Abstract:
This study aimed to investigate the effect of rice bran oil (RBO) and rice bran wax (RBW) on properties of soy protein emulsion film. Either RBO or RBW (5 to 20% of total solids) was added to a film-forming solution containing 5% soy protein isolate and 55% glycerol by weight. An improvement in moisture barrier property was signified upon lipid incorporation. For instance, the films containing 15% RBO and 15% RBW exhibited 27 and 16% decrease in water vapor permeability as compared to the soy protein control film. Both emulsion films also demonstrated lower water solubility than the control. In terms of mechanical properties, a reduction in tensile strength was revealed with increasing lipid concentration. For example, the films containing 15% RBO and 15% RBW exhibited 34 and 43% decrease in tensile strength as compared to the control. The emulsion films also exhibited a decrease in transparency and an increase in yellowness. Scanning electron micrographs revealed a less homogeneous film matrix for the films containing RBW as compared to those containing RBO. Secondly, the determination of prebiotic activity score was conducted and it was shown that in the case of commercial prebiotics, the highest prebiotic activity score was demonstrated for Lactobacillus paracasei Lpc-37 with oligofructose and in the case of prebiotic-containing plant extracts, the highest prebiotic activity score was demonstrated for L. paracasei Lpc-37 with Jerusalem artichoke extract. Thirdly, the next step is the development of edible emulsion film from soy protein with synbiotic property. The film bases that will be used were chosen from the first part of this study in which the soy protein film with 15% rice bran oil was found to possess the lowest water vapor permeability. The prebiotics which had the highest prebiotic activity score were added in the concentration up to 2% of the film-forming solution. For probiotic, L. paracasei LPC-37 was incorporated after cooling step prior to casting film. The film then was then analyzed the properties as well as %viability of the probiotic. The result was indicated that the film drying step led to a significant decrease in the viability of L. paracasei Lpc-37, especially when no prebiotics were included in the films. Furthermore, The concentration of prebiotic did not place a significant effect on the viability of L. paracasei Lpc-37.