100B-28 |
Mechanisms to enhance functionality of peanut-protein biopolymer films |
M. E. CASTELL-PEREZ and C. C. Liu. Biological and Agricultural Engineering, Texas A&M University, 303E Scoates Hall, College Station, TX 77843-2117 Peanut protein is a potential ingredient for development of biopolymeric films for packaging applications. However, mechanical and barrier properties of peanut-protein films are inferior to those of synthetic films. Our objective was to elucidate the mechanisms for improving the functional, mechanical and barrier properties of peanut-protein films subjected to several modification treatments. Distilled water was added to peanut protein isolate (> 95% protein). Films were casted by pouring 10 mL of solution (heated at 95C for 25 min, filtered) into Teflon petri dishes and allowed to dry overnight at room temperature. The pH was adjusted to 9.0 by adding 1N NaOH. Films were formed at 90°C for 16 h, then peeled off after cooling and kept in Ziploc bags in a desiccator until further testing. Different methods to enhance film functionality were tested: (1) plasticizer type and amount (glycerol and polyethylene glycol @ 25, 50, 75, 90%); (2) heat curing (60, 70, 80, and 90C for 30 min); (c) UV light for 0, 2, 4, 8, 16, 24 h; (d) ultrasound dosage at 10 and 30 min; and (e) addition of anhydrides and aldehydes. Film thickness, color, solubility, mechanical strength, water vapor and oxygen permeability were measured. The degree of crosslinking was quantified using glass transition theory and viscoelasticity data from stress relaxation tests. Microstructural techniques (ESEM) were used to relate the microstructure changes to the film properties. Glycerol and cross-linking due to UV and heat curing at 80C promoted favorable changes in the functional, physical, and barrier properties as related to the modified molecular size and shape. Film strength and flexibility were significantly improved. Barrier properties improved by 20%. Ultrasound treatment did not affect the film's functionality. The enhanced film performance was related to endothermic polymerization of protein denaturation, more aggregated structures with a denser protein matrix and larger pores.
Session 100B, Food Packaging
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