不同分子质量壳聚糖的制备及其整理织物的抗折皱性和抗菌性

以H2O2为氧化剂,研究了酸性、中性氧化降解法制备不同分子质量壳聚糖的工艺条件;以柠檬酸作为交联剂,将不同分子质量的壳聚糖对棉织物进行整理并测定其抗折皱性和抗菌性. 结果表明整理织物抗折皱性随壳聚糖分子质量减少而提高;质量分数为1.0%时,分子质量为17.0万、2.6万的壳聚糖对阴、阳性菌均有优异的抗菌性;分子质量为0.1万的壳聚糖抗阴性菌优于抗阳性菌.     

超声波辅助氧化剂降解壳聚糖的研究

讨论了超声波条件下用H2O2降解壳聚糖的方法,研究了壳聚糖用量、乙酸用量、温度、H2O2用量、超声波功率、降解时间对降解壳聚糖的影响,并对降解产物进行红外光谱分析.超声波辅助H2O2降解壳聚糖的最佳条件:2.0%壳聚糖的4%乙酸溶液,n(H2O2)/n(壳聚糖)=1.0、40℃、超声波工作频率为40kHz.超声波能够加速壳聚糖的降解反应,其对壳聚糖降解速度的影响与降解条件有较大关系.降解后壳聚糖结构基本不发生变化,获得了低分子质量壳聚糖,同时不改变其基本结构.     

副干酪乳杆菌Z17-壳聚糖复配对大肠杆菌O157:H7的抑菌效果及作用机制

目的：研究副干酪乳杆菌Z17-壳聚糖复配对草莓中大肠杆菌O157:H7抑菌活性及作用机制。方法：采用流式细胞术、傅里叶变换红外光谱、拉曼光谱及扫描电子显微镜技术分析副干酪乳杆菌Z17-壳聚糖对大肠杆菌O157:H7细胞膜的影响。结果：质量分数1.0%壳聚糖溶液与副干酪乳杆菌Z17复配处理能有效去除草莓上的大肠杆菌O157:H7,减菌率达99%;壳聚糖溶液与副干酪乳杆菌Z17共同作用3 h使大肠杆菌O157:H7 DNA胞外释放量达（381.00±3.53）ng/μL,细胞膜破损率为58.3%;细胞壁膜中脂肪酸、蛋白、肽聚糖、糖苷环、多糖结构成分被破坏;细胞膜局部位移变薄,大分子物质黏附于菌体细胞表面,细胞表面出现孔洞,胞内物质泄漏,最终导致菌体死亡。结论：副干酪乳杆菌Z17-壳聚糖能够有效地抑制草莓中大肠杆菌O157:H7,其抑菌作用靶点为大肠杆菌O157:H7的细胞膜,研究可为大肠杆菌O157:H7的生物防治提供参考。     

低聚壳聚糖制备及黏均分子量的测定

研究了壳聚糖的降解和黏均分子量的测定,确定了壳聚糖降解的适宜条件。亚硝酸钠降解壳聚糖的最佳条件是10% NaNO2用量0.6mL、温度35℃、时间35min、醋酸浓度3%;双氧水降解的最佳条件是H2O2浓度6%、温度70℃、时间6h、醋酸浓度4%;中温α-淀粉酶的最佳工艺条件为温度40℃、时间90min、酶用量1200U/g。     

糖化酶/H2O2二步法降解壳聚糖的研究

研究糖化酶/H2O2二步法降解壳聚糖的工艺条件。以降解产物壳寡糖的相对分子质量和收率为指标,采用单因素和正交试验确定壳聚糖降解的优化工艺条件为酶底质量比0.008,酶解温度62℃,酶解时间33h,H2O2的添加量12.6%,该条件下可以将相对分子质量为2.5×105的壳聚糖降解为分子量为470～1 102的壳聚糖,收率为83.3%。二步法可以更好地降解高分子量的壳聚糖,为壳聚糖的综合利用提供了新途径。     

壳聚糖延长高水分含量番薯果脯保质期的研究

目的:为生产低糖、高水分含量番薯果脯;方法:研究果脯中水分含量与水分活度的关系及细菌总数和霉菌数在保温试验中的变化,并采用不同黏均分子量的壳聚糖降低果脯的水分活度;结果:果脯中霉菌数是影响产品保质期的主要微生物指标,壳聚糖的黏均分子量越低,降低水分活度的幅度越大;结论:通过添加0.5%、9kD黏均分子量的壳聚糖,产品水分含量为20%、总糖为26%时,番薯果脯常温放置保值期达到12个月.     

酶降解壳聚糖在棉织物抗皱抗菌整理中的应用

利用酸性纤维素酶在不同时间条件下降解壳聚糖,得到不同黏均分子质量的系列壳聚糖,并用于棉织物的防皱抗菌整理;研究壳聚糖黏均分子质量对棉织物防皱与抗菌效果、毛细效应及柔软度的影响。结果表明,用于棉织物防皱抗菌整理壳聚糖的最佳黏均分子质量为1×105,整理棉织物的折痕回复角为246°,对大肠埃希菌抑菌率为86%,对金黄葡萄球菌抑菌率为88%,毛效为95mm,弯曲长度为3.4cm。     

泡叶藻聚糖低分子质量降解片段组成特征及其体外免疫诱导活性

目的：对从泡叶藻（Ascophyllum nodosum）中提取的泡叶藻聚糖进行化学法降解,将得到的低分子质量降解产物进行分离纯化,分析其基本组成特征和体外免疫诱导活性,为泡叶藻聚糖或其他海藻多糖的生物活性和基本结构特征研究提供参考。方法：通过酸水解法和双氧水氧化降解法制备泡叶藻聚糖低分子质量降解片段,利用超滤法和Sephadex G-50凝胶柱层析分离纯化得到4 个泡叶藻聚糖低分子质量片段：HCl-F1、HCl-F2、H2O2-F1、H2O2-F2;采用对氨基苯甲酸乙酯柱前衍生样品后进行高效液相色谱及化学方法分析其单糖组成和化学组成;采用高效分子排阻色谱法测定其重均分子质量;通过小鼠巨噬细胞RAW264.7模型分析HCl-F1、HCl-F2、H2O2-F1、H2O2-F2的体外免疫诱导活性。结果：泡叶藻聚糖低分子质量片段的组成特征表明HCl-F1、HCl-F2、H2O2-F1、H2O2-F2均为杂多糖,且单糖组成存在较大差异,其重均分子质量分别为4.80、4.20、5.30、2.30 kDa。免疫活性分析细胞模型结果表明,HCl-F1、HCl-F2、H2O2-F2在所测定质量浓度范围（0～200 μg/mL）内能明显诱导RAW264.7细胞活化,释放NO和肿瘤坏死因子-α（tumor necrosis factor-α,TNF-α）,而H2O2-F1诱导RAW264.7细胞释放NO和TNF-α的活性明显低于HCl-F1、HCl-F2和H2O2-F2。结论：泡叶藻聚糖低分子质量降解片段（HCl-F1、HCl-F2和H2O2-F2）具有明显的免疫诱导活性,其中HCl-F1和H2O2-F2的免疫诱导活性明显高于泡叶藻聚糖。结合其化学组成分析的结果,提示泡叶藻聚糖低分子质量降解片段的免疫诱导活性是由单糖组成和硫酸根质量分数共同决定的。     

酸性纤维素酶降解壳聚糖及其用于棉织物防皱抗菌整理

利用酸性纤维素酶在不同时间条件下降解壳聚糖，得到系列不同黏均分子质量的壳聚糖，并用于棉织物的防皱抗菌整理。研究了壳聚糖黏均分子质量对棉织物防皱与抗菌效果、毛细效应及柔软度的影响。结果表明，用于棉织物防皱抗菌整理的壳聚糖最佳黏均分子质量为1×105，整理棉织物的折痕回复角为246°，对大肠埃希菌抑菌率为86%，对金黄葡萄球菌抑菌率为88%，毛效为95 mm，弯曲长度为3.4 cm。     

壳聚糖用于真丝绸的抗皱整理

将壳聚糖的柠檬酸溶液用于真丝绸织物的抗皱整理,并采用傅立叶红外变换光谱技术对壳聚糖在真丝绸上的状态进行了分析;以H2O2氧化降解壳聚糖,控制氧化条件,得到不同分子质量的壳聚糖,用作真丝绸抗皱整理剂,并测定了织物的抗皱效果.     

羧甲基壳聚糖的降解及其抗氧化性能的研究

羧甲基壳聚糖是壳聚糖的一种重要衍生物。本研究采用过氧化氢氧化法对羧甲基壳聚糖进行降解,并考察了降解时间及过氧化氢用量对降解的影响。用粘度法和改进的Schales’方法测定了降解产物的分子量。并用流动注射化学发光分析法检测了降解产物的抗氧化能力--对羟基自由基的清除活性。结果表明:随着过氧化氢在降解体系中的浓度的增大,降解产物的分子量将趋于一固定值;当H2O2在总反应体系中浓度大于1.3mol/L,降解时间大于16h,将得到分子量低至1100左右的羧甲基壳聚糖;经降解得到的羧甲基壳聚糖均具有一定的羟基自由基清除活性,且分子量越小,其抗氧化性能越强。     

壳聚糖在中式煮制肉制品中的应用研究

对壳聚糖在中式煮制肉制品中的应用进行了研究.首先比较酸解和菠萝蛋白酶酶解这两种工艺的优劣,确定菠萝蛋白酶水解壳聚糖在工艺上优于盐酸水解法;然后考察不同添加量和不同水解度(即不同粘均分子量)的壳聚糖对中式煮制猪肉的抑菌效果和感官品质的影响.结果表明酶解时间越长(即粘均分子量越低),壳聚糖的抑菌效果越好,添加6%经菠萝蛋白酶酶解30 min的壳聚糖可将中式煮制肉制品的货架期延长3 d.可见,壳聚糖在中式煮制肉制品的生产中的具有很高的应用价值.     

壳聚糖在冷却鲜猪肉保鲜中的应用研究

利用不同脱乙酰度、不同浓度和不同溶解特性的壳聚糖,对冷却鲜猪肉进行保鲜处理,比较其保鲜效果.结果表明,壳聚糖在鲜猪肉中有明显的保鲜作用,且脱乙酰度越高,壳聚糖的保鲜效果越好;1%的壳聚糖醋酸溶液(醋酸浓度为1%)能使冷却猪肉的货架期达到一周;2.5%的水溶性壳聚糖的保鲜效果接近于1%的酸溶性壳聚糖,且感官品质更好.     

APPLICATION OF CHITOSAN TO MAINTAIN THE QUALITY OF KAMABOKO GELS MADE FROM GRASS CARP (CTENOPHARYNGODON IDELLUS) DURING STORAGE

Chitosan was added to kamaboko gels made from grass carp ( Ctenopharyngodon idellus ), and the effects on preservation quality were determined by biochemical (pH, total volatile basic nitrogen [TVBN], thiobarbituric acid [TBA], peroxide value) and microbiological (total bacterial count) determinations during storage at 4C. Application of chitosan, at a level of 1% (w/w), exhibited a beneficial effect on inhibiting lipid oxidation and bacterial growth in the gels. The preservative function was related to the molecular weight of chitosans. Relative low molecular weight chitosan showed a higher antioxidant capacity than high molecular weight chitosan. However, mixture of 300 and 10 kDa chitosans exhibited the highest antibacterial activity. Increases of pH, TVBN, TBA and peroxide values in gels during storage were significantly reduced when chitosan was applied. The present study provides a possible application of chitosan as a food additive for surimi-based foods.

PRACTICAL APPLICATIONS

Surimi-based product processing is an effective way to utilize freshwater fish with low commercial value, but the shelf life of surimi products is quite limited. Therefore, preservatives are commonly added to surimi products to extend the shelf life. This research has investigated the effect of chitosan, a natural preservative and antioxidant, on maintaining the quality of grass carp gels during storage at 4C. Results showed that chitosan could inhibit the growth of microorganism and prevent lipid oxidation, which was related to the molecular weight of chitosans. The present study should provide a possible application of chitosan as a natural food additive for surimi foods.     

壳聚糖对细菌细胞膜及膜蛋白的作用

研究壳聚糖对受试菌株大肠杆菌(E.coli)和金黄色葡萄球菌(St. aureus)的抑制作用;通过测定壳聚糖作用前后菌液的相对电导率变化和以1-N- 苯萘胺为荧光探针荧光强度的变化,分别考察壳聚糖对E.coli 和St. aureus 细胞膜和E.coli 外膜渗透性的影响;运用荧光分光光度计研究壳聚糖对E.coli 细胞膜中色氨酸(Trp)荧光强度的影响。结果表明,壳聚糖具有很好的抑菌性能,能改变细菌细胞膜的渗透性,从而破坏细胞膜。壳聚糖对细胞膜中Trp 的荧光具有明显的猝灭作用,且对细胞膜蛋白的猝灭作用 属于静态猝灭。     

壳聚糖的降解及对浆水防腐效果研究

运用H_2O_2-HAc均相体系降解制备了不同分子量的壳聚糖,研究了它们对浆水的防腐作用。研究结果表明：壳聚糖对酵母菌的抑制作用与其分子量有关,分子量越高其对酵母菌的抑制效果越好；分子量80万以上的壳聚糖防腐作用最好,在常温下,保质期可达2个月之久,完全可应用于食品保鲜,而分子量8000以下的壳聚糖不仅对酵母菌起不到抑制作用,反而具有促进其生长的作用。在此基础上对壳聚糖的抑菌机理也做了初步探讨。     

Chitosan Coating Improves Shelf Life of Eggs

ABSTRACT: Internal and sensory quality of eggs coated with chitosan was evaluated during a 5-wk storage at 25 °C. Three chitosans with high (HMw, 1100 KDa), medium (MMw, 746 KDa), and low (LMw, 470 KDa) molecular weight were used to prepare coating solutions. Coating with LMw chitosan was more effective in preventing weight loss than with MMw and HMw chitosans. The Haugh unit and yolk index values indicated that the albumen and yolk quality of coated eggs can be preserved up to 5 wk at 25 °C, which is at least 3 wk longer than observed for the control noncoated eggs. Based on external quality, consumers could not differentiate the coated eggs from the control noncoated eggs. Overall acceptability of all coated eggs was not different from the control and commercial eggs.     

Antibacterial Activity of Ozone‐Depolymerized Crawfish Chitosan

ABSTRACT: Antimicrobial activities of chitosan samples with different molecular weights (1333, 432, 201, 131, and 104 kDa) prepared by ozone treatment were examined against 2 Gram‐positive bacteria (Listeria monocytogenes and Staphylococcus aureus) and 2 Gram‐negative bacteria (Escherichia coli and Pseudomonas fluorescen) to investigate the effect of chitosan's molecular weight and concentration on the inhibition of bacterial growth. Antimicrobial activity of chitosan varied depending on the molecular weight, concentration of chitosan, and type of microorganism. Generally, the effectiveness of the chitosans significantly increased with increasing chitosan concentration, regardless of molecular size and types of bacteria. Chitosan with molecular weights ranging from 104 to 201 kDa showed relatively greater antimicrobial activity against L. monocytogenes, S. aureus, and P. fluorescen; whereas for E. coli, intermediate molecular weight chitosan was more effective in growth inhibition than lower or higher molecular weight chitosan particularly at 0.1% concentration.     

Characterization of casein micelle precipitation by chitosans

We have found that the addition of chitosan, a cationic polymer, on whole or skim milk produces destabilization and coagulation of casein micelles that takes place without changes in the milk pH or the stability of most whey proteins. The amount of lipids recovered in the chitosan-casein aggregates was similar or higher than that obtained with rennet or acid precipitation. Approximately 70% of milk Ca2+ (approximately 750 mg/L) was found in the chitosan-induced aggregates, which is 10 and 50% higher than the amounts observed with acid or rennet coagulations, respectively. Purified alpha, beta-, and kappa-caseins were extensively precipitated by different molecular weight chitosans at pH 6.8. The phosphate groups of caseins seem not to be relevant in this interaction because dephosphorylated alpha- and beta-caseins were equally precipitated with chitosans. Analysis by optical microscopy of the chitosan-casein complex reveals that the size of the aggregates increase as the molecular weight of chitosans increase. Hydrophobic and electrostatic interactions particpate in the association and coagulation of casein micelles with chitosans of different molecular weights. The phenomenon is observed over a broad range of temperature (4 to 70 degrees C) with a reduction in the concentration of chitosan needed to precipitate the caseins that parallels a reduction in the viscosity of the chitosan solutions. Taken together, the results indicate that the electrostatic interactions may contribute energetically to the association between the two biopolymers, but the hydrophobicity of the complex would be the key determinant in the overall energetics of the reaction.