Abstract Chitosan is obtained at industrial scale through a process of alkaline deacetylation of chitin the major waste of shrimp industry. Its utilization could both diminish industrial environmental impact and add value to foods and other industrial products. In this study, an industrial chitosan obtained in Argentina and a commercial chitosan were physicochemically characterized and evaluated as edible coating for biopreservation of minimally processed lettuce. Based on Nuclear Magnetic Resonance, X-ray diffraction and thermogravimetric and viscosimetric assays we conclude that both biopolymers have similar molecular weight and deacetylation degree. The chitosan coatings were applied by spraying to lettuce leaves that had been removed and cleaned after the harvest. Each sample composed by four whole leaves, packed into a low-density polyethylene bag, was stored at 4 °C for 15 d. Microbial quality, weight and color losses, antioxidant contents, stomatal closure and sensorial attributes were evaluated during storage. An initial reduction of 2 log in molds and yeast counts were obtained for both types of chitosan coatings. As a result, the counts remained below the limit value of 6 log for 12 d in the chitosan coatings, while in the control samples this limit was reached 6 d after storage. Total mesophilic bacteria counts were also reduced by both types of chitosan coatings, keeping counts under the threshold value of 7 log for 12 d while in control samples this value was exceeded at 9 d. Both chitosans increased chlorophyll content, total phenolic compounds and antioxidant activity in lettuce leaves during the storage. Besides, the leaf weight loss was minimized by both chitosan coatings, in accordance to a higher proportion of stomatal partial closure as seen by SEM. The overall visual quality was not affected by chitosan coatings. In conclusion, the industrial chitosan showed similar effects on stored minimally processed lettuce than the commercial chitosan adding value to a material that is currently considered a waste.

中文翻译：

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通过产生壳聚糖涂层来重新评估渔业废物，以提高质量并延长最低限度加工生菜的保质期

摘要 壳聚糖是通过对虾工业的主要废物甲壳素进行碱性脱乙酰化过程以工业规模获得的。它的利用既可以减少工业环境影响，又可以增加食品和其他工业产品的价值。在这项研究中，对在阿根廷获得的工业壳聚糖和商业壳聚糖进行了物理化学表征并评估为可食用涂层，用于最低限度加工的生菜生物防腐。基于核磁共振、X 射线衍射以及热重和粘度测定，我们得出结论，这两种生物聚合物具有相似的分子量和脱乙酰度。壳聚糖涂层通过喷洒到收获后已被去除和清洁的生菜叶子上。每个样本由四片完整的叶子组成，装入低密度聚乙烯袋中，4 ℃保存15 d。在储存期间评估微生物质量、重量和颜色损失、抗氧化剂含量、气孔闭合和感官特性。对于两种类型的壳聚糖涂层，最初的霉菌和酵母计数减少了 2 log。结果，壳聚糖涂层中的计数保持在 6 log 的限值以下 12 天，而在对照样品中，该限值在储存后 ​​6 天达到。两种类型的壳聚糖涂层也减少了嗜温细菌总数，将计数保持在 7 log 的阈值以下 12 天，而在对照样品中，该值在 9 天时被超过。两种壳聚糖都增加了储存期间生菜叶片的叶绿素含量、总酚类化合物和抗氧化活性。除了，根据 SEM 所见的更高比例的气孔部分闭合，两种壳聚糖涂层都使叶片重量损失最小化。整体视觉质量不受壳聚糖涂层的影响。总之，与商业壳聚糖相比，工业壳聚糖对储存的最低限度加工的生菜显示出相似的效果，为目前被认为是废物的材料增加价值。