Development and evaluation of antimicrobial natamycin‐incorporated film in gorgonzola cheese conservation

Conservation of food products depends on product quality and packaging suitability. The objective of this work was to develop and evaluate the antimicrobial efficiency of natamycin‐incorporated film in the production process of Gorgonzola cheese. It aims to optimize the production process and increase shelf‐life and food safety for the consumer. Films with different concentrations of natamycin were produced and tested in Gorgonzola cheeses to evaluate its efficiency against Penicillium roqueforti on the cheese surface. Films with 2 and 4% natamycin presented satisfactory results for fungus inhibition and the amount of natamycin released to the cheese was below that allowed by the legislation. Copyright © 2006 John Wiley & Sons, Ltd.     

纳他霉素的研究现状

纳他霉素是一种高效生物防腐剂。文章介绍了纳他霉素的理化性质，抑菌特点，作用机理及安全性等特征。综述了其在食品工业中的应用现状，并对其应用前景进行展望，以期为纳他霉素的进一步研究和应用提供参考。     

纳他霉素高产菌株的选育

以恰努塔加链霉菌株(Streptomyces Chattanoogensis)ATCC13358为出发菌株,依次利用紫外线和微波进行诱变处理,通过诱变剂量与致死率的关系确定最适诱变剂量。采用60 s的紫外线照射和微波处理50 s对恰努塔加链霉菌株ATCC13358进行诱变,得到1株青霉素和制霉菌素双抗性突变株M102,在相同发酵条件下,产量达到3.298 g/L,较出发菌株ATCC13358提高了2.18倍。连续传代10次,产量性状无大变化,表明该菌株遗传性状稳定。     

Antimicrobial Activity of Nisin and Natamycin Incorporated Sodium Caseinate Extrusion‐Blown Films: A Comparative Study with Heat‐Pressed/Solution Cast Films

Antimicrobial edible films based on sodium caseinate, glycerol, and 2 food preservatives (nisin or natamycin) were prepared by classical thermomechanical processes. Food preservatives were compounded (at 65 °C for 2.5 min) with sodium caseinate in a twin‐screw extruder. Anti‐Listeria activity assays revealed a partial inactivation of nisin following compounding. Thermoplastic pellets containing food preservatives were then used to manufacture films either by blown‐film extrusion process or by heat‐press. After 24 h of incubation on agar plates, the diameters of K. rhizophila growth inhibition zones around nisin‐incorporated films prepared by solution casting (control), extrusion blowing or heat pressing at 80 °C for 7 min of nisin‐containing pellets were 15.5 ± 0.9, 9.8 ± 0.2, and 8.6 ± 1.0 mm, respectively. Since heat‐pressing for 7 min at 80 °C of nisin‐incorporated pellets did not further inactivate nisin, this indicates that nisin inactivation during extrusion‐blowing was limited. Moreover, the lower diameter of the K. rhizophila growth inhibition zone around films prepared with nisin‐containing pellets compared to that observed around films directly prepared by solution casting confirms that nisin inactivation mainly occurred during the compounding step. Natamycin‐containing thermoplastic films inhibited Aspergillus niger growth; however, by contrast with nisin‐containing films, heat‐pressed films had higher inhibition zone diameters than blown films, therefore suggesting a partial inactivation of natamycin during extrusion‐blowing.     

超滤和纳滤膜分离提取纳他霉素

为提高纳他霉素(natamycin)生产提取得率,减少溶剂使用,本文采用超滤、纳滤操作对工业生产的纳他霉索发酵液进行处理。实验结果表明:操作压力、操作时间及料液流速对超滤过程有很大影响。通过超滤可将蛋白质等大分子杂质去除,然后再用纳滤膜对超滤渗透液进行浓缩纯化,对纳滤工艺的操作条件如进料压力、料液pH、浓缩倍数等进行了研究。采用超滤、纳滤技术提取纳他霉素,其收率可达62.74%。     

培养条件对褐黄孢链霉菌发酵合成纳他霉素的影响

对褐黄孢链霉菌摇瓶发酵合成纳他霉素的研究表明: 种龄、接种量和装液量对纳他霉素合成的影响显著;在实验范围内,随着种龄、接种量和装液量的增加,纳他霉素产量均表现出先增加后减少的趋势,而菌体干重则变化很小.最适宜产物合成和菌体生长的发酵培养基初始pH值各不相同,分别为7.5～8.0和6.5～7.0.当发酵温度从31℃下降到25℃时,纳他霉素产量大幅度增加,而菌体干重在31℃达到最大值.在种龄48 h、接种量10%、25℃、初始pH值 7.6、装液量10%的优化条件下,纳他霉素最高产量达到1.5 g/L, 基于菌体干重的产率为4.917%.     

纳他霉素和茶多酚在酱油中的应用研究

酱油是常用调味品,目前市售的酱油中添加的防腐剂多为化学合成的,而天然防腐剂较少在酱油使用.文章分别对天然防腐剂纳他霉素和茶多酚在酱油中的防腐效果及其复配使用后的效果进行了研究,并与化学合成防腐剂山梨酸钾进行了对照实验,得知天然防腐剂纳他霉素和茶多酚在酱油中都具有一定的防腐作用,两者复配使用后与山梨酸钾具有等同的防腐效果,可达到酱油的国家标准,但安全性大大提升.而且茶多酚具有一定的保健功效,对人体健康十分有利,可提高酱油的营养价值和保健功能.     

1-MCP结合纳他霉素对富士苹果贮后货架品质和芳香物质的影响

以富士苹果为实验试材,研究1-甲基环丙烯（1-methylcyclopropene,1-MCP）（1 μL/L）结合不同质量浓度纳他霉素（0、400、800、1 200 mg/L）对贮后常温货架期间果实品质的影响及其货架期芳香物质的变化。结果表明,与对照组相比,1-MCP结合纳他霉素处理富士苹果后能更好地减缓果实质量损失率的增加和硬度的下降,保持果实VC、可滴定酸和可溶性固形物含量,其中800 mg/L纳他霉素处理保鲜效果优于其他处理;主要特征香气成分有己醛、反式-2-己烯醛、乙酸-2-甲基丁酯、乙酸己酯和正己醇等,不同处理富士苹果芳香物质种类存在一定差异性,其组成及相对含量在货架期内发生相应变化,4 种处理醇类物质相对含量均减少,对照组与1 200 mg/L纳他霉素组酯类、醛类物质以及总芳香物质相对含量增加,400 mg/L纳他霉素组酯类物质相对含量增加,800 mg/L纳他霉素组酯类物质相对含量减少,总芳香物质相对含量略有减少,其变化规律与理化指标分析结果相吻合。