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。     

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.     

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.     

茶叶籽淀粉提取工艺研究

以茶叶籽为原料,利用超声波辅助水提法工艺从中提取淀粉。响应面分析得出茶叶籽淀粉的最佳提取条件为：原料粉碎度60～80目,液固比为6．9：1（mL/g）,浸提温度48℃,浸提时间3．7h,兑浆水pH为9,超声时间40min。此条件下,淀粉提取率可达81．93％,粗淀粉中淀粉含量为84．53％。     

米糠蛋白的起泡特性及其泡沫微观形态

考察pH值和NaCl浓度对米糠蛋白起泡特性及泡沫微观形态的影响,并对二者之间的内在关系进行阐述。结果表明,当米糠蛋白溶液中不添加NaCl、pH?4时起泡能力较差,但泡沫稳定性可达最大值（88.3±7.3）%,而当溶液的pH值偏离4时起泡能力增加,在pH10和12条件下起泡能力分别可达（73.3±0）%和（168.9±10.2）%,泡沫稳定性分别为（74.7±2.5）%和（68.5±2.1）%;另外在米糠蛋白溶液pH值为4和7条件下分别添加1%的NaCl后,可显著提高起泡能力至（77.8±3.8）%和（90.0±5.8）%。米糠蛋白泡沫的微观形态随时间变化规律说明,不同pH值条件下起始阶段气泡的直径大小分布与泡沫稳定性相关,而当添加NaCl后米糠蛋白起泡能力和泡沫稳定性的改变则与气泡数量和平均面积二者的综合效应有关。     

添加豆渣对苏打饼干制作过程及品质的影响

以黄豆渣和低筋面粉为原料,制作无糖苏打饼干。通过添加不同比例的豆渣粉,来探究豆渣对面粉品质、饼干制作过程以及饼干成品品质的影响。结果表明,添加6%~12%的豆渣可以改善面粉的粉质特性,使其更适合做饼干。添加豆渣会增大面粉的糊化焓。通过与纯面粉对比发酵率、烘烤时间、烘烤胀发比,发现添加3%~6%的豆渣可以促进面团发酵,添加6%~12%的豆渣可以减短饼干烘烤时间,增大烘烤胀发率。结合质构和感官评价,得出添加9%的豆渣,饼干的口感和质构特性最佳。     

三种杂粮及其复合低温火腿肠营养成分分析及评价

分别检测了燕麦、苦荞麦、小米3种杂粮原料,以及所对应的杂粮复合低温火腿肠的营养成分,并对其进行了营养价值评价。结果表明:燕麦片、苦荞麦粉、小米3种杂粮原料的脂肪含量都较低,均在10%以下。燕麦片的蛋白质含量最高,达到13.4%,且所含钙、铁、锌均较高,分别为683、48.1、25.3mg/kg。苦荞麦粉硒元素的含量最高,达到0.12mg/kg。对杂粮原料进行了氨基酸营养评价,小米的E/N值为55.03%,最接近FAO/WHO标准模式。杂粮复合低温火腿肠中,蛋白质含量均高于GB/T 20712—2006《火腿肠》国家标准指标,淀粉含量均在10%以下。小米复合低温火腿肠中VB1、VB2含量相对较高,分别达到156.6μg/100g和12.8μg/100g。其他的功能性营养成分检测结果表明:苦荞麦复合低温火腿肠中特有的生物活性物质黄酮含量达到了2mg/kg,膳食纤维含量最高,达到了3.4%。对杂粮低温复合火腿肠进行了INQ值评价,3种复合低温火腿肠的钙、铁、锌、VB1的INQ值均高于1,其中小米复合低温火腿肠的INQ值总体最高。杂粮复合低温火腿肠理化及卫生指标结果表明,3种低温火腿肠的理化及卫生指标均符合GB/T 20712—2006《火腿肠》的相关规定,表明产品卫生安全指标合格。     

氨基酸组成及溶剂环境对淡水鱼胶原蛋白热稳定性能的影响

本文探讨了氨基酸组成、分布以及溶剂环境对鱼源胶原蛋白蛋白热稳定性能的影响。利用不同鱼类的胶原蛋白为实验样本,测定胶原蛋白氨基酸组成和热变性温度,通过相关性分析明确了影响胶原蛋白热变性温度的主要氨基酸种类和分布指标。结果表明,胶原蛋白中脯氨酸羟基化率、碱性氨基酸、带电荷极性氨基酸和总极性氨基酸含量与胶原蛋白热变性温度呈正相关,而亚氨基酸与非极性氨基酸含量与胶原蛋白热变性温度呈负相关(p0.01)。运用逐步多元回归分析方法,建立了脯氨酸羟基化率和带电荷极性氨基酸与胶原蛋白热变性温度之间的相关性数学模型,经验证,该模型能较好的预测鱼源胶原蛋白的热变性温度。在此基础上,进一步研究了胶原蛋白所处溶剂环境对其热稳定性能的影响。结果表明,提高水分子浸润胶原蛋白程度和体系离子强度,或降低体系pH均会显著降低胶原蛋白热稳定性能。