猪肉中挥发性盐基氮的实验室质量考核研究

挥发性盐基氮(TVB-N)是动物性食品由于酶和细菌的作用,蛋白质分解而产生的的氨以及胺类等碱性含氮物质,表明氨基酸被破坏程度。     

冻猪肉挥发性盐基氮的测定

冻猪肉测定挥发性盐基氮时,采样部位应以背部或臀部深层肌肉最为合适;样品处理后尽可能在1h内完成测定;指示剂为甲基红溴甲酚绿效果更好;所用电炉为500W为最好。     

电子鼻技术对猪肉挥发性盐基氮的预测研究

为预测不同肥瘦配比猪肉的新鲜度,对4℃恒温贮藏条件下的新鲜猪肉进行挥发性盐基总氮(Total Volatile Basic Nitrogen,TVB-N)检测和营养成分检测,同时利用电子鼻技术检测挥发性气味的信息。以传感器阵列特征值为自变量建立蛋白质、脂肪的回归预测模型,分别对不同肥瘦配比的猪肉样本建立不分类和分类2种TVB-N神经网络预测模型。结果表明:先分类再建立神经网络模型预测的效果更优,将样本进行二分类建立2个模型后,模型训练组的相关系数达0.994、0.985(p<0.01),预测组的相关系数达到0.984、0.979(p<0.01);模型的绝对误差小而且分布区间集中,训练组和预测组各有86%、62.6%的样本的绝对误差在0~1之间;训练组中没有绝对误差大于2.5的样本,预测组中仅有8.5%的样本绝对误差大于2.5。电子鼻传感器特征信号与TVB-N数据具有很强的相关性,电子鼻可以快速预测出不同肥瘦配比猪肉在贮藏期间TVB-N含量的变化,进而无损的评价猪肉的新鲜度。     

不同储存温度对猪肉中挥发性盐基氮本底值测定水平的影响

目的探寻猪肉在存储过程中能够准确测定猪肉中挥发性盐基氮本底值的最佳储存温度。方法以正规超市售卖的普通新鲜猪肉(黄淮海黑猪、滇南小耳猪、太湖猪、大花白猪)为原料制成样品,测定该样品在不同的存储温度(–18、–8、2、12、22℃)下存储24、48、72、96、120h后猪肉中挥发性盐基氮含量的值。结果猪肉在–18℃的存储条件下保存120 h,挥发性盐基氮含量几乎不变(4种猪肉变化量分别为升高5.1%、5.6%、5.5%、4.3%),其他存储温度越高、保存时间越久,肉中pH值越高,挥发性盐基氮含量也越高。结论猪肉样品在–18℃以下密封保存时,更能够准确测定样品中的挥发性盐基氮的本底值。     

提取近红外光谱有效变量快速检测猪肉挥发性盐基氮

以市售新鲜冷藏(4℃)猪肉为研究对象,采用蒙特卡洛-无信息变量消除算法和连续投影算法对原始近红外光谱的800个波长变量进行提取,共筛选出与挥发性盐基氮含量直接和间接相关的有效波长变量36个,并采用偏最小二乘法构建预测模型,验证集的相关系数和标准偏差分别为0.876 4和1.205 7 mg/100 g。     

猪肉中挥发性盐基氮含量光谱检测模型的修正方法

目的 研究猪肉新鲜度指标挥发性盐基氮(TVB-N)含量检测模型修正方法, 以提高光谱校正模型对不同品种猪肉样品的适用性。方法 建立基于偏最小二乘回归(PLSR)的杜长大猪肉TVB-N模型, 采用光谱信号补正与模型更新两种方法对该模型进行修订, 比较修正后杜长大模型对恩施山猪样本的预测效果。结果 建立的杜长大猪肉样本模型预测决定系数R2p为0.884, 预测标准差RMSEP为1.792, 将此模型用于预测恩施山猪TVB-N值, R2p为0.552, RMSEP为4.733。修正后的杜长大猪肉样本模型预测恩施山猪TVB-N值时, R2p分别提高到0.964和0.943, RMSEP分别降低为1.329和1.885。结论 光谱信号补正和模型更新方法均能有效改善模型预测性能, 提高模型适应性。     

反射光谱法测定食品中挥发性盐基氮

采用反射光谱法测定鱼，肉食品中挥发性盐基氮，方法精密度（ＲＳＤ）为２．６％（ｎ＝６）线性范围为１～８μｇ／ｍｌ，检出限为０．５μｇ／ｍｌ，用于猪肉和鱼鲜度检验，并有对鲜鱼做了连续监测，结果满意。     

猪肉在冻藏中挥发性盐基氮含量的变化

挥发性盐基氮（TVBN）是动物性食品中蛋白质在腐败过程中,由于酶和细菌的作用,分解后产生的氨和胺类等碱性含氮物质,TVBN的含量是评定动物性食品新鲜度的重要指标,本试验测试了猪肉在冻藏中TVBN的变化及冻藏工艺对TVBN含量的影响。结果表明,正确的冻藏工艺对冻藏肉的品质没有明显影响。     

冷冻贮藏对冻猪肉冰晶形态、TVB-N及TBARS的影响

研究了冻藏(-10、-15、-19、-22℃,150d)对猪肉品质的影响.结果显示:冷冻温度越低,形成的冰晶越小,冷冻结束时,各处理的冰晶面积的分布范围为4045.855～ 5509.739μm2,相当直径分布范围为69.381～ 81.439μm;经150d贮藏后,尽管温度越低,冰晶重结晶速度越慢,冰晶的体积仍显著增大(p<0.01),面积为7546.855～ 11273.890μm2,相当直径为98.945～ 106.670μm;而圆度和长度则没有显著变化(p>0.05).挥发性盐基氮含量(TVB-N含量)和硫代巴比妥酸还原值(TBARS值)同样也显著增大(p<0.05).冰晶体积、TVB-N含量和TBARS值变化显示了很好的时间相关性.实验说明冰晶形态也可用于反应猪肉的新鲜程度.     

东坡肘子风味电子鼻分析与感官评价相关性探究

电子鼻作为新兴的智能感官仪器,在食品加工与质量控制方面具有良好的应用。本试验以东坡肘子为对象,利用感官评价和电子鼻技术对其风味特征进行分析,并结合方差分析(ANOVA)、主成分分析(PCA)、聚类分析(CA)和偏最小二乘法(PLS),研究感官评价与电子鼻传感器之间的相关性。结果表明,感官评价结果与电子鼻分析之间具有良好的一致性,传感器LY2/LG与香辛料香味和姜葱蒜香味具有较好的相关性,传感器P30/2、T30/1、P40/2、P30/1、PA/2、T40/2、T70/2、P10/2、P10/1、TA/2、P40/1和T40/1与基本肉香味、特征肉香味和焦糖香味相关性良好。     

Significance of fat supplemented diets on pork quality - Connections between specific fatty acids and sensory attributes of pork

The influence of two diets with different fatty acid compositions has been studied with regard to overall pork quality and significance of specific fatty acids on sensory attributes in fried chops and oven roasts. Twenty castrates and 20 females were in a balanced experimental set-up fed with a standard diet supplemented with α-tocopherol (200mg/kg feed) where the fat source was either 3% of palm oil or 3% rapeseed oil. After slaughter, despite differences in lipid composition and sensory attributes, no significant difference in overall meat quality parameters and flavour precursors was found. Comparison of the two diets showed that supplementation with rapeseed oil resulted in a significantly higher content of C18:3n-3 (polar lipid (PL), neutral lipid (NL)), C18:2n-6c (NL) and C20:2 (NL) in LD and C18:1n-9c, C18:2n-6c, C18:3n-3, C20:3n-3, C22:5n-3 in backfat, while supplementation with palm oil resulted in a higher content of C16:0 (NL), C16:1 (PL), C18:1n-9t (NL) in LD and C16:0, C17:0, C18:0, C16:1, C20:4n-6 in backfat. A positive and significant correlation between the contents of C18:2n-6c, C20:3n-6 in the PL fraction and the sensory attributes fried meat odour and sweet odour were found in fried pork chops from female pigs. Likewise, positive correlations were seen between the content of C18:1n-9c in the PL fraction and sensory attributes such as sourish odour, piggy odour and piggy flavour in whole oven roasts. These data substantiate the view that specific fatty acids in the PL fraction influences flavour attributes in pork.     

利用模糊数学感官评价法研究猪肉丸加工工艺

以猪肉为原料,通过单因素和正交试验,结合模糊数学感官评价方怯,研究猪肉丸的加工工艺.结果表明,产品的最佳配方:食盐2.0％,脂肪10％,混合磷酸盐0.3％,卡拉胶0.7％.该工艺条件下,产品的蒸煮产率为75.9％.     

膨化米糊流变学特性及其感官指标的相关性研究

通过对籼稻、粳稻和糯稻三种不同类型稻米的膨化米糊的流变学特性与感官指标进行研究,确定膨化米糊的流体类型,分析其流变学特性与感官指标之间的联系。结果表明：膨化米糊为假塑性流体,其感官指标（色泽、香气、总分）与流变指数呈显著负相关,其黏度系数对感官指标有影响。     

Elucidation of the relationship between cooking temperature, water distribution and sensory attributes of pork - a combined NMR and sensory study

Low-field NMR T(2) relaxation was measured continuously during cooking of pork samples (m. longissimus dorsi) to a final temperature of 75 °C. Simultaneously the remaining muscle was cooked in an oven to a core temperature of either 62 or 75 °C and subsequently evaluated by a sensory panel. Highly significant effects of final cooking temperature on the sensory attributes juiciness (initial and final), hardness, tenderness, crumbliness and chewing time were found. Juiciness and tenderness decreased with increasing temperature, while hardness, crumbliness and chewing time increased with increasing temperature. Distributed T(2) relaxation data revealed marked effects of temperature (62 vs. 75 °C) on the water distribution within the meat. Partial least squares (PLS) regressions were used to examine a potential prediction of sensory attributes from the distributed T(2) relaxation data, and high correlations were obtained. Moreover, loadings from the PLS regressions were analysed to evaluate the alterations in the water distribution as a function of temperature that contribute to changes in juiciness. This analysis revealed that the reduction in juiciness at 75 °C can be ascribed to changes in the size of the pores confining the myofibrillar water together with an expulsion of water.     

Evaluation of pork colour sensory colour assessment using trained and untrained sensory panellists

M. longissimus dorsi and M. psoas major minced pork patties from three dietary treatment groups of DLY (Duroc/Landrace/Yorkshire) cross bred pigs were packaged in polythene bags and placed in a retail refrigerated display cabinet at 5±1?°C, under fluorescent light (1000 lux) for up to 5 days. Each dietary treatment group consisted of pigs (n=7) fed either a low vitamin E diet (80 mg dl-α-tocopheryl acetate/kg of feed), supplemental iron [7 g iron (II) sulphate/kg feed] or supplemental vitamin E (200mg dl-α-tocopheryl acetate/kg of feed)+supplemental iron. Samples were subjected to visual colour evaluation by a trained sensory panel (n=8) and an untrained panel (n=8) on days 0, 1, 3 and 5 of display. The signal to noise (S/N) ratios for assessors and replicates for the trained assessor group were higher than those of the untrained assessor group indicating greater reliability in the trained assessor results. The trained assessor group produced relatively normal percentile distributions for sensory terms in the assessment of both M. longissimus dorsi and M. psoas major muscles. The untrained assessor group displayed more skewed or non-symmetric distributions for M. longissimus dorsi, but produced a normal distribution for M. psoas major. Quantitative and qualitative analysis of the sensory profiling by both the trained and untrained groups of test subjects showed that in general sensory training contributed to a more effective visual sensory evaluation of M. longissimus dorsi in terms of metmyoglobin development. However, this is not the case for M. psoas major where both groups of assessors produced comparable results. Use of uniploar scaling did not improve the discriminative ability of assessors, both trained and untrained, in assessment of blue and yellow. The untrained group of assessors were even less effective in the use of these scales. It appeared that the sensory visual assessment of meat products can be performed effectively without training when the product colour is familiar to the assessors. However, training of panellists becomes relevant when a more unfamiliar product of unfamiliar colour is to be assessed and the unintuitive aspect of discrimination may play a greater role in the objective sensory colour assessment of meat.     

红烧肉感官描述属性与各分指标测定值之间的相关性分析

在对我国6种具地域性代表的红烧肉进行感官分析,并建立感官描述词汇表的基础之上,采用仪器分析法分别对红烧肉感官描述属性各分指标进行测定,应用偏最小二乘法(PLS)分析红烧肉各感官描述属性与分指标的相关性。结果表明,颜色分析a*值与以红色为主调的词汇(绯红、枣红等)相关性较好,L*值与红润相关性较好;酱香、卤香主要与棕榈酸、茴香脑相关,大料味与草蒿脑、大茴香醛、桂皮醛、苯丙醛具较好相关性;焦糖味与大部分氨基酸相关性较好,酱油味、咸味与鲜味核苷酸具较好相关性;皮的回复性与弹、韧相关性较好,粘聚性与胶黏感、黏性具一定相关性;肥肉的胶着度、咀嚼度、硬度与入口即化、黏、润泽、烂、多汁、滑嫩、平滑具较强负相关性;瘦肉的硬度、胶着度、咀嚼度与嚼劲具较好正相关,与细腻、鲜嫩、软烂具呈较强负相关。     

The relationship between different pork carcass lean yield definitions and the market carcass value

Cutout and dissection data from 265 carcasses were used to study the impact of the lean yield definition on their ability to discriminate lean carcasses from fat carcasses. The same data were used to evaluate the relationship between the various definitions of lean yield, such as the lean yield predicted by the Destron optical probe (LYDESTRON), the saleable meat yield (SMY), the Canadian lean yield (LY2000) and the lean meat percentage (TVM), and the market carcass value. Based on the highest number of carcasses assigned to the extreme grades (leaner and fatter), the TVM had the greatest discriminating capability based on carcass leanness. The correlation coefficients obtained between market carcass value and LYDESTRON, SMY, LY2000 and TVM were 0.14, 0.54, 0.36 and 0.23, respectively. These weak correlations demonstrate that lean yield alone does not adequately explain the variation in market value between carcasses. Lean yield therefore cannot be used to estimate market value independently of the definition used.