Consumer Assessment of Beef Tenderloin Steaks from Various USDA Quality Grades at 3 Degrees of Doneness

A consumer study was conducted to determine palatability ratings of beef tenderloin steaks from USDA Choice, USDA Select, and USDA Select with marbling scores from Slight 50 to 100 (USDA High Select) cooked to various degrees of doneness. Steaks were randomly assigned to 1 of 3 degree of doneness categories: very‐rare, medium‐rare, or well‐done. Consumers (N = 315) were screened for preference of degree of doneness and fed 4 samples of their preferred doneness (a warm‐up and one from each USDA quality grade treatment in a random order). Consumers evaluated steaks on an 8‐point verbally anchored hedonic scale for tenderness, juiciness, flavor, and overall like as well as rated steaks as acceptable or unacceptable for all palatability traits. Quality grade had no effect (P > 0.05) on consumer ratings for tenderness, juiciness, flavor, and overall like scores, with all traits averaging above a 7 (“like very much”) on the 8‐point scale. In addition, no differences (P > 0.05) were found in the percentage of samples rated as acceptable for all palatability traits, with more than 94% of samples rated acceptable for each trait in all quality grades evaluated. Steaks cooked to well‐done had lower (P < 0.05) juiciness scores than steaks cooked to very‐rare or medium‐rare and were rated lower for tenderness (P < 0.05) than steaks cooked to a very‐rare degree of doneness. Results indicate consumers were not able to detect differences in tenderness, juiciness, flavor, or overall like among beef tenderloin steaks from USDA Choice and Select quality grades.     

大理石花纹评分与猪背最长肌凝胶特性的关系研究

以猪背最长肌为材料,对第5～6根肋骨背最长肌横切面的大理石花纹进行等级评定,在不同离子强度和冷却方式下,研究大理石花纹评分与猪背最长肌凝胶特性的关系。结果表明：在0.60mol/L NaCl条件下,各等级花纹肉的凝胶特性好于同条件下离子强度0.45mol/L的凝胶(P＜0.05)。在0.60mol/L NaCl和同一冷却方式下,各等级之间的凝胶保水性(P＜0.01)和凝胶强度(P＜0.05)差异显著;而凝胶弹性差异不显著(P＞0.05)。在0.60mol/L NaCl和10℃冷却时,等级3具有最好的凝胶特性。此外,花纹等级与凝胶保水性呈显著正相关(P＜0.05),与蛋白溶解度和凝胶强度达到极显著正相关(P＜0.01)。大理石花纹分为3个等级,猪背最长肌的凝胶特性随着大理石花纹评分的增加而提高。     

基于图像处理和支持向量机分类的牛肉大理石花纹等级评定

牛肉胴体质量等级评定是牛肉依质论价的基础。其中，大理石花纹是评定牛肉质量等级的主要指标。由于人工评定存在许多缺点，采用机器视觉来判定牛肉胴体质量等级是一种很好的方法。研究了一种基于图像处理和支持向量机（SVM）分类的牛肉大理石花纹等级评定技术。首先应用阈值分割、形态学腐蚀及膨胀的方法来分割牛肉图像中的有效区域（用于大理石花纹等级评定的区域）；然后用矩方法来提取图像特征参数，最后用支持向量机的模式识别技术来构造牛肉大理石花纹等级分类模型。结果表明：该模型对我国国家标准规定的牛肉大理石花纹等级的正确识别率分别达到95.9％（一级）、89.2％（二级）、93．2％（三级）、100％（四级）。研究的牛肉大理石花纹等级的机器视觉检测方法是可行的，这为牛肉等级的在线检测装置设计提供了条件。     

Beef Marbling and Color Score Determination by Image Processing

Sixty steaks with various degrees of marbling and color were subjected to sensory evaluation and image processing. Marbling and color scores were assigned to each steak with USDA marbling score cards and a lean color guide. Images were recorded for each steak under the same conditions as used for sensory analysis. Steak images were processed for color and marbling characteristics. Image processing effectively predicted the lean color (R²= 0.86) and marbling scores (R²= 0.84). Image processing was an effective tool for determining USDA quality attributes of fresh meat.     

牛眼肌区域大理石花纹评级特征的研究

针对我国牛肉分级制度中的大理石花纹等级评定特征不确定的问题,提出用几何、粒度及形状参数来表征花纹几何、形状及分布特点的方法。选择对牛肉大理石花纹等级评定起主要作用的特征参数,对中国、美国及日本3个国家的牛肉等级图进行深入地研究,找寻3个国家牛肉大理石花纹分级标准的侧重点。对选取的参数数据进行相关性分析,剔除原特征集中相关性较强的特征,应用主成分分析法对影响大理石花纹等级的参数进行线性组合,选取适合的主成分建立大理石花纹的等级预测模型。     

Predicting intramuscular fat content and marbling score of pork along the longissimus muscle based on the last rib

The possibility of using IMF content/MS at the last rib to predict the corresponding fat attribute of loin chops at the 2nd last to the 7th last thoracic ribs and the mean of IMF content/MS of the whole loin joint was investigated. Linear and quadratic regression, cross‐validation analysis and analysis of variance were employed for the study. For either IMF or MS, linear and quadratic regression models had similar performance. The best mean correlation coefficients of calibration (R_c) of 0.91 and cross‐validation (R_v) of 0.88 were obtained for linear regression model of IMF content of the whole loin, while R_c of 0.90 and R_v of 0.88 were obtained for quadratic regression model of MS of the whole loin. The results indicated that IMF content and MS at the last rib had great potential for the prediction of IMF content and MS at the other ribs.     

脂肪含量对雪花牛排在高氧气调包装贮藏期间肉色稳定性的影响

为探究雪花牛排在高氧气调包装贮藏期间的肉色稳定性,该实验选用两种不同脂肪含量(A1和A3等级)的雪花牛排,进行高氧气调包装(80%O₂+20%CO₂)。在每个时间点(0、5和10 d),测定其各个指标的变化。结果表明,随着贮藏时间的延长两种等级的牛排脂质氧化程度均逐渐增大,肌红蛋白还原力逐渐减弱,使高铁肌红蛋白比例显著升高(p<0.05)。在贮藏至5 d时,两种等级的牛排肉色值未出现显著变化。而贮藏至10 d时,A3等级牛排褐变程度和脂肪氧化程度均显著大于A1等级,A1牛排的a^*值仅下降至17.43,而A3牛排的a^*值却下降至12.22;A3等级牛排脂肪氧化值达到1.82 mg MDA/kg,而A1等级牛排脂肪氧化值仅为1.09 mg MDA/kg;A3等级牛排MMb含量已经超过40%,肉色已完全褐变。因此,对于脂肪含量较高的高等级雪花牛排,高氧气调包装只能在较短的贮藏时间内使其保持良好的肉色,生产中若对此类高档牛排进行长期贮藏应谨慎使用高氧气调包装。     

基于不变矩和改进SVM的牛肉大理石纹评级

针对牛肉大理石纹人工评级过程中人为误差干扰大的问题,研究利用图像处理技术提高牛肉大理石纹评级的客观性并增强自动化程度,提出基于不变矩、灰度共生矩阵和混沌蜂群优化混合核函数支持向量机(Support Vector Machine,SVM)的牛肉大理石纹评级法。首先计算牛肉大理石纹图像的不变矩和灰度共生矩阵统计量并由此构造特征向量;然后将训练和测试样本输入到混合核函数SVM,采用混沌蜂群算法优化SVM中的惩罚因子及核参数,使其分类识别性能达到最优;最后输入待评级样本进行分类识别,得到最优评级结果。大量实验结果表明:根据我国NY/T676-2010牛肉大理石纹标准图谱,评级正确率分别达到100%(一级)、93.3%(二级)、93.3%(三级)、96.7%(四级)、100%(五级)。与基于灰度矩和SVM法、基于灰度共生矩阵和BP(Back Propagation)神经网络法相比,本文所得评级正确率最高,且与专业评级师的实际评级情况最相符。     

牛肉大理石花纹分级系统软件设计

目的 运用机器视觉技术, 开发牛肉大理石花纹自动检测系统。方法 该软件设计以VC++6.0为开发工具, 首先从牛肉大理石花纹检测系统人机界面着手, 通过对CCD相机的控制, 得到大理石花纹图像, 并最终用图像处理的方法得到牛肉大理石花纹的分级结果。结果 该软件运行效率高, 对牛肉大理石花纹的分级准确率达到87.5%。结论 该系统可以满足企业实际需要。     

机器视觉技术在牛肉大理石花纹识别中的应用

牛肉眼肌区域大理石花纹的丰富程度是牛肉分级的重要指标之一。采用工业相机采集多幅牛肉眼肌切面图像,利用VC++ 图像处理技术,对图像进行平滑去噪操作,采用自适应阈值法将眼肌区域从背景中分离,然后运用数学形态学的方法以及基于区域分割的方法确定有效眼肌区域,最终通过数理统计的算法识别大理石花纹。结果表明,该技术能有效识别眼肌区域中的大理石花纹,其耗时短、识别结果准确,利于牛肉等级的准确判定。