Effects of the shape of intracellular ice crystals in frozen vegetables on drip loss after thawing
2018
Sawada, S. ((Mukogawa Women's University, Nishinomiya, Hyogo (Japan). Department of Food Science and Nutrition), (Mukogawa Women's University, Nishinomiya, Hyogo (Japan). Research Institute of Nutrition Science)) | Fukuda, M.
Frozen vegetables are very useful as food materials. However, most of the vegetable content is moisture, and ice crystals produced during the freezing process injure the vegetable cells and generate a large amount of drip during freeze-thawing, thereby causing deterioration. If the growth and aggregation of intracellular ice crystals during vegetable freezing are reduced, it may prevent deterioration by decreasing drip emission. In the present study using cryo-scanning electron microscopy, we investigated how the shape of ice crystals in frozen tissues of raw and branched vegetables (Japanese white radish, potato, broccoli, and pumpkin) could affect drip emission during thawing after three kinds of freezing treatments (A, liquid nitrogen freezing; B, air blast freezing; C, windless freezing). The drip ratio (mL/g vegetable) was increased most by method C, followed by B and A. The cytoplasmic membrane structures and sol of raw vegetable cells were not broken by method A, whereas the structures were broken considerably by method B and remarkably by method C. Fine ice particles in blanched potato seem to depend on the vitrification phenomenon of starch. Ice crystal growth in frozen vegetables was reduced by blanching, and a tendency for the drip ratio to decrease was observed in all vegetables except for pumpkin.
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