Effect of relative humidity on the metabolite profiles, antioxidant activity and sensory acceptance of black garlic processing

Fresh garlic (FG) was processed at five different relative humidities (RH) at 55 °C for 40 days. The moisture content, aw, browning intensity and DPPH scavenging capacity were determined during processing under controlled conditions. After processing, sensory acceptance and metabolite differences were analyzed using 1H-NMR. Furthermore, a chemometric analysis was performed using both the 1H-NMR chemical profiles and the sensory evaluation of the 40-day black garlic (BG) samples. An increase in the antioxidant capacity at higher browning rate was observed. The variability for twenty-five compounds showed main changes in amino and organic acids, sugars, organosulfur compounds, ethanol, methanol GABA, choline and 5-hydroxymethylfurfural. Higher acceptance values on the sensory evaluation were for BG processed at 58 and 71% RH, indicating that intermediates RH results in a better sensory quality. An OPLS-DA chemometric analysis showed that sugars, formic acid, 5-HMF, amino acids, ethanol, and choline were the main contributors.