Glass Transition Values of Muscle Tissue

Reports of glass transition (Tg') values for frozen muscle tissue are not common and reported values are mostly much lower than would be expected. Tg’ values for muscle tissue and isolated proteins were studied using differential scanning calorimetry. Apparent Tg's of mackerel, cod and beef were similar (ca ?11 to ?13°C) and substantially higher than most published values (?15 to ?77°C for tuna and beef), but in accord with expectations for substances of high molecular weight. Dialyzed insoluble and soluble protein fractions from mackerel yielded apparent Tg’ values (ca ?7°C) that were similar, with both being higher than those for whole muscle. Apparent Tg’ values of ca ?7°C were determined for aqueous samples of gelatin and collagen, but none was detected for zein.     

胶原和明胶的玻璃化转变

本文综述了胶原和明胶的玻璃化转变的研究现状及进展，讨论了影响其玻璃化转变温度（Ｔｇ）的各种因素，以及Ｔｇ在皮胶原化学研究中的作用。     

大豆蛋白的玻璃化转变

在有关玻璃态和玻璃化转变理论的基础上,综述了大豆蛋白玻璃化转变的分析方法、转谷氨酰胺酶处理的大豆蛋白低水分的玻璃化转变及大豆蛋白分子结构与其玻璃化转变关系,并对今后的研究方向作了展望。     

Glass Transition Explanation for the Effect of Polyhydroxy Compounds on Protein Denaturation in Dehydrated Solids

Dehydrated proteins are frequently subjected to thermal stress in the presence of other components. The effect such substances may have upon protein structure, and therefore function, has not been fully investigated. Thus, the effect of added polyhydroxy components on the denaturation of lyophilized β-lactoglobulin, ovalbumin, and ribonuclease, as determined by differential scanning calorimetry, was evaluated. The denaturation temperature, T_m, of the globular proteins decreased in the dry state after the addition of sucrose, sorbitol, or glycerol. The thermal stability (based on T_m) of the dehydrated proteins appeared to correlate with the glass transition temperature (T_g) of the polyhydroxy component, which was assumed to be related to the T_g of the mixture. The lower the T_g of the component, the greater was the degree of protein destabilization. Thus, glass transition data may be used to predict the effect that a component would have on denaturation of dehydrated proteins at elevated temperatures.     

水分含量对草莓玻璃化转变温度的影响

在冻干和低温保存中,玻璃化转变温度是一个非常重要的参数。本文用差示扫描量热仪测量得到不同湿基水分含量的草莓汁的玻璃化转变温度。实验发现水分含量较高时(>50%),草莓发生的是部分玻璃化转变,不同湿基水份含量草莓汁的Tg’基本相同,水分对其的影响较小。而水分含量较低时(<45%),草莓降温时往往出现完全玻璃化转变,不同湿基水分含量草莓的Tg有很大不同,完全玻璃化转变温度随着水分含量的减少而升高,拟合得到Tg随水分变化的公式。     

Co‐extrusion of pearl millet‐whey protein concentrate for expanded snacks

A study was conducted to develop pearl millet‐based extruded snacks with whey protein concentrate (WPC) to enhance its acceptability and nutritional value. Pearl millet grits (841 μ) was extruded with different levels (0%, 2.5%, 5.0% and 7.5%) of WPC at constant feed rate (10.5 kg h^?1) and moisture content (14%). Addition of whey protein at 7.5% level significantly (P ≤ 0.05) increased T_g from 75.1 ± 0.26 °C to 120.5 ± 1.28 °C and T_m from 89.1 ± 1.51 °C to 158.7 ± 1.37 °C, which resulted in less expanded and harder extrudates. The expansion index of extrudates was negatively correlated (P ≤ 0.05) with protein (r = ?0.940), bulk density (r = ?0.949), hardness (r = ?0.971) and breaking strength (r = ?0.921), while positively correlated (P ≤ 0.05) with overall acceptability (OAA; r = 0.988). Keeping in view the nutritional, textural and consumer's acceptability, incorporation of 5% WPC in pearl millet grits (841 μ) was recommended for preparation of acceptable expanded snacks.     

Functionality of spray-dried strawberry powder: effects of whey protein isolate and maltodextrin

The effectiveness of two drying agents, namely whey protein isolate (WPI) and maltodextrin (MD), was evaluated during spray-drying of strawberry puree. With the increase of WPI substitution in the feed material, the surface tension of strawberry puree decreased, and powder recovery increased. Powder recovery (R_p) increased from 39.2 ± 2.3% (S:MD:WPI = 60:40:0) to 56.5 ± 2.8% when MD was replaced by WPI (S:MD:WPI = 60:39:1). Surface morphology of powders showed that the addition of WPI resulted in shrunken particle surface, which gave rise to smaller D_B and particle size. The particles were not spherical, and even with the addition of 0.5% WPI, the particle morphology was altered. The surface shrinkage of strawberry powder increased with increase in WPI from 0.5% to 10%. The production efficiency of strawberry powder could be greatly improved when MD was replaced by 1% WPI.     

磺甲基化蛋白填料的合成及性能研究

以工业明胶为原料,采用磺甲基化技术合成蛋白填料,并对其物化性能如溶解性、pH值等,和磺甲基化蛋白填料的用法进行了研究。试验表明:通过该方法合成的蛋白填料在水中有很好的溶解性能,而且在复鞣填充时使用具有优良的填充性能。填充后的革手感丰满、柔软且粒面细致,尤其可以显著地改善皮革的松面情况,减小皮革的部位差,改善革的手感,提高成品革的质量与档次。     

杂交水稻的育种战略设想

为提升稻谷干燥品质,本实验以籼粳杂交稻为对象,通过爆腰率、整精米率、能耗、干燥时间进行评价,结合单因素、响应面分析优化干燥工艺;同时采用差示扫描量热仪、傅里叶红外光谱、荧光光谱等技术手段,探究了变温-缓苏干燥对籼粳杂交稻蛋白结构及热特性的影响。结果显示：变温-缓苏干燥（变温区间30~60 ℃）在升温温度5 ℃、风速1 m/s、缓苏比0.6条件下可使稻谷始终保持在玻璃态,干燥后的爆腰率和整精米率比恒温组（60 ℃）分别降低79.89%和提高39.54%。在此条件下稻谷蛋白质发生极性减弱、分子间聚集现象,提高了蛋白质热稳定性,α-螺旋含量由16.21%提升至17.64%;扫描电镜结果表明,变温-缓苏干燥未对蛋白质表面结构造成明显影响。实验探究并验证了杂交稻谷变温-缓苏干燥机制,为杂交稻谷高品质干燥研究提供了理论和实践参考。

     

Measurement of Glass-Rubber Transition Temperature of Rice by Thermal Mechanical Compression Test (TMCT)

TMCT (Thermal Mechanical Compression Test) was applied to measure the T_g-r (glass-rubber transition temperature) of rice flour and individual rice kernels at low moisture content (2.4–19.5% wet basis). As expected, T_g-r decreased with increasing moisture content. The T_g-r temperatures measured by TMCT were comparable with those measured by DSC (Differential Scanning Calorimetry), TMA (Thermo-mechanical Analysis), and DMTA (Dynamic Mechanical Thermal Analysis) as reported in the literature. These results indicated that the TMCT technique could be applied to measure the glass-rubber transition of a single grain of rice or the rice in powder form. The sensitivity of the test was observed higher for the rice kernel than rice flour. TMCT technique has the advantage of usefulness and cost-effectiveness compared with the other techniques.     

超细纤维合成革玻璃化温度影响因素的探讨

采用差示扫描量热法(DSC)对超细纤维合成革的各个组分进行测试,探讨了尼龙-6、聚氨酯PU含量和表面活性剂及其它助剂对超细纤维合成革玻璃化温度(Tg)的影响。试验结果表明:尼龙-6对合成革的Tg影响最大,聚氨酯也有一定影响,其它成分影响不明显,研究结果为改善超细纤维合成革的Tg和使用性能,提供一定的理论依据。     

浅述玻璃化转变温度与食品成分的关系

食品体系的玻璃化转变温度会对食品的加工和贮藏过程及食品的品质产生重要影响。重视食品体系的玻璃化转变温度并分析其影响因素,可帮助人们更好的了解食品加工和贮藏特性,提高产品品质。该文就水分含量、碳水化合物、蛋白质、平均分子量及食品添加剂等因素与一定的食品体系的玻璃化转变温度的关系进行了综述。     

喷雾干燥微胶囊技术中的玻璃化转变

应用高聚物玻璃化转变理论,论述了微胶囊在喷雾干燥过程中的玻璃化转变,探讨了影响微胶囊包埋率和和贮藏稳定性的因素,并提出了改善微胶囊技术的方法。     

论玻璃化转变温度与食品成分的关系

食品体系的玻璃化转变温度,会对食品的加工和贮藏过程及食品的品质产生重要影响.重视食品体系的玻璃化转变温度并分析其影响因素,可帮助人们更好地了解食品加工和贮藏特性,提高产品品质.该文就水分含量、碳水化合物、蛋白质、平均分子量及食品添加剂等因素与一定的食品体系的玻璃化转变温度的关系进行了论述.     

鱼鳞明胶及蛋白肽涂膜对鲫鱼保鲜效果的影响

研究鱼鳞明胶和蛋白肽涂膜剂对鲫鱼保鲜效果的影响。将明胶、蛋白肽、壳聚糖混合制成涂膜剂,涂布在鲫鱼鱼片的表面,在4℃环境下存储,每隔一段时间进行1次测定,分别检测鲫鱼鱼片的p H值、重量损失、TVB-N、菌落总数、色差等指标,以检验混合膜对鲫鱼的保鲜效果。经过15天的存储,明胶、蛋白肽、壳聚糖涂布鱼片表面,能延长鱼片的保质期。试验证明明胶、蛋白肽在鲫鱼鱼片保鲜中的可行性和保鲜效果。     

利用从铬革废弃物中提取的明胶研制皮革涂饰剂

利用从铬革废弃物中提取的明胶为原料 ,通过采用适宜的双官能团单体与明胶中的活性基团反应 ,并借助接枝共聚、种子聚合和胶乳互穿聚合物网络等乳液聚合技术 ,在合适的丙烯酸类单体和改性石蜡的作用下 ,使水解胶原通过物理改性和化学改性 ,制备出新型蛋白类皮革涂饰剂。应用结果表明 :该系列涂饰剂产品性能优良 ,能满足高档皮革的涂饰要求。