Enzymatic modification of hydrolysis products from collagen using a microbial transglutaminase. II. Preparation of films

The use of renewable resources in the production of goods traditionally made from petroleum products has recently gained increasing research interest. Environmental concerns, such as biodegradability and ever increasing landfill fees, could be allayed by use of these products. During the conversion of hides and skins into leather, a high percentage of the original collagen substrate becomes waste. This waste has potential for recycling into useful products. Historically, gelatins (a collagen by-product) have been modified chemically, and the physical properties of these products have been improved. However, because of cost and the toxicity issues associated with some crosslinking chemicals, enzymatically modified products would be highly desirable. Commercial gelatins were treated enzymatically with a microbial transglutaminase, mixed with glycerol as plasticizer, and films were prepared. It was found that the amount of glycerol added affected the mechanical properties, particularly the maximum strain. Increasing the concentration of cross-linking agent gave products with higher tensile strengths that were less soluble in water and had improved water absorption properties. The products resulting from these studies have implications not only in the preparation of edible films and sausage casings, but also in the packaging material market, a market not previously utilized because of poor mechanical properties of gelatin films.