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°Brix) on impregnation parameters were evaluated using response surface methodology. Second-order polynomial equations were developed (R2 > 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/V o) 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°Brix and 500 mmHg, the lower V/V o 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. • Impregnation with grape juice concentrate increase bioactive compounds in apple. • Analysis of apple tissue staining allows mass transfer parameters evaluation. • Response surface models adequately describe apples' mass transfer characteristics. • Image processing was used to analyze staining of apple tissue during impregnation. [ABSTRACT FROM AUTHOR]