊肉品质的影响

研究不同烹调方式（蒸煮、烘烤和煎炸）对羊肉品质的影响,分别对样品中氨基酸、脂肪酸和核苷酸的组成及含量、质构指标以及肌肉微观结构进行检测。结果表明：蒸煮方式的损失率最低,对氨基酸、脂肪酸和核苷酸的组成及含量的影响最小;在3 种烹调方式对肉样处理过程中,肉样的氨基酸模式和脂肪酸模式均发生不同程度的变化;煎炸肉样中呈味氨基酸含量为55.33%,显著高于蒸煮肉样呈味氨基酸含量（50.67%）和烘烤肉样呈味氨基酸含量（49.33%）;烘烤肉样呈味核苷酸含量最低;蒸煮、煎炸和烘烤对肉样的脂肪酸组成及含量虽有影响,但组间并无差异显著性。烘烤肉样咀嚼性优于煎炸肉样和蒸煮肉样。在3 种烹调方式处理过程中,烘烤肉样肌纤维束变形、肌束膜破坏、肌间脂肪受损程度最严重。     

Radio frequency cooking of ground, comminuted and muscle meat products

The effect of radio frequency (RF) cooking, on the quality (colour, water holding capacity, texture), heating rate, and temperature history of three types of meat products (ground, comminuted and muscle), was investigated after heating to centre temperature of 72?°C in a 1.5 kW RF heater operating at 27.12 MHz. The results were compared with that obtained from heating in a water bath. RF cooking of processed meat products resulted in a decreased cooking time (5.83, 13.5, and 13.25 min for ground beef, comminuted meat, and muscle, respectively compared to 151, 130, and 109 min in water bath), lower juice losses, acceptable colour, water holding capacity and texture. The results indicate that when using RF, ground beef has the highest power efficiency (60.17%) followed by comminuted meat (44.41%), and muscle (43.38%). However, the texture of ground beef was too chewy and elastic. The muscle's colour was inferior. The comminuted and muscle meat products exhibited average energy efficiency with improved texture. The comminuted meat displayed a large cross-sectional temperature differential, possible due to uneven salt distribution. The well mixed comminuted and ground meat products appeared to be most promising for RF cooking.     

Effect of chloride on the formation of 3-monochloro-1,2-propanediol fatty acid diesters and glycidol fatty acid esters in fish,meats and acylglycerols during heating

The effects of the presence of chloride on the formation of 3-monochloro-1,2-propanediol fatty acid esters (3-MCPDEs) and glycidol fatty acid esters (GEs) in saltwater fish, meats and acylglycerols (diacylglycerol and triacylglycerol) during heating were investigated in this study. Five saltwater fish species (salmon, saury, yellowtail, mackerel and Spanish mackerel) were grilled with a fish griller. 3-MCPDEs and GEs were detected in all of the grilled fish samples. The total amount of GEs was higher than 3-MCPDEs. Beef and pork patties with or without sodium chloride (1.5%) were cooked using gaseous fuel. The formation of 3-MCPDEs was significantly increased by the addition of sodium chloride to the meat patties, whereas the concentration of GEs in the cooked meat patties was not changed by the content of sodium chloride. Hexadecane solutions of diacylglycerol or triacylglycerol containing FeCl₃ were heated at 240°C. The formation of 3-MCPDEs was greatly increased by adding FeCl₃ to the solutions of triacylglycerol. The amounts of 3-MCPDEs decreased with the extension of the heating time. From these results, it is suggested that 3-MCPDEs and GEs are formed in saltwater fish and meats by cooking, and that the formation of 3-MCPDEs was affected by chloride in foodstuffs.     

Determination of aromatic amino acid content in cooked meat by derivative spectrophotometry: Implications for nutritional quality of meat

The technique of second derivative spectrophotometry was used to determine the level and the heat stability of the three aromatic amino acids (tryptophan, tyrosine and phenylalanine) in bovine meat (M. Longissimus thoraci). This paper presents a method which measures the second derivative absorbance values at a wavelength specifically assigned to each aromatic amino acid with corrections for the interference from other amino acids at the same wavelength. Three cooking temperatures were tested in this study (60, 100 and 140 °C). Due to important cooking losses, results differ slightly according to the method of calculation (level expressed by gram of wet meat or by gram of proteins). Whatever the calculation method, heating at 60 °C had little effect on aromatic acid levels while higher temperatures had a dramatic effect on aromatic amino acids stability. The stability of the three aromatic amino acids during cooking decreased in the order tryptophan > phenylalanine > tyrosine.     

不同烹制模式对鸡汤中鸡肉营养及风味特征的影响

研究电磁加热、电热盘加热和瓦罐烹制模式对鸡肉营养成分、质构和风味特性、蛋白质和脂肪消化性的影响。结果表明：烹制模式对鸡肉的感官品质和营养特性具有较大影响。电磁加热模式烹制鸡肉的综合感官品质优良,具有质地柔嫩、香气浓郁、滋味鲜美、风味成分较丰富等特点,同时鸡肉的维生素、脂肪、必需氨基酸含量较高,蛋白质的消化率较好;瓦罐模式烹制鸡肉中蛋白质和矿物质含量较高,脂肪消化率高;电热模式烹制鸡肉的各项指标介于上述2 种烹制模式之间,其中,电磁加热模式烹制鸡肉中的VB3含量达10.34 mg/100 g,粗脂肪含量为5.58%,蛋白质消化率为33.31%;另外,鸡肉中的醛、酮、酯类物质含量亦较高,挥发性物质种类可达37 种。总体来讲,电磁加热是一种较好的鸡肉烹制模式。     

Ohmic cooking of ground beef: Effects on quality

Conventional cooking tends to be slow and the surface of the food always receives a much more severe heating treatment than the rest of the food. Ohmic heating has the potential to be much faster and produces even more cooking. In this work cylindrical ground beef samples having different initial fat contents (2%, 9% and 15%) were cooked ohmically (20, 30 and 40 V/cm) and conventionally. Ohmic cooking was faster than the conventional cooking (p < 0.05). Ohmically cooked samples were firmer than those conventionally cooked but yield and fat retention was similar. However, the reduction in volume during cooking was significantly smaller from 5.36% to 6.97% in ohmic cooking than the conventional system which was measured from 26.01 to 31.59. The voltage gradient applied during ohmic cooking was not related to the quality of the cooked meat. These results show that ohmic cooking could be a fast-alternative method for meat products.     

Changes in free nucleotides, nucleosides and bases during preparation of pre-cooked dehdyrated minced meats

Changes in free nucleotides, nucleosides and bases during preparation of pre-cooked dehydrated minced meats from goat and sheep are reported. Major changes took place during cooking stage only; the changes during dehydration were relatively minor. Addition of EDTA at 500 ppm level significantly reduced the rate of dephosphorylation during curing process. Concentration of free nucleotides and related compounds were very low in commercially prepared accelerated freeze dried meat chunks.     

Changes in free nucleotides,nucleosides and bases during Preparation of Pre-Cooked dehydrated minced meats

Changes in free nucleotides, nucleosides and bases during preparation of pre-cooked dehydrated minced meats from goat and sheep are reported. Major changes took place during cooking stage only; the changes during dehydration were relatively minor. Addition of EDTA at 500 ppm level significantly reduced the rate of dephosphorylation during curing process. Concentration of free nucleotides and related compounds were very low in commercially prepared accelerated freeze dried meat chunks.     

加热处理对北京油鸡和黄羽肉鸡质构以及蛋白特性的影响

北京油鸡和黄羽肉鸡加热过程中的蒸煮损失、pH、剪切力变化及肌肉蛋白降解对其特殊质构和风味的形成具有重要意义。本研究以北京油鸡和黄羽肉鸡不同加热阶段为研究对象,采用常规物化特性测定方法及SDS-PAGE电泳分析北京油鸡和黄羽肉鸡肌肉质构的变化及蛋白降解情况。结果表明:随着加热温度的升高,北京油鸡和黄羽肉鸡的蒸煮损失均有明显的增加,而两者的剪切力和pH值以及蛋白质的降解呈现不同的变化。     

Packaging and Irradiation Effects on Lipid Oxidation and Volatiles in Pork Patties

Raw-meat patties were prepared from three pork muscles, irradiated in different packaging environments, and stored for 0 or 3 days before cooking. Lipid oxidation by-products were formed in the raw meat during storage and the baseline lipid oxidation data of raw meat was used to measure the progression of lipid oxidation after cooking. Thiobarbituric acid-reactive substances (TBARS) and volatiles data indicated that preventing oxygen exposure after cooking was more important for cooked meat quality than packaging, irradiation, or storage conditions of raw meat. Propanal, pentanal, hexanal, 1 -pentanol, and total volatiles correlated highly (P < 0.01) with TBARS values of cooked meat. Hexanal and total volatiles represented the lipid oxidation status better than any other individual volatile components.     

Concentration of Umami Compounds in Pork Meat and Cooking Juice with Different Cooking Times and Temperatures

This study examined the concentrations of umami compounds in pork loins cooked at 3 different temperatures and 3 different lengths of cooking times. The pork loins were cooked with the sous vide technique. The free amino acids (FAAs), glutamic acid and aspartic acid; the 5′‐nucleotides, inosine‐5′‐monophosphate (IMP) and adenosine‐5′‐monophosphate (AMP); and corresponding nucleoside inosine of the cooked meat and its released juice were determined by high‐performance liquid chromatography. Under the experimental conditions used, the cooking temperature played a more important role than the cooking time in the concentration of the analyzed compounds. The amino acid concentrations in the meat did not remain constant under these experimental conditions. The most notable effect observed was that of the cooking temperature and the higher amino acid concentrations in the released juice of meat cooked at 80 °C compared with 60 and 70 °C. This is most likely due to the heat induced hydrolysis of proteins and peptides releasing water soluble FAAs from the meat into the cooking juice. In this experiment, the cooking time and temperature had no influence on the IMP concentrations observed. However, the AMP concentrations increased with the increasing temperature and time. This suggests that the choice of time and temperature in sous vide cooking affects the nucleotide concentration of pork meat. The Sous vide technique proved to be a good technique to preserve the cooking juice and the results presented here show that cooking juice is rich in umami compounds, which can be used to provide a savory or brothy taste.     

Effect of radio frequency cooking on the texture, colour and sensory properties of a large diameter comminuted meat product

Radio frequency (RF) cooking is a form of dielectric heating similar to microwave heating. In this study an optimised cooking protocol was developed for pasteurising 1 kg cased meat emulsion samples, which were immersed in 80 °C circulating water during cooking. Subsequently, selected quality attributes of RF pasteurised samples were compared to steam pasteurised samples, by instrumental and sensory methods. Instrumental assessments show that RF heated meat batters had a greater ability to hold water, were significantly harder, chewier and gummier (P<0.001), while having less cook colour development than their steam cooked counterparts. Differences were also detected by sensory methods. In conclusion, while differences were detected, it is possible that these could be eliminated by adjusting the cooking protocol to produce similar cook values in RF samples to those in products cooked by steam.     

Effect of ohmic treatment on quality characteristic of meat: A review

Ohmic cooking, a well-known electro-heating technique, provides an alternative method for cooking meat products due to its ability for rapid heat generation. Ohmic heating uses the resistance of meat products to convert the electric energy into heat. The rate of heat generation depends on the voltage gradient applied and the electrical conductivity of the meat product. The advantages of ohmic cooking over conventional heating include shorter processing times, higher yields, and less power consumption while still maintaining the colour and nutritional value of meat products. In recent years, ohmic cooking has increasingly drawn interest from the meat industry as a method to ensure the quality and the safety of meat products. The present paper reviews the effects of ohmic cooking on the physical, chemical, sensory, and microbiological quality characteristics and toxicological properties of meat and meat products.     

LOW-TEMPERATURE, LONG-TIME HEATING OF BOVINE MUSCLE 1. Changes in Tenderness, Water-Binding Capacity, pH and Amount of Water-Soluble Components

SUMMARY: Relationships between the tenderness of very slowly cooked meat and its waterholding capacity, pH and the amount of water-soluble components were studied. Beef muscle portions from the longissimus, semitendinosus and rectus femoris muscles were heated under fixed temperature programs with samples from each analyzed at 1-hr intervals between the 3rd and the 10th hr of heating. Weight losses after holding at the final temperature to the 24th hr were determined. During the first 4 hr of heating there were only minor changes in tenderness. The major decrease in shear values occurred between the 4th and 6th hr, when the meat was warming from 50-60°C. The weight losses increased rather linearly to the 7th hr and remained constant for the longissimus and the semitendinosus muscle. The pH values gradually increased during heating. During the first 3 hr of heating, up to 45°C, there was only a slight decrease in the amount of the water-soluble fraction. During the following 3 hr. from 45 to 58°C, the water-soluble fraction decreased more rapidly and the decrease was only slight during a following 4-hr holding period. After 6 hr of heating to 60°C there were still uncoagulated water-soluble proteins. These studies indicate that the final temperature of meat has great influence on tenderness and weight loss. The significance of the shrinkage of collagen in long-time, low-temperature cooking is considered.     

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.     

水煮鱼微波烹饪过程中鱼肉水分及组织变化对嫩度的影响

采用物性分析方法表征鱼肉的最大剪切力,借助低场核磁共振等手段从水分状态、蛋白质变性和微观结构等角度探索水煮鱼微波烹饪过程中鱼肉嫩度变化的原因。结果表明,微波加热初期(150s),鱼肉中结缔组织迅速破裂,肌浆蛋白几乎完全变性,部分结合水转化为不易流动水,赋予鱼肉特有的嫩度;加热中期(300s),鱼肉嫩度达最大值,且与传统水煮法相近。加热时间过长(390s)可能会导致鱼肉肌肉组织发生断裂收缩、重新联结、口感变硬。因此,微波一步法烹饪水煮鱼模式设计时可适当缩短微波处理时间,有利于维持水的结合状态以及组织完整性,从而保证鱼肉的嫩度。     

Changes in the amounts of water-soluble umami-related substances in porcine longissimus and biceps femoris muscles during moist heat cooking

Time course changes in amounts of glutamic acid, total free amino acid, inosine monophosphate (IMP), and 2%-trichloroacetic acid-soluble oligopeptides in whole, muscle only, and cooking juice during wet-heat cooking in pork longissimus and biceps femoris muscles were investigated because the movements of umami-relevant substances during cooking treatment had not previously been clarified in detail. The amounts of glutamic acid, total free amino acid, and IMP significantly (P<.05) decreased and increased in muscle and cooking juice during 180min of cooking, respectively. The whole amounts of glutamic acid and total free amino acid remained unchanged during cooking treatment. The whole amount of IMP, however, increased significantly at 10min of cooking (P<.05) and was maintained after the 10-min period. The extramuscular oligopeptides amount increased significantly in response to the cooking treatment (P<.05). The intramuscular amount of oligopeptides decreased at 30min of cooking but increased significantly (P<.05) after 60min. The whole meat oligopeptides amount increased significantly during a 180-min cooking treatment (P<.05). These results indicate that glutamate, total free amino acid, and IMP were released from the muscle during cooking, and that IMP levels increased in the initial phase of cooking. In addition, oligopeptides increased during wet-heat cooking of pork muscles.     

Effect of cooking and cooling method on the processing times, mass losses and bacterial condition of large meat Joints

This study compares the heating and cooling times of and mass losses from meat joints in three systems: convective air, water immersion and pressure/vacuum. Cooling times were compared with the UK Department of Health (DoH, 1989) guidelines which state that joints should be cooled to 10°C or below in less than 150 min.
Five types of joint were used: 50-mm thick (0.94kg) slabs of beef m. semitendinosus, 2.7kg rolled beef forequarter and silverside, 6.4kg rolled turkey and 7.1kg boned-out ham joints. Six replicates of all joints were cooked from 5 to 75°C (beef), 80°C (ham) or 85°C (turkey) and then cooled to a maximum internal temperature of 10°C.
Average cooking times for convection, immersion and pressure were 263, 278 and 135 min, respectively. Average cooling times for convection, immersion and vacuum were 433, 298 and 50 min, respectively. Vacuum cooling times did not depend on joint size but may have been affected by porosity of the meat. The DoH guidelines could be achieved by immersion or vacuum methods when cooling the small beef slabs but only vacuum cooling was sufficiently rapid when cooling the larger joints.
Mass losses due to pressure cooking (mean 37.4%) were greater than those during convection heating (28.9%). Vacuum cooling resulted in an average mass loss of 8.2% but losses were smaller after convection cooling (2.5%). Average total viable counts (log10 no. of bacteria cm⁻²) after processing and 12h storage were 1.0 at both the surface and interior.