壳聚糖对芒果香蕉腐败病菌的抑菌性能研究

以芒果炭疽病菌、蒂腐病菌及香蕉潜伏炭疽病菌、冠腐病菌为实验菌株，研究了不同pH、酸溶剂的种类对壳聚糖抑菌性能的影响。结果表明：壳聚糖的抑菌率随壳聚糖浓度的提高而提高；在pH4．8或pH6．0的环境中，壳聚糖的抑菌能力较强；壳聚糖的乳酸溶液对芒果蒂腐病菌及香蕉潜伏炭疽病菌、冠腐病菌有很强的抑制力；壳聚糖连续刺激诱导40代后，芒果炭疽病菌、蒂腐病菌及香蕉潜伏炭疽病菌、冠腐病菌的EC50值均有所提高，说明壳聚糖的抑菌能力下降；其中以芒果球二孢霉蒂腐病菌的EC50值变化最显著，说明壳聚糖对其抑菌稳定性最差。     

不同抑菌剂对芒果病原菌的抑制作用研究

采用生长速率法,以相对抑菌率、有效中浓度(EC50)值为指标,测定了壳聚糖、硝酸锌、山梨酸钾以及它们复配于膨润土时,对芒果蒂腐和芒果炭疽病菌的抑制效果。结果表明:在病原菌离体平板培养试验中,蒂腐与炭疽菌分别于28℃的恒温培养箱中培养2、4 d,通过观察菌丝生长情况发现,上述材料对2种芒果病原菌菌丝的生长均有良好抑制效果,且随着抑菌剂浓度的增加其抑制效果增强;其中以壳聚糖的抑菌活性最为显著,EC50值分别为2.0188、1.1288 g/L。与3种抑菌剂复配的膨润土基材料对芒果病原菌有一定的抑菌效果,但抑菌效果略低于单一使用的抑菌剂。     

芥末精油对芒果采后病原真菌抑制效果和保鲜效应的研究

以"小腰芒"品种为材料,研究芥末精油熏蒸处理对芒果采后病原菌的抑制效应及对芒果采后保鲜效果。体外实验表明,在室温20～22℃下,芥末熏蒸对炭疽病菌和蒂腐病菌具有较强的抑制活性,0.002mL/L能完全抑制病原菌的生长,且随浓度增大,抑制效应增强。活体实验表明,0.005～0.01mL/L空间熏蒸处理,能明显抑制芒果炭疽病菌和蒂腐病菌在芒果果实上的生长,20℃下6d对照果实整果发病,0.01～0.05mL/L处理的芒果果实没有发病。经芥末精油熏蒸24h,浓度在0.05mL/L以下的芒果常温贮藏12d对其食用品质没有明显的影响。     

韭菜提取物对芒果炭疽菌和蒂腐菌的抑制作用

利用生长速率法、活体接种试验法、自然感病试验法研究了韭菜提取物对芒果炭疽病菌colletotrichum gloeosporioides Penz.和芒果蒂腐病菌Botryodiplodia theobromae Pat.的抑制作用。结果表明韭菜提取物对芒果炭疽菌和芒果蒂腐菌都具有抑制作用,其有效中浓度(EC50)分别为3.6%、5.8%;活体接种试验中,用试液处理,从开始有发病情况出现的第5天,能使芒果在20℃的条件下,其由外接芒果炭疽菌引发的芒果炭疽病发病率为8%～19%,抑菌率为67.7%～88.6%,而对照组的发病率为100%;在芒果自然感病试验中,韭菜提取物处理芒果也能够明显减轻芒果蒂腐病的发病程度。     

非生物性因素对壳聚糖抗菌活性的影响

以具有代表性的两类病原菌：金黄色葡萄球菌和大肠杆菌为实验菌种，研究了不同的酸溶液、金属离了、离了强度和pH等非生物性因素对壳聚糖抗菌活性的影响。结果表明：在壳聚糖的酸溶液中，低碳数的有机酸比高碳数的有机酸和常见的无机酸更有利于壳聚糖抗菌活性的发挥；在pH6．0的环境中，壳聚糖的抗菌活性最强；由于与壳聚糖的螯合作用，Zn^2 的加入对十壳聚糖的抗菌效率影响最大，Mg^2 的影响相对最小；离了强度的增大可以更好地提高壳聚糖的抗菌活性。     

23种中草药提取物对芒果炭疽病菌的抑制作用研究

探讨了23种中草药提取物对芒果炭疽病菌的抑制作用，结果表明：丁香和黄芩2种中草药的提取物对芒果炭疽病菌具有很好的抑制作用，而夏枯草、紫草、艾叶和白茅根对炭疽病菌的生长具有促进作用。试验同时得出丁香提取物随浓度的降低，抑菌作用逐渐下降；而黄芩提取物浓度变化对抑菌作用没有明显影响。通过紫外一可见吸收光谱分析得知，丁香提取物中主要成分可能为丁香酚，黄芩提取物中主要成分可能为黄芩甙。     

生物质热解液和壳聚糖复合保鲜剂对辣椒炭疽病菌抑菌作用研究

为探究生物质热解液在农业生产中的应用及复合保鲜剂开发,采用气相色谱-质谱联用仪分析检测了生物质热解液的化学成分,以辣椒炭疽病菌为实验菌种,用生长速率法进行了生物质热解液和壳聚糖对辣椒炭疽病菌的抑菌实验,通过共毒因子法确定了生物质热解液和壳聚糖的相互作用。结果表明:生物质热解液和壳聚糖对辣椒炭疽病菌的EC_(50)值分别为50倍和0.7 g/L;生物质热解液对辣椒炭疽病菌的最小抑菌浓度(MIC)和最小杀菌浓度(MFC)分别为32.5倍和29倍;两者以不同比例混合使用时对辣椒炭疽病菌的抑制具有增效作用,且生物质热解液和壳聚糖EC_(50)溶液按1∶1比例混合时共毒因子最大。     

壳聚糖抗菌性能的研究

本实验研究了客观因素对壳聚糖抗菌性能的影响，以确定壳聚糖的最佳抗菌条件。以金黄色葡萄球菌为实验菌，接种到含一定量壳聚糖的液体培养基中，通过测定光密度值研究壳聚糖的浓度、溶解度、分子量、培养基pH值对其抗菌活性的影响。抑菌实验结果表明：脱乙酰度、分子量相同的壳聚糖，对金黄色葡萄球菌的抑制能力随浓度的降低而减弱；壳聚糖溶于浓度为2%的醋酸溶液中，培养基pH控制在6.0最有利于发挥壳聚糖的抗菌活性；通过微波辐射法制得的低分子量壳聚糖水溶性很好，但对金黄色葡萄球菌的抑制能力有所下降。     

谷氨酸离子液体对壳聚糖的溶解及抗香蕉炭疽病菌活性影响的研究

采用谷氨酸离子液体作为溶解壳聚糖的绿色溶剂,研究了谷氨酸离子液体对溶解析出壳聚糖的分子结构特性的影响及对香蕉炭疽病菌的抗菌活性。实验结果表明,谷氨酸离子液体溶解析出的壳聚糖分子量下降,脱乙酰度增大。红外光谱分析表明谷氨酸离子液体溶解壳聚糖的过程中分子骨架结构保持不变,伴随着壳聚糖的部分降解,引起了β(1→4)糖苷键部分断裂,降解过程伴随脱乙酰反应发生;紫外光谱分析表明,溶解析出前后壳聚糖的分子结构没有发生明显变化;电镜观察表明,谷氨酸离子液体对壳聚糖有一定的降解作用;壳聚糖谷氨酸离子液体对香蕉炭疽病菌表现出明显的抑菌活性,抑菌率达到44.07%。     

草果提取物抑菌活性和稳定性研究

研究采用平板打孔法测试草果提取物对多种微生物的抑菌活性、最低抑菌浓度(MIC)和抑菌稳定性.实验结果表明:草果提取物对11种微生物的抑菌活性依次为金黄色葡萄球菌＞南阳K氏酵母菌＞炭疽杆菌＞芒果蒂腐病菌＞白色念珠菌＞枯草芽抱杆菌＞黑曲霉＞产紫青霉＞普通变形杆菌＞大肠杆菌＞肠炎沙门氏菌;其中对金黄色葡萄球菌的MIC为0.75 mg/mL;对大肠杆菌、白色念珠菌的MIC为1.5 mg/mL;对枯草芽孢杆菌、普通变形杆菌的MIC为3.0 mg/mL;对黑曲霉的MIC最高达6.0 mg/mL;且通过对草果提取物的抑菌稳定性研究显示,草果提取物对盐、温度、紫外光和pH有较强的稳定性,但是对糖不稳定.     

The effect of chitosan on the properties of emulsions stabilized by whey proteins

The influence of the cationic amino polysaccharide chitosan content (0–0.5%) on particle size distribution, creaming stability, apparent viscosity, and microstructure of oil-in-water emulsions (40% of rapeseed oil) containing whey protein isolate (WPI) (4%) at pH 3 was investigated. The emulsifying properties, apparent viscosity and phase separation behaviour of aqueous WPI/chitosan mixture at pH 3 were also studied. The interface tension data showed that WPI/chitosan mixture had a slightly higher emulsifying activity than had whey protein alone. An increase in chitosan content resulted in a decreased average particle size, higher viscosity and increased creaming stability of emulsions. The microstructure analysis indicated that increasing concentration of chitosan resulted in the formation of a flocculated droplet network. This behaviour of acidic model emulsions containing WPI and chitosan was explained by a flocculation phenomenon.     

Modification of chitosan using hydrogen peroxide and ascorbic acid and its physicochemical properties including water solubility,oil entrapment and in vitro lipase activity

Chitosan was modified using H₂O₂ and ascorbic acid with different incubation temperatures (4–40 °C). The properties of modified chitosan, including its oil entrapment ability, water solubility and the lipase-resistant activities, using in vitro intestine model system were determined. Nuclear magnetic resonance analysis showed that ascorbic acid was bound to modified chitosan. All of the modified chitosan from 4 to 40 °C demonstrated improved water solubility (even in pH 7) compared to non-modified chitosan, which was only soluble at pH 4. Modified chitosan from 4 °C exhibited 27.40% of oil entrapment ability which was approximately four times higher than 6.87% of non-modified chitosan. Modified chitosan from 4 and 40 °C had increased resistance against lipase activity compared to other biopolymers, including beeswax, carnauba wax and non-modified chitosan. Modified chitosan could be used as a new food ingredient due to their high water solubility, oil-entrapping ability and resisting lipase activity.     

Antioxidant, antifungal and antiviral activities of chitosan from the larvae of housefly, Musca domestica L.

Antioxidant activity of the chitosan from the larvae of Musca domestica L. was evaluated in two different reactive oxygen species assays, and inhibitory effects against seven fungi were also tested. The results showed that the chitosan had scavenging activity for hydroxyl and superoxide radicals which were similar to that of ascorbic acid. Also the chitosan exhibited excellent antifungal activity, especially in the low concentration, it could significantly inhibit the growth of Rhizopus stolonifer. Besides, antiviral results demonstrated that the chitosan could effectively inhibit the infection of AcMNPV and BmNPV. These results suggested that the chitosan from the larvae of housefly could be effectively used as a natural antioxidant to protect the human body from free radicals and retard the progress of many chronic diseases. Furthermore, the chitosan with antiviral and antifungal activity might provide useful information for antiviral breeding technology of economic insect and development of plant pathological control.     

壳聚糖双胍盐酸盐涂膜保鲜龙眼及其抑菌活性的研究

以龙眼为试材,对比壳聚糖(CTS)与其衍生物壳聚糖双胍盐酸盐(CSG)对龙眼在常温下的涂膜保鲜效果及两者对龙眼焦腐病菌和龙眼炭疽菌生长的抑制作用。将龙眼分别浸泡于质量分数为1.0%的CTS与0.2%、0.5%、1.0%的CSG溶液中,取出晾干,分装于聚乙烯篮中,于(28±2)℃的室内存放5d。测定果实的细胞膜渗透率、丙二醛(MDA)、失重率、VC、可溶性固形物(TSS)、可滴定酸(TA)含量的变化和烂果率。结果表明,用质量分数为1.0%CSG处理后的龙眼的各项生理指标均优于其他各组,说明1.0%CSG的保鲜效果优于其他几种涂膜处理。当CSG浓度为4.0mg/mL时,可完全抑制龙眼焦腐病菌菌丝的生长,当浓度大于1.0mg/mL时对龙眼炭疽菌菌丝的生长有明显的抑制作用。     

Synthesis of chitosan-caffeic acid derivatives and evaluation of their antioxidant activities

In this study, the antioxidant activities of different molecular weights (M_w) and grafting ratios of chitosan–caffeic acid derivatives were investigated. The grafting process was achieved using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDAC) as covalent connector under different conditions such as molecular-weight of chitosan, molar ratio of chitosan and caffeic acid, reaction temperature, pH, and reaction time. The half-inhibition concentrations (IC₅₀) of products were calculated by reduction of the 1,1-diphenyl picryl hydrazyl in the radical-scavenging assay and reduction of the Fe³⁺/ferricyanide complex to the ferrous form in reducing power assay. The EDAC showed maximum activity at 3-h, pH 5.0 and room temperature conditions, except high-molecular-weight chitosan in pH 2.0. The products were water-soluble in all pH and showed lower viscosity than native chitosan. The highest grafting ratio of caffeic acid was observed at 15% in low-molecular-weight chitosan. After 5% grafting of caffeic acid into chitosan, the grafting efficiency was increased by decreasing molecular-weight of chitosan at the same conditions. Caffeic acid has main role in the antioxidant activity of products. The maximum IC₅₀ of radical-scavenging activity (0.064 mg/ml) was observed at the highest caffeic acid containing derivative. Water-soluble chitosan and caffeic acid derivatives were obtained by this study without activity loss.     

壳聚糖及其金属锌配位络合物的抑菌性能研究

本研究在合成一种壳聚糖锌配合物后，测试了合成的壳聚糖锌、合成原材料壳聚糖的抑菌效果，以及不同PH条件对抑菌效果的影响，并比较了壳聚糖锌和常见的食品防腐剂苯甲酸钠、山梨酸钾对大肠杆菌ATCC8099、金黄色葡萄球菌ATCC6538、枯草杆菌黑色变种ATCC9372、白色念珠菌ATCC10231和黑曲霉ATCC16404的最低抑菌浓度。结果表明：合成的壳聚糖锌与合成前的壳聚糖相比抑菌性能大大提高；合成后的壳聚糖锌对细菌的抑菌效果与常见的食品防腐剂苯甲酸钠、山梨酸钾相当，但对真菌的抑制时效没有苯甲酸钠、山梨酸钾好。同时系统的pH对壳聚糖锌和壳聚糖都有较大的影响，酸性条件下抑菌效果较好。     

Properties of Chitosan Films as a Function of pH and Solvent Type

ABSTRACT: Two different deacetylated chitosans were dissolved in formic, acetic, lactic, or propionic acid to prepare chitosan films. The pH values of the film-forming solutions were adjusted to 3, 4, and 5. Water vapor permeability (WVP), tensile strength (TS), elongation (E), and total soluble matter (TSM) were significantly ( P < 0.05) affected by acid type, pH, and degree of deacetylation (DA). Low DA (LDA) chitosan films had lower WVP and TSM, higher TS compared with high DA (HDA) chitosan films. The E values were not affected by DA. As pH increased, WVP and TSM of chitosan films tended to increase while TS decreased significantly ( P < 0.05). Chitosan films with acetic and propionic acid solvents had low WVP and TSM and high TS, while films with lactic acid solvent had high E and TSM and the lowest TS. Fourier-transform infrared showed peak shifting in the spectra with different solvents and at different pH values. Chitosan films with lactic acid solvent showed a peak shift to a lower frequency range. The NH₃⁺ band was absent in the pH 5.0 chitosan film spectra.     

Modulation of physicochemical properties of emulsified lipids by chitosan addition

Electrostatic interactions between polysaccharides and proteins at oil–water interfaces alter the physicochemical properties and stability of emulsions. In this research, we studied the influence of chitosan addition on the properties of oil-in-water emulsions containing whey protein-coated lipid droplets. Experiments were carried out under conditions where the protein and polysaccharide had similar charges (pH 3.0) or opposite charges (pH 6.5). At pH 3.0, chitosan addition (0–0.025%) had little influence on droplet charge, aggregation, creaming stability or shear viscosity of whey protein emulsions, which was attributed to the fact that the cationic chitosan molecules did not adsorb to the cationic droplet surfaces due to electrostatic repulsion. At pH 6.5, chitosan addition caused a decrease in particle negative charge, an increase in particle size, a decrease in creaming stability, and an increase in viscosity. These effects were attributed to droplet aggregation caused by charge neutralization and bridging resulting from attraction of cationic chitosan molecules to anionic patches on the protein-coated droplet surfaces. Addition of cationic polyelectrolytes to protein-stabilized emulsions may be utilized to control their physicochemical properties, stability and biological fate, which may be useful for developing commercial products with novel or improved functional properties.     

Characterization of a chitosan sample extracted from Brazilian shrimps and its application to obtain insoluble complexes with a commercial whey protein isolate

The rheological behaviour of chitosan solutions in 250 mM acetate buffer was studied at different pHs (25 °C). The intrinsic viscosity decreased from ∼17 dL/g to ∼14 dL/g when the pH increased from 4.7 to 6.0. Concentrated solutions (0.5–3.0% w/w) exhibited a shear-thinning behaviour which increased with increasing chitosan concentration and decreasing pH. A good fitting of the experimental data to the Cross and Carreau flow models was obtained. The elasticity of the solutions decreased with increasing pH and decreasing chitosan concentration, as a consequence of increased chain flexibility.