Functional Biopolymer Edible Film-Coating Development for Its Commercial Applications

NON-TECHNICAL SUMMARY: Antimicrobial/antioxidant biopolymer edible films and coatings have recently been in the spotlight of food science for microbial safety. However, their commercial application in food industry has not been populated due to (i) high cost of pure biopolymer materials to purchase for commercial production; (ii) insufficient mechanical (tensile), barrier, and color properties of the film-coatings to be practically used; and (iii) lack of kinetic studies supporting the advantages of antimicrobial/antioxidant edible films and coatings against direct applications of antimicrobial/antioxidant substances. The purpose of this project is to develop biopolymer edible film-coatings that are practically applicable to commercial production of food products with their reduced material costs and improved mechanical, barrier, and color properties as well as antimicrobial/antioxidant properties.<P>APPROACH: Biopolymer edible film-coatings will be produced from the waste streams of potato peels, fish (trout) skin, and whey. Mechanical (tensile), barrier, and color properties of the biopolymer edible film-coatings will be enhanced to satisfy requirements for commercial application by optimizing film-forming variables and using a nano-emulsion technology. We are going to incorporate natural antimicrobials/antioxidants into the matrix of biopolymer-based-nano-emulsion films to develope antimicrobial/antioxidant-active packages (edible film-coatings). The antimicrobial film-coating is expected to show potential for inhibiting foodborne pathogens already present on food products, as well as for inhibiting their growth from contamination of film-wrapped or coated food products. Using mathematical models, we would be able to develop a method to predict requirements of antimicrobial/antioxidant edible film-coating for obtaining microbial safety or controlling lipid oxidation . For example, we would predict the time during which an antimicrobial remains above a minimum inhibitory concentration (MIC) on the film, as well as the necessary values for initial concentration of the antimicrobial and film-coating thickness for the inhibition for a selected period of time, using a MIC and previously-developed mathematical models. We also expect to identify factors most critical for controlling the release of active compounds and to elucidate relationships between compound migration and composition, processing, structure, and properties. This will greatly facilitate the development of both research and industrial-scale edible film technologies for food applications. The potential to produce the films in an industrial scale using a co-rotating twin screw extruder will be also evaluated in this research. Research collaborations will be made between the two campuses of University of Idaho and Washington State University. <P>

PROGRESS: 2007/01 TO 2007/12<BR> 1. Antioxidant activity of a potato peel extract as a natural antioxidant: The 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay and the 2- thiobarbituric acid reactive substances (TBARS) value test were conducted to determine antioxidant activity of potato peels. The results from the TBARS test indicated that a potato peel extract is a potential material to be used as a natural food antioxidant. <BR>2. Development of edible biopolymer edible films: A potato peel solution was treated by homogenization at high-pressure (22,000 psi, 25-50 C), ultrasound (400 W, 24 kHz, 120 micrometer, 30-60 C, 30 min), or gamma-irradiation (10-20 kGy) to obtain small biopolymer particles in the solution. A fish skin gelatin solution was prepared with tout skin-extracted gelatin and commercial fish gelatin (6.8% (w/w)). The solutions were heated to 90 C for 30-60 min. After cooling, 10-100% (w/w) glycerol of potato peel was added to form a film-forming solution. Films were formed by casting degassed film-forming solutions and their film properties of tensile properties, water vapor permeability, water solubility, and color (lightness) were measured. The film properties of the potato peel-based film produced from the homogenized (22,000 psi) film-forming solution were better than those of the films from the solutions treated by ultrasound or irradiation. The tensile strength, % elongation at break, and elastic modulus, water vapor permeability, and solubility of the film were 4.9 MPa, 14.4%, 101.7 MPa, and 27.4%, respectively. The fish gelatin films exhibited better film properties compared to the WPI films, with the exception of solubility. The tensile strength, % elongation at break, elastic modulus, and water vapor permeability of the films were 10.6 MPa, 6.2 %, 313.7 MPa, and 3.5 g-mm/kPa-h-m2, respectively, for trout skin films, 23.0 MPa, 37.3 %, 600.5 MPa, and 2.3 g-mm/kPa-h-m2, respectively, for commercial fish gelatin films. Trout gelatin films and commercial fish gelatin films had 76.4 and 100% (w/w) soluble matters, respectively, as compared to WPI at 19% soluble matter. Fish gelatin films have slightly better clarity than WPI films. Potato peels and fish (trout) skin waste have potential value as protein and natural product sources that can be utilized to form biopolymer films for practical applications in the food industry. <BR>3. Production of whey protein edible films by extrusion: Extrusion was investigated for producing whey protein films in a large scale. A co-rotating twin screw extruder (Haake-Leistritz Micro-18, Sommerville, NJ) was used to produce the films. The screw speed and the production temperature were controlled at 200-300 rpm and 120-150 C, respectively. We identified temperature profiles in barrel, screw type, screw speed, production rate (wet feed and dry feed), water content, and plasticizer (glycerol) content as major variables in producing whey protein films by extrusion. Whey protein-based sheets containing 48.8% glycerol (dry basis) were obtained at screw speeds of 200, 225, 275, and 300 rpm. Feed rates were proportionally decreased or increased depending on the screw speed.