不同采收期对沙田柚采后品质的影响

研究了不同采收期对梅州沙田柚（ＣｉｔｒｕｓｇｒａｎｄｉｓＯｓｂｅｋ）果实的品质及呼吸作用的影响。结果表明：过早采收的沙田柚,其可溶性固形物、可溶性糖、维生素Ｃ等的含量较适时采收的要低,而其有机酸含量及呼吸作用则较高。提出了梅州沙田柚最佳的采收期应是１１月上、中旬,即立冬前后,适宜采收的生理指标是可溶性固形物的质量分数为１３％。     

冬小麦茎秆生长过程中内源激素动态的系统研究

以冬小麦为材料,研究了小麦茎秆各节间伸长形成过程中内源激素系统的动态变化。结果表明,茎秆伸长启动期 IAA 含量与节间长度和节位相关密切。节间长度与伸长启动期的 IAA 含量呈极显著正相关(r=0.9353~(**));CTKs 在1,5节间含量较低;2,3,4节间含量较高;伸长过程中,随节间序位的上升,GAs 含量增加百分比大幅度提高;ABA 在整个茎秆伸长过程中含量极低。可见,IAA 与 GAs 互作,共同调控节间的伸长,其中 IAA 可能是决定节间长度的基础,与基因型有关;GAs 在调控节间长度上起主要作用。随节间的伸长和充实,IAA 含量与最大节间单位长度干重成极显著正相关(r=0.9227~(**))。IAA 与CTKs 保持原有的变化趋势,并维持到充实期末,CTKs 在第3节间含量最高,其上位和下位节间则逐步减少,似乎与茎粗有关;ABA 仍维持较低水平。节间单位长度干重达高峰后,贮存物质开始输出(撤退),IAA 和 ABA 含量在生长后期各节间均有较大幅度上升;CTKs 在输出率较高的3,4节间含量较高,而输出率较低的1,5节间含量较低;GAs 含量随节间伸长、充实、物质输出的进程逐渐增加。     

沙田柚果实贮藏期水分变化与枯水的关系

沙田柚采后经１０ｄ预贮藏于常温室内,用＾３Ｈ２Ｏ示踪,定期测定果蒂部、果皮,果肉（汁胞）的放射性比活度和果实的失重率,果汁率,组织含水量,呼吸速率及营养物质含量变化,结果表明,沙田柚贮藏期间,果瓣之间,果肉和果皮之间水分是相互流动的,果实枯水时,水分从果肉到果皮的转移速度大于正常果,沙田柚果实枯水的原因可能与果肉营养物质消耗和果皮组织相对再生长同步进行有关。     

大孔吸附树脂分离纯化罗汉果皂甙的新方法

该文对大孔树脂分离纯化高含量罗汉果皂甙提取物的新方法进行了研究。结果表明：大孔树脂D101对罗汉果皂甙的分离效果较好,最佳柱分离条件为：上样液pH值9.0,在40℃下依次用pH值9.0的碱水溶液、蒸馏水、30%乙醇及60%乙醇进行洗脱,将60%乙醇洗脱液浓缩,冷冻干燥即得高含量罗汉果皂甙提取物。高效液相分析表明,罗汉果皂甙中几种主要成分的含量均高于分离前的罗汉果皂甙水提物,其中罗汉果皂甙V的含量为69.24%,提高了41.12%。     

藏灵菇益生菌奶片的制作及其品质分析

为了以藏灵菇为发酵剂研制出新型片剂乳制食品,该文通过口味正交试验确定了藏灵菇益生菌奶片的最佳制作工艺配方,其配方的质量分数分别为10%脱脂藏灵菇奶冻干粉+40%全脂奶粉+14%白砂糖粉+2.5%硬脂酸镁+2.5%羧甲基纤维素钠（CMC-Na）+31%脱脂奶粉。通过电子鼻检测不同配比的脱脂藏灵菇益生菌奶片,绘制线性判别分析（LDA）图,客观地描述了脱脂(包括不同评分)和全脂藏灵菇益生菌奶片在LDA图上的分布区域。藏灵菇益生菌奶片的初始乳酸菌总数对数值为9.26,经过120 d的4℃保存,乳酸菌总数对数值为7.41,满足市售要求。将藏灵菇和脱脂藏灵菇奶片的扫描电镜图进行比较展示了其结构以及内部菌种的分布。综合成本和品质分析,认为藏灵菇益生菌奶片的生产可行性强。     

锥形配流副弹流润滑模型与数值计算方法

为求解高压条件下锥形配流副的润滑模型,该文提出了综合应用有限差分法、液阻网络法和约束最优化复合形法的二元二目标复合形法,研究表明了模型解的存在性和唯一性,并通过实例应用二元二目标复合形法对润滑模型进行了求解。实例结果显示,平衡油槽的无量纲压力随工作压力的变化保持恒定,配流间隙随工作压力增大呈线性减小,而偏心率在工作压力范围内均略小于0,最小为-0.036。研究为锥形配流副弹流润滑特性的分析及其设计提供了参考。     

崇明岛草鱼池塘沉积物中多环芳烃的分布状况及生态风险

为探究崇明岛池塘养殖持久性污染状况,采用气相色谱-质谱联用法对崇明岛不同区域草鱼池塘沉积物中16种优先控制多环芳烃(PAHs)的含量及分布情况进行了研究,同时运用主成分分析法、特征比值法和质量标准法等对草鱼池塘中PAHs的来源及生态风险进行了分析。结果显示,崇明岛草鱼池塘养殖沉积物中的PAHs总含量为未检出(ND)~1 654.09 μg/kg,平均含量为95.13 μg/kg,其中4~5环PAHs对总浓度的贡献率最高;崇明岛不同区域草鱼池塘沉积物中的PAHs含量差异较大,表现为岛中部池塘含量低,沿岛四周池塘含量较高,尤其是岛西部沿岸区池塘含量最高且种类多;分析发现,崇明岛草鱼养殖池塘中的PAHs主要来源于岛内生物燃烧和石油燃烧,总体处于中等偏下污染水平,生态风险较低,但在西北部池塘存在潜在生态风险,应予以重视。     

Effect of oil source on growth performance,antioxidant capacity,fatty acid composition and fillet quality of juvenile grass carp (Ctenopharyngodon idella)

This study was conducted to evaluate the dietary use of vegetable oil sources in grass carp (Ctenopharyngodon idella). Fish were fed diets having the same lipid level from fish oil (FO), palm oil (PO), rapeseed oil (RO), soybean oil (SO) or linseed oil (LO). The results showed that dietary vegetable oils significantly decreased the feed utilization and a significantly lower growth was observed in SO group, while palm oil showed no effect on the growth performance. Dietary vegetable oils suppressed intestinal digestion by inhibiting the activities of digestive enzymes. Vegetable oils significantly elevated the activities of lipase, hepatic lipase and total lipase in liver, and a phenomenon of intense lipid accumulation emerged in liver of PO and SO groups. Furthermore, linseed oil significantly decreased plasma antioxidant capacity, whereas no significant difference was found between RO and FO groups. Dietary vegetable oils caused a significantly lower EPA and DHA in muscle, and further influenced fillet quality through an increase in cohesiveness, gumminess, chewiness and/or springiness, together with a decrease in hardness. Overall, our results indicated that rapeseed oil may be a suitable alternative oil source for grass carp from a point of growth, feed conversion ratio, antioxidative capacity and hepatic histology.     

Establishment of a crop evapotranspiration calculation model and its validation

In order to contribute knowledge on the method used to calculate the actual crop evapotranspiration, soil, crop, atmosphere, and water spatial structure were integrated into a complete system. Based on the energy balance equation and aerodynamic equation, the meteorological data was reduced and the crop physiological parameter was increased, then the crop evapotranspiration calculation model under natural conditions was derived. The crop evapotranspiration calculation model was verified by the water balance formula using data generated from corn, potato, and flue-cured tobacco grown under field conditions for three consecutive years from 2017 to 2019. The results showed that: from 2017 to 2019, the average root mean square error for measured and calculated evapotranspiration of corn, potato, and flue-cured tobacco at different growth times were 0.5948, 0.4753, and 0.3326, respectively, the mean deviation, mean absolute error, and mean relative error were small, and the coefficient of determination and consistency index were both greater than 0.9100. The measured and calculated crop evapotranspiration of the selected crops increased at first and then decreased gradually as the crops matured, and finally decreased to harvest evapotranspiration, showing a parabolic trend. The crop evapotranspiration calculation model not only reflects the actual evapotranspiration of crops at different growth time but also reflects the change law of actual crop evapotranspiration. The model does not need the correction of soil moisture content, irrigation method, and crop coefficient and can directly calculate the actual crop evapotranspiration. It has the characteristics of consistency between the calculated value and the measured value, strong applicability, simple calculation process, and high accuracy and has the best effect on monitoring soil moisture and crop water shortage sensitivity. The model is significance in that it guides for monitoring soil moisture, determining actual crop evapotranspiration, crop water shortage index, and high yield and efficiency under water-saving conditions.