Gelation of Persimmon Puree and Its Prevention by Enzymatic Treatment

Fresh persimmon puree showed a rheological behavior corresponding to a weak gel, where storage modulus (G′) prevailed over loss modulus (G″). In a temperature sweep test (from 25–80–25 °C), G′ values increased at temperatures above 60 °C and continued increasing during the subsequent cooling step showing a wide scattering. These changes indicated a gelation phenomena that resulted in a more rigid and irregular gel structure. The gelation was lower in the acidified puree (pH 4.4) than in the puree at its natural pH (5.9). The addition of ethylenediaminetetraacetate sodium avoided the increase of G′ during the heating and reduced the G′ increase in the cooling step. Thus, gelation in persimmon puree occurred by a heat-set gelation influenced by pH, and also by cold-set gelation depending on an ionotropic mechanism. The incubation of persimmon puree with Viscozyme L (1 g/L, 25 °C, 30 min) allowed to obtain a more fluid product able to tolerate a thermal processing at 85 °C without gelation. During the incubation with Viscozyme L, the pH of the persimmon puree decreased monotonically as a consequence of its pectinmetylesterase activity, and the continuous measurement of pH could be used to monitor this process.