Investigation of the Distribution of 5-Hydroxymethylfurfural in Black Garlic from Different Regions and Its Correlation with Key Process-Related Biochemical Components

Black garlic is a thermally processed product derived from fresh garlic through controlled high-temperature and -humidity conditions. During this process, the formation of 5-hydroxymethylfurfural (5-HMF), a potentially harmful byproduct, is a major quality and safety concern in food processing. This study systematically investigated the distributions of 5-HMF and key process-related biochemical components in black garlic samples from three major production regions in China—Jiangsu, Yunnan, and Shandong. Additionally, correlations between 5-HMF and biochemical components—reducing sugars, amino acids, and organic acids—were analyzed to inform process optimization strategies. Results showed significant regional variation in 5-HMF content, with Jiangsu black garlic exhibiting the highest levels, followed by Yunnan and Shandong (p< 0.05). Partial least squares regression analysis (PLSR) indicated that the key biochemical factors regulating 5-HMF accumulation are primarily organic acids. Among them, citric acid was identified as the most important negative regulator (VIP = 3.11). Although acetic acid (VIP = 1.38) and malic acid (VIP = 1.03) showed positive correlations with 5-HMF, aspartic acid (VIP = 0.41) and fructose (VIP = 0.43) exhibited a weak positive correlation, and arginine (VIP = 0.89) showed weak negative correlations, their effects were far less significant than that of citric acid. Based on these findings, we propose a potential strategy for reducing 5-HMF content in black garlic—selecting raw material cultivars with higher endogenous citric acid levels or exploring the exogenous addition and regulation of citric acid during processing. This study provides a theoretical foundation for understanding the accumulation mechanism of 5-HMF in black garlic and suggests new potential regulatory directions for controlling its content.