冷却牛肉质量评定系统开发

本文以计算机视觉系统为基础，以面向对象的C＋＋程序语言为开发工具，综合运用人工神经网络，模糊评价，模式识别等理论，在VC6．0开发平台上，编制了高效实用的图像处理软件，开发出冷却牛肉新鲜度和嫩度指标的质量自动评定系统。操作人员能够方便地运用键盘和鼠标对系统直观的图像化界面进行操作，使得本系统具有方便，灵活的特点，便于推广应用。     

延迟冷却对牛肉品质影响的研究

研究了常规冷却和延迟冷却对中国杂交黄牛(鲁西黄牛×西门塔尔)宰后冷却过程中牛胴体pH、温度的变化、胴体冷却失重、背最长肌汁液损失、蒸煮损失、保水性、肉色及成熟过程中剪切力值的变化。结果表明:延迟冷却减缓了牛胴体温度的降低速率(P<0.05),加快了牛胴体pH的降低(P<0.05);延迟冷却提高了牛背最长肌的嫩化速度,改善了肉色(P<0.05),但增加了汁液损失和蒸煮损失,降低了保水性(P<0.05)。因此,优化延迟冷却程序是必要的。     

冷却方式和电刺激对牛肉品质的影响

肉的嫩度是肉最重要的食用品质,它决定了肉的商品属性。动物宰前、宰后24h内的技术处理决定了肉的嫩度。本文主要综述了对牛屠宰后的处理方式如冷却方式、电刺激处理等对牛肉嫩度的影响。     

冷却牛肉贮藏期间嫩度变化的研究

本实验探讨了冷却牛肉在贮藏过程中嫩度变化趋势及其与pH值变化之间的相关性,以及冷却牛肉嫩度与失水率的关系.实验结果显示衡量嫩度的指标剪切力值总体趋势是随着贮藏时间的延长而增大,在45天左右达到最大值后呈下降趋势;冷却牛肉贮藏期间嫩度变化与pH值变化无相关性;失水率是影响冷却牛肉嫩度变化的主要因素.     

冷却牛肉新鲜度评价及图像分析方法研究

本文探讨了冷却牛肉pH值和挥发性盐基氮含量与冷却牛肉存放时间之间的关系，并利用回归方程对冷却牛肉的新鲜度进行了评价。研究引入模糊评判方法，利用pH值和挥发性盐基氮含量两个指标对牛肉新鲜度进行了综合评价。对基于图像处理技术的牛肉新鲜度评价方法进行了深入的研究。研究表明，利用pH值和挥发性盐基氮含量两个指标综合评价牛肉新鲜度，评价的正确率比单独使用两个指标有所提高；采用图像分析方法对牛肉新鲜度评价，不仅评价正确率高，而且可省去繁琐的化学试验，是一种方便快捷的冷却牛肉新鲜度评价方法。     

牛肉嫩化机制的初步研究

对牛肉分别注射300mmol／LCaCl2溶液、EDTA溶液、ZnCl2溶液（注射量为肉重的5％），然后将处理样品在4℃下分别腌制24h、48h，通过对其剪切力值、MFI的测定，初步研究牛肉嫩化的机制。结果表明，注射CaCl2能促进肌原纤维的分解，进而加速肉的嫩化；而注射EDTA和ZnCl2却抑制肌原纤维的分解，阻止肉的嫩化。牛肉的嫩化是Ca^2＋通过促进肌原纤维的分解而实现的。     

牛肉嫩化技术的研究进展

肉品嫩度是肉的首要食用品质,它是消费者评判肉质优劣的最常用指标。肉嫩度的改善,多年来一直是国内外肉品科学研究的热点之一。宰后肉类的后期成熟和嫩化处理,是改善肉品嫩度的关键环节。对影响肉嫩度的宰前和宰后因素、目前嫩化方法及嫩化机制进行综述,最后对肉的嫩化趋势作出展望。     

牛肉嫩化技术的研究进展

牛肉的品质受多方面因素的影响,其中最重要的一个因素就是嫩度。本文介绍了影响牛肉嫩度的因素,以及目前通常使用的嫩化方法,最后提出了展望。     

冷却牛肉贮藏过程中的品质变化

分析冷却牛肉贮藏过程中各品质指标的变化,确定理化指标和微生物指标的相关性,为提高牛肉的品质提供依据。文中测定了4℃贮藏的冷却牛肉在0、2、4、6、8、10、12、14 d的菌落总数、嗜冷菌总数、pH值、挥发性盐基氮、失水率、色差值,确定了各指标随保存时间的变化规律及其相关性。结果表明:在贮藏过程中,pH值呈现先下降后上升的趋势;挥发性盐基氮呈上升趋势;系水力逐渐下降;肉色a值、DE(d ifference error)值不断降低。在品质变化的各指标中,微生物菌落总数、嗜冷菌总数与pH值呈正相关,且差异显著(P<0.05);菌落总数与系水力、a值呈负相关性,差异显著(P<0.05)。其中菌落总数与挥发性盐基氮、a值的相关性较大且极显著相关(P<0.01)。由此可知,微生物的活动能引起牛肉理化指标的变化,通过测定挥发性盐基氮和a值可以客观反映冷却牛肉的微生物污染状况。     

冷却牛肉嫩化及保鲜

冷却肉又称冷鲜肉,冷却肉保持了肉品原有的组织结构和天然成分,营养破坏少,冷却牛肉制品具有脆软、可口、鲜嫩、风味佳、营养损失小等优点。本文综述了我国冷却牛肉的发展现状,冷却牛肉的嫩化方法及冷却牛肉的保鲜方法。     

不同包装材料对冷鲜牛肉品质的影响

采用感官评分、菌落总数、挥发性盐基氮、pH值为指标,研究保鲜袋、聚酯袋、铝箔复合袋三种不同包装材料对冷鲜牛肉在0～4℃条件下品质的影响。实验结果显示,在相同的冷藏条件下,聚酯袋包装的牛肉品质最佳,保鲜效果最好,铝箔复合袋包装的牛肉保鲜效果次之,保鲜袋包装的牛肉保鲜效果最差。     

减菌液涂布方法对冷鲜牛肉贮藏品质的影响

为筛选冷鲜牛肉加工时较优的减菌液涂布方法,分别将25℃、0.1%(w/w)的乳酸链球菌素(Nisin)、植酸、壳聚糖、溶菌酶和乳酸等天然减菌剂以喷涂法和浸渍法处理牛肉,考察4℃下贮藏10d后牛肉的p H值、蒸煮损失率、TBAS值、剪切力等理化指标和细菌总数的变化。结果表明:浸渍法比喷涂法更能保持冷鲜牛肉的嫩度,降低蒸煮损失率,减轻脂肪氧化和抑制细菌的生长,从而更适合做冷鲜牛肉保鲜剂的涂布方法。     

冷却牛肉保鲜技术的进展

为了改善新鲜牛肉不易保存、运输和销售的缺陷,综合概括了冷却牛肉保鲜技术,继而对常用的气调保鲜、辐照保鲜、保鲜剂保鲜、复合保鲜及延缓褪色等技术进行了较详细介绍。     

Ozone treatment of chilled beef

Summary. The initial specific rate of ozone decomposition by muscle was 1.02 ± 0.23 m/hr, for tissue stored at 0.3°C and equilibrium relative humidities (EH) of 99.3, 98.5 or 98.0% in air with ozone concentrations between 0.15 and 38.3 mg/m³, or in air-ozone mixtures containing 11% CO₂. the value was not affected by the presence or absence on the muscle surface of meat spoilage bacteria, yeasts or moulds but considerably lower values were obtained for lean and high fat surface tissues (0.44 and 0.31, respectively).
The slope α of the linear course of the logarithm of reaction velocity-time curves was a power function α= - 9.74 10^-4[O₃]^1.54 for ozone concentrations [O₃] 5 mg/m³. the slope was not significantly different from zero when muscle of EH 98.5% was exposed to 0.7 mg/m³ ozone, but significant values were determined when muscle had an EH of 98.0, and also when tissue (EH 99.3%) was exposed to ozone concentrations > 0.7 mg/m³. Values of α determined for surface tissue and muscle tissue were not significantly different when the same treatment was applied.     

Influence of HPP conditions on selected beef quality attributes and their stability during chilled storage

The aim of this work was to determine the effects of combined pressure and temperature treatments on beef quality attributes after processing and during chilled storage. Beef M. pectoralis profundus samples were pressurised at 400 and 600 MPa at 35, 45 and 55°C and compared with non-treated (NT) and oven cooked samples. High pressure processing (HPP) at higher temperatures (55°C) resulted in lower Warner Bratzler Shear Force (WBSF) and cook loss values than processing at 35°C. Thiobarbituric acid reactive substances (TBARS) values of pressurised samples were lower than cooked samples after processing and throughout refrigerated storage. An increase (p<0.001) in the omega 6/omega 3 (n6/n3) fatty acid ratio was found when pressure-temperature treatments were compared to raw samples, however, oven cooked samples presented the highest n6/n3 ratio among all of the treatments examined. The reported results show that HPP alters meat quality to a lesser extent than conventional cooking, thereby minimising the processing impact.     

Microbiological quality of chilled beef carcasses in Northern Ireland: a baseline survey

To standardize the assessment of the hygienic quality of beef carcasses in Northern Ireland (NI) abattoirs, swabbing techniques were evaluated. Six materials, including two commercially produced swabs, were compared for their ability to recover spoilage and pathogenic bacteria and for their ease of use as carcass swabs. A sponge retailed for domestic use was selected on the basis of efficiency of recovery of microorganisms, ease of use, and cost. On sample carcasses, 1,000 cm2 of the brisket was swabbed, since this site is normally readily contaminated. For 9 months, 420 carcasses in seven of the nine European Union-approved abattoirs in NI were sampled while in the chiller (24 to 48 h after kill). Total viable count (TVC), yeasts and molds, and Enterobacteriaceae were enumerated after incubation at 22 (48 h) and 37 degrees C (48 h), and the results were expressed as log CFU/cm2. The mean TVC results at 22 and 37 degrees C were 2.80+/-0.70 and 2.75+/-0.64, respectively. Although 63% of samples had yeasts that grew at 22 degrees C, only 35% were positive at 37 degrees C. The respective mean yeast counts were 1.12+/-0.59 and 0.46+/-0.51. Enterobacteriaceae were present in 15% of samples at 22 degrees C and 21% of samples at 37 degrees C. The mean counts for positive samples were 0.41+/-0.37 and 0.40+/-0.30, respectively. Molds were found in less than 4% of samples. Given that the brisket is normally one of the most heavily contaminated parts of the carcass, these results suggest that good hygienic practices are in operation in NI abattoirs. The results also enabled the abattoirs with the cleanest carcasses to be identified, hence permitting best practices to be found.     

Influence of various preservatives on the quality of minced beef under modified atmosphere at chilled storage

The effect of preservatives on microbial quality, pH, drip-loss, roasting-loss, colour, and sensorial properties of modified atmosphere packaged (70% O₂ and 30% CO₂) minced beef (M. semimembranosus) stored at (2 ± 0.5 °C) for 12 days was investigated. Beef cubes (approx. 20 × 20 × 20 mm size) were immersed in solutions of 2% and 5% lactic acid, 2% lactic acid combined with 0.5% sodium ascorbate, 20% potassium lactate and 20% potassium sorbate before mincing. Addition of lactic acid was associated with pH drop, which increased drip-loss and roasting-loss. Application of all additives inhibited aerobic micro-organisms (10³–10⁴ CFU g⁻¹ on day 12) compared to reference sample (9 × 10⁵ CFU g⁻¹ on day 12). Lactic acid discoloured samples, while sodium ascorbate seemed to improve colour stability. Despite good visual colour characteristics, potassium sorbate treated samples were organoleptically unacceptable with massive off-flavour.     

包装方式对冷鲜牛肉保鲜效果的影响

采用真空包装、热收缩膜包装、保鲜剂配合热收缩膜包装冷鲜牛肉,对其贮藏期间的质量变化进行研究。结果表明:对照组在第10d色泽变暗、表面发粘、肉质松散、有异味,挥发性盐基氮为20.35 mg/100g、菌落总数为1.6×106CFU/g;试验组Ⅰ、Ⅱ、Ⅲ在16d、19d、25d挥发性盐基氮分别为20.16 mg/100g、21.22 mg/100g、19.02 mg/100g,菌落总数分别为1.1×106CFU/g、1.2×106CFU/g、3.2×106CFU/g,已超过标准要求。保鲜处理有效地提高了冷鲜牛肉的货架期,其中采用热收缩膜配合复合保鲜剂的保鲜效果最好(25天)。     

中草药防腐剂在冷却牛肉中的保鲜应用研究

研究了三组中草药防腐剂结合两种包装对冷却牛肉的防腐保鲜效果,对冷却肉的微生物、感官品质和理化指标三方面进行了检测。结果显示,紫丹参提取液在维持冷却牛肉在贮藏期间的感官品质、微生物和理化指标上效果明显,均优于未经保鲜液处理的对照。复配液FP2保鲜效果要好于复配液FP1和紫丹参提取液,复配液FP2结合抗菌PE[T200-4＋负离子粉]3‰～5‰纳米薄膜包装可使冷却牛肉贮存至15d时仍符合国家二级鲜肉标准。     

推进“放心肉”服务体系建设 倡导食用卫生安全优质品牌冷却肉

为加强全国生猪屠宰行业监管,落实监管责任,切实提升肉品质量保障水平.国务院、商务部、财政部印发<关于开展放心肉服务体系建设试点工作的通知>,上海和北京、山东、江苏、福建、湖北、四川、青岛、厦门、广州等十个省市列为全国"试点"区域.将积极探索和尝试多种保障肉品质量安全的新举措,创建屠宰及肉品加工流通行业健康发展新机制.加强和规范检疫和肉品品质检验管理,引导和支持大中型屠宰肉类加工企业延伸产业链;开辟冷藏储运物流,生产冷却肉分割小包装,不断扩大卫生、安全、优质品牌肉品市场供应量.加大科普宣传力度,倡导食用卫生安全优质品牌冷却肉品.