Comparison of various drying methods on color, texture, nutritional components, and antioxidant activity of tumorous stem mustard

Abstract

Exploring new dehydration technology can help to deal with the challenge of quality preservation and high salt waste brine problem in pickled mustard industry. In the current study, effects of vacuum freeze-drying (FD), heat pump drying (HPD), air-impingement jet drying (AIJD), and hot air drying (HD), on color, texture, nutritional component, and antioxidant capacity of tumorous stem mustard were determined. All drying methods significantly affected color and texture. The ascorbic acid (Vc), reducing sugar, protein, total phenolic content (TPC), ABTS, DPPH, and FRAP level of tumorous stem mustard were 123.20–768.74 mg/100 g, 2.49–17.90 g/100 g, 30.74–53.03 g/100 g, 1.98–4.13 mg gallic acid equivalent (GAE)/g, 1.42–8.28 mg Vc/g, 1.04–9.73 mg Vc/g, and 2.11–6.83 mg Vc/g, respectively. The content of individual phenolics were influenced by drying methods, and ferulic acid was determined as a major phenolic compound for all samples (8.15–65.43 μg/g). The content of total phenolic and monomeric polyphenols except for ferulic acid, positively correlated to their antioxidant activity. Furthermore, HD, FD, and AIJD were beneficial to promote the production of umami amino acids and reduce bitter amino acids, thus improving the flavor of tumorous stem mustard. The quality of tumorous stem mustard of FD was closest to that of fresh tumorous stem mustard. Overall, the drying technology is promising to replace the salt infiltration process to realize the dehydration of tumorous stem mustard in the manufacturing of pickled mustard.