Effects of dimethyl dicarbonate (DMDC) on the fermentation of litchi juice by Lactobacillus casei as an alternative of heat treatment.

Abstract

This study investigated the effects of dimethyl dicarbonate (DMDC) on the fermentation of litchi juice by Lactobacillus casei as an alternative of heat treatment that may have undesirable effect on the juice. Quality attributes and products stability of both the fermented heat- and DMDC-treated litchi juice by L. casei were compared. It was found that residual indigenous microorganisms in both the heat- and DMDC-treated litchi juice cannot grow into dominant bacteria during further fermentation of litchi juice by L. casei. Compared with fermented heat-treated litchi juice, fermented DMDC-treated litchi juice showed a better color, flavor, and overall acceptance, and also retained more total phenolics and antioxidant capacity. The viability counts of L. casei in both the heat- and DMDC-treated litchi juice were more 8.0 lg CFU/mL after 4 wk of storage at 4 °C. Also, some quality attributes in both the fermented heat- and DMDC-treated litchi juices, including pH, total phenolics, ascorbic acid, antioxidant capacity, and so on, showed the tendency to slow decrease during storage at 4 °C, but the scores of overall acceptance showed no reduction after the storage of 4 wk at 4 °C. On the whole, the application of DMDC treatment could be an ideal alternative of heat treatment to ensure the microbial safety, consistent sensory, and nutritional quality of fermented litchi juice prior to fermentation. The pasteurization treatment is often recommended prior to fermentation of fruit juice by probiotics, as it would lead to a rapid inactivation and inhibition of spoilage and pathogenic bacteria, and ensure the fermented products with consistent sensory and nutritional quality. Dimethyl dicarbonate (DMDC) is a powerful antimicrobial agent, which was approved for use as a microbial control agent in juice beverages by FDA. This study provides a scientific basis for the application of DMDC prior to fermentation of litchi juice.