Apple Peel‐Based Edible Film Development Using a High‐Pressure Homogenization

Abstract

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.

Plasticization and moisture sensitivity of potato peel-based biopolymer films

“…3). This finding is in accordance with a previous study demonstrating that the water uptake of biopolymer films made of apple peels was not affected by varied levels of HPH pressure (138-207 MPa) (6).…”

“…The use of an emulsifier is suggested to avoid reagglomeration and, subsequently, to more accurately investigate the effects of different pressure levels on WVP. The non-significant effects of treatment pressure and pass number on the WVP of the PP films are consistent with the results of investigations of biopolymer films generated from apple peel and Hizikia fusiformis using HPH (6,24).…”

“…A reduced particle size could decrease WVP due to the formation of a more difficult pathway that water molecules must cross to diffuse through the matrix (23). However, no such effect of increased pressure or pass number on the WVP of the films was observed in the present study, possibly due to the reagglomeration of small biopolymer particles during film formation (6). The use of an emulsifier is suggested to avoid reagglomeration and, subsequently, to more accurately investigate the effects of different pressure levels on WVP.…”

“…The diffusion coefficient (D) for water in the film samples was calculated from the slope of the plots of W t /W α as a function of for W t /W α 0.6 where L is the halfthickness of the film and W α is the weight of the water absorbed at equilibrium (6).…”

“…Glycerol is a common plasticizer that is compatible with various food ingredients, including potato starch (5). The concentrations of glycerol used in the preparations of agricultural processing byproduct-based edible films are typically 33 or 44% (w/w, dry basis) for apple peel-based films (6) and 17 or 33% (w/w, dry basis) for mustard meal-based films (7).…”