73D-27 |
Microbial safety of solution cast edible films |
C. W. OLSEN and T. H. McHugh. USDA-ARS-Western Regional Research Center, 800 Buchanan St., Albany, CA 94710 Edible films can extend the shelf life and enhance the quality of food products. Edible films are commonly made through a solution casting process where the films are dried from 2 to 18 hours. Given the neutral pH, high water activity and/or moderate temperature conditions present during dehydration the potential for microbial growth exists, yet it has not been previously studied. Our objective was to investigate the potential for microbial growth during the formation of protein (whey protein isolate, WPI), polysaccharide (carboxymethylcellulose), fruit (peach and strawberry) and vegetable (carrot and broccolli) films through physical measurements (pH, water activity, temperature) and aerobic plate counts. Film forming solutions were prepared using standard procedures. Films were cast on plates and dried at 22° C and 30° C. The pH, water activity and moisture were taken at various times during drying. Microbial counts were enumerated on petri films (aerobic plate count, coliform count and mold/yeast count) at different points in the process. Significant microbial growth occurred in fruit, vegetable and WPI films (1.0 to 2.0 log CFU increase) during drying. Heat treatment of film forming solutions and elevated dehydration temperatures reduced microbial loads to below detectable levels in solutions and dried films. Final film water activities ranged from 0.48 to 0.50. Cast films took 10 to 13 hours to dry at 22° C to below water activity levels suitable for microbial growth. Through control of initial microbial counts and drying times, films with no significant microbial contamination were formed from all film forming materials. Knowledge of critical control points is necessary to reduce the risk of microbial growth during the formation of solution cast edible films. The quality of the starting materials, as well as the use of heat and good sanitation during casting and drying are necessary to insure safety.
Session 73D, Food Packaging
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