不同脱乙酰度蚕蛹壳聚糖抑菌性能的比较

研究了3种不同脱乙酰度蚕蛹壳聚糖对9种供试菌的抑菌效果。结果表明:3种壳聚糖对蜡状芽孢杆菌、鼠伤寒杆菌、枯草芽孢杆菌、白色念珠球菌、绿脓假单胞菌、大肠杆菌和金黄色葡萄球菌有明显的抑制作用,对巨大芽孢杆菌和嗜热脂肪芽孢杆菌的抑制作用不明显。随着壳聚糖溶液浓度的增大,其抑菌能力也增强。3种壳聚糖的抑菌活性为:脱乙酰度为95.96%的壳聚糖>脱乙酰度为86.45%的壳聚糖>脱乙酰度为78.12%的壳聚糖。壳聚糖的抑菌活性呈现随pH降低而增加的趋势,当pH值在pH 4.0～5.0,壳聚糖对所有供试菌均能完全抑制。高脱乙酰度蚕蛹壳聚糖作为热加工食品的防腐剂,可稳定保持其抑菌防腐性能。     

缫丝蚕蛹蛋白酶解产物体外抗氧化能力研究

目的:研究缫丝蚕蛹蛋白酶解产物的抗氧化能力,为缫丝蚕蛹蛋白的深度开发利用提供参考。方法:还原力法、DPPH自由基法、超氧阴离子自由基法、羟自由基法。结果:五种水解度较高的缫丝蚕蛹蛋白多肽中,蚕蛹蛋白水解专用酶的水解产物(E1)的还原力能力最强,酶解原液稀释100倍后吸光度为0.75;对O-2·和DPPH·的清除率也最高,酶解原液分别稀释10倍和100倍,其清除率分别为34.54%和79.38%,·OH的清除率次之,酶解原液稀释10倍清除率为43.77%。结论:蚕蛹蛋白水解专用酶水解得到的缫丝蚕蛹蛋白肽在体外表现出较好的抗氧化活性。     

红葡萄酒、啤酒和白酒抗氧化作用研究

采用二苯苦味酰肼(2,2-Diphenyl-1-picryl-hydrazyl radical,DPPH)法、ABTS(3-ethyl benzot hiazoline-6-sulfonic acid)法、邻苯三酚自氧化法及羟自由基抑制法对红葡萄酒、啤酒和白酒的清除自由基活性进行比较.结果表明,红葡萄酒对DPPH自由基、ABTS·+自由基、超氧阴离子自由基的清除率分别为73.05%、64.37%和50.08%.啤酒对上述3种自由基的清除率分别为2.31%、1.40%和4.03%.白酒对这3种自由基的清除率分别为0.19%、0.04%和0.11%.红葡萄酒、啤酒和白酒对羟自由基的抑制率分别是43.39%、4.99%和1.24%.结果显示,葡萄酒对DPPH自由基、ABTSS·+自由基、超氧阴离子自由基、羟自由基的清除作用最强,啤酒其次,白酒最弱.     

紫甘薯花色苷体外清除自由基的研究

以紫甘薯花色苷为原料,研究其体外清除自由基的能力。通过测定花色苷的红外光谱,以及对羟自由基、超氧阴离子和DPPH自由基清除率的检测,结果表明：紫甘薯花色苷随体系pH值增大,其特征吸收峰发生红移,颜色由红到蓝,最后成淡黄色,并有少量絮状沉淀产生。紫甘薯花色苷具有良好的清除自由基能力,在试验浓度范围（0.2～1.0mg/mL）内,对羟自由基、超氧阴离子和DPPH自由基的最大清除率分别达到85.63%、87.56%和90.69%。     

壳聚糖及其衍生物抗氧化活性的研究

以壳聚糖、羧甲基壳聚糖和盐酸壳聚糖为材料,研究3种壳聚糖及其衍生物对DPPH自由基、超氧阴离子自由基和羟自由基的清除能力以及还原能力和抗脂质氧化能力,并通化曲线拟合方法明确壳聚糖及其衍生物的IC50值。结果表明,随着浓度的增加,壳聚糖及其衍生物的抗氧化活性逐渐增强。3种壳聚糖及其衍生物中壳聚糖的抗氧化活性最强,其对DPPH自由基、超氧阴离子自由基和羟自由基的半清除率IC50值分别为0.91、4.87、0.28 mg/m L。     

盐酸水解处理对人参茎叶抗氧化活性的影响

对人参茎叶提取液盐酸水解前后的抗氧化活性进行了比较。以DPPH·、羟自由基、超氧阴离子及ABTS~+·的清除率、还原能力评价抗氧化活性。结果表明经盐酸水解后的人参茎叶水解液对DPPH自由基清除率由75.08%提高至85.12%,羟自由基清除率由43.87%提高至77.90%,超氧阴离子清除率由77.48%提高至90.09%,ABTS~+·清除率由83.40%下降至50.89%,还原能力由55.41%下降至24.48%。结果说明盐酸水解前后的人参茎叶提取液和水解液均有很好的抗氧化作用。     

林蛙油蛋白小肽抗氧化活性比较

在对林蛙油蛋白质进行酶解后,经超滤,获得P1及P2两种小肽。从DPPH自由基、羟自由基和超氧阴离子自由基清除能力3个方面对林蛙油蛋白小肽的体外抗氧化活性进行考察。结果表明,林蛙油蛋白小肽对DPPH自由基、羟自由基和超氧阴离子自由基均有一定的清除效果,且清除率与样品溶液的浓度存在剂量依赖关系;在10 mg/m L时,林蛙油蛋白小肽P1,P2对羟自由基清除率分别为30.46%和24.24%;对超氧阴离子的清除率分别为39.57%和36.19%;DPPH自由基清除率则分别为51.49%和44.21%。     

陕北野生枸杞多糖的体外抗氧化活性

目的：测定陕北野生枸杞中总糖含量、糖醛酸含量以及体外抗氧化活性。方法：采用苯酚- 硫酸法,测定枸杞提取物的总糖含量;用硫酸- 咔唑法,测定枸杞多糖的糖醛酸含量;通过红外光谱技术初步分析枸杞多糖基团的构成;并以VC 为对照,比较枸杞多糖对二苯代苦味酰基(DPPH)自由基、超氧阴离子自由基、羟自由基的 体外抗氧化活性及还原力。结果：陕北枸杞提取物中的总糖含量为58.31%,糖醛酸含量为32.17%。 当枸杞多糖的质量浓度为1mg/mL 时,对DPPH 自由基、超氧阴离子自由基、羟自由基清除率分别为81.30%、50.33% 和60.57%,还原能力比VC 稍低。结论：陕北野生枸杞多糖有很强的抗氧化活性。     

大蒜多糖对几种自由基的影响

为探寻大蒜多糖清除自由基的能力,测定大蒜多糖对DPPH、超氧阴离子自由基和羟自由基三种自由基的影响.结果显示:大蒜多糖对于DPPH无清除作用,但对超氧阴离子自由基在浓度为1-10mg/mL时,清除率为24.04%～85.13%;对羟自由基在浓度为1～10 mg/mL时,清除率为46.11%～66.46%.     

乳酸菌对自由基清除能力的研究

研究了52株乳酸菌的细胞和无细胞提取物清除DPPH自由基的能力,从中筛选出了3株对DPPH自由基清除率较高的乳酸菌,并对它们清除超氧阴离子自由基、羟自由基的能力及其还原能力做了进一步研究。结果表明,ZS-2的无细胞提取物对DPPH的清除率最高(46.53%),对羟自由基具有较高的清除率(48.72%),但对超氧阴离子自由基没有清除作用;而FS-3和BCX-9细胞对羟自由基的清除率均高于它们的无细胞提取物,同时也具有较强的清除超氧阴离子的能力。其中,FS-3无细胞提取物对超氧阴离子自由基的清除率最高,3株菌均有一定的还原能力。研究表明,乳酸菌的细胞和无细胞提取物在体外实验中对各种自由基具有不同的清除能力。     

响应面法优化丰年虫卵壳脱乙酰度壳聚糖提取工艺

以丰年虫卵壳制备的甲壳素为原料,通过单因素试验和响应面设计法,确定丰年虫卵壳壳聚糖微波辅助提取技术的最佳工艺条件为微波时间33.4min、乙醇浸泡时间86min、碱液质量分数57.27%。按此工艺条件提取可获得脱乙酰度为84.12%的丰年虫壳聚糖。     

高脱乙酰度蛹渣壳聚糖制备工艺优化

制备高脱乙酰度蛹渣壳聚糖。在蛹渣壳聚糖制备工艺单因素试验研究的基础上,应用二次回归正交旋转组合设计方法研究无水乙醇浸泡时间、氢氧化钠溶液质量分数、处理温度、处理时间及料液比对壳聚糖脱乙酰度的影响,建立脱乙酰度对5 个试验因素的正交回归模型,通过频率分析法确定蛹渣壳聚糖较优的制备条件范围并得到蛹渣壳聚糖的最佳制备工艺。最佳工艺为：无水乙醇浸泡1.7h、氢氧化钠溶液质量分数44%、处理温度94℃、处理时间9h、料液比1:28(g/mL)、每2h 换碱1 次。在此工艺条件下,壳聚糖的脱乙酰度95.96%、相对分子质量7.45 × 105、产率56.98%、水分含量3.20%、灰分含量0.35%,产品为原白色,外观色泽好,主要指标均达到相关企业标准。     

壳聚糖对亚硝酸盐清除作用的研究

研究了体外模拟胃液条件下壳聚糖对亚硝酸盐的清除作用；用分光光度法测定了壳聚糖对亚硝酸盐的清除率，考察了反应时间、壳聚糖用最、壳聚糖的脱乙酰度和分了量对清除亚硝酸盐效果的影响；结果表明：随反应时间的延长、壳聚糖用晕的增加，壳聚糖脱乙酰度的增高和分了量的降低，壳聚糖对亚硝酸盐的清除能力升高；分了量0．98万的壳聚糖37．5mg能完全清除亚硝酸盐。     

脱乙酰化反应条件对壳聚糖性能的影响

本文研究了甲壳素在脱乙酰化反应时不同反应条件,如碱浓度、反应时间、反应温度和处理方法对壳聚糖性能,如分子量、脱乙酰化度的影响,探讨了分子主链降解反应与脱乙酰化反应之间的关系。结果表明:随着碱浓度和反应时间的增加,壳聚糖脱乙酰化度提高,而分子量降低;脱乙酰化越高,主链降解程度增加;反应温度升高,脱乙酰化反应速度加快;而采用短时重复多次反应的处理方法,则可增加壳聚糖的脱乙酰化度,并减少主链降解程度。     

Radical scavenging activity of hetero-chitooligosaccharides

Nine hetero-chitooligosaccharides (hetero-COSs) consisting of relatively high molecular weights (90-, 75-, and 50-HMWCOS), medium molecular weights (90-,75-, and 50-MMWCOS), and low molecular weights (90-, 75-, and 50-LMWCOS) were prepared from partially deacetylated hetero-chitosans (90%, 75%, and 50% deacetylated chitosan), and their antioxidant activity based on their scavenging potency on the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical was investigated. The results showed that the 90-MMWCOS, prepared from 90% deacetylated chitosan, showed the highest scavenging activity on the DPPH radical. Their scavenging pattern was dose- and time-dependent. Electron spin resonance (ESR) spectrum of DPPH treated with 90-MMWCOS decreased in a time-dependent manner and the reducing power of hetero-COSs increased in a dose-dependent manner. These results indicated that hetero-COSs have an antioxidant activity which is dependent on their degree of deacetylation and molecular weight.     

Conformational Role of Xanthan Gum in its Interaction with Guar Gum

ABSTRACT: :
Ubbelohde viscometry, texture analysis, and centrifugation were used to investigate the effects of chain conformational changes of xanthan or deacetylated xanthan gum on its interaction with guar gum. Guar gum was not effective in denaturing xanthan gum when the xanthan helical structure was stabilized by salt. The intrinsic viscosities of deacetylated xanthan and guar blends were higher than those calculated from the weight averages of the 2. Conformational change was not observed for deacetylated xanthan, presuming deacetylated xanthan was in the exact conformation for guar to bind so that the most stable heterotypic structure between deacetylated xanthan and guar was formed directly, thus the strongest interaction was observed between deacetylated xanthan and guar.     

黑曲霉电解法制备甲壳素的研究

本试验以实验室发酵的黑曲霉菌丝体为原料,采用电解法从中提取甲壳素,再将甲壳素碱法脱乙酰转化为壳聚糖。通过单因素试验和正交试验分析了电解时间、电压、碱浓度及料液比对壳聚糖的脱乙酰度、得率、粘均分子量等指标的影响,以此间接反映电解法各因素对甲壳素产品的影响。黑曲霉电解法制备甲壳素的最优条件为:电解时间1.25h,NaOH浓度3%,电压8V,液料比12:1。试验证明,利用电解法从黑曲霉中提取甲壳素实践上是可行的。     

Anticoagulant activity of heterochitosans and their oligosaccharide sulfates

Three kinds of partially deacetylated heterochitosans, 90% deacetylated chitosan, 75% deacetylated chitosan and 50% deacetylated chitosan, were prepared from crab chitin by N-deacetylation with 40% sodium hydroxide solution for different durations. Nine kinds of heterochitooligosaccharides (hetero-COSs) with relatively high molecular weights (5,000–10,000 Da; 90-HMWCOSs, 75-HMWCOSs, and 50-HMWCOSs), medium molecular weights (1,000–5,000 Da; 90-MMWCOSs, 75-MMWCOSs, and 50-MMWCOSs), and low molecular weights (below 1,000 Da; 90-LMWCOSs, 75-LMWCOSs, and 50-LMWCOSs) were prepared using an ultrafiltration membrane reactor system, respectively. In addition, their sulfated derivatives were prepared by a method using a trimethylamine-sulfur trioxide, and the anticoagulant properties of the heterochitosans and their COS sulfates with different chain lengths and degrees of deacetylation were investigated. Clotting times in thrombin-time assay were prolonged in the presence of various concentrations of the heterochitosans and their COS sulfates using normal human plasma. The 90% deacetylated chitosan sulfate exhibited the highest anticoagulant activity among all the heterochitosans and their COS sulfates.     

Short communication: Stabilization of milk proteins at pH 5.5 using pectic polysaccharides derived from potato tubers

Potato pectin has unique molecular characteristics that differentiate it from commercially available pectins sourced from citrus peels or apple pomace, including a higher degree of branching and a higher acetyl content. The objective of this study was to evaluate the ability of potato pectin to stabilize milk proteins at an acidic pH above their isoelectric point, pH 5.5, at which no citrus- or apple-derived pectins are functional. Potato pectin was extracted from raw potato tubers by heating at pH 4.5 and 120°C for 30 min after removing starch solubilized using a dilute HCl solution adjusted to pH 2. The potato pectin was found to have a galacturonic acid content of 17.31 ± 3.29% (wt/wt) and a degree of acetylation of 20.20 ± 0.12%. A portion of the potato pectin was deacetylated by heating it in an alkaline condition. The deacetylation resulted in a galacturonic acid content of 19.12 ± 4.64% (wt/wt) and a degree of acetylation of 3.03 ± 0.03%. Particle size distributions in acidified milk drink (AMD) samples adjusted to pH 5.5 demonstrated that the acetylated and deacetylated potato pectins were capable of inhibiting the aggregation of milk proteins to the largest degree at a pectin concentration of 1.0 and 0.25% (wt/wt), respectively. Pectin molecules that were not bound to milk proteins in these AMD samples were quantified after centrifugally separating milk proteins and pectin bound to them from the serum. We found that, for the acetylated and deacetylated potato pectins, all or approximately half of the pectin molecules were bound to milk proteins at a pectin concentration of 0.25 or 1.0% (wt/wt), respectively. These results suggest that the presence of acetyl groups is a critical factor that determines how potato pectin molecules bind electrostatically to milk protein surfaces, form 3-dimensional structures there, and function as a stabilizer. The present results demonstrate that potato pectin can stabilize milk proteins at pH 5.5 and potentially enable the development of novel AMD products with improved functionality for casein-containing products with moderately acidic pH profiles.