Vacuum impregnation on apples with grape juice concentrate: Effects of pressure, processing time, and juice concentration

Apple cubes were subjected to vacuum impregnation using grape juice concentrate. The effect of pressure reduction (VP = 100-500 mmHg), immersion time (t = 10-30 min), and concentration of grape juice (C = 40-60 degrees Brix) on impregnation parameters were evaluated using response surface methodology. Second-order polynomial equations were developed (R-2 >= 0.895) to describe the behavior of water loss, total soluble solids, L*, a*, Hue, total color difference, the color of impregnated/treated areas (A(U)/A(OP)), antioxidant activity, total monomeric anthocyanin, and dimensionless volume (V/Vo) in the impregnated product. VP had a significant (p <= 0.05) effect on mass transfer parameters, color parameters, A(U)/A(OP), and bioactive compounds. However, at 60 degrees Brix and 500 mmHg, the lower V/Vo values were reached due to cell disruption. Therefore, it is recommended to use a VP = 500 mmHg and t less than 20 min to significantly impregnate compounds and obtain a product without considerable morphometric modification.