干酪乳杆菌6033蛋白酶降解肌肉蛋白质的作用研究

本试验将干酪乳杆菌(Lactobacillus casei，Lc)6033蛋白酶液按5％的比例分别加入肌浆蛋白和肌原纤维蛋白提取液，然后设定不同的pH值，于15℃培养7d，定时取样，测定反应后的pH值、十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)检测蛋白质的变化。结果发现：不同设定的肌浆蛋白和肌原纤维蛋白试验组在反应初期pH值均稍稍降低，随着反应进程，各试验组的pH值呈现出逐步升高的趋势；其中，肌浆蛋白以pH5．0、4．5组的变化较为明显，肌原纤维蛋白则以pH6．0、5．0、4．5组的变化较为明显。经7d振荡培养后，电泳检测发现，各试验组肌浆蛋白均表现出分解现象，尤其以pH5．0组和pH4．5组更为明显；而肌原纤维蛋白也都表现出了明显的分解现象，尤以pH5．0组肌原纤维蛋白分解最明显。     

Comparative study of proximate composition and amino acid in farmed and wild Pseudobagrus ussuriensis muscles

The proximate composition and amino acid compositions of the muscle of wild and farmed Pseudobagrus ussuriensis were compared. The lipid content of the farmed fish was significantly higher, while moisture content was significantly lower, than those of the wild fish. Pseudobagrus ussuriensis protein has a well‐balanced amino acid composition. The percentages of total amino acids, essential amino acids, nonessential amino acids and delicious amino acids were significantly higher in the wild than those in farmed fish. The ratios of W_EAA to W_TAA (42.78%–43.02%) and W_EAA to W_NEAA (85.52%–87.74%) were comparable to the reference values of 40% and above 60% recommended by FAO/WHO. According to the amino acid scores, methionine would have been described as the first limiting amino acid, and Lys had the highest score for the protein in both wild and farmed Pseudobagrus ussuriensis. This study shows that Pseudobagrus ussuriensis under investigation have high nutritional qualities and are good protein resources.     

牛肉对小白鼠体重及运动能力的影响

目的：探讨牛肉对小白鼠运动能力的影响。方法：雄性小白鼠50 只,随机分为2 组,对照组20 只、牛肉组30 只,单笼饲养。限制采食量,初始量为6.0g/(d·只)喂养4 周。测小白鼠力竭运动时间、抓力、体质量,取肝组织和后腿肌肉测定肝糖原、肌糖原含量。结果：牛肉组与对照组相比。有降低体质量,增加速度,提高游泳力竭时间和抓力的趋势,但无显著差异。采食牛肉后,不论对小白鼠是否施加负荷,都能提高肝糖原、肌糖原、血清SOD 水平(P ＜ 0.05),能显著降低MDA 水平(P ＜ 0.05)。 结论：在日粮蛋白质和能量摄取量相同条件下,牛肉日粮具有控制小白鼠体质量和提高小白鼠的抓力和游泳力竭时间的趋势。不论是否附加负荷,都能提高肝脏和肌肉组织的糖原水平,并且显著提高机体的抗氧化能力。     

Antioxidant mechanism of grape procyanidins in muscle tissues: Redox interactions with endogenous ascorbic acid and α-tocopherol

The present study investigates the antioxidant mechanism of grape procyanidins and, in particular, their aptitude to establish redox interactions with two important components of the endogenous antioxidant system of muscle tissues, α-tocopherol (α-TOH) and ascorbic acid (AA). To this end, the progress of lipid oxidation was monitored in fish muscle supplemented with grape procyanidins at the concentrations usually employed in antioxidant food applications, and then related to the redox stability of the endogenous α-TOH and AA. In addition to the lipid oxidation protective effect, the incorporation of procyanidins also provided an improvement of the redox stability of the endogenous components in a straight procyanidinic concentration-dependent manner. Results showed the capacity of procyanidins to repair oxidised α-TOH at medium-long term, and to delay the AA depletion. Therefore, such cooperative redox interaction of exogenous procyanidins adequately complements the natural α-TOH regenerative system supplied by AA that is efficient at the early post mortem stages.     

A study of the ice crystal sizes of red muscle of pre-rigor Atlantic salmon (Salmo salar) fillets during superchilled storage

Pre-rigor salmon fillets were superchilled in an impingement freezer and stored at −1.7 ± 0.3 °C for 29 days. The objective of this work was to study the ice crystal sizes in red muscle of pre-rigor salmon fillets that were partially frozen at fast (−30 °C, 227 W/m² K, 2.1 min) which is referred to as process F and slow (−20 °C, 153 W/m² K, 4.2 min) which is referred to as process S during superchilled storage. It was observed that the size of intracellular ice crystals in pre-rigor muscles at faster superchilling rate was significantly (p < 0.05) smaller than that at slower superchilling rate. The size of ice crystals formed in pre-rigor muscle was significant (p < 0.05) smaller than that formed in post-rigor muscle. It was also observed that the size of intracellular ice crystals formed in pre-rigor red muscles was significant smaller than that in white muscle. In addition, a large number of small ice crystals are formed within the muscle during partial freezing of pre-rigor muscle compared to post-rigor muscle. Future research should focus on tests of the quality parameters separately in red and white muscles (pre- and post-rigor) during superchilled storage of food products in order to understand more about their characteristics (quality and shelf life).     

三种麻醉剂对小鼠离体子宫平滑肌收缩性影响的比较

目的探讨氨基甲酸乙酯、戊巴比妥钠、水合氯醛3种麻醉剂对小鼠离体子宫平滑肌收缩性的影响。方法将制备的小鼠离体子宫标本置入37℃低钙洛氏液,用BL-410生物机能实验系统记录加麻醉剂前、后及更换低钙洛氏液后各10min的收缩曲线,测量收缩频率和收缩强度,计算运动指数。结果3种麻醉剂对子宫平滑肌的收缩频率、收缩强度、运动指数都有明显的抑制作用,去除麻醉剂后都可恢复收缩。水合氯醛的抑制作用最强,为完全抑制,去除麻醉剂后很长时间才能恢复收缩;戊巴比妥钠的抑制作用最弱,去除麻醉剂后很快恢复收缩,且收缩强度和运动指数的恢复率都最高。3种麻醉剂在抑制率、恢复率上大都呈现量-效关系。结论在以动物子宫为研究对象的实验中宜用戊巴比妥钠作为麻醉剂。     

Optimisation of rancidity stability in long‐chain PUFA concentrates obtained from a rainbow trout (Oncorhynchus mykiss) by‐product

This research was focused on the production of polyunsaturated fatty acid concentrates from a farmed rainbow trout (Oncorhynchus mykiss) by‐product (i.e. belly muscle). The effect of different process variables (urea/fatty acids (FA) contents ratio, crystallisation time and temperature and stirring speed of the urea/FA mixture) on the lipid oxidation development during the urea complexation process was investigated. For this purpose, an experimental design (26 runs) following the response‐surface methodology was developed. As a result, peroxide value and TOTOX index showed to be dependent on the crystallisation time and temperature and the urea/FA ratio, while no influence of the crystallisation stirring speed was detected on both indices; additionally, polyene index was affected by the urea/FA ratio and its interaction with the crystallisation time. An optimised desirability score near 1.0 was attained provided values of 2.8 °C, 3.05 h and 3.57 were applied for crystallisation temperature, crystallisation time and urea/FA ratio, respectively.     

Role of pH and Ionic Strength on Water Relationships in Washed Minced Chicken-breast Muscle Gels

ABSTRACT The relationship between pH, ionic strength, and water balance of chicken-breast muscle gels was investigated. An increase in gel pH (pH 6.4 to 7.4) without added NaCl led to dramatic increases in water-holding capacity and water uptake (P < 0.05). Gels at 150 mM NaCl exhibited less ability to adsorb water than salt-free gels (P < 0.05 at pH 6.8 to 7.4) and had lower water-holding capacities (P < 0.05) and fold scores at and below pH 7. Varying salt concentration of the gel-bathing solutions had dramatic effect on the water uptake of the gels. The results show that strong water-absorbing gels can be produced at low ionic strengths and suggest that the negative charge of the muscle proteins is the driving force for water uptake and retention.