正常肉和白肌肉的蛋白质变化

测定白肌肉(Pale,Soft,Exudative,PSE)和正常猪肉(Reddish-pink,Firm,Non-exudative)持水性指标和在宰后不同时间的蛋白溶解性和蛋白降解程度。结果显示:PSE肉的各种蛋白溶解性都显著低于正常肉(p<0.05),宰后4 h的总蛋白、肌浆蛋白和肌原纤维蛋白的溶解性与滴水损失和贮藏损失都呈显著负相关,与持水力呈显著正相关。正常肉和PSE肉的肌浆蛋白和肌原纤维蛋白的SDS-PAGE电泳条带存在差异,PSE肉早期伴肌动蛋白(Nebulin)含量明显低于正常肉。可见PSE肉肌原纤维的降解较快,宰后早期的蛋白溶解性可以用于预测猪肉的持水性。     

煮制过程中食盐引起猪肉汤成分含量变化的研究

本文以煮制30、60、90、120 min猪肉汤为研究对象,通过测定加盐与无盐猪肉汤煮制过程中的蛋白质降解产物含量、性质、分子量分布范围、氨基酸组成、脂肪和脂肪酸含量等变化,分析食盐对猪肉汤成分含量差异性的影响。结果表明,在不同煮制时间下,加盐肉汤中的粗蛋白含量、非蛋白总氮含量、可溶性蛋白氮含量、盐溶性蛋白含量、氨基酸总含量、脂肪含量及脂肪酸总含量等均高于无盐肉汤。加盐肉汤中水解氨基酸总含量为5.897 mg/mL,与肉汤中粗蛋白含量的测定结果趋势一致,每煮制30 min,其盐溶性蛋白含量约增加0.6 mg/mL,且在煮制90 min后,其游离氨基酸含量显著(P<0.05)高于无盐肉汤。根据凝胶电泳图谱分析,食盐的添加使大分子蛋白降解为小分子蛋白,分子量由135~245 kDa向35~48 kDa转移。加盐肉汤中单不饱和脂肪酸含量显著(P<0.05)高于无盐肉汤,其中C18:1含量最高,并在煮制120 min时高达3.763 mg/mL。综上,食盐的添加促进肉汤中蛋白质的溶解、渗出及降解,提高了必需氨基酸占比,并在一定程度上防止不饱和脂肪酸被氧化,有利于被人体吸收和利用。     

不同熟制方式下调理鸡排蛋白质结构及水相分布的变化

为了探究熟制方式对调理鸡排蛋白质结构和水相分布的变化的影响,以预制的调理鸡排为研究对象,用三种不同的熟制方式（香煎熟制、鼓风烤制、普通烤制）进行熟制（生鸡排为对照）,测定蛋白质二级结构,观察肌纤维微观结构并分析水分迁移情况。结果表明：蛋白质二级结构中酰胺I带变化量为9.64 cm-1（普通烤制）、11.579 cm-1（鼓风烤制）、13.49 cm-1（香煎熟制）;呈凝胶网状的蛋白质微观结构由疏松到紧密的大小为：普通烤制>鼓风烤制>香煎熟制;各组自由水峰面积P23分别为0.31%（生鸡排）、1.85%（普通烤制）、2.97%（鼓风烤制）、3.56%（香煎熟制）;系水力大小为：普通烤制>鼓风烤制>香煎熟制。以上结果为明确不同熟制方式对调理鸡排食用品质的影响提供理论指导依据。     

纯瘦猪肉丸的组分配比及工艺标准

对烹饪不常用的纯瘦猪肉丸的调配工艺进行优化,以用量配比以及加热时间对内丸质量的影响进行比较试验,通过对内丸弹性、口味、形态的感官综合评价结果分析,找出纯瘦猪肉丸配比的优化参数.首先进行单因素试验分析,分别对盐浓度、水浓度、淀粉浓度、加热时间对内丸感官质量的影响进行对比试验.得出盐、水、淀粉、加热时间的基本范围.在单因素分析的基础上,再进行正交试验,找出肉丸调配的最佳配比组合和加热时间,在对样品进行弹性和硬度分析,将检测结果与感官鉴别结果进行综合评估,最终得出纯瘦猪肉丸的工艺参数即水用量220 g、盐用量4 g、淀粉用量20g、加热时间50mim.     

3种猪肉汤体系中蛋白质降解产物的比较研究

对3种不同烹制方法(水煮、炖煮和高压蒸煮)制得的猪肉和汤汁进行感官评定、总蛋白SDS-PAGE凝胶电泳以及总氮(TN)、水溶性氮(WSN)、非蛋白氮(NPN)和游离氨基酸(FAA)含量的比较研究。感官评定结果表明3种工艺分别为水煮30min,炖煮2h和高压蒸煮15min时,烹制所得肉和汤汁口感与风味最佳。总蛋白SDS-PAGE凝胶电泳图谱显示炖煮肉中大分子蛋白降解最为显著,炖煮肉汤中水溶性蛋白含量最高。水煮、炖煮和高压蒸煮使肉汤体系水溶性氮总量分别比鲜肉增加12%、24%和5%,非蛋白氮总量分别增加42%、59%和33%,游离氨基酸总量分别增加61%、78%和51%。炖煮猪肉的蛋白质降解程度比水煮和高压蒸煮高,且大部分蛋白质降解产物转移到汤汁中,赋予肉汤最优的营养和风味。     

Steam Assisted Hybrid Cooking Behavior of Semitendinosus Muscle: Heterocyclic Amines Formation,Soluble Protein Degradation,Fat Retention,Surface Color,and Cooking Value

Beef (Semitendinosus muscle) was cooked in natural convection, forced convection and steam assisted hybrid oven and saturated steam oven at different oven temperatures until the geometric center of samples reached different end temperatures. Heterocyclic amine (HCA) compounds formation, soluble protein degradation kinetics, cook value, changes in fat content, surface colour and overall acceptance of cooked beef were determined. Soluble protein degradation of beef was considered as first order reaction kinetics and the reaction rate constants, k, were determined in the range of 0.014-0.052 min^?1. In steam assisted hybrid oven had higher reaction rate constants compared to that of the convection ovens. The effect of cooking temperature on soluble protein degradation for natural convection, forced convection and steam assisted hybrid oven followed the Arrhenius type of equation with activation energies of 12.45, 14.57 and 60.16 kJ/mol, respectively. Lower HCAs contents, shorter cooking times, lower cook values and lower fat retention were obtained by steam assisted hybrid oven cooking. Steam assisted hybrid cooking could be considered as an alternative cooking method to obtain a healthier product without compromising the eating habits of conventional methods due to better appearance (moderate burned surface) than saturated steam oven samples and a product retaining the most of the nutritional values.     

Thawing Prior to Cooking Affects Sensory, Shear Force, and Cooking Properties of Beef Patties

Patties from 6 commercial formulations were cooked to 71°C from either the frozen state or after thawing for 24 to 27 h at 4 °C to eliminate the pink/red color exhibited when cooked to 71 °C from the frozen state. Thawed patties had shorter cooking times, higher cooking yields, and lower shear force peak load and peak energy values. Patties cooked from the thawed state increased in thickness during cooking, while patties cooked from the frozen state decreased in thickness during cooking. Thawing prior to cooking increased sensory evaluation scores except for patties made with carrageenan. Thawing not only eliminated the problem of pink/red color after cooking but also improved sensory, shear force, and cooking properties of beef patties.     

Inhibition of Oxidant-Induced Biochemical Changes of Pork Myofibrillar Protein by Hydrolyzed Potato Protein

ABSTRACT:  The objective of the study was to investigate the role of hydrolyzed potato protein (HPP) in protecting myofibril protein isolate (MPI) from oxidative modification. MPI prepared from pork muscle was suspended (30 mg protein/mL) in 15 mM piperazine- N , N -bis(2-ethane sulfonic acid) buffer (pH 6.0) with 0, 0.3, 0.75, and 1.5 mg/mL of antioxidative HPP (1-h Alcalase hydrolysate). Oxidation was induced by incubating the protein suspensions at 4 °C for 24 h with (1) an iron-catalyzed oxidizing system (IOS: 0.01 mM FeCl₃, 0.1 mM ascorbic acid, and 1.0 mM H₂O₂) and (2) a metmyoglobin-oxidizing system (MOS: 0.1 mM metmyoglobin and 0.1 mM H₂O₂). Changes in oxidized MPI were measured as thiobarbituric acid-reactive substances (TBARS), protein carbonyl content, Ca- and K-ATPase activities, and ultraviolet (UV) spectra. Oxidation increased the production of TBARS and protein carbonyls by 2.9- and 0.24-fold in IOS and 5.6- and 2.2-fold in MOS, respectively. The 2 oxidizing systems altered the Ca- and K-ATPase activities and exposed hydrophobic groups buried in MPI. The presence of HPP reduced the extent of MPI oxidation in all physicochemical categories tested. Therefore, HPP may be used as a potential functional ingredient in meat products to enhance their oxidative stability.     

大豆蛋白挤压蒸煮处理过程中系统功耗的研究

利用双轴挤压蒸煮机处理大豆蛋白,考查了挤压操作参数对挤压系统参数的影响。采用可旋转的中心组合设计,以螺杆转速(X1)、腔体温度(X2)及系统供水率(X3)为输入变量,以挤压蒸煮系统的运行电流(I)为响应变量,探索在蛋白质挤压蒸煮处理过程中挤压参数与系统功耗的关系。结果表明:螺杆转速的变化对系统的比能值影响不大,随着系统进水率的不断减小,系统的比能值逐渐变大,腔体温度对系统比能值的变化影响显著。得到挤压操作参数(X1、X2、X3)与系统功耗(y)的拟合模型为:y=3242+0.29x1-1.45x2-2.18x3+0.98x1x2-0.50x1x3-1.37x2x3+0.46x21+2.05x22+1.35x23。     

中式菜肴红烧肉烹饪过程中丙烯酰胺含量变化的动态监测

研究动态监测中式菜肴红烧肉烹饪过程中丙烯酰胺含量的变化情况。样品经水提取、液液萃取脱脂和固相萃取柱净化处理后,采用高效液相色谱-串联四极杆质谱方法,以内标法定量,在多重反应监测模式测定目标化合物。方法的线性范围为10～1 000 ng/mL,线性相关系数为0.999 9。方法的定性检出限和定量限分别为0.1 μg/kg和1 μg/kg,回收率为91.4%～105.8%,相对标准偏差小于8%。采用该方法测得红烧肉在烹饪过程中丙烯酰胺含量呈倒V形走势,在加入糖、酱油等调味料后丙烯酰胺的平均含量达到顶点值42.4 μg/kg。     

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.     

Changes in Moisture, Protein, and Fat Content of Fish and Rice Flour Coextrudates during Single-Screw Extrusion Cooking

Changes in proximate composition of fish and rice flour coextrudates like moisture, protein, and fat content were studied with respect to extrusion process variables like barrel temperature, x ₁ (100–200 °C); screw speed, x ₂ (70–110 rpm); fish content of the feed, x ₃ (5–45%); and feed moisture content, x ₄ (20–60%). Experiments were conducted at five levels of the process variables based on rotatable experimental design. Response surface models (RSM) were developed that adequately described the changes in moisture, protein, and fat content of the extrudates based on the coefficient of determination (R ²) values of 0.95, 0.99, and 0.94. ANOVA analysis indicated that extrudate moisture content was influenced by x ₄, protein content by x ₁ and x ₃, and fat content by x ₃ and x ₄ at P?<?0.001. Trends based on response surface plots indicated that the x ₁ of about 200 °C, x ₂ of about 90 rpm, x ₃ of about 25%, and x ₄ of about 20% minimized the moisture in the extrudates. Protein content was maximized at x ₁ of 100 °C, x ₂?>?80 rpm, x ₃ of about 45%, and x ₄?>?50%, and fat content was minimized at x ₁ of about 200 °C, x ₂ of about 85–95 rpm, x ₃?<?15%, and x ₄ of about >50%. Optimized process variables based on a genetic algorithm (GA) for minimum moisture and fat content and maximum protein content were x ₁?=?199.86, x ₂?=?109.86, x ₃?=?32.45, x ₄?=?20.03; x ₁?=?199.71, x ₂?=?90.09, x ₃?=?15.27, x ₄?=?58.47; and x ₁?=?102.97, x ₂?=?107.67, x ₃?=?44.56, x ₄?=?59.54. The predicted values were 17.52%, 0.57%, and 46.65%. Based on the RSM and GA analysis, extrudate moisture and protein content was influenced by x ₁, x ₃, and x ₄ and fat content by x ₂, x ₃, and x ₄.     

Ohmic Cooking of Processed Meats and its Effects on Product Quality

ABSTRACT: A basic bologna emulsion (lean and fatty pork meat, sodium chloride, sodium erythorbate, and sodium nitrite) was cooked in 1-kg portions, either in a smokehouse (180-min cycle; to 70 °C at core) or by ohmic heating (64 to 103 V; 3.9 °C/min to 10.3 °C/min; to 70 °C to 80 °C), and the finished products were compared for color, texture, pH, drip, Eh, and rancidity. Heating rates, final temperatures, and a 20-min holding time had little influence on the quality of ohmic sausages. In addition, ohmic sausages were always found to be similar to smokehouse products except for texture, which was significantly softer (P > 0.05) in ohmic products but could be hardened by use of binders.     

猪背最长肌蛋白质在冷冻贮藏过程中的变化

为研究冻藏时间对猪背最长肌蛋白质特性的影响,本文主要采用凝胶电泳、差示量热扫描技术分析了猪背最长肌在-18 ℃冻藏0 d和1、3、6、9、12、15月后,其蛋白质的疏水性、巯基含量、降解情况、热稳定性的变化。结果表明:随冻藏时间的延长,蛋白质溶解度显著降低(p<0.05),肌原纤维蛋白(MPI)的表面疏水性和巯基含量升高,发生降解的MPI主要集中在67 kDa和20~29 kDa;肌球蛋白和肌浆蛋白的变性温度和焓值呈现逐渐降低的趋势,表明这两类蛋白的热稳定性降低。在冻藏的前3个月内,猪背最长肌的各项指标维持在较好的水平,从第6个月开始,所有指标的变化幅值增加,变化速率加快。研究发现,冻藏6个月以后,猪背最长肌蛋白质品质开始加速下降。     

蛋白质降解对猪肉制品品质影响的研究进展

蛋白质不仅是生命体最重要的且是除水分外含量最高的组成成分之一,也是食品主要的成分之一。在肉与肉制品中,蛋白质和氨基酸不仅是主要营养素,也是形成产品质构、风味和色泽的物质基础,并具有乳化、凝胶和稳定等多种功能作用。因此;肉与肉制品中蛋白质的降解会对产品品质有很大的影响。本文主要综述了猪肉蛋白质的主要种类、蛋白质降解伴随着的结构和组成的变化、蛋白质降解对猪肉制品品质的影响以及相关的分析测定研究进展,旨在为开展相关研究提供参考。     

高温水煮和酸煮对猪骨硬度及化学成分的影响

为研究高温水煮和酸煮对猪骨硬度及化学成分的影响。以猪骨为实验对象,研究120℃条件下猪骨在水中煮制不同时间(40、50、60、70、80 min)和不同体积分数(0.0%、0.2%、0.4%、0.6%、0.8%、1.0%)的醋酸溶液中煮制80 min后猪骨硬度的变化。用凯氏定氮法和电感耦合等离子体原子发射光谱法测定未煮制猪骨、120℃条件下水中和1.0%醋酸溶液中煮制80 min后猪骨蛋白含量、钙、磷元素含量和钙、磷元素溶出量,用扫描电子显微镜观察猪骨粉碎后微观结构,测定猪骨红外吸收光谱,探究煮制后猪骨成分和结构的变化。结果表明,高温煮制能使猪骨硬度下降,水煮时间从40 min延长到80 min,猪骨硬度从(16 445±867)g下降到(10 995±546)g,醋酸溶液体积分数从0.0%增加到1.0%,猪骨硬度从(10 995±546)g下降到(6 003±153)g。高温煮制能使猪骨蛋白含量降低,猪骨表观钙、磷含量增加,钙、磷溶出量增加。水煮后猪骨蛋白含量为(28.5±2.3)g/100 g,降低了7.4%;猪骨表观钙、磷元素含量分别为(210.0±8.2)mg/g和(96.0±4.0)mg/g,分别增加了11.8%和8.9%;猪骨钙、磷含量溶出量分别为(0.57±0.04)mg/g和(0.17±0.01)mg/g。1.0%醋酸煮后猪骨蛋白含量为(25.9±0.9)g/100 g,降低了10.0%;猪骨表观钙、磷元素含量分别为(230.0±6.4)mg/g和(100.0±2.3)mg/g,分别增加了18.3%和14.8%;猪骨钙、磷元素溶出量分别为(1.73±0.01)mg/g和(0.75±0.01)mg/g。经扫描电子显微镜观测发现,煮制后的猪骨易粉碎,1.0%醋酸煮后的猪骨最容易粉碎。红外光谱发现,煮制后猪骨成分发生了变化,图谱的峰比未煮制简单,成分比未煮制猪骨单一,而加水煮制和加酸煮制后猪骨图谱的峰相似,煮制后猪骨红外光谱图更接近人工合成的羟基磷灰石晶体。高温水煮和酸煮均能引起猪骨蛋白、钙元素和磷元素等化学成分含量的变化,导致猪骨硬度显著下降(P0.05)。     

欧姆加热与水浴加热对羊肉糜滋味物质及游离脂肪酸的影响

分别以不同电压欧姆加热(5 V/cm、8 V/cm、11 V/cm)以及水浴加热的方法将羊肉肉糜加热至中心温度95℃,用高效液相色谱法(HPLC)测定其中重要滋味物质(游离氨基酸、5’-核苷酸及其降解产物和丁二酸)含量,同时测定水分、粗脂肪、粗蛋白与盐含量等基本指标,并用气相色谱法(GC)测定其在20 d贮藏期内游离脂肪酸的变化情况。结果发现:欧姆加热低中电压(5 V/cm、8 V/cm)组所得样品具有比水浴加热组样品更浓的鲜味,而高电压组(11 V/cm)滋味较淡。欧姆加热对游离脂肪酸产生具有促进作用,且电压越高,促进作用越强。但高电压组贮藏过程中多不饱和脂肪酸氧化作用较强,可能更易产生不愉快气味。综合来看,欧姆加热低中电压组羊肉糜具有较好的滋味与香味,且略优于传统水浴加热。     

欧姆加热不同电压与终温对羊肉蛋白质降解及肉品品质的影响

本文研究了欧姆加热不同电压及终温对羊肉半膜肌蛋白质的影响及其与肉色、保水性等基本质量指标之间的相关性。羊肉半膜肌分别以10 V/cm与20 V/cm加热至中心温度50℃、60℃、80℃、100℃,测定肉色、蒸煮损失,并进行差示量热扫描(DSC)及可溶解肌浆蛋白SDS-PAGE电泳。结果表明:20 V/cm组样品与10 V/cm组相比,颜色较浅,蒸煮损失较高(p0.05),肌浆蛋白变性程度高(p0.05)。肌浆蛋白溶解性与肉色指标以及可蒸煮损失之间具有显著相关性,其中红度值a*与可溶性肌浆蛋白含量显著正相关,而蒸煮损失CL与之显著负相关。对以10 V/cm与20 V/cm加热至95℃后储藏7 d的样品,测定其羰基含量、巯基含量、非血红素铁含量以及丙二醛含量,发现20 V/cm组样品在储藏期间氧化程度显著(p0.05)高于10 V/cm的样品,表明10 V/cm处理的样品具有较好的品质。     

Edam牦牛干酪成熟过程中品质变化及蛋白质降解

为研究Edam牦牛半硬质干酪成熟机理，分别测定成熟0、20、40、60、80 d Edam牦牛干酪的感官、理化、物性、蛋白质和脂肪分解指标，采用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳和傅里叶变换红外光谱等方法研究酪蛋白降解情况，通过Pearson相关性分析成熟时间与各指标间的相关性。结果表明：随着成熟时间延长，感官评分先下降后上升；水分含量、pH值下降；亮度值（L*）下降，红度值（a*）和黄度值（b*）值上升；硬度、弹性、胶黏性均上升，凝聚性逐渐下降；储能模量和损耗模量升高，损耗角正切值始终小于1；成熟时间与总氮含量、pH 4.6和12%三氯乙酸条件下干酪中可溶性氮含量等呈极显著正相关（P<0.01）；脂肪含量先升高后降低，游离脂肪酸含量和硫代巴比妥酸值逐渐增加。酪蛋白（casein,CN）降解研究结果表明：αs1-CN、αs2-CN、β-CN及κ-CN均随成熟时间延长而不断降解，成熟80 d时大分子蛋白降解明显；成熟过程中β-折叠、α-螺旋逐渐向无规卷曲转化；成熟时间与羰基含量、表面疏水性呈极显著正相关（P<0.01），与总巯基含量呈显著负相关（P<0.05）。