Effects of different drying methods on the storage stability of barley grass powder

Barley grass (BG) powder has gradually attracted researchers' attention for its abundant nutritional components and functional activity. Yet, the effect of different drying methods on storage stability is still unclear. In this study, BG was subjected to hot-air drying (HAD), steam blanching prior to hot-air drying (SHAD), vacuum freeze drying (VFD), and far-infrared drying (FID). Effects of different drying methods on BG powder during storage were evaluated.

Moisture content of dried samples during storage decreased at 50 °C, but at 37 °C increased first and then remained stable. The a* value of SHAD BG powder before storage was the highest (-6.51), followed by FID, HAD and VFD. Moreover, the a* value increased during the storage process. Contents of l-ascorbic acid and total chlorophyll in samples dried by VFD were 28.29 and 7.8 g kg^-1 , respectively. The degradation of chlorophyll a and b followed a first-order kinetics model and was modeled by the Arrhenius equation. The activation energies for chlorophyll a were 83.68, 83.21, 62.29 and 76.64 kJ mol^-1 in BG powder dried by SHAD, FID, VFD and HAD, respectively. The activation energies for chlorophyll b were 66.76, 48.03, 61.02 and 58.01 kJ mol^-1 in SHAD, FID, VFD and HAD BG powder, respectively.

VFD had the highest preservation of color, l-ascorbic acid and chlorophyll compared to HAD, SHAD and FID. SHAD shortened the drying time and delayed the degradation of l-ascorbic acid and chlorophyll during storage. © 2021 Society of Chemical Industry.