Retention of Flavour and Elasticity of “Tokoroten” by Freeze-drying

Abstract

The present study was undertaken to find a proper method for the production of dried “tokoroten, ” gelidium jelly, which, on reconstitution, gives a jelly having favourable flavour and elasticity similar to those of the original one.
The jellies were dehydrated by the following four different methods: A) Freeze-drying after vacuum freezing, B) Freeze-drying after still air freezing at -21°C, C) Drying at room temperature after still air freezing at -25°C and subsequent thawing in still air, and D) Drying at room temperature after still air freezing at -25°C and subsequent thawing in running tap water. Among them, the latter two methods correspond to the conventional one for the production of agar-agar in Japan.
After being stored in carton boxes at room temperature for a definite period, the dried samples were reconstituted into jellies for examination of various properties.
Immediately after processing, the dried products obtained by the former two methods gave the jellies quite similar to the original one in all the properties examined, although the jellies prepared from the stored products showed a slight discolouration, increase of jelly strength and off-flavour.
On the other hand, the properties of jellies from the dried samples produced by the latter two methods were considerable different from those of original one even immediately after drying. This may be due to the loss of water-soluble constituents.