Formation and Safety Evaluation of 5-Hydroxymethylfurfural in Black Garlic

5-Hydroxymethylfurfural (5-HMF), exerting both toxic and pharmacological effects, is produced by thermal degradation of carbohydrates and the Maillard reaction during the aging process of black garlic. Understanding the formation and safety of 5-HMF is important for evaluating the food safety of black garlic. To investigate the formation of 5-HMF in black garlic during the aging process, in this study we measured the contents of 5-HMF, reducing sugar, total acid and total free amino acids during the processing of black garlic, and analyzed the correlations between 5-HMF and other compounds. The effect of 5-HMF on the food safety of black garlic was investigated by a 28-day oral toxicity test in mice. This research found that the contents of 5-HMF and total acids increased with processing time, while the contents of reducing sugar and total free amino acids increased first and then decreased. 5-HMF content was positively correlated with the contents of total acid and reducing sugar, but negatively correlated with the content of total free amino acids. Meanwhile, the oral toxicity test showed that a dose of 2 g/kg m_b of black garlic had no adverse effect on the health of mice, but a certain dose of 5-HMF caused an increase in the activity of glutamic oxaloacetic transaminase and mild degeneration of renal tubular epithelial cells in mice. The results showed the no observed adverse effect level (NOAEL) of 5-HMF in mice was 200 mg/kg m_b, which was 1176 times higher than the possible daily intake of 5-HMF by black garlic consumption. Therefore, although a certain dose of 5-HMF was slightly toxic to mice, the daily intake of 5-HMF by black garlic consumption was much lower than the NOAEL of 5-HMF in mice. Hence it can be concluded that 5-HMF has no adverse effect on the food safety of black garlic in the case of normal consumption.