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The effects of hot air drying (HAD), microwave-assisted hot air drying (MHAD) and vacuum freeze drying (VFD) on the antioxidant and volatile profiles of blueberry pomace (BP) were investigated. The dried BP produced by VFD showed the highest content of antioxidant components and strongest antioxidant activity. MHAD shortened the drying time by 62.5 % with weakened antioxidant profiles. A total of 14 anthocyanin monomers were monitored by UPLC-ESI-MS while 49 typical volatile compounds (VOCs) were identified by HS-GC-IMS. According to orthogonal partial least squares-discriminant analysis (OPLS-DA) and variable influence in projection (VIP) models, 21 VOCs were selected as key marker compounds. High temperature (≥ 50 °C) was beneficial to produce characteristic VOCs. The dried BP exhibited enhanced antioxidant profiles and pleasant aroma compared with the whole blueberry fruit. Overall, concerning the cost, antioxidant and aroma profiles, HAD at 60 °C is a suitable technique for the drying of BP. • BP produced by VFD showed the highest content of antioxidant components and activity. • MHAD improved the drying efficiency but weakened the antioxidant profile. • HAD at 60 °C was a suitable method to dry BP with low cost and high product quality. • A total of 14 anthocyanin monomers were monitored by UPLC-ESI-MS in BP. • In total, 49 VOCs in dried BP were identified with fruit, floral, and roasted aroma.
Zhang et al. (Tue,) studied this question.