Optimization of black garlic production parameters using response surface methodology: Assessment and characterization of bioactive properties

This study was performed to determine the optimum process parameters for black garlic production. Central composite design (CCD) of the response surface methodology (RSM) was utilized to examine the effects of fermentation conditions (temperature, humidity and time) on the alliin, S-allyl cysteine (SAC), total phenolic content (TPC), antioxidant capacity, moisture, and 5-Hydroxymethylfurfural (HMF) contents of the black garlic samples. Liquid chromatography coupled to diode array detection and electrospray ionization tandem mass spectrometry (LC-DAD-ESI-MS/MS) was used for the identification and quantification of alliin, SAC and HMF. SEM and FT-IR techniques were also utilized to characterize the samples. The optimized fermentation parameters were determined as 65 °C temperature, 85% humidity, and a duration of 24 days. TPC was found to be 1152.46 mg GAE/100 g dry matter with the highest antioxidant capacity while SAC and alliin contents were 80.21 and 5.16 mg/100 g, respectively. The HMF was quantified as 0.60 g/kg using the optimized parameters. It was also found that decreased temperature and fermentation time yielded a decrement in HMF and an increment in the bioactivity of black garlic.