Evaluation of temporal variations in soil moisture based on the microwave polarization difference index using in situ data over agricultural areas in China

Soil moisture plays a critical role in the energy exchange and water redistribution of the land-atmosphere system. Knowledge of the temporal variations in soil moisture is vital in agricultural applications. Microwave indices are often used to characterize the temporal variations in soil moisture. In this study, we evaluate the temporal variations in soil moisture based on the microwave polarization difference index (MPDI) using ground-based measurements in China. In situ soil moisture at six test sites during the crop-growing season from 2009 to 2011 is obtained. The consistency of the temporal variations between the MPDI values and the in situ soil moisture is analysed in terms of (1) microwave frequencies, (2) satellite overpass times, and (3) measurement depths of soil moisture. The results show that the accuracies of the consistency vary from approximately 40% to 90%. Compared with the in situ soil moisture at 0–10 cm, the temporal variations in soil moisture are best characterized by the 6.9 GHz MPDI values from the ascending overpasses (MPDI_06A). Furthermore, the accuracies of the consistency between MPDI_06A and the in situ soil moisture at 0–10 cm are greater than those between MPDI_06A and the in situ soil moisture at 10–20 cm.     

Comparison of membrane filtration rates and hydrophobic grid membrane filter coliform and Escherichia coli counts in food suspensions using paddle-type and pulsifier sample preparation procedures

Food suspensions prepared by Pulsifier contained less debris and filtered 1.3x to 12x faster through hydrophobic grid membrane filters (HGMFs) than those prepared by Stomacher 400. Coliform and Escherichia coli counts made by an HGMF method yielded 84 and 36 paired samples, respectively, positive by both suspending methods. Overall counts of pulsificates and stomachates did not differ significantly for either analysis, though coliform counts by Pulsifier were significantly higher in mushrooms and significantly lower in ground pork (P = 0.05). Regression equations for log10 counts of coliform and E. coli by Pulsifier and Stomacher were: Pulsifier = 0.12 + 0.97 x Stomacher, and Pulsifier = 0.01 + 1.01 x Stomacher, respectively.     

乳清蛋白胶体物化特性的应用研究进展

乳清蛋白是生产干酪时的一种天然副产物,是牛奶中乳蛋白的主要成分之一,它不仅具有优异的营养特性,还具有独特的胶体物化特性。本文综述了利用乳清蛋白胶体特性发展的微胶囊和可食用包装膜技术的研究进展。利用乳清蛋白的凝胶特性,在合适的条件下制备以乳清蛋白为壁材的微胶囊,可以对功能成分进行包埋并实现肠溶缓释;制备具有一定机械强度和阻隔性的可食性蛋白膜,可以运载多种功能因子,作为食品包装减缓食品中的营养流失并延长食品的货架期。     

风味干酪调香调味工艺的研究进展

随着国民生活水平的提高,对干酪的需求逐渐提高,干酪的调香调味对于改善干酪的风味,提高其市场接受度至关重要。本文介绍了国内外不同干酪的风味特点,以及针对其原始风味的不同,利用味强化、掩蔽、派生、干涉和反应等原理对不同风味干酪进行调香调味。根据辅料形式和投放时间的不同,分别介绍了天然干酪和再制干酪调香调味的常用方法。总结了我国干酪调香调味的研究特点并对我国风味干酪的发展方向提出了建议,以期为提高我国风味干酪产品的水平提供参考。     

食品中着色剂的检测方法研究进展

着色剂是食品添加剂中的一大类分支,在食品加工和生产中有着广泛的应用。由于食品的基质类型复杂多样,着色剂的种类也非常多、性质差异大,给分析检测工作带来挑战。本文对近年来的食品中着色剂的检测方法进行综述,包括样品前处理和分析检测技术,并根据应用方法和适用的食品基质及检测目标物进行分类总结,为进一步开展食品中着色剂的检测方法的研究工作提供参考。     

食品多元素检测质控图及国际比对结果在 质量控制中的应用

摘要：目的 通过分析本实验室根据标准参考物测定结果绘制的质控图和2013年10月参加食品中多种微量元素含量测定的国际实验室间比对考核结果,探讨质控图及国际比对考核在实验室质量控制中的应用。方法 以Z比分数法评价由国际原子能机构组织的食品中多种微量元素含量测定的国际比对结果,分析食品样品中多种微量元素的测定情况。结果 绝大多数元素的考核结果 <1,结果优秀。结论 质控图和国际比对实验研究是分析实验室质量控制的有效方法,应鼓励有条件的实验室更多地参与国际比对考核,提高检测能力及测定结果的可靠性。     

高效液相色谱—串联质谱法快速测定胶原蛋白粉中呋喃类代谢物

目的简化测定胶原蛋白粉中呋喃类代谢物残留的实验过程,缩短实验的检测时间。方法在GB/T21311-2007的基础上,对其进行方法改进,建立高效液相色谱-串联质谱法(HPLC-MS/MS)测定胶原蛋白粉中呋喃西林(SEM)、呋喃妥因(AHD)、呋喃唑酮(AOZ)、呋喃它酮(AMOZ)等4种呋喃代谢物的快速检测方法。采用55℃衍生化,对衍生品按照离心、调p H值、离心的步骤进行处理,使得调节p H值更容易,同时避免传统试验方法中使用分液漏斗时样品乳化成胶状体而不能达到液液分离的目的的现象。结果实验结果表明,本方法与《GB/T21311-2007动物源性食品中硝基呋喃类药物代谢物残留量检测方法高效液相色谱串联质谱法》相比,结果并无很大的差异,但是大大缩短了实验的检测时间、简化了实验过程。结论本实验方法更加适合大批量样品的试验检测。