著者

松田 由美子

出版者

The Japanese Society of Fisheries Science

雑誌

日本水産学会誌 (ISSN:00215392)

巻号頁・発行日

vol.34, no.9, pp.836-840, 1968

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Effect of pre-freezing rate on the quality of lyophilized "tokoroten", <i>gelidium</i> jelly, was examined.<br> The jellies were freeze-dried in a vacuum freeze dryer at a platen temperature of 60°C and chamber pressure of 20-300μHg after being frozen by the following methods: spraying with liquid nitrogen, vacuum freezing, air blast (3m/sec) freezing at -30°C freezing on a cold plate at -30°C and still air freezing at -21°C (Fig. 1).<br> When the jelly was frozen at a higher rate, the shape of lyophilized product remained unchanged and its tissue was fine (Fig. 3-2), whereas the one frozen at a slower rate gave a shrinked product and its tissue was rough (Fig. 3-5).<br> Although the ultra-quick freezing by spraying with liquid nitrogen gave a product whose tissue was very fine, remarkable cracks and projections resulted during the subsequent freeze-drying (Fig. 3-1). The colour of lyophilized jelly was more preferable as the rate of prefreezing was higher. A slight difference was observed in the distribution of ash and dissolution velocity in hot water. However, the freezing rate did not affect the reconstitution of the products: the quality of all the jellies made from the dried products was similar to that of original jelly.<br> It may be concluded from these results as well as the simplicity in processing that the vacuum freezing is the most preferable method for pre-treatment of the jelly.