Biopolymer films were developed from apple peels of apple process co-products and their physical properties were determined. Apple peel-based films with glycerol (23%, 33%, and 44%[w/w, dry basis]) were prepared using high-pressure homogenization (HPH) at different levels of pressure (138, 172, and 207 MPa). An evaluation of the rheological properties (elastic modulus [G'], viscous modulus [G''], and viscosity) of the film-forming solutions was performed. For the apple peel films, the water sorption isotherms, the kinetics of water absorption, the water vapor permeability (WVP), the oxygen permeability (OP), and the tensile properties were determined. The G' and viscosity of the film-forming solutions decreased significantly with increasing processing pressure (P < 0.05). However, no difference was observed in G'' values at different homogenization pressures (P > 0.05). The viscosity decreased from 644 to 468 kPa.s as the pressure increased from 138 to 207 MPa at 90 degrees C. The monolayer water content of the apple peel films decreased with increasing content of glycerol from 23% to 33%. Further increase in glycerol content did not change the monolayer water content. The water diffusion coefficient of the films was highest at the intermediate level of glycerol content. The barrier properties (WVP and OP) of the films increased with increasing level of glycerol, while processing pressure did not influence the gas barrier properties. The films prepared at 207 MPa were less stiff and strong, but more stretchable than those prepared at 138 and 172 MPa.

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The objective of this study was to evaluate the ability of the Weibull distribution to predict the inactivation of Salmonella in three meat products cooked under isothermal and non-isothermal conditions. Ground turkey thigh (5.09% fat, pH 6.45), turkey breast (0.47% fat, pH 6.04) and pork (17.04% fat, pH 6.36) were inoculated with an 8 strain Salmonella cocktail. The meat was cooked isothermally at 50, 54, 58, 62 and 66ºC, and non-isothermally at two heating rates (5 or 10 ºC/min) to 54, 60 and 66 ºC. Surviving Salmonella were enumerated at intervals during the cooking process. Isothermal survival curves were described by the Weibull distribution, log S (t) = -b (T) t n(T) , and its simplified form as a linear equation (n=1). Nonlinearity was observed in Salmonella survival curves. The Weibull distribution described pathogen inactivation better than its simplified linear form for all isothermal trials. The b and n parameters from isothermal data were used to predict the non-isothermal survival curves. Piecewise cubic hermite interpolating polynomial was used to estimate b and n in the non-isothermal program. At 54 and 66 ºC, the Weibull model well predicted the non-isothermal Salmonella survival curves for all meats. The model over-predicted the destruction of Salmonella in three meats at 60 ºC for both heating rates. The accurate prediction of Salmonella destruction at 66 ºC was at a higher temperature than the range of validity reported in the literature.

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