以丙酸钙和硫酸锌为原料合成新型食品添加剂丙酸锌的研究

研究利用以丙酸钙和硫酸锌为原料,经复分解反应制备新型食品添加剂——丙酸锌的主要合成工艺条件,确定了丙酸钙用量和各反应物的最适浓度,即n(丙酸钙)∶n(硫酸锌)=1.16∶1、C(丙酸钙)=1.075 mol/L、C(硫酸锌)=1.239 mol/L,在上述条件和80℃时反应40 min,丙酸锌收率可达93.6%以上。同时还对丙酸锌的生物利用度、药动学和营养强化效果等作了探讨,为其在食品领域的推广使用提供了依据。     

碱法预提取玉米秆半纤维素及对后续制浆的影响

利用NaOH在较温和的温度条件下从玉米秆原料中预提取出了半纤维素,分析了提取液中糖类组分及含量,采用NaOH-AQ法对提取过半纤维素的玉米秆进行了制浆实验,考察了预提取对制浆以及黑液中SiO_2含量的影响.结果表明,玉米秆半纤维素的主要成分是木聚糖,在温度75℃,碱浓10%时,提取液中木糖总量占原料中木糖的91.8%.黑液中SiO_2含量的检测结果表明玉米秆中SiO_2含量较低,未经预提取原料NaOH-AQ蒸煮黑液中SiO_2含量为163 mg/L,经预提取之后,相同条件下蒸煮所得黑液中SiO_2含量均有不同程度的下降.在碱浓达到8%时,硅含量比未经预提取玉米秆的制浆黑液降低了79.8%.提取后原料的制浆结果表明半纤维素预提取可以显著提高纸浆的白度,降低纸浆卡伯值,但同时也会在一定程度上降低纸浆的得率和黏度.     

双表面活性剂增敏光度法测定丙酸钙中的痕量铅

目的 建立了一种测定食品添加剂丙酸钙中痕量铅的方 法。方法 采用Cl-型阴离子交换树脂的分离技术,以二 甲酚橙为显色剂,并加入表面活性剂作为增敏剂,结合水 相分光光度法测定痕量铅。结果 最大吸收波长为 574nm,在0.02-4μg/mL范围内符合Beer定律(r= 0.9997),线性回归方程为A=0.1333C 0.0022(C:μg/mL), 表观摩尔吸光系数为2.80×104L／(mol·cm)。结论本法 操作简单,显色反应灵敏度高、重现性及稳定性好,用于 测定丙酸钙中的痕量铅,获得了较满意的结果。     

Prebiotic potential of xylooligosaccharides derived from finger millet seed coat

The present study deals with the enzymatic production of xylooligosaccharides (XOS) from water-soluble xylan (WSX) extracted from finger millet CO9 seed coat and the evaluation of its prebiotic potential. The yield of XOS was 72%, when the WSX of the finger millet seed coat was treated with commercially available xylanase of Thermomyces lanuginosus. The XOS obtained when analyzed using high-performance liquid chromatography–evaporative light scattering detector (HPLC-ELSD) indicated a degree of polymerization (DP) of 2 and Electro Spray Ionization Mass Spectra (ESI-MS) revealed xylobiose as the major sugar. The presence of β-glycosidic linkages of XOS was identified by Fourier Transform Infrared Spectrometer (FTIR) and Nuclear Magnetic Resonance (NMR) studies. The XOS exhibited an antioxidant activity of 75% and prebiotic efficacy. Prebiotic activity in the presence of probiotic strains was strain specific and differences in the prebiotic activity score (PAS) between strains were evident. The cell-free supernatant of Lactobacillus plantarum grown on the XOS from finger millet seed coat showed strong antibacterial activities against four pathogenic microorganisms compared with commercial XOS. Finger millet seed coat represents an abundant and alternative source for the extraction of xylan and its use for prebiotic XOS production.     

Whole-body propionate and glucose metabolism of multiparous dairy cows receiving folic acid and vitamin B12 supplements

This study was undertaken to evaluate the effect of supplementation of folic acid and vitamin B₁₂ on glucose and propionate metabolism. Twenty-four multiparous cows were assigned according to a complete block design in a 2 × 2 factorial arrangement to one of the following treatments: (1) saline 0.9% NaCl, (2) 320 mg of folic acid, (3) 10 mg of vitamin B₁₂, or (4) 320 mg of folic acid and 10 mg of vitamin B₁₂. Intramuscular injections were given weekly from 3 wk before the expected calving date until 9 wk postpartum. At 63 d in milk, d-[6,6-²H₂]-glucose (16.5 mmol/h; jugular vein) and [1-¹³C]-sodium propionate (13.9 mmol/h; ruminal vein) were simultaneously infused for 4 h; blood samples were collected from 2 to 4 h of the infusion period. Liver biopsies were carried out the following day. Supplements of folic acid and vitamin B₁₂ respectively increased folate and vitamin B₁₂ concentrations, both in milk and liver. Although dry matter intake was unaffected by treatments, milk and milk lactose yields tended to be lower by 5.0 and by 0.25 kg/d, respectively, for cows receiving the folic acid supplement. Plasma β-hydroxybutyrate concentration with the folic acid supplement followed the same tendency. Hepatic gene expression of methylmalonyl-CoA mutase and S-adenosylhomocysteine hydrolase was higher for cows receiving the combined folic acid and vitamin B₁₂ supplement compared with cows receiving only the supplement of folic acid, whereas no treatment effect was noted for cows not receiving the folic acid supplement. Whole-body glucose rate of appearance and the proportion of whole-body glucose rate of appearance secreted in milk lactose decreased by 229 g/d and 5%, respectively, for animals receiving the folic acid supplement, concomitant with the lower milk lactose synthesis in these cows, indicating that supplementary folic acid may alter energy partitioning in cows. The absence of treatment effect on plasma concentrations of methylmalonic acid as well as on the proportion of glucose synthesized from propionate, averaging 60%, supports the fact that vitamin B₁₂ supply was sufficient in control cows in the current study. Our results suggest that the folic acid supplement reduced glucose-derived lactose synthesis by redirecting glucose for other metabolic activity in the mammary gland or in other tissues.     

竹片化学机械法提取木聚糖及残余物抄纸利用研究

为实现竹原料的综合利用,探索通过化学机械法提取木聚糖,并对残余物进行抄纸利用研究。结果表明,化学机械法木聚糖提取的较佳工艺条件为：竹片以35%的进料浓度螺旋挤压4次后,采用用碱量6%、液比1∶4、常温下浸渍90 min后,调节用碱量为80%（碱浓10%）,液比为1∶8,通过转数为5000的PFI磨（进刀间距为0.1 mm）处理后,最后在高压灭菌锅中于125℃下保温处理45 min,木聚糖得率达到85.1%。通过傅里叶变换红外光谱仪（FT-IR）、核磁共振波谱仪（¹H NMR）分析表明,所得粗木聚糖主成分是木聚糖,还含有少量阿拉伯糖、葡萄糖醛酸等;提取木聚糖后的残余物所抄纸张的强度性能指标达到箱纸板国家标准GB/T 13024—2016中合格品的要求。     

高压蒸汽处理玉米芯提取木聚糖动力学研究

研究了不同温度下(170℃～210℃)高压蒸汽处理玉米芯提取木聚糖的动力学模型.考察了提取主要产物木聚糖的动力学规律,并得出高压蒸汽处理玉米芯过程中木聚糖水解的动力学参数.结果表明,用0.05％的稀硫酸浸泡可以降低玉米芯降解过程中的活化能.     

超声波辅助碱法制备玉米芯木聚糖

以玉米芯为原料,经高温预处理后,采用超声波辅助碱法提取玉米芯木聚糖,在单因素实验的基础上,通过正交试验对玉米芯木聚糖提取工艺进行优化。结果表明:木聚糖的最佳制备工艺为氢氧化钠浓度7%,料液比1∶25,超声功率250 W,超声时间40 min,超声温度60℃。在此条件下,提取液中以玉米芯计还原糖的含量为64.10 mg/g,可溶性总糖含量为100.14 mg/g,木聚糖得率为9.01%。     

Structural Characteristics of Cellulose and Xylan during in vitro Fermentation by Pig Fecal Bacteria

In this study,cellulose and xylan were in vitro fermented by pig fecal bacteria.Rapid fermentation (40 h) and extended fermentation (eight weeks)were performed.The properties and ultra-structure changes of post-fermented solid residues were studied.In the end effluent,acetic acid,propionic acid,and butyric acid were observed to be the principal short-chain fatty acids (SCFAs) produced by anaerobic fermentation.Xylan was more accessible to bacteria than cellulose,leading to higher SCFA and lactic acid production.In addition,the crystalline structure of cellulose changed,leading to 16.3％ and 42.1％ increases in crystallinity index for rapid and extended fermentation,respectively.Through this research,a systematic and advanced method to study the degradation chemistry of cellulose and xylan during fermentation was developed.     

以丙酸钙作抑菌剂制备猕猴桃酒工艺研究

该研究采用Box-Behnken响应面法对以丙酸钙作抑菌剂制备猕猴桃酒的工艺进行了优化,以最优工艺制备猕猴桃酒,对其理 化指标进行了检测,并采用顶空固相微萃取技术和气相-质谱联用技术（HS-SPME-GC-MS）分析其挥发性风味物质成分。结果显示, 猕猴桃酒最优工艺条件为发酵温度24 ℃,初始pH值为3.5,接种量0.09%,所得猕猴桃酒与以SO2为抑菌剂制得的猕猴桃酒具有相似 的理化性质和挥发性风味物质成分组成,但挥发性风味物质含量具有较大差别。