提高蛋清粉起泡性能的工艺

在实际生产中,蛋清中常会混入蛋黄,这些少量脂质的存在会降低蛋清粉起泡性。为减少混入的蛋黄中脂类物质对蛋清粉起泡性的影响,该试验采用脂肪酶水解脂类来提高蛋清粉起泡性能。试验考察了酶添加量、pH值、水解时间、水解温度对蛋清粉起泡性能的影响,确定了脂肪酶水解脂类的较适条件为酶添加量5000U/g,pH值8.0,水解时间6h,水解温度42℃。与原工艺相比,蛋清粉起泡力由36.67%提高到88.42%,泡沫稳定性从26.58提高到32.02。研究所确定的较佳工艺对高起泡性蛋清粉的生产具有指导意义。     

How relevant is recalcitrance for the stabilization of organic matter in soils?

Traditionally, the selective preservation of certain recalcitrant organic compounds and the formation of recalcitrant humic substances have been regarded as an important mechanism for soil organic matter (SOM) stabilization. Based on a critical overview of available methods and on results from a cooperative research program, this paper evaluates how relevant recalcitrance is for the long‐term stabilization of SOM or its fractions. Methodologically, recalcitrance is difficult to assess, since the persistence of certain SOM fractions or specific compounds may also be caused by other stabilization mechanisms, such as physical protection or chemical interactions with mineral surfaces. If only free particulate SOM obtained from density fractionation is considered, it rarely reaches ages exceeding 50 y. Older light particles have often been identified as charred plant residues or as fossil C. The degradability of the readily bioavailable dissolved or water‐extractable OM fraction is often negatively correlated with its content in aromatic compounds, which therefore has been associated with recalcitrance. But in subsoils, dissolved organic matter aromaticity and biodegradability both are very low, indicating that other factors or compounds limit its degradation. Among the investigated specific compounds, lignin, lipids, and their derivatives have mean turnover times faster or similar as that of bulk SOM. Only a small fraction of the lignin inputs seems to persist in soils and is mainly found in the fine textural size fraction (<20 µm), indicating physico‐chemical stabilization. Compound‐specific analysis of ¹³C : ¹²C ratios of SOM pyrolysis products in soils with C3‐C4 crop changes revealed no compounds with mean residence times of > 40–50 y, unless fossil C was present in substantial amounts, as at a site exposed to lignite inputs in the past. Here, turnover of pyrolysis products seemed to be much longer, even for those attributed to carbohydrates or proteins. Apparently, fossil C from lignite coal is also utilized by soil organisms, which is further evidenced by low ¹⁴C concentrations in microbial phospholipid fatty acids from this site. Also, black C from charred plant materials was susceptible to microbial degradation in a short‐term (60 d) and a long‐term (2 y) incubation experiment. This degradation was enhanced, when glucose was supplied as an easily available microbial substrate. Similarly, SOM mineralization in many soils generally increased after addition of carbohydrates, amino acids, or simple organic acids, thus indicating that stability may also be caused by substrate limitations. It is concluded that the presented results do not provide much evidence that the selective preservation of recalcitrant primary biogenic compounds is a major SOM‐stabilization mechanism. Old SOM fractions with slow turnover rates were generally only found in association with soil minerals. The only not mineral‐associated SOM components that may be persistent in soils appear to be black and fossil C.     

豌豆光系统Ⅰ中脂类物质的分离及反相高效液相色谱分析

为进一步探讨脂类物质在类囊体膜及其蛋白复合物中的分布及作用,该研究提取了经DOC-PAGE分离的豌豆光系统Ⅰ中的脂类物质,采用 RP-HPLC-UV梯度洗脱分析方法,以乙腈与水为流动相组成,在25 min内进行了较好的分离. 所得的色谱图基线平稳、分离度高. RP-HPLC-UV分析图上有6个主要色谱峰,通过所对应的紫外吸收光谱图,确认它们均属于脂类化合物.      

Low body fat content prior to declining day length in the autumn significantly increased growth and reduced weight dispersion in farmed Atlantic salmon Salmo salar L.

Based on the regulatory effects of body fat on appetite and seasonal variations in fat deposition and growth of Atlantic salmon, the present study tested the hypothesis that body fat content prior to declining day length in the autumn can significantly modulate growth rate. The growth rate of salmon (mean initial body weight, BW = 2.3 kg) with different muscle fat content prior to autumn, subjected to natural photoperiod and temperature, during a 7‐month period (mean final BW = 6.6 kg) was studied. In August, three fish groups (HF, LF and 0.5LF group) with significantly different muscle fat content (HF = 16.4%, LF = 13.2% and 0.5LF = 11.3%), individually marked with PIT‐tag, were mixed into the four net‐pens and fed a standard high‐energy diet until March the following year. The muscle fat content prior to the autumn had a highly significant (p < .0001) effect on growth during the 7‐month main‐dietary period, even after identical fat stores among the groups were restored, indicating a more complex explanation than just a lipostatic regulation mechanism. Mean thermal growth coefficients were HF = 2.9, LF = 3.4 and 0.5 LF = 3.9, resulting in increased final weight gain for LF and 0.5LF of 590 g and 980 g, respectively, compared to the HF group. The LF groups obtained a significantly higher homogeneity in BW and shape than HF‐fed fish in March, optimizing automatic gutting and filleting at slaughter. The improved growth response among the LF groups by reducing lipid levels can potentially be utilized in closed and semi‐closed production units where photoperiod can be manipulated.     

类风湿关节炎合并心血管疾病的研究进展

类风湿关节炎(RA)患者心血管疾病(CVD)的风险高于年龄和性别相匹配的一般人群的1.5～2.0倍。因全身慢性炎症导致的心血管风险增高是RA的特征之一。RA最优化心血管风险管理的挑战包括改进预测心血管风险的方法和确定目标危险因素以减少心血管风险。从RA研究中吸取经验教训,对于一般人群同样收益,因为炎症在动脉粥样硬化的发病机制中有着重要作用。     

低氮诱导小麦灌浆期旗叶衰老与膜脂的关系

小麦产量主要来自于小麦灌浆期旗叶的光合产物, 低氮造成的灌浆期旗叶早衰对小麦产量影响极大。本试验以小麦品种“长旱58”为试验材料, 在大田环境下设置低氮(120 kg hm ^-2)和正常氮(180 kg hm ^-2)处理, 研究低氮诱导的小麦旗叶衰老与膜脂的关系。结果表明, 开花14 d后, 低氮处理小麦旗叶的光合速率、叶绿素含量、旗叶总氮含量均显著降低; 旗叶中膜脂各组分含量均显著下降, DGDG/MGDG的比值升高; 以C18:3、C18:2为代表的不饱和脂肪酸含量显著下降, 以C16:0为代表的饱和脂肪酸含量显著增加, 不饱和双键指数显著降低; 此外类囊体蛋白质堆积密度也显著降低。综合分析认为低氮处理导致小麦灌浆期旗叶早衰, 早衰过程伴随着膜脂降解和组分改变, 降低了膜的流动性和通透性, 导致叶绿素降解, 使光合功能受损。同时, 植物通过调整DGDG/MGDG比例来响应低氮胁迫, 利用DGDG的双层特性来部分弥补其它双层膜脂的降解对膜功能造成的损伤。     

三种不同海洋脂质对溃疡性结肠炎小鼠及其肠道菌群的影响

为了研究3种不同海洋脂质——二十碳五烯酸(eicosapentaenoic acid,EPA)、二十二碳五烯酸(docosapentaenoic acid,DPA)和二十二碳六烯酸(docosahexaenoic acid,DHA)对溃疡性结肠炎(UC)小鼠及其肠道菌群的影响,本实验采用葡聚硫酸钠(dextran su...     

驴乳营养成分研究进展

驴乳因其乳清蛋白、乳糖、溶菌酶、不饱和脂肪酸和VC含量较高而酪蛋白及脂肪含量较低的特点，被誉为人乳的理想替代品，同时具有低致敏性、抑菌性和抗癌活性等多种生理功能。本文介绍驴乳的营养成分特点，包括蛋白质、氨基酸、脂肪、矿物质、维生素等，并与人乳、牛乳、水牛乳、羊乳和骆驼乳进行比较，以期为驴乳的综合加工与利用提供参考。