Feng Tianlin, Chen Huizhi, Zhang Min
State Key Laboratory of Food Science and Resources, Jiangnan University, Wuxi 214122, China.
China General Chamber of Commerce Key Laboratory on Fresh Food Processing & Preservation, Jiangnan University, Wuxi 214122, China.
Foods. 2023 Sep 19;12(18):3489. doi: 10.3390/foods12183489.
Freshness is one of the main factors affecting consumers' purchase of food. The freshness indicator labels of packaged fresh green bell pepper ( L.) and greengrocery ( L.) were constructed, and pH-sensitive indicator labels based on the dye of anthocyanin and the mixing dye of methyl red and bromothymol blue were prepared in this study. At the same time, the color, chlorophyll content and vitamin C content of vegetables were measured in order to explore the applicability of indicator labels in the cool chain transportation of vegetables. Compared with the nature dye, the chemical dye-type indicator labels are more sensitive to pH changes. The results showed that the mixed indicator intelligent label had the best indication effect, and the MB 2 (mixing 1 g/L methyl red and bromothymol blue solutions at a ratio of 3:2 with a concentration of 70 mL/L in indicator film solution) indicator label could effectively indicate the freshness changes in vegetables during storage. Meanwhile, the color changes of the MB 2-type indicator label were correlated with the colors change of the sample, changes in nutrients, and changes in CO content inside the packaging. In addition, freshness detection models for green bell pepper and greengrocery by using color information of MB 2 intelligent labels were established. Hence, this pH-sensitive label can be applied as a promising intelligent packaging for non-destructively monitoring the freshness of respiratory and non-respiratory climacteric vegetables.
新鲜度是影响消费者购买食品的主要因素之一。本研究构建了包装新鲜青椒（L.）和蔬菜水果（L.）的新鲜度指示标签，并制备了基于花青素染料以及甲基红与溴百里酚蓝混合染料的pH敏感指示标签。同时，对蔬菜的颜色、叶绿素含量和维生素C含量进行了测定，以探讨指示标签在蔬菜冷链运输中的适用性。与天然染料相比，化学染料型指示标签对pH变化更敏感。结果表明，混合指示剂智能标签指示效果最佳，MB 2（在指示剂膜溶液中以3:2的比例混合1 g/L甲基红和溴百里酚蓝溶液，浓度为70 mL/L）指示标签能够有效指示蔬菜在储存期间的新鲜度变化。同时，MB 2型指示标签的颜色变化与样品的颜色变化、营养成分变化以及包装内CO含量变化相关。此外，利用MB 2智能标签的颜色信息建立了青椒和蔬菜水果的新鲜度检测模型。因此，这种pH敏感标签可作为一种有前景的智能包装，用于无损监测呼吸跃变型和非呼吸跃变型蔬菜的新鲜度。
