Freezing and Drying Prooess of 'Kori-tofu' and Agar : A few industrial and scientific problems

Abstract

A similarity in the flow chart is found between 'Kori-tofu'(frozen and dried soybean curd) and agar through the whole processes. In this respect, following things were lectured and discussed. Moist heating for drying of the defrosted material in Kori-tofu manufacture is one characteristic technique. The nitrogen-gaseous pressure freezing is useful to form a spongy structure in the defrosted intermediate product which has enough strength for the succeeding pressing dehydration and drying processes. It possibly eliminates the 2〜3 weeks aging period of frozen material in the conventional method. Kori-tofu is characteristic because of its lipids content as much as 30% in the air dried product and its unexpected stable properties in a long term storage. The textural quality of Kori-tofu is evaluated by either the ratio of water absorption or bulk density. Phospholipids are considered to have an important role for the expanding and water holding capacity. Sucrose prevents the freezing denaturalization of the protein but has a favorable effect to the textural property. The unchangeabillity of gelling properties of agar and the migration of the acidic constituents in the freezing process of gel are introduced.