Effect of Freezing Pretreatment on the Processing Time and Quality of Black Garlic

Abstract

Because freezing treatment can destroy the cell structure of garlic, we investigated the effect of freezing pretreatment on black garlic processing with the traditional processing method as contrast. Results showed that freezing for 30 h had the greatest impact on the reducing sugar content. The control garlic processing 21–24 days had the best quality. Freezing pretreatment can affect the black garlic quality through the browning degree, reducing sugar content, amino‐N content, total phenolic content and 5‐hydroxymethyl‐2‐furaldehyde (5‐HMF) levels. The freezing garlic had a faster color change than control samples. When the processing ended, the reducing sugar content, total phenols content and 5‐HMF content of freezing pretreated garlic were increased by 51.88, 58.54, 25%, respectively, compared with the control samples. The amino‐N content of freezing‐pretreated garlic decreased 50.97% compared with the control one. The results indicated that freezing pretreatment can promote the generation of functional materials. Practical Applications Although garlic has been used worldwide as food or herbal supplement, some people feel discomfort because of its strong pungent odor. Black garlic is one of the garlic‐processed products, eliminating its stimulating odor. However, the quality of black garlic products on the market is varied and the processing time is long. As is known, freezing is widely used to destroy cell structure. In the present study, the use of freezing pretreatment in black garlic processing can promote the generation of functional materials and significantly reduce processing time from 60–90 to 22 days. These provided potential method to the black garlic processing.

Effects of temperature on the quality of black garlic

“…The total score was considered as the score of sensory evaluation. We chose the optimal processing condition concerning temperature and time on the basis of the highest score of sensory evaluation of black garlic …”

Formation, nutritional value, and enhancement of characteristic components in black garlic: A review for maximizing the goodness to humans

“…Li et al. () reported that the optimized freezing time (30 hr) could significantly accelerate the browning speed of BG, reduce the processing time (from 60 to 90 days down to 22 days), and increase the contents of reducing sugars, total phenols, and 5‐HMF (by 51.88%, 58.54%, and 25%, respectively), while decreasing the Amino‐N content by 50.97%. The freezing pretreatment facilitated the hydrolysis of the fructans in garlic, the release of bound phenolics (that is, phenolics in esterified and glycosylated forms), and the reactions among different substances.…”

The Comparison of the Contents of Sugar, Amadori, and Heyns Compounds in Fresh and Black Garlic

“…During processing, the color of the product turned black compared with fresh garlic, and the taste of black garlic is sweeter than fresh garlic. Some studies reported that the 5‐HMF content in black garlic increased, the color of garlic extracts changed to black, and the pH value decreased from 7.46 to 3.93 (Li and others ; Liang and others ). In addition, some studies reported that the polysaccharides in black garlic were easily degraded into monosaccharides and oligosaccharides during the thermal processing of black garlic (Zhang and others ).…”