Effects of Processing Relative Humidity on Physicochemical Properties and Antioxidant Capacity of Black Garlic

ABSTRACT Black garlic (BG) was prepared at 70°C–75°C with different processing relative humidities (RHs) for 9 days. The effects of processing RH (65%–95%) on the physicochemical properties and antioxidant capacity of BG were investigated. The results showed that higher processing RH was not conducive to the browning of BG. When the processing RH increased from 65% to 95%, the glucose and fructose contents in BG obviously increased by 42.96% and 112.80% ( p < 0.05), respectively; while the browning degree, total acid, total polyphenol, total flavonoid, allicin, and alliin contents decreased by 4.01%, 11.44%, 27.36%, 44.26%, 40.98%, and 48.10% ( p < 0.05), respectively. The potentially harmful substances acrylamide and 5‐hydroxymethylfurfural (5‐HMF) also significantly decreased by 69.63% and 82.61% ( p < 0.05), respectively. However, the IC 50 values for DPPH and ABTS increased by 28.75% and 46.96% ( p < 0.05), respectively, indicating the decrease in antioxidant capacity of BG. The changes in fructose content and IC 50 values could be well simulated by the zero‐order kinetic models, while other physicochemical parameters all followed the pseudo‐first‐order kinetic models with different regression equations. Overall, 85% processing RH can effectively balance sensory, nutritional, and antioxidant properties of BG, as well as better inhibit the formation of acrylamide and 5‐HMF, which can be used as a reference to guide the industrial production of BG for enhancing its quality and safety.