壳聚糖-酪蛋白酸钠可食性抑菌膜结构表征及抑菌性的研究

用热溶法制备壳聚糖-酪蛋白酸钠复合基膜,添加天然抑菌剂纳他霉素和溶菌酶,制成可食性抑菌膜。采用红外光谱(FT-IR)表征不同抑菌膜的结构,同时测定3种膜的透光率、力学性能、紫外吸收性和抑菌性。结果表明:不同抑菌膜中的各成分之间相互作用良好,在制得的抑菌膜中,M2膜的相容性最优;M1膜各力学性能最佳,M2膜抗拉强度增强;M1膜和M3膜对紫外光的吸收较大;M2膜对不同菌种的抑菌效果较优,特别对霉菌和酵母菌的抑菌性最好,差异达到显著水平(P0.05),对细菌的抑制作用为假单胞菌金黄色葡萄球菌大肠杆菌。综合考虑,M2膜在干酪包装中具有广阔的应用前景。     

壳聚糖、溶菌酶和牛至油对大豆分离蛋白膜抑菌效果的影响

采用双倍稀释法研究壳聚糖、溶菌酶和牛至油对大肠杆菌和金黄色葡萄球菌的最小抑菌浓度。采用抑菌圈法研究添加天然抑菌剂壳聚糖、溶菌酶和牛至油的大豆分离蛋白膜对大肠杆菌、金黄色葡萄球菌、酿酒酵母和黑曲霉的抑菌效果。结果表明,添加壳聚糖、溶菌酶和牛至油的大豆分离蛋白膜对大肠杆菌、金黄色葡萄球菌、酿酒酵母和黑曲霉均有抑制作用。对大肠杆菌和金黄色葡萄球菌抑制效果为:牛至油>壳聚糖>溶菌酶。对酿酒酵母的抑制效果为:壳聚糖>牛至油>溶菌酶;对黑曲霉的抑制效果为:牛至油>壳聚糖>溶菌酶。因此,添加壳聚糖、溶菌酶和牛至油的大豆分离蛋白膜具有较好的抑菌效果和应用前景。     

壳聚糖复合抑菌保鲜膜的研制及其性能研究

以壳聚糖为主要原材料,辅佐以溶菌酶和纳他霉素两种抑菌剂,优化壳聚糖复合抑菌保鲜膜的配方。试验考察了溶菌酶和纳他霉素的最佳抑菌添加量及壳聚糖、海藻酸钠、甘油、羧甲基纤维素钠（CMC-Na）等原料对复合保鲜膜性质的影响,并采用正交试验优化了保鲜膜的配方。结果表明,保鲜膜最佳配方为：溶菌酶添加量0.06%,纳他霉素添加量0.03%,壳聚糖添加量2.0%,海藻酸钠添加量0.15%,羧甲基纤维素钠添加量0.15%,甘油添加量1.5%。复合抑菌保鲜膜抗拉强度良好（29.37 MPa）,断裂延伸率较高（116.9%）,水蒸气透过率低（0.221 [（g·mm）/（h·m2·KPa）]）,透光性较好（91.17%）且具备良好抑菌特性,综合评分为97分。     

壳聚糖基复配液抑菌条件的优化

以壳聚糖为基材,添加纳他霉素和纳米二氧化钛(TiO_2)两种抑菌剂以增强对金黄色葡萄球菌和黑曲霉的抑菌效果。采用单因素试验和响应面优化分析法研究纳他霉素添加量、纳米TiO_2添加量和搅拌温度对壳聚糖基复配液抑菌性的影响,并优化工艺参数。结果表明:壳聚糖基复配液抑菌剂的最佳条件为:纳他霉素添加量为0.075%,纳米TiO_2添加量为0.08%,搅拌温度为50℃。在此条件下,对金黄色葡萄球菌抑菌圈直径为27.21mm、对黑曲霉抑菌圈直径为44.73mm。说明在以壳聚糖为基材,复配纳他霉素和纳米TiO_2两种抑菌剂时,可以达到复配液的最佳抑菌效果。     

天然保鲜剂在鲜腐竹保藏中的应用

鲜腐竹因营养成分丰富、水分含量较高而极易腐败变质。通过单因素试验和正交试验研究了茶多酚、纳他霉素和溶菌酶3种天然保鲜剂对鲜腐竹保藏效果的影响。单因素试验结果表明:随着茶多酚、纳他霉素和溶菌酶添加量的增加,鲜腐竹的菌落总数均呈现先降低后升高的趋势,当三者添加量分别为0.012%、0.025%和0.25%时,鲜腐竹的菌落总数最低。正交试验表明:3种天然保鲜剂对鲜腐竹的菌落总数影响最大的是纳他霉素,其次为茶多酚,溶菌酶的抑菌效果最差;三者的最优组合为茶多酚0.012%、纳他霉素0.025%、溶菌酶0.30%,在此条件下,鲜腐竹在37℃时可保存6 d,在常温25℃条件下,其货架期可达到(19~22)d。     

干酪可食性涂膜保鲜剂配比的研究

为研究开发可食用干酪保鲜剂,以酪蛋白酸钠为基材,添加天然抑菌材料构成基液,在此基础上分别对单一添加纳他霉素和溶菌酶的基液进行了抑菌效果的对比,供试菌为大肠杆菌、金黄色葡萄球菌、假单胞菌、酵母菌和霉菌。同时对混合添加纳他霉素和溶菌酶的基液的抑菌效果进行了研究并对其配比进行优化。结果表明:单一添加纳他霉素的抑菌保鲜液对霉菌和酵母菌的抑菌性随其用量增加而增强,而且不同用量之间均存在显著差异(p0.05),对金黄色葡萄球菌、假单胞菌的抑菌效果呈先增加后减小,而对大肠杆菌的抑菌作用在不同用量之间不存在显著差异(p0.05);单一添加溶菌酶的抑菌保鲜液对酵母菌的抑制作用较强(p0.05),对其它菌种抑菌圈小于12 mm。运用响应面优化法以吸光值增量为指标对壳聚糖、那他霉素、溶菌酶混合添加的的配比进行优化,结果表明:那他霉素0.07 g/100 m L基液、溶菌酶1.0 g/100 m L基液,所得吸光值增量达到最小值为1.225,且壳聚糖与那他霉素和壳聚糖与溶菌酶之间存在显著的交互作用(p0.05),那他霉素和溶菌酶交互作用不显著(p0.05),并在此配比下的抑菌圈直径分别是大肠杆菌13.67 mm,金黄色葡萄球菌14.33 mm,假单胞菌15.66 mm,酵母菌18.00 mm和霉菌17.76 mm。     

溶菌酶在酱油中的抑菌效果研究

溶菌酶为多肽链组成的蛋白质分子,酶活在酸性条件下具有良好的热稳定性,且对革兰氏阳性细菌具有专一的抑制杀灭作用,是成品酱油的一种良好的天然抑菌防腐剂。本文研究了溶菌酶在酱油中的抑菌防腐效果。结果表明:(1)在酱油中,溶菌酶的抑菌防腐效果理想,且具有缓慢杀菌的功能,其最佳添加量为150 mg/kg,抑菌防腐效果比0.1%苯甲酸钠要好;(2)在高盐分含量酱油中的抑菌防腐效果比低盐分含量酱油要好,添加溶菌酶后菌落总数下降趋势更加明显;(3)酱油的巴氏灭菌操作对溶菌酶的活性无显著影响;(4)在起始菌落总数为10000 cfu/ml或以下的酱油中使用溶菌酶能使酱油具有较好的抑菌防腐效果,在货架期内菌落总数增长缓慢,产品质量稳定。     

工业酒精发酵污染菌的分离及新型抑菌剂的应用

为了研究新型抑菌剂在酒精发酵染菌控制中的应用,从工业酒精发酵污染液分离出主要污染菌HG-201,其16S rDNA与Pantoea ananatis(JX215331)的核苷酸序列同源性为99%。在菌株HG-201生长对数中期添加新型抑菌剂葡萄糖氧化酶和溶菌酶,以确定对菌株HG-201的抑菌效果。将酿酒酵母与菌株HG-201以1∶30的接种比例进行混合培养,并在发酵开始添加低浓度的抑菌剂。结果表明:10 U/m L的葡萄糖氧化酶和0.25 g/L的溶菌酶即可完全抑制菌株HG-201的生长和代谢,并且在实验条件下对酿酒酵母生长以及乙醇的产量没有影响,为新型抑菌剂在工业酒精发酵杂菌控制中的应用提供了参考。     

冷却猪肉中复合保鲜剂配比优化研究

按照五因子二次旋转正交组合设计方案,确定了Nisin、纳他霉素、溶菌酶、茶多酚和壳聚糖复合保鲜冷却猪肉的交互作用,获得最佳配比。结果表明:5种保鲜剂的抑菌效果依次为溶菌酶>壳聚糖>茶多酚>Nisin>纳他霉素;溶菌酶与Nisin、溶菌酶与壳聚糖间存在显著交互效应(P<0.05);浸泡用复合保鲜剂的最佳配比为Nisin0.10%、纳他霉素0.13%、溶菌酶0.20%、茶多酚1.8%、壳聚糖1.8%。     

三种生物防腐剂联合处理对龙眼汁抑菌效果的研究

目的研究纳他霉素、乳酸链球菌素和溶菌酶三种生物防腐剂对龙眼汁抑菌效果的影响。方法设计两两复配和响应面实验,以菌落总数为指标,观察贮藏期间内的抑菌率变化,得出最优抑菌组,并测定最优组的一些理化指标。结果由两两复配实验得出,当添加总浓度为200 mg/kg,纳他霉素:溶菌酶=3:7、Nisin:溶菌酶=5:5、Nisin:纳他霉素=9:1时的抑菌效果明显;响应面实验结果显示三种生物防腐剂浓度均为225mg/kg时的抑菌效果最好,最大抑菌率为84.2%。结论三种生物防腐剂复配后添加于龙眼汁中,能显著提高抑菌率,延长保存期,同时可在一定程度减缓Vc含量、总酸含量和色差的变化。     

Antimicrobial activity of lactoferrin against foodborne pathogenic bacteria incorporated into edible chitosan film

The objectives of this research were to develop and characterize edible chitosan film containing lactoferrin as a natural antimicrobial agent, and to investigate the combination effects of lactoferrin with lysozyme in chitosan film against the growth of Escherichia coli O157:H7 and Listeria monocytogenes. Chitosan films containing lactoferrin, lysozyme, or nisin were fabricated, and the antimicrobial concentrations were 0.5, 1, or 2 mg in a circular disc of chitosan film. Three concentrations of lactoferrin or EDTA (0.28, 0.56, or 1.12 mg per disc) were also incorporated into the chitosan film containing lysozyme to investigate the combination effects of lactoferrin. The water barrier properties of the chitosan films containing lactoferrin were characterized. The antimicrobial activities against E. coli O157:H7 and L. monocytogenes were determined using the agar diffusion assay and cell count assay. The chitosan films containing lactoferrin less than 1 mg per disc did not alter the water vapor permeability of the chitosan film. Although the film containing lysozyme exhibited significant antimicrobial activity, the incorporation of lactoferrin alone into chitosan film did not exhibit significant antimicrobial activity against both E. coli O157:H7 and L. monocytogenes. However, the combination of lactoferrin with lysozyme-containing chitosan film significantly decreased the growth of E. coli O157:H7, exhibiting a comparable effect to that of the combination of EDTA with lysozyme (P < 0.05). Furthermore, the combination of lactoferrin with lysozyme in chitosan film exhibited greater reduction in the growth of L. monocytogenes than did the combination EDTA with lysozyme, resulting in an approximate 3-log reduction.     

不同聚乳酸膜的抗菌性比较

为了研究添加抗菌剂后,聚乳酸复合膜的抗菌性能,选取了壳聚糖、茶多酚、MgO和银四种抗菌剂,与聚乳酸形成四种复合膜,对比了不同抗菌剂的效果,并利用红外光谱仪对复合膜的结构进行了表征。实验发现,无论哪种抗菌剂,均表现了良好的抗菌效果。当壳聚糖/聚乳酸、茶多酚/聚乳酸均按质量比5:5组成复合膜时,抗菌率分别为68.54%和70.26%,当MgO的添加量为2%时,抗菌率为71.01%,而银表现出了极强的抗菌效果,添加量为1%时,抗菌率达到了98.53%。透光率随着抗菌剂的加入都有不同程度的减小,其中茶多酚的影响最大,从88.67%下降到33.75%。薄膜DSC曲线显示,未添加抗菌剂时,薄膜T_m为80.3℃,添加Ag和MgO后,薄膜T_m分别下降了1.7℃和1.4℃,说明抗菌剂的添加对薄膜T_m几乎无影响。由此可以看出,天然抗菌剂的抗菌效果要略差于无机抗菌剂。     

Lysozyme release from isolate pea protein and starch based films and their antimicrobial properties

The objective of the current research was to analyze the effects of the pea protein and corn starch films as well as the temperature influence (10 and 25 °C) on the release of lysozyme to a food simulant (agar gel). Lysozyme concentration at different depths of food simulant was measured, as a function of diffusion time, through its enzyme activity. In both polymer matrices, a loss of lysozyme activity was observed after film formation. Diffusion of lysozyme was enhanced when temperature increased, mainly when pea protein films were tested. A higher retention of lysozyme in the film starch matrix was significantly detected which could be attributed to the different hydration degree of the film in contact with the agar medium and the different interactions between the enzyme and the film polymer chains. The antimicrobial effectiveness of pea protein and starch films containing lysozyme (0, 50, 75 and 100 mg lysozyme/g hydrocolloid), against Listeria monocytogenes was proved. At 10 °C, both matrices were effective against the pathogen. At 25 °C, the effectiveness of films significantly decreased and pea protein films showed the best antimicrobial activity.     

Functional Properties of Antimicrobial Lysozyme-Chitosan Composite Films

ABSTRACT: Lysozyme-chitosan composite films were developed for enhancing the antimicrobial properties of chitosan films. A 10% lysozyme solution was incorporated into 2% chitosan film-forming solution (FFS) at a ratio of 0%, 20%, 60%, and 100% (w lysozyme/w chitosan). Films were prepared by solvent evaporation. Lysozyme release from the film matrix, the antimicrobial activity of films against Escherichia coli and Streptococcus faecalis , and basic film properties were investigated. The lysozyme release proportionally increased with increasing initial concentration of lysozyme in the film matrix, and the amount of released lysozyme was in natural log relationship with time. The films with 60% lysozyme incorporation enhanced the inhibition efficacy of chitosan films against both S. faecalis and E. coli , where 3.8 log cycles reduction in S. faecalis and 2.7 log cycles reduction in E. coli were achieved. Water vapor permeability of the chitosan films was not affected by lysozyme incorporation, whereas the tensile strength and percent elongation values decreased with increased lysozyme concentration. Scanning electron microscopy images revealed that lysozyme was homogeneously distributed throughout the film matrix. This study demonstrated that enhanced antimicrobial activity of lysozyme-chitosan composite films can be achieved by incorporating lysozyme into chitosan, thus broadening their applications in ensuring food quality and safety.     

Immobilization of lysozyme on polyvinylalcohol films for active packaging applications

A new technique for the immobilization of lysozyme onto the surface of polyvinylalcohol films is presented. The active compound was sprayed along with a suitable bonding agent onto the surface of the cross-linked polymeric matrix. Active compound release tests determined the amount of lysozyme immobilized on the film surface. With the use of Micrococcus lysodeikticus, the antimicrobial activity of the films was determined and the results correlated with the amount of immobilized lysozyme. This new technique was effective for immobilizing the enzyme, and the developed films were active against the test microorganism. Results were compared with those obtained with a different immobilizing technique, in which the active compound was bound into the bulk of the polymeric film. As expected, the surface-immobilized lysozyme films have a higher antimicrobial activity than bulk-bound films.     

Mechanical,Physical, Antioxidant,and Antimicrobial Properties of Gelatin Films Incorporated with Thymol for Potential Use as Nano Wound Dressing

The aim of this study was to determine the properties of gelatin films incorporated with thymol. Gelatin films were prepared from gelatin solutions (10% w/v) containing thymol (1, 2, 4, and 8% w/w), glycerol (25% w/w) as plasticizer, and glutaraldehyde (2% w/w) as cross‐linker. Cross‐likened films showed higher tensile strength, higher elongation at break, lower Young's modulus, lower water solubility, lower swelling, lower water uptake, and lower water vapor permeability. Incorporation of thymol caused a significant decrease in tensile strength, increase in elongation at break, decrease in Young's modulus, increase in water solubility, decrease in swelling and water uptake, and increase in water vapor permeability slightly. The films incorporated with thymol exhibited excellent antioxidant and antibacterial properties. The antibacterial activity of the films containing thymol was greatest against Staphylucoccus aureus followed by Bacillus subtilis followed by Escherichia coli and then by Pseudomonas aeruginosa. Thus, gelatin films‐containing thymol can be used as safe and effective source of natural antioxidant and antimicrobial agents with the purpose of evaluating their potential use as modern nano wound dressing. Practical Application : This study clearly demonstrates the potential of gelatin films incorporated with thymol as natural antioxidant and antimicrobial nano film. Such antimicrobial films exhibited excellent mechanical, physical, and water activities and could be used as antibacterial nano wound dressing against wounds burn pathogens.     

Characterization of Fish-Skin Gelatin Gels and Films Containing the Antimicrobial Enzyme Lysozyme

ABSTRACT:  Fish skins are rich in collagen and can be used to produce food-grade gelatin. Films cast from fish-skin gelatins are stable at room temperature and can act as a barrier when applied to foods. Lysozyme is a food-safe, antimicrobial enzyme that can also produce gels and films. When cold-water, fish-skin gelatin is enhanced with lysozyme, the resulting film has antimicrobial properties. The objective of this study was to characterize the effect on strength and barrier properties of lysozyme-enhanced fish-skin gelatin gels and films, and evaluate their activity against potential spoilage bacteria. Solutions containing 6.67% fish-skin gelatin were formulated to contain varying levels of hen-egg-white lysozyme. Gels were evaluated for strength, clarity, and viscoelastic properties. Films were evaluated for water activity, water vapor permeability, and antimicrobial barrier capabilities. Fish-skin gels containing 0.1% and 0.01% lysozyme had pH (4.8) and gelling-temperatures (2.1 °C) similar to lysozyme-free fish-skin gelatin controls. However, gel strength decreased (up to 20%). Turbidities of gels, with or without lysozyme, were comparable at all concentrations. Films cast with gelatin containing lysozyme demonstrated similar water vapor permeabilities and water activities. Lysozyme was still detectable in most fish gelatin films. More antimicrobial activity was retained in films cast with higher lysozyme concentrations and in films where lysozyme was added after the gelatin had been initially heated. These results suggest that fish-skin gelatin gels and films, when formulated with lysozyme, may provide a unique, functional barrier to increase the shelf life of food products.     

Physicochemical,Microstructural, and Antibacterial Properties of β‐Chitosan and Kudzu Starch Composite Films

Abstract: This study investigated physicochemical, microstructural, and antibacterial properties of β‐chitosan–kudzu starch composite films with addition of 0%, 20%, 60%, or 100% kudzu starch (w starch/w chitosan) in 1% chitosan solution. Molecular interactions between chitosan and kudzu starch and the crystal structure of the films were also determined. Adding 60% kudzu starch reduced water vapor permeability and solubility of pure β‐chitosan film by about 15% and 20%, respectively, whereas mechanical strength and flexibility of the film were increased about 50% and 25%, respectively. Micrograph showed that β‐chitosan film was totally amorphous, and the composite films generally became rougher with more starch added. Fourier transform infrared and X‐ray diffraction spectra showed that the 2 film‐forming components were compatible with each other. Pure β‐chitosan film resulted in 9.5 and 11.5 log CFU/mL reduction in Escherichia coli and Listeria innocua based on plate count method, respectively. Addition of kudzu starch reduced the antibacterial activity of film, but still achieved 8.3 and 10.3 log CFU/mL reduction in E. coli and L. innocua, respectively when kudzu starch to chitosan weight ratio was 1:1. Reduced antibacterial activity might attribute to the interaction of amino groups in β‐chitosan with the hydroxyl groups in kudzu starch. This study demonstrated that kudzu starch effectively improved water barrier of β‐chitosan film, and the composite films retained strong antibacterial ability. Practical Application: One percent of β‐chitosan containing 60% kudzu starch (w/w chitosan) composite films possessed better mechanical and water barrier properties than pure β‐chitosan films, and showed strong antibacterial activity against both Gram‐positive and Gram‐negative bacteria. The films may be used as wraps or coatings to prolong the shelf life of different foods or other similar applications.