ผลของพลาสติไซเซอร์และแทรนส์กลูทามิเนสจากจุลินทรีย์ต่อสมบัติของฟิล์มจากโปรตีนถั่วเหลืองสกัด

• Main Author: อรนันท์ เลิศศรัณย์
• Other Authors: ธนจันทร์ มหาวนิช
• Format: Theses and Dissertations
• Language: Thai
• Published: จุฬาลงกรณ์มหาวิทยาลัย 2010
• Subjects: พลาสติไซเซอร์; โปรตีนถั่วเหลือง; Plasticizer; Transglutaminase
• Online Access: https://digiverse.chula.ac.th/Info/item/dc:34843

This research aimed to study the effects of plasticizer (glycerol) concentration, plasticizer ratio (glycerol-to-sorbitol) and microbial transglutaminase on properties of soy protein isolate film, as well as the application of such film to food product. The effect of different glycerol concentrations (50, 55, 60, 65 and 70% by weight of soy protein isolate) on film properties was investigated in the first part of this study. In general, as glycerol concentration increased, the film tensile strength (TS) was found to significantly decrease (p≤0.05) while the film thickness, moisture content, transparency and water vapor permeability were found to significantly increase (p≤0.05). Increased elongation at break (EB) with increasing glycerol concentration was demonstrated in the 50-65% glycerol concentration range. However, the film containing 70% glycerol possessed lower EB than that containing 65% glycerol. The film containing 65% plasticizer, which yielded the highest EB, was therefore chosen for further study. The second part of this research aimed to examine the effects of plasticizer ratio and transglutaminase treatment on properties of soy protein isolate film. Six different glycerol-to-sorbitol ratios (100:0, 80:20, 60:40, 50:50, 40:60 and 20:80) as well as the addition of 4 units of transglutaminase/g soy protein isolate were used in this study. Different plasticizer ratios did not significantly affect film thickness, transparency and water vapor permeability (p>0.05). Meanwhile, decreases in moisture content and EB, together with an increase in TS, were observed in those films with decreasing glycerol concentration. For the effect of transglutaminase treatment, the enzyme-treated films were higher in thickness and water vapor permeability, while lower in moisture content, EB and transparency, as compared to the untreated films (p≤0.05). At the glycerol-to-sorbitol ratios of 100:0 and 80:20, transglutaminase-treated film exhibited increased TS. However, no significant difference (p>0.05) in TS was observed between the enzyme-treated and untreated films with glycerol-to-sorbitol ratios of 60:40, 50:50, 40:60 and 20:80. Protein pattern as studied using SDS-PAGE showed a decrease in band intensity of 84, 66 and 45 kDa proteins, corresponding to the α’-, α- and β-subunits of soy β-conglycinin, with a presence of proteins of higher molecular weight at the top of the gel. On the other hand, different plasticizer ratios appeared to have no effect on the protein pattern. From this study, the film with glycerol-to-sorbitol ratio of 80:20 which was treated with 4 units of transglutaminase/g soy protein isolate exhibited high values of both TS and EB (1.23 MPa and 244.31%, respectively). The film sample was therefore used to investigate moisture sorption isotherm and storage stability of a food product (Gluay Guan, banana-and-coconut milk candy). From moisture sorption isotherm, the soy protein isolate film exhibited reduced rate of moisture change in the 0.1-0.8 water activity range. Gluay Guan wrapped with the soy protein isolate film demonstrated slower changes in moisture content, water activity, hardness and color than the unwrapped one. However, the rates of these changes were still higher as compared to that wrapped with polypropylene film. Interestingly, thiobarbituric acid value was lower in Gluay Guan wrapped with the soy protein isolate film, as compared to that wrapped with polypropylene film. This coincided with lower oxygen permeability of the soy protein isolate film.