Effects of different drying methods on the antioxidant profiles and volatile organic compounds of blueberry pomace

Abstract

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.

Keywords: Antioxidant profiles; Blueberry pomace; Hot air drying; Microwave-assisted hot air drying; Vacuum freeze drying; Volatile organic compounds.

Fig. 1

DPPH scavenging activity (a) and FRAP assay (b) of dried blueberry pomace and fruit.

Fig. 2

Airscape maps (a) and fingerprint of VOCs (b) by HS-GC-IMS in dried blueberry pomace and fruit.

Fig. 3

PCA scores plot of VOCs in dried blueberry pomace and fruit.

Fig. 4

OPLS−DA scores (a), displacement test (b) and VIP scores (c) of VOCs in dried blueberry pomace and fruit.