肌内脂肪含量对猪肉嫩度的影响

<正>畜禽肌肉嫩度的生化物质基础,国内外研究颇多,其中,肌肉脂肪含量和分布状况被看作是嫩度的重要影响因素之一.沈元新等认为:肌束间积聚脂肪时,结缔组织失去弹性,肌束易分离,易咀嚼,Kauffman等也有报道:肌肉脂肪趋向冲淡基质中的结缔组织,并提供水解胶原蛋白漂移的良好环境,从而,使肌肉嫩度得到改善.嫩度评定有感官评定和客观评定.感官评定是咀嚼过程中根据口腔粘膜和舌粘膜对肌肉柔嫩度的感觉进行评定;客观评定方法颇有几种,应用东北农学院试制的嫩度计测定剪切力值便是其中之一.本试验以不同肌肉脂肪含量猪肉为样本,感官评定和客观评定方法兼用,并结合加热过程,旨在进一步探索肌肉脂肪含量对猪肉嫩度的影响问题.     

杂交山猪骨骼肌PPARγ、RARα基因与脂代谢关系的研究

以3个山猪杂交组合为对象,分别测定18头猪的体脂和背最长肌(LD)脂代谢表观性状及LD肌细胞上PPARγ和RARα基因,研究上游基因对脂代谢的调控作用。首先优化该基因扩增条件,并采用qRT-PCR荧光定量技术检测LD肌细胞上PPARγ和RARα基因表达量。结果表明,PPARγ和RARα基因均可在骨骼肌细胞上有效表达并与体脂和IMF代谢间呈一定关联度。1/2山猪血统母猪骨骼肌细胞PPARγ和RARα基因表达量均较高,且呈现PPARγ基因为主导的脂肪合成代谢倾向,表现为皮下和肌内BF和IMF明显增加,肉质改善(p<0.05和p<0.01)。1/4山猪血统的杂交公猪和母猪骨骼肌细胞PPARγ基因表达量趋于下降,在雄性激素伴随下DDS的RARα基因升高,呈现RARα基因主导下抑制皮下或肌内脂肪原母细胞分化,脂肪沉积量明显减少。     

4种食品添加剂对猪肉嫩度的影响

研究卡拉胶、变性淀粉、氯化钙和木瓜蛋白酶4种食品添加剂对猪肉嫩度的影响。在单因素试验的基础上,通过正交试验,确定猪肉添加剂的最佳配方为木瓜蛋白酶的添加量0.05%、变性淀粉的添加量0.3%、氯化钙的添加量0.1%、卡拉胶的添加量0.15%;在优化条件下对猪肉进行嫩化处理,其剪切力为11.95N,油炸质量损失率为23.59%,感官评价值为50.3。此外,在4种食品添加剂中,木瓜蛋白酶对猪肉嫩度的影响最大,其次为变性淀粉,再次为氯化钙,卡拉胶影响最小。     

猪十三块肌肉嫩度秩位的确定

<正>嫩度是肉食口感惬意程度的综合指标,是肉食最重要的食用品质之一.长期以来,嫩度一直是肉类科学研究领域内的重要课题.过去对影响嫩度的各种因素以及嫩度的主客观评定方法,都进行了广泛深入的研究.     

猪骨骼肌组织学特性与猪肉嫩度关系的研究

目的:研究背最长肌和腰大肌的肌纤维直径、肌纤维密度及肌内脂肪百分面积对肌肉嫩度等的影响力或贡献力;方法:对6个杂交组合猪(N=36)的骨骼肌组织形态特征进行二维显微图像重建和与肌肉嫩度的数学关系拟合(n=36×2或×3);结果:腰大肌的肌纤维直径和密度分别比背最长肌细且密,但肌内脂肪百分面积普遍小于背最长肌.肌纤维直径对肌肉嫩度的影响力最大(r=0.966,P<0.01),直径越粗肌肉嫩度越差.肌纤维密度随直径而变化,肌纤维直径越粗,单位面积肌纤维密度越低,且与肌肉嫩度呈显著性相关(r=0.905,P<0.05),肌纤维密度越大肌肉嫩度越好,但贡献力小于肌纤维直径.肌内脂肪百分面积仪占与肌肉总面积的3%左右,本实验数据证实其不足以影响猪肉嫩度;结论:骨骼肌嫩度受肌纤维直径和密度影响较大,一定范围内肌内脂肪可能更多地影响猪肉的风味,而不是嫩度.     

复合磷酸盐对鸭肉饼嫩度的影响

研究焦磷酸盐与三聚磷酸盐的复合磷酸盐添加量和冰水添加量对鸭肉饼嫩度的影响.结果表明鸭肉饼较好嫩化的条件为:焦磷酸盐:三聚磷酸盐为1∶2,复合磷酸盐添加量为0.4％,冰水添加量为25％.其中,在3个因素中复合磷酸盐添加量对鸭肉饼嫩度的影响最大,其次为焦磷酸盐:三聚磷酸盐,水分影响最小.     

肌内结缔组织与肉嫩度关系研究

动物肌内结缔组织对肉的嫩度起到重要的影响作用,这些影响主要是通过肌内膜和肌束膜内胶原蛋白的变化而影响肉的嫩度。本文综述了肌内结缔组织结构及其组成特点,胶原蛋白的含量、溶解性、交联度,另外,分析了胶原蛋白在成熟过程中的变化对肉嫩度的影响,阐述了结缔组织在肉嫩化中的作用。     

肉的嫩度

肉的嫩度ＥｒｉｃＤｒａｎｓｆｉｅｌｄ著刘丽摘译周光宏校（南京农大动物科技学院，２１００９５）肉的质量问题一直为消费者所关注。尤其是肉的嫩度，在烹调前是无法评估的。肉的嫩度主要取决于多种生物学因素：动物品种、年龄、性别、肌肉类型、一些合成代谢和再分配剂...     

肉的嫩度与烹饪致嫩

影响肉类嫩度的因素包括；肌纤维的种类，结构和性质，结缔组织的含量和性质，肉类的持水性及肌肉经肪组织的分布和含量等，在烹饪加工过程中，刀口致嫩，保护性致嫩，火候致嫩，烹调技术致嫩主添加某些物质致嫩等是保证和提高菜肴柔嫩度的重要手段。     

梯度加热对羊肉嫩度的影响

以色泽、系水力、胶原蛋白溶解性、剪切力为评价指标,研究在常规加热的基础上,水浴与烘烤2种加热处理在50~60℃温度范围内保温一段时间是否对羊半腱肌与背最长肌嫩度有影响。结果表明:梯度加热过程中,羊半腱肌剪切力值有显著上升的趋势(P0.05),其中两段式加热的这一趋势较三段式加热更明显,与常规加热方式相比,梯度加热对肉色及系水率无明显影响,但对胶原蛋白溶解性影响显著(P0.05),与常规加热相比,梯度加热过程是相对比较理想的加热方式。     

Bovine longissimus muscle tenderness as affected by postmortem aging time, animal age and sex

Strip loins were removed from 10 bulls and 10 steers ～14 mo old and from 10 cows ≥ 44 mo. Samples were removed at 3, 7, 14, and 28 days postmortem. Shear-force values were measured. Sensory evaluation was done by a 15-member trained panel. Animal age and postmortem aging time had more influence on tenderness attributes than did sex of the animal. Increased postmortem aging time improved tenderness attributes regardless of sex or age.     

原子力显徽镜在牛肉嫩度测定中的应用研究

【目的】探讨原子力显微镜在牛肉嫩度测定中的应用,为肉品嫩度提供可靠、直观的测定方法。【方法】用100、150、200mmol/L不同浓度氯化钙(CaCl2)处理牛肉,肉样真空包装后于4℃下成熟72h后测定剪切力、肌原纤维指数(MFI),并用原子力显微镜观察肌原纤维小片,比较三者结果。【结果】三种测定方法结果基本一致,但有一定差异,原子力显微镜观察肌原纤维小片直观地反映了肌原纤维小片化程度。【结论】原子力显微镜能直观地反映肉的嫩化情况,是对剪切力和MFI测定方法在形态学上的完善。     

肌纤维类型与肉嫩度的关系

阐述了肉的肌纤维与宰后嫩度形成之间的联系,发现由于肌肉宰后消耗能量、产生代谢产物与活体具有不一样的方式,而这个方式因肌纤维差异而存在不同之处,这就会影响到肌肉宰后能量与代谢水平的平衡,进而对肌肉宰后成熟产生调控作用,最终极有可能影响其嫩度的形成。      

Comparison of methods for measuring shear force and sarcomere length and their relationship with sensorial tenderness of longissimus muscle in beef

Slice shear force (SSF) and laser diffraction, considered faster methodologies, for measuring beef instrumental tenderness and sarcomere length, were compared with reference methodologies Warner–Bratzler shear force (WBSF) and phase contrast microscopy. Striploin samples (n = 74) were analyzed for pH, sarcomere length, instrumental tenderness, myofibrillar fragmentation index, and sensorial tenderness. Pearson's correlation measured the association of meat evaluation methods with residual analysis of the multivariate analysis of variance model. The n-dimensional profile to evaluated methods was presented by biplot to identify the behavior of the correlation between the methods (variables). There was moderate correlation between SSF and WBSF (r = .63; p < .01) and both presented moderate correlation with sensorial tenderness (r = − .62 and −.55, to SSF and WBSF, respectively; p < .01). However, WBSF was more efficient to classify samples as tender (68%) than SSF (47%), comparing with sensorial tenderness (80%). There was a moderate correlation for laser and microscopy for sarcomere length (r = .57; p < .01). Sarcomeres were shorter when measured by laser than microscopy. Either with low correlation coefficients, sarcomere measured by laser (r = .29; p < .05) presented higher correlation with sensorial tenderness than with microscopy (r = .22; p < .10). Results highlighted that SSF was faster and easier to run, while WBSF was more appropriate to classify samples by sensorial tenderness grades. Laser diffraction is more suitable to explain effects on tenderness; however, microscopy revealed results of sarcomere length that were more realistic, once laser can underestimate sarcomeres.     

反复冻融的猪肉蛋白对N-亚硝胺形成量的影响

目的:探讨反复冻融的猪肉蛋白对N-亚硝胺形成量的影响。方法:设计两个体外模拟反应系统,模拟反应体系Ⅰ只含有Na NO2,模拟反应体系Ⅱ由二乙胺盐酸盐(DEA·HCl)和Na NO2组成。将反复冻融(0、1、2、3、4、7、10次)造成的不同氧化程度的肌肉蛋白(muscle protein,Mep)、肌浆蛋白(sarcoplasmic protein,SP)和肌原纤维蛋白(myofibrillar protein,MP)分别加入上述两个反应系统发生亚硝化反应,测定N-亚硝基二乙胺(N-nitrosodiethylamine,NDEA)的形成量,同时测定硫代巴比妥酸反应物(thiobarbituric acid reactive substance,TBARS)值、羰基和巯基含量等指标。结果:系统Ⅱ中NDEA的形成量是系统Ⅰ的20~80倍,表明底物DEA·HCl存在对NDEA的形成产生显著影响(P0.05)。反复冻融4次后,3种蛋白的羰基含量显著增加(P0.05),巯基含量显著下降(P0.05),意味着猪肉蛋白均发生了明显的蛋白氧化,其中以SP的氧化速率最快,氧化程度最严重,形成的NDEA量最多,Mep次之,MP氧化程度相对较轻,形成的NDEA量相对较少。结论:反复冻融造成的蛋白氧化促进了NDEA的形成。因而在肉品冻藏过程中应防止温度波动,避免反复冻融引起蛋白氧化,进而控制N-亚硝胺的形成。     

Relationship of texture profile analysis and Warner-Bratzler shear force with sensory characteristics of beef rib steaks

Cyclical texture profile analysis (TPA) parameters measured using a star-shaped probe with two cycles of 80% penetration and Warner-Bratzler shear force (WBS) were compared as predictors of objective tenderness and subjective sensory characteristics of rib steaks from 52 beef loins. The TPA parameters of hardness, cohesiveness and chewiness were negatively correlated (P<0.05) with trained panel sensory characteristics of initial tenderness (r=−0.64, −0.41, −0.62, respectively), amount of connective tissue (r=−0.57, −0.27, −0.55, respectively), overall tenderness (r=−0.68, −0.39, −0.64, respectively) and overall palatability (r=−0.56, −0.37, −0.53, respectively). These sensory characteristics were also negatively correlated (P<0.05) with WBS (r=−0.61, −0.49, −0.60, −0.56, respectively). Stepwise regression analysis generated prediction equations that included the TPA parameters of hardness and adhesiveness, which accounted for 47, 36, 51 and 38% of the variation in initial tenderness, amount of connective tissue, overall tenderness and overall palatability, respectively. Prediction equations using WBS accounted for 37, 24, 36 and 31% of the variation in initial tenderness, amount of connective tissue, overall tenderness and overall palatability, respectively. Hence, TPA explained more of the variation in subjective sensory tenderness of the rib steaks than WBS.     

Relationship between proteolytic changes and tenderness in prerigor lactic acid marinated beef

A meat tenderising procedure involving injection of a lactic acid solution into prerigor muscle was investigated using beef M pectoralis profundus. The distribution of lysosomal enzymes in subcellular fractions, densities of myofibrillar protein bands after SDS‐PAGE and shear force were measured in non‐injected, 0.5 M and 1.0 M lactic‐acid‐injected samples during a 21 days ageing period. The activities of cathepsin B + L and β‐glucuronidase in the soluble fraction increased with level of lactic acid and with time post‐mortem (P < 0.001). Lactic acid and storage decreased densities of SDS‐PAGE bands migrating at the position of myosin heavy chain (MHC) and α‐actinin and increased densities of a 150 kDa band (P < 0.01). SDS‐PAGE of isolated perimysium cleaved with CNBr showed proteolytic cleavage of collagen after prolonged storage. Lactic acid injection significantly reduced shear force (P < 0.001). The cathepsin B + L activity in the soluble fraction correlated to shear force (r = −0.8), the degradation of MHC and α‐actinin (r = −0.88 and −0.90) and the generation of the 150 kDa fragment (r = 0.90) but not to the generation of a 31 kDa fragment (r = 0.05). A major part of the tenderness improvement after lactic acid injection was complete at 24 h post‐mortem, and was therefore due to a rapid process, eg pH‐induced swelling of the muscle structure. The data on enzyme activities and protein degradation, however, suggested that the action of lysosomal cathepsins also contributed to textural changes. © 1999 Society of Chemical Industry     

Optical scattering in beef steak to predict tenderness using hyperspectral imaging in the VIS-NIR region

The objective of this research is to develop a non-destructive method for predicting cooked beef tenderness using optical scattering of light on fresh beef muscle tissue. A hyperspectral imaging system (λ = 496–1,036 nm) that consists of a CCD camera and an imaging spectrograph, was used to acquire beef steak images. The hyperspectral image consisted of 120 bands with spectral intervals of 4.54 nm. Sixty-one fresh beef steaks, including 44 strip loin and 17 tenderloin cuts, were collected. After imaging, the steaks were cooked and Warner-Bratzler shear (WBS) force values were collected as tenderness references. The optical scattering profiles were derived from the hyperspectral images and fitted to the modified Lorentzian function. Parameters, such as the peak height, full scattering width at half maximum (FWHM), and the slope around the FWHM were determined at each wavelength. Stepwise regression was used to identify 7 key wavelengths and parameters. The parameters were then used to predict the WBS scores. The model was able to predict WBS scores with an R = 0.67. Optical scattering implemented with hyperspectral imaging shows limited success for predicting current status of tenderness in beef steak.     

Effect of long-term betaine supplementation on chemical and physical characteristics of three muscles from the Alentejano pig

BACKGROUND: The use of betaine as a dietary supplement to reduce fat deposition and increase lean muscle mass in pigs is increasing. However, there is no available information on its effect on the physical and chemical (i.e. fatty acid (FA) profile) characteristics of pork. RESULTS: The effects of long‐term betaine intake (1 g betaine kg^?1 diet for 20 weeks) on the chemical and physical characteristics of Musculus longissimus dorsi, M. biceps femoris and M. semimembranosus from the Alentejano pig were investigated. The contents of total protein, intramuscular lipids (neutral and polar), myoglobin and total collagen as well as the water‐holding capacity, physical colour characteristics and FA profile of the three muscles were determined. With the exception of a significant increase in the intramuscular lipid content of M. longissimus dorsi and M. biceps femoris, betaine supplementation did not influence muscle chemical and colour characteristics or body fat deposition. CONCLUSION: These data suggest that long‐term betaine supplementation selectively increases intramuscular lipid deposition (a trait related to meat quality) while not affecting other chemical (including the atheroprotective FA profile) and physical characteristics of the Alentejano pig muscles studied. Copyright © 2012 Society of Chemical Industry