Physicochemical Characteristics and Antioxidant Activities of Freezing Pretreated Black Garlic

Freezing pretreatment can destroy the cell membrane of garlic and may improve some food-quality of garlic. Therefore we investigated the effect of freezing pretreatment at -20°C and -70°C on quality of aged black garlic, compared with traditional processing methods. Our results showed that freezing pretreatment at -70°C had the greatest impact on qualities and antioxidant activities of black garlic. Browning degree and pH of black garlic after both the freezing pretreatment and aging process were 3.14 and 3.55, respectively. Furthermore, 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity and reducing power of aged black garlic can be enhanced by pre-freezing processing. Reducing sugar and 5-hydroxymethyl-2-furaldehyde (5-HMF) contents of freezing pretreated and aged black garlic were increased by 1.69 and 1.14 fold, respectively, compared with the control samples. The results indicated that freezing pretreatment had improved the overall qualities (such as browning degree, pH, reducing sugar) and functional materials of black garlic.

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