- Krochta, John
- University of California - Davis
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- End date
- An edible film resembles plastic film wrap, but it is formed from edible protein and/or polysaccharide. Edible films can be used as food wraps or formed into pouches for foods, thus reducing use of synthetic plastic films. An edible film can also be formed directly on the surface of the food as a coating to protect or enhance the food in some manner, becoming part of the food and remaining on the food through consumption. The potentials of many proteins and polysaccharides for edible films and/or coatings are being explored throughout the world. One protein of particular interest for California is whey protein. Whey is the liquid portion of milk remaining after the milk casein and fat are formed into solid cheese curd. Increased production of whey resulting from increased cheese production in the U.S. and particularly in California has made identifying new uses for whey protein an important goal.
The overall goal of this project is Development of whey-protein-based edible films and film-coatings to improve food safety and quality and minimize the amount and cost of packaging and related packaging waste.
Specific objectives include:
- Incorporation of antioxidant compounds in whey-protein-based films and film-coatings and demonstration that the activities of these compounds are maintained to protect foods from oxidation.
- Production of sealable pouches from whey-protein-based films and demonstration that the pouches can protect the contained foods from the environment.
- Blending of whey protein with other edible biopolymers to produce films and coatings that have barrier, mechanical and optical properties that are superior to the component biopolymers.
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- NON-TECHNICAL SUMMARY: An edible film resembles plastic film wrap but is formed from renewable edible protein (e.g., milk protein) and/or polysaccharide (e.g., cornstarch). Edible films can be used as food wraps or formed into pouches for foods, thus reducing use of synthetic plastic films. Edible films can also be formed directly on the surfaces of the food as coatings to protect or enhance the food in some manner, becoming part of the food and remaining on the food through consumption. Both edible films and coatings can help control food oxidation as well as moisture, aroma and oil loss or gain, resulting in improved food quality and shelf life. They also have potential to carry and hold antioxidants and antimicrobials at food surfaces, thus further improving food quality and safety. Edible films and coatings acting as primary (closest to food) packaging can reduce the cost and complexity of packaging systems designed to protect foods. An edible film or coating can allow simplification of the secondary packaging (next layer of packaging), thus making it more easily recycled. One protein of particular interest is whey protein. Whey is the liquid portion of milk remaining after manufacture of cheese. Once regarded mainly as an animal feed product, whey and whey components such as whey protein are being considered for higher-value human food use. Increased production of whey resulting from expanded cheese production in the U.S. and particularly in California has made identifying new uses for whey protein an important goal. In past years, we found that whey protein films and coatings are excellent oxygen, aroma and oil barriers, have good mechanical properties, and have excellent gloss and transparency. We have also demonstrated that whey protein oxygen-barrier coatings on nuts can increase nut shelf life, whey protein gloss coatings on chocolate can replace environmentally un-friendly shellac, and whey protein coatings incorporating natural antimicrobial compounds can inhibit growth of pathogenic microorganisms on foods. The overall goal of the proposed project is to extend both fundamental understanding and product applications of the whey protein films and coatings, so as to improve food safety and quality and minimize the amount and cost of packaging and related packaging waste. This will be done by: 1) investigating addition of the natural antioxidant ascorbic acid to whey protein films so as to improve the films' abilities to protect foods from oxidation, 2) developing approaches to producing sealable pouches from whey protein film that can contain foods of different composition, and 3) exploring potential of improving whey protein film properties by blending the whey protein with other biopolymers such as starch from corn, sodium alginate from sea weed, and derivatives of cellulose. The overall results from the improvement of properties and development of applications for edible films and coatings based on whey protein will be improvement in food quality and safety, reduction in food cost and waste, reduction in packaging cost, improved recycling of packaging materials, and a new value-added use for whey protein.
Objective #1: Ascorbic acid (AA) will be added to heat-denatured whey protein isolate (WPI) film-forming solutions. The pH of film-forming solutions will be adjusted to 2.0 (below pKa1 of AA), in order to stabilize the AA against oxidation. Films will be cast on Teflon casting plates and stored 48 hr at 30, 50 or 95% RH to reach equilibrium water activity (aw) values of 0.30, 0.50 and 0.95, respectively. Three food models rich in omega 6 fatty acid, including dry baby formula, peanut butter and mayonnaise will be used to represent dry food (0 < aw < 0.55), intermediate moisture food (0.55 < aw < 0.9) and high moisture food (0.90 < aw < 1.0), respectively. The food models will be analyzed for aw and pH according to AOAC method 978.18 and AOAC method 981.12, respectively. The food models will be filled up to the brim of test cups, which will be sealed with the AA-WPI test films. The cup openings be sealed with the test films in contact with the food models, so that the film aw, pH and metal content can be affected by the foods. The packaged food models will be stored at room temperature in a dark controlled %RH cabinet, corresponding to the food aw values. Foods will be analyzed for the oxidation product hexanal as a function of time using solid phase microextraction-gas chromatography (SPME-GC) analysis, to determine the AA-WPI films' abilities to protect the foods from oxygen.
Objective #2: Both native WPI (NWPI) films and heat-denatured WPI (HWPI) films will be made by pipetting film-forming solutions onto Teflon casting plates and drying. Dried films will be preconditioned at 23¢ªC, 50% RH for 40 hrs prior to experiments. Both NWPI and HWPI films will be heat-sealed into pouches using an impulse heat-sealer. NWPI films will also be formed into pouches using water-soluble adhesive made from gelatinized cornstarch. Seal strengths will be determined using an Instron universal testing machine according to ASTM F-88. Foods, such as instant-coffee-mix (aw = 0.527), dry salad-dressing-mix (aw = 0.370) and muffin-mix (aw = 0.434), will be sealed into the pouches and then prepared according to instructions for each product, without removal of the edible pouches. The prepared foods will be evaluated for dissolution of the NWPI and HWPI pouches, with the goal that the pouches will be completed dissolved and disappeared.
Objective #3: WPI-polysaccharide blend films will be made from film-forming solutions of WPI mixed with methylcellulose, hydroxypropyl methylcellulose, sodium alginate and cornstarch. Oxygen permeability of the blend films will be determine using an Ox-Tran 2/20 ML modular system according to ASTM standard method D 3985. Water vapor permeability of the blend films will be determined according to ASTM E96-90. Mechanical properties of the blend films will be determined using an Instron universal testing machine to measure tensile strength, elastic modulus and percent elongation of the films according to standard method ASTM D882-91. % Light transmission of the films will be measured using a UV-visible recording spectrophotometer.
- Funding Source
- Nat'l. Inst. of Food and Agriculture
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