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Research Project: New Sustainable Processing Technologies to Produce Healthy, Value-Added Foods from Specialty Crops

Location: Healthy Processed Foods Research

Title: Study of combined effects of glycerol and transglutaminase on properties of gelatin films

Author
item Liu, Fei - Jiangnan University
item Chiou, Bor-sen
item Avena Bustillos, Roberto
item Zhang, Yuzhu
item Li, Yue - Jiangnan University
item Mchugh, Tara
item Zhong, Fang - Jiangnan University

Submitted to: Food Hydrocolloids
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/3/2016
Publication Date: 10/3/2016
Citation: Liu, F., Chiou, B., Avena Bustillos, R.D., Zhang, Y., Li, Y., McHugh, T.H., Zhong, F. 2016. Study of combined effects of glycerol and transglutaminase on properties of gelatin films. Food Hydrocolloids. 65:1-9. doi:10/1016/j.foodhyd.2016.10.004.

Interpretive Summary: Gelatin, due to its low production cost on a large scale, biodegradability and excellent film forming properties, has made it a potential candidate as a natural polymer for film formulations. Unfortunately, its hygroscopic nature limits its applications in foods with high moisture contents. Cross-linking is an effective approach to reduce the moisture susceptibility of gelatin films. Transglutaminase (TGase) has been successfully used to cross-link gelatin films, with subsequent improvements in water resistance, mechanical, barrier, thermal and morphological properties. Gelatin films plasticized with different glycerol contents (0-40%) were cross-linked using TGase. Cross-linking degree of the films decreased linearly with increasing glycerol content, resulting in an increase in water solubility and reduced tensile strength and more smooth and compact microstructures.

Technical Abstract: Gelatin films plasticized with different glycerol contents (0-40%) were cross-linked using transglutaminase (TGase). Unmodified films were prepared as controls. Cross-linking degree of the films decreased linearly with increasing glycerol content, resulting in an increase in water solubility. Glycerol increased the mobility and free volume of the gelatin film matrix as observed by differential scanning calorimetry, thus increasing the moisture content and thickness. Tensile strength and Young’s modulus had a negative linear correlation with glycerol content, with no significant differences between TGase-modified and unmodified films (p > 0.05). However, TGase-modified films showed a 294% and 187% relative increase in elongation at break and toughness, respectively, in comparison with controls at 30% glycerol content (p < 0.05). X-ray diffraction and circular dichroism spectroscopy both showed a linear decrease in triple-helix content as glycerol content increased, and TGase-modified films had lower triple-helix contents. Also, the second derivative of FTIR spectra showed that TGase-modified films had increased single a-helix structures, but decreased disordered coil structures. In addition, SEM results indicated that TGase-modified films had more smooth and compact microstructures, especially at high glycerol contents (30-40%).