Unconventional technologies as a strategy to improve the phenolic and antioxidant potential of zucchini products enriched with blueberry juice

Abstract

In this study, unconventional technologies were used to enhance the phenolic and antioxidant content of zucchini pieces by enriching them with blueberry juice. Our results indicated that ohmic heating (OH) increased the extraction rates of compounds with antioxidant potential in blueberry juice, mainly at 70 °C for 15 min and 7.8 V cm¹. Furthermore, OH applied after vacuum impregnation led to higher retention rates of phenolic compounds and antioxidant capacity in zucchini pieces impregnated with blueberry juice, especially at 70 °C for 30 min and 7.8 V cm^‐−1. The impregnation process also promoted the darkening of zucchini pieces (due to anthocyanin retention) and increased soluble solids. After drying by hot air and vacuum microwave, the phenolic content, antioxidant capacity, physicochemical and color characteristics of the impregnated and non-impregnated zucchinis were distinctly altered. However, vacuum microwave drying at 120 and 460 W can be suggested as the most suitable conditions for both zucchini products, as it resulted in high concentrations of individual phenolic compounds (e.g. up to 44.25, 8.15, and 2.56 mg 100 g^‐−1 dry weight (DW) for catechin, gallic acid, and cyanidin, respectively), as well as total phenolic content of up to 484.37 mg gallic acid equivalent 100 g¹ DW, total flavonoid content of up to 197.69 mg catechin equivalent 100 g^‐−1 DW, and total monomeric anthocyanins of up to 9.48 mg cyanidin 3-glucosideo equivalent 100 g^‐−1 DW.