鸡源乳杆菌微胶囊的制备及特性研究

为了提高益生菌对不良环境的抗性,使其以活性状态到达肠胃并发挥相应的功效,采用微胶囊包被与冷冻干燥相结合的技术,以实验室分离的鸡源乳杆菌为对象,设计L9（34）正交试验,筛选制备乳杆菌微胶囊的最佳配方,并检测乳杆菌微胶囊的特性。试验结果证明,海藻酸钠浓度为3%,氯化钙浓度为2%,脱脂奶粉浓度为4%,乳糖浓度为6%时,制备的微胶囊中活菌包埋产率最高,达到92.40%,且产品具有较好的耐酸性与肠溶性,在室温下具有较好的贮存稳定性。     

两栖类结冰耐受机制及其研究策略

综述了近年来美洲林蛙的研究进展,总结了两栖类动物结冰耐受的主要机制,并提出该领域研究的新方向。     

陕西省关中地区大棚蔬菜低温冻害预报服务方法

通过比较系统的大棚蔬菜温度观测,建立了不同天气类型下棚内外最低温度的回归模式,确定了大棚蔬菜低温冻害的气象预报指标,以泾阳为代表分析了关中地区大棚蔬菜低温冻害的时间分布特点,并提出了不同低温冻害等级下的防御对策建议.     

苹果冷冻-热风联合干燥体积收缩机制

为降低冻干苹果能耗,同时获得具有良好外观的脱水产品,该研究将冷冻-热风联合干燥应用于苹果脱水加工,并从水分迁移角度探究此过程中产品的收缩机制。选取4个水分转换点（干基含水率分别为1.00、0.76、0.53和0.33 g/g）对苹果进行联合干燥处理,并对脱水产品收缩率、质构特性、微观结构、孔隙分布及样品在热风干燥阶段的水分迁移与分布进行测定及分析。结果表明,联合干燥样品的收缩情况显著（P<0.05）优于单一热风干燥样品,且转换点对样品收缩率影响较大（收缩率6%～45%）,当转换点干基含水率低于0.53 g/g时,联合干燥样品没有出现明显的体积收缩现象。随着转换点干基含水率的升高,样品的收缩程度增大,并出现不同程度的中心塌陷,且孔隙率逐渐减小,但相应能耗降低。产品收缩主要发生在热风干燥过程的升速阶段,在此阶段样品自由水含量大幅减少,结合水与不易流动水未发生明显改变,样品内部水分在湿度差的作用下向表面迁移,这是导致联合干燥样品发生体积收缩的关键机制。该研究结果可为冷冻-热风联合干燥高效生产良好外观的脱水苹果提供数据支撑及理论参考。     

真空冷冻干燥过程参数对罗非鱼片冻干时间及其除水率的影响

通过四因数三水平正交试验,研究了真空冷藏干燥主要过程参数--预冻温度、鱼片(物料)厚度、干燥室压强和加热板温度对罗非鱼Tilapia片冻干时间及其除水率的影响.结果表明:单一过程参数对罗非鱼片单位厚度冻干时间的影响为鱼片厚度越厚,冻干时间越长;预冻温度越高,冻干时间越长;加热板温度越低,冻干时间越长;真空冷冻干燥过程参数对罗非鱼片单位厚度升华冻干时间及其除水率影响的主次因数依次为鱼片厚度>真空室压力>加热板温度>预冻温度.     

渠内水对寒旱区渠基土冻结过程影响的试验研究

为研究渠内水对渠基土冻结过程的影响,采用由箱体、制冷系统、补水系统和量测系统构成的冻胀装置,进行了开放系统下的停水渠道和过水渠道的室内模型试验,研究渠基土的温度场、冻后含水率和冻结过程中马氏瓶补水量的变化规律.试验结果表明：渠道断面形状和渠内水体影响渠基土温度场的分布,停水渠道和过水渠道在靠近渠槽线附近的等温线形状和疏密程度不同,渠基土的断面温度场分布不均,过水渠道仅在水位线以上的渠基土内出现负温;停水渠道和过水渠道的马氏瓶累积补水量分别为16 873 mL和16 051 mL,马氏瓶补水分为快速补水、补水速率减缓和停止补水3个阶段;与初始含水率17%相比,无论渠内是否过水,从渠顶沿渠坡向下冻后含水率的值均增大.在工程设计与理论计算时应分别考虑运行方式改变对渠道冻结的影响.     

基于遗传算法的苦瓜片真空冷冻干燥工艺优化

为提高苦瓜片干制品品质,应用真空冷冻干燥技术对新鲜苦瓜片进行干燥,以得到最佳工艺参数。采用响应面分析法设计四因素三水平试验,对苦瓜片试验指标（含水率和复水比）和干燥工艺参数（切片厚度、温度、绝对压强和干燥时间）建立二次多项式回归模型,并对模型的有效性及因素间的交互作用进行分析,利用Matlab中的遗传算法对结果进行综合优化。结果表明：建立的回归方程拟合度较好,模型显著,所得工艺参数合理可用。苦瓜片真空冷冻干燥的最佳工艺参数为：切片厚度为4mm,隔板温度为46℃,绝对压强为73Pa,干燥时间为8.7h。该条件下含水率为6.23%,复水比为11.75。     

Soil respiration during freeze–thaw cycles in a temperate Korean Larch (Larix olgensis herry.) plantation

Successive effects of freeze–thaw cycles (FTCs) on soil respiration rate (Rs) were explored in a Korean Larch (Larix olgensis Herry.) plantation during the winter to spring season. In March 2014, laboratory incubation with severe FTCs at the extreme minimum temperatures of ?16°C and mild FTCs (?8°C) and field-based methods through five days continuous measurements of Rs at eight time points in one day were applied to determine the diurnal and seasonal Rs variations during FTCs, and to analyze the effects of FTCs regimes on Rs. The Rs increased rapidly as thawing proceeded, generating two peaks during severe FTCs, but with no obvious CO₂ peaks in mild FTCs or field-based measurements. In severe FTCs, the Rs in first three FTCs changed dramatically, subsequently tended to stabilize. The diurnal Rs dynamics both followed unimodal type, with no fixed peak in laboratory study but the maximum value at 14:00 in field study. Laboratory- and field-based FTCs studies both highlighted the significant effects on soil carbon release. Initial response of soil respiratory bursts during early FTCs appeared to be driven by extreme minimum temperatures, while response of soil carbon release in late cycles was controlled by reduction in soil organic matter during early cycles.     

抑制素基因重组质粒转染大肠杆菌菌种冷藏与冷冻保存的效果分析

通过平皿培养进行抑制素基因重组的质粒转染菌种的冷藏、冷冻两种保存方法与复苏实验,结果表明,冷冻保存方法对于保存抑制素转染菌种的效果好于冷藏保存方法.     

Maturation ability after transfer of freeze‐dried germinal vesicles from porcine oocytes

The purpose of this study was to examine whether freeze‐dried germinal vesicles (GV) can be matured in vitro after being injected into enucleated fresh oocytes in pigs as an alternative method for conservation of genetic resources. Although no reduction of the size of GV (p = .094), resveratrol treatment significantly enhanced the survival rates following GV transfer (GVT) (p < .001). Supplementation with 100 or 200 mmol/L trehalose in freeze‐drying medium significantly increased the proportions of GVs with intact nuclear membrane and DNA integrity compared with the control group. Following transfer of freeze‐dried GVs into enucleated fresh oocytes, the proportion of reconstructed oocytes reached the metaphase‐II stage (2.4% ± 1.4%) was significantly lower (p < .05) than that of the in vitro matured control group (83.2% ± 2.5%), it was comparable with the GVT control group (7.4% ± 2.7%). The rates of freeze‐dried GVs with intact nuclear membrane and DNA stored at ?20°C for 5 days were significantly higher (p < .05) than those at 4°C and room temperature. The rates of intact nuclear membrane and DNA in the freeze‐dried GV stored for 15 or 30 days at ?20, 4°C and RT were not significantly different. In conclusion, matured oocytes were produced derived from freeze‐dried GVs.