Effect of Ca-Salt on Prevention of Texture Softening of Pickled Ume Fruit

Abstract

For the prevention of texture softening of pickled ume apricot fruit, the effect of treatment with CaCl₂ solution before salting was studied. The changes in its composition of pectic substances consisting of the water soluble(W-P), the hot-water-soluble(HW-P), the hexametaphosphate-soluble (HP-P), and the HCl-soluble(HCl-P)was measured during salting with or without Ca-salt. The results were obtained as follows: (1)During salting of the fresh fruit, a remarkable decrease of HClP and an increase of W-P accomparied softening the texture. (2)The treatment with CaCl₂ before salting increased HP-P and HCl-P, decreasing W-P, and kept the texture well hardened. (3)During salting without Ca-salt, a decrease of the Ca-content in the ethyl alcohol-insoluble substance (AIS)of the pickled product was found, while with Ca-salt, the Ca-content was increased. (4)The amount of Na in the AIS was also increased during salting. As a result of our experiments, the following reaction mechanism of Ca-salt to hold hard texture was presumably proposed: (1)During salting, a part of permiates into the tissues of ume apricot and causes the ion exchange reaction with Ca or Mg ions combined with pectic substances, which changes HP-P and HCl-P to W-P to some degree, and make the texture softer. (2)During salting with Ca-salt, the Ca ions, being increased in its amount in the tissue might form much more additional cross-linkages between or amoung the pectin molecules, which increase HP-P and cause the increase of the hardness of texture.