The effect of hygroscopicity on quality characteristics of different freeze-drying fruit and vegetable products

Abstract

Objective: This study aimed to explore the changes of hygroscopicity and quality characteristics of different freeze-dried (FD) fruits and vegetables in the storage. Methods: Taking four kinds of fruits and vegetables, including potato, king oyster mushroom, apple and white radish, as the research objects, the changes of microstructure, hygroscopicity, color and texture characteristics of the four kinds of freeze-dried fruits and vegetables were observed, and the correlation analysis was conducted. Results: The results showed that the cell structure of fresh fruits and vegetables was plump and regular; The FD apple slices was observed with relatively complete tissue structure, thicker cell wall, slightly rupture, larger aperture, stronger hygroscopicity, and significantly reduced L* value was (P＜0.05). The pore structure of lyophilized potato slices was hexagonal, and there were a lot of starch particles in the cells. With small pores, the hygroscopicity was lower than that of lyophilized apple slices, and the color change was significant (P＜0.05). The lyophilized radish slices had compact structure and smooth surface, while the cells were wrinkled and deformed, and the pore size was not uniform, and the hygroscopic property was lower than that of lyophilized potato slices; the color of the material had no significant change after hygroscopic (P＞0.05). The structure boundary of lyophilized Pleurotus eryngii slices was filamentous, and the cell wall was broken seriously; the cell integrity was low, and the hygroscopicity was lower than that of lyophilized white radish slices. The color and luster of lyophilized white radish slices had no significant change (P＞0.05). The difference in quality indexes between the material before and after moisture absorption was obvious, while there was a significant or extremely significant correlation between the hygroscopicity and texture properties of materials (P＜0.05). Conclusion: There is a big difference in the texture of the material without moisture absorption and moisture absorption during the storage process, which affects the quality characteristics of the product.

Keywords

• freeze-drying
• hygroscopicity
• texture properties
• cluster analysis