Effect of blanching and freezing on the physical properties, bioactive compounds, and microstructure of garlic (Allium sativum L.)

摘要

The aim of this work was to evaluate the impact of blanching on the physical properties of frozen garlic cloves and to explore the relationship between quality changes and microstructure. A short-term blanching treatment (100 °C for 45 s, 90 °C for 45 s, and 80 °C for 60 s) before freezing did not affect the total organosulfur compound content. In a preliminary research, blanching conditions were determined to be 100 °C for 45 to 80 s. Under these conditions, peroxidase was inactivated, but organosulfur compounds were retained. Mechanical and color tests showed a damaging effect of blanching and freezing on frozen garlic blanched for 60 and 80 s at 100 °C . Compared to frozen fresh garlic, frozen garlic treated by blanching for 45 s at 100 °C retained 2871.49 ± 200.24 μg/g of allicin, although 81.83% of peroxidase was inactivated; browning and hardness improved by 49.97 and 48.01%, respectively. According to scanning electron microscopy, significant damage to the microstructure was observed in both frozen fresh garlic and frozen garlic after 60 s and 80 s of blanching at 100 °C . Moreover, ~1H low-field nuclear magnetic resonance (LF-NMR) indicated that blanching for 60 s and 80 s induced an increase in free water in garlic tissues, resulting in further damage after freezing. As peroxidase was efficiently inactivated, the microstructure and organosulfur compounds were better preserved, and blanching treatment at 100 °C for 45 s before freezing is a potential method for obtaining frozen garlic with high sensory and nutritional qualities.