ศูนย์นวัตกรรมเทคโนโลยีหลังการเก็บเกี่ยว

Effects of freezing rate on astringency reduction in persimmon during and after thawing

Satoshi Taira, Miki Ono and Masako Otsuki

Postharvest Biology and Technology. Volume 14, Issue 3, 9 November 1998, Pages 317-324.

1998

บทคัดย่อ

We compared the reduction of astringency in the flesh of persimmon fruit (Diospyros kaki Thunb. cv. `Hiratanenashi') either slowly frozen in a conventional freezer or rapidly frozen with liquid nitrogen, during and after thawing. Astringency and concentration of soluble tannins in flesh frozen by either method had decreased little by the start of thawing. In slowly frozen flesh, soluble tannins decreased greatly during thawing, and the thawed flesh was almost non-astringent. However, rapidly frozen flesh was still astringent after being thawed. Astringency reduction in frozen and thawed persimmon flesh is probably not related to changes in pectic substances, which changed little during and after thawing, whatever the mode of freezing. Microscopic observations suggested that these differences may be related to the degree of damage that occurred in flesh cell walls and plasma membranes during freezing. Soluble tannins, released from tannin cells during thawing, became insoluble on contact with fragments of cell walls and plasma membranes. The process of tannin insolubilization was greatest for slowly frozen flesh. Such adhesion of soluble tannins to fragments of cell walls and plasma membranes may be a factor that reduce astringency in persimmon fruit frozen slowly during and after thawing.