Abstract: In order to optimize and control the processing conditions of black garlic, a fermented garlic product, single garlic and multi-clove garlic were used as raw materials to ferment black garlic via an ultrasonic assisted microwave technique and three stage variable temperature fermentation method. The physical and chemical properties of black garlic were determined by low field nuclear magnetic resonance (LF-NMR). The results showed that T2 free water activity decreased and gradually transferred to the surface of garlic cloves with the increase of processing time. The correlation analysis of physical and chemical properties showed that the characteristics of black garlic were related to its chemical properties. It was found that the properties of single black garlic changed regularly. The three-stage fermentation process improved the taste and quality of single black garlic, but the effect on multi-clove black garlic was inconspicuous. Finally, a simple grading model of black garlic quality was established, and garlic brightness was used as the main factor to evaluate the black garlic products, which provided a theoretical basis for the subsequent optimization and control of black garlic processing technology.
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