天然植物甾醇的分离纯化

天然植物甾醇具有多种重要生理功能，目前广泛应用于医药、食品及化妆品等行业。随着这些行业对天然植物甾醇需求量的增加，如何制备高纯度的天然植物甾醇逐渐受到研究者的关注。由此，对国内外天然植物甾醇的分离与提纯方面研究进展做了概述。     

Efficiency of acetic acid and formic acid as a catalyst in catalytical and mechanocatalytical pretreatment of barley straw

In this study, the potential of organic acids (formic acid, acetic acid) in a catalytical and mechanocatalytic conversion of lignocellulosic barley straw to valuable sugars is explored using sulfuric acid as a reference. Acid-catalyzed hydrolysis has been carried out with acid-impregnated samples as well as unmodified barley straw. In the mechanocatalytical approach, pretreatment consists of impregnation with the acid catalyst and mechanical treatment by ball milling following chemical hydrolysis. Straw samples and residues were analyzed by Fourier transform infrared spectrometry (FT-IR) whereas hydrolysate analysis was based on total reducing sugar (TRS) determination following the DNS method and capillary electrophoresis (CE) analysis. The results indicated that acetic acid and formic acid are rather mild acids yielding low TRS levels compared to the reference acid. Mechanocatalytical pretreatment slightly increased TRS yields, but not significantly. Strikingly, sulfuric acid showed an efficient conversion efficiency yielding almost 45% of TRS. Furthermore, this study provided evidence for the acetylation of straw components when acetic acid was used as catalyst. Alkali hydrolysis induced the de-esterification, but revealed no significant increase of TRS yields.     

腺嘌呤柱前衍生化-HPLC-FLD法测定3-氯-1,2-丙二醇的方法优化

3-氯-1,2-丙二醇(3-MCPD)经高碘酸钠溶液氧化裂解、腺嘌呤衍生化后的产物——1,N6-亚乙烯基腺嘌呤(ε-Ade)为强荧光物质,通过对其荧光光谱与重要影响因素进行研究与优化,结合测定体系背景干扰的抑制,对高效液相色谱-荧光法(HPLC-FLD)测定3-MCPD水溶液的条件进行了优化。得到优化条件为:使用耐碱性反相C18色谱柱进行测定,流动相中甲醇体积分数为20%,水相为pH 9.0的碳酸钠-碳酸氢钠缓冲液。食用油中3-MCPD的测定需以0.01 g/mL的NaCl溶液作为萃取水相,氧化裂解3-MCPD的高碘酸钠可采用等量的亚硫酸钠还原、1.1倍量的醋酸铅沉淀予以去除,从而抑制空白峰的干扰,将该方法应用于多种食用植物油样品的测定,结果表明:该方法准确度高、重现性好(RSD在0.32%～4.63%之间);样品谱图显示基质干扰很小,方法选择性高。     

甘二酯对油脂中抗氧化剂活性的影响

研究sn-1,3-棕榈酸甘二酯对纯净菜籽油氧化稳定性的影响,以期探明其作用机理,为油脂加工和储存提供科学的依据。通过柱层析的方法制备仅含甘三酯成分的纯净菜籽油,测定DAG在菜籽油中形成反相胶束的临界浓度,并在反相胶束体系中,研究DAG及与天然抗氧化剂γ-生育酚及合成抗氧化剂(TBHQ、BHA、BHT)联合作用对纯净菜籽油氧化稳定性的影响。结果表明:DAG在菜籽油中的临界胶束浓度为0.5%;在反相胶束体系中,DAG的添加促进了纯净菜籽油的氧化,DAG对不同种类的抗氧化剂活性的影响存在差异,DAG增强了弱极性抗氧化剂γ-生育酚、BHT的活性,但是减弱了极性较强的抗氧化剂TBHQ、BHA的活性。     

Dissolution and stability of chitosan in a sodium hydroxide/urea aqueous solution

Medium‐molecular‐weight chitosan (MMWC; 157.5 kDa) and low‐molecular‐weight chitosan (LMWC; 53.4 kDa) samples were dissolved in an NaOH/urea solution by freeze–thaw treatment. The factors affecting dissolution were optimized, and the stability of chitosan in the produced solution was investigated. NaOH and urea concentrations of 2 and 0.67 mol/L, respectively, and a treatment temperature of ?18°C were optimized as the dissolving conditions. MMWC and LMWC could be completely dissolved in the 2 mol/L NaOH/0.67 mol/L urea solution after six and five cycles of freeze–thaw treatments, respectively. Dissolution and storage in the 2 mol/L NaOH/0.67 mol/L urea solution slightly increased the deacetylation degree of chitosan and slightly decreased the molecular weight. The solution stability of LMWC was better than that of MMWC. MMWC tended to form a gel during storage. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39819.     

高氯酸盐对高脂膳食小鼠脂质代谢的影响

目的 探究高氯酸盐对高脂膳食小鼠脂质代谢的影响。方法 将C57BL/6J小鼠分为4组,分别为对照组(CG)、高氯酸盐低剂量组[LG,每天0.1 mg/(kg·bw)]、中剂量组[MG,每天1.0 mg/(kg·bw)]和高剂量组[HG,每天10.0 mg/(kg·bw)],连续暴露12周,通过对肝脏油红O染色、血生化指标检测、脂代谢调控酶测定和脂肪酸组成及含量测定进行高氯酸盐对高脂膳食小鼠脂质代谢的评估。结果 高于1.0mg/(kg·bw)的暴露剂量可在小鼠肝脏内形成脂滴累积,总胆固醇、甘油三酯和高密度脂蛋白胆固醇含量均显著性升高(P<0.05),并且HG组脂质代谢关键调控酶乙酰辅酶A羧化酶(acetyl-CoAcarboxylase,ACC)和脂肪酸合成酶(fattyacidsynthase,FAS)含量显著性升高(P<0.05),表明高氯酸盐可能会促进脂肪的合成。随着高氯酸盐暴露浓度的增加,棕榈酸(C16:0)、珍珠酸(C17:0)、硬脂酸(C18:0)、花生四烯酸(C20:4)和二十二碳六烯酸(C22:6)体内水平显著下降,而棕榈亚酸(C16:1)、油酸(C18:1)...     

Synergistic effects of modified TiO2/multifunctionalized graphene oxide nanosheets as functional hybrid nanofiller in enhancing the interface compatibility of PLA/starch nanocomposites

The aim of this study is to investigate the synergistic effects of modified TiO₂/multifunctionalized graphene oxide nanosheets at different ratios on the interface compatibility between starch and poly(lactic acid) (PLA). To this end, silanylated nano-TiO₂ (MTiO₂, 1 and 2%) and alkylated maleic anhydride grafted graphene oxide (f-GO, 0.1, 0.2, and 0.4%) at different combinations are blended with the PLA-starch composites using solution blending technique. Then, the synergistic effects of MTiO₂ and f-GO on PLA/starch matrix are investigated in terms of the morphology, crystallinity, structural characterization, thermal stability, dynamic mechanical, and antiaging properties, and the related mechanisms. The Raman and Fourier transform infrared spectroscopy spectra verify the successful synthesis of the two modified nanofillers (f-GO and MTiO₂) and the formation of strong hydrogen bond within the PLA-starch nanocomposites. Due to the strong interfacial interaction and the synergistic effect from the combination of 1% MTiO₂ and 0.2% f-GO, obvious improvement was observed in PLA-starch versus other nanocomposites in terms of morphology, thermal stability, surface hydrophobicity, storage modulus, ultraviolet-shielding capacity, and aging-resistance. Furthermore, differential scanning calorimeter (DSC), isothermal crystallization kinetic, and X-ray diffraction analysis demonstrate that f-GO and the M-TiO₂ significantly synergize in enhancing the crystallization rate and crystallinity of PLA/starch matrix. These results provide novel insights for constructing high-performance nanocomposites and facilitate their applications in food packaging.     

冷鲜猪肉内外细菌菌群分离鉴定及变化规律研究

采用选择性培养基,分别对冷鲜猪肉内外的菌相组成进行分析鉴定,并研究其在储藏过程中的变化规律。实验鉴定出热杀索丝菌、假单胞菌、乳酸菌、肠杆菌科各2株以及葡萄球菌属1株;热杀索丝菌为托盘包装冷鲜猪肉的主要优势菌;整个培养过程中肠杆菌科和假单胞菌生长趋势明显;肉块内部的微生物生长速度高于肉块表面。     

乙醇及热处理对鲜切荸荠褐变的影响

以延缓鲜切荸荠在贮藏过程中的褐变并延长其货架期为 目的,研究了贮藏温度为4℃时,乙醇浸泡及热处理对鲜切荸荠色差、褐变度、总酚含量、苯丙氨酸解氨酶、多酚氧化酶和过氧化物酶等指标的影响.结果表明,几种处理延缓鲜切荸荠褐变效果为:联合处理＞乙醇处理＞热处理.与对照组相比,乙醇处理中PAL和POD的活性较低,热处理及联合处理组...