Effect of Immersion Freezing on Texture of Huangguan Pear

In order to explore the effect of immersion freezing on fruit texture, Huangguan pear was used as the test material, and different immersion freezing temperature (−20, −40 ℃) and immersion solution (single 30% calcium chloride impregnation solution, 30% calcium chloride+4% trehalose+0.05% polylysine composite impregnation solution). Hardness, the content of pectin and microstructure of tissue cells were determined, and the effect of immersion freezing on the texture characteristics of pear was analyzed. The results showed that the loss of pectin and decomposition of original pectin could be better controlled in the trehalose and polylysine immersion solution group when frozen at −40 ℃ (P<0.05). The water-soluble pectin content in the −40 ℃ composite immersion solution group was reduced by 31.85% compared with that in the −20 ℃ single immersion solution group, which maintained the hardness of pears and reduced the penetration of solute in the impregnation solution. The Fourier infrared spectroscopy and atomic force microscopic results also showed that the immersion freezing treatment affected the water-soluble pectin changes in pear. After freezing with −40 ℃ of compound immersion solution, the pear cells showed clear texture, regular arrangement, which was more similar to that of fresh fruit cells. It can be seen that reducing freezing temperature and using freezing protection liquid can better maintain the texture of frozen food, reduce the damage of freezing to food tissue cells, and inhibit the large migration of impregnating liquid solute, thus improving the quality of frozen fruit.