SORPTION ISOTHERMS OF EDIBLE FILMS OF TILAPIA MYOFIBRILLAR PROTEINS

摘要

One of the main problems of edible films is their high water vapor permeability (WVP).rnThe moisture sorption behavior of the proteins and its edible films is thus, interestingrnand was the objective of this work. Freeze-dried Tilapia myofibrillar proteins (TMP)rnand its edible films (EF) plasticized with glycerol (30 and 70 g/100 g of protein) werernconditioned for adsorption (ads.) and desorption (des.) according to COST90 projectrnmethod at 15, 25 and 35oC for TMP isotherms, and at 25oC for EF isotherms, in a waterrnactivity (Aw) range from 0.11 to 0.85. Edible films WVP was also determined at 25oCrnand 100% relative humidity differential. Up to Aw = 0.75, the equilibrium moisturerncontent was under 30% (db) showing that TMP would effectively be a low hygroscopicrnmaterial. However, EF was more hygroscopic. These two factors, glycerol and moisturerncontent, increased the EF WVP from 3.8 10-12 (30% glycerol) to 7.4 10-12 mol.s-1m-1Pa-1rn(70% glycerol). All isotherms were well represented by GAB model. The lowrnhygroscopic character of TMP was lost in the EF mainly because of the glycerol contentrnand Ph (2.5) reduction, the latter causing the exposition of hydrophilic groups of TMP.