'Laba' garlic processed by dense phase carbon dioxide: the relation between green colour generation and cellular structure, alliin consumption and alliinase activity

New insights on low-temperature storage regulating garlic greening and the accumulation of pigment precursors via glutathione metabolism and energy cycles

To explore regulation mechanism of temperature on garlic greening and pigment precursors' accumulation, greening capacities, pigment precursors and critical metabolites, enzyme and genes involved in glutathione and NADPH metabolism of garlic stored at five temperatures (4, 8, 16, 24 and 30 ℃) were analyzed. Results showed that garlic pre-stored at 4, 8 and 16 ℃ were more likely to green than ones at 24 and 30 ℃ after pickling. After 25 days, more S-1-propenyl-l-cysteine sulfoxide (1-PeCSO) were detected in garlic stored at 4, 8 and 16 ℃ (753.60, 921.85 and 756.75 mAU, respectively) than that at 24 and 30 ℃ (394.35 and 290.70 mAU). Pigment precursors' accumulation in garlic was mainly realized by glutathione and NADPH metabolism under low-temperature storage, through enhancements of activities or expressions for GR (GSR), GST (GST), γ-GT (GGT1, GGT2), 6PGDH (PGD) and ICDHc (IDH1). This study enriched the mechanism of garlic greening.

Quality comparison of "Laba" garlic processed by High Hydrostatic Pressure and High Pressure Carbon Dioxide

The production of "Laba" garlic is limited to the homemade method with long processing time and non-uniform color quality. Innovative food processing technologies including high hydrostatic pressure (HHP) and high pressure carbon dioxide (HPCD) were applied to the processing of "Laba" garlic. Products prepared at different treatment pressures (200, 350 and 500 MPa of HHP; 4, 7 and 10 MPa of HPCD) were compared by evaluating the texture, color, flavor and sensory qualities. The results indicated that HHP treatment at 200 MPa was optimal for retaining the textural quality of "Laba" garlic, which was mainly attributed to the compacted cells and the increased Ca2+-cross linked cell-cell adhesion. HHP had greater effect on facilitating the formation of the attractive green color of "Laba" garlic than HPCD. The flavor profiles of "Laba" garlic were modified after treatments, with pungent compounds decreased to non-detectable. The results from sensory study confirmed that "Laba" garlic treated by HHP at 200 MPa was most acceptable to consumers. Moreover, considering the treatment capacity and feasibility of commercialization, HHP would be a promising technology in production of "Laba" garlic with improved quality and efficiency.