海藻酸钠/聚乙烯醇pH指示水凝胶的制备及其对鲜切哈密瓜的新鲜度指示

Preparation of pH indicating hydrogel based on sodium alginate/polyvinylalcohol and application for freshness monitoring of fresh-cut cantaloupe

为制备能稳定且灵敏指示鲜切果蔬新鲜度的指示器,该研究以海藻酸钠和聚乙烯醇为基材,复配甲基红和溴百里酚蓝为指示剂,制备pH显色水凝胶。首先以指示剂添加量、交联剂浓度以及交联时间为影响因素进行单因素试验,以水凝胶的变色灵敏度和力学性能为指标,对水凝胶制备工艺进行优化;然后,对最优工艺制备的水凝胶进行结构表征和性能测定;最后,将其用于鲜切哈密瓜的新鲜度监测。结果表明,指示剂添加量为5%,交联剂质量浓度为7 g/L,交联时间为18 h的条件下制备的水凝胶结构完整,内部呈多孔结构,具有较好的硬度和弹性,在pH 3~11内有良好的颜色响应。将其应用到鲜切哈密瓜的新鲜度指示中发现,在4℃贮藏3 d时,哈密瓜从新鲜转变为次新鲜,此时水凝胶从黄绿色变为橙色。因此,该研究所制备的水凝胶在鲜切果蔬的新鲜度指示中具有较好的应用前景,有助于提高鲜切果蔬的安全性和消费者体验。

To prepare an indicator that can stably and sensitively indicate the freshness of fresh-cut fruits and vegetables,indicator hydrogels were prepared using sodium alginate(SA)and polyvinyl alcohol(PVA)as the hydrogel-forming materials,and methyl red&bromothymol blue mixture was used as the indication agent in this study.Firstly,the preparation parameters such as the indication agent addition amount,crosslinking agent concentration,and crosslinking time were optimized by using the color-changing sensitivity and mechanical properties as the optimization indexes.Then the structures and properties of the hydrogels prepared by the optimal technology were characterized.Finally,it was used to monitor the freshness of fresh-cut cantaloupe.Results showed that the hydrogel prepared with 5%of indication agent,7 g/L of crosslinking agent concentration,and 18 h of crosslinking time had complete structures and porous interior,good hardness and elasticity,and an active color response in the range of pH 3-11.Furthermore,when it was applied to monitor fresh-cut cantaloupe freshness under refrigeration(4℃),the fresh-cut cantaloupe changed from fresh to sub-fresh on the third day,and the color of the indicator hydrogel from yellow-green to orange.Therefore,the hydrogel prepared in this study has good application prospects as a freshness indicator for fresh-cut fruits and vegetables and helps to improve the safety of fresh-cut fruits and vegetables and the consumer experiences.