Use of Polyphosphates in Agar Processing

Part III. Residual phosphate in agar reproduced through freezing processs

Abstract

To obtain informations on the interaction between the added polyphosphates and agar, the ash composition of agar which was reproduced from the agar gel containing polyphosphate through the repetition of usual manufacturing process was analyzed. The contents of total and HCl-soluble ash, and soluble P²O⁵ were closely correlated with the amount of added H-polyphosphate^*1, respectively. The highest value of ash increase was equal to 11% of the added polyphosphate for h-agar^*2, and 17% for m-agar^*3. The additives less than 200ppm did not always increase ash contents of the products. Soluble Fe³⁺ was reversely proportional to P₂O₅ in the product. Magnesium showed similar tendencies to ionic iron. Total ash and soluble SO₃ decreased with the prolongation of cooking the agar solution.
*1 H polyphosphate: Commercial sodium polyphosphate consisted of 85% of metaphosphate and 15% of pyrophosphate.
*2 h-agar: Powdered agar of h brand which was processed from the alkali treated seaweeds, Gracilaria species.
*3 m-agar: Mixed agar in powder which was experimentally processed from several kind of seaweeds, Gelidium and Gracilaria species.