Effect of curcumin on the quality properties of millet fresh noodle and its inhibitory mechanism against the isolated spoilage bacteria

Fresh noodle product has attracted increasing attention due to its nutritive value and convenience. However, the relative short shelf life of fresh noodle is still a concern that needs to resolve. The objective of this study was to evaluate the preservative effect of curcumin (CUR) on millet fresh noodle during storage and its inhibitory mechanism against two isolated spoilage bacteria (Bacillus cereus and Escherichia coli). The effects of CUR were evaluated with regard to the quality and sensory evaluation of millet fresh noodle, the changes of bacterial growth curve, cell intracellular substances, cell viability, and bacterial morphology. The results showed that CUR could decrease the total colony number and prolong the shelf life of millet fresh noodle stored at 25°C from 20 to 30 hr. Quality and sensory evaluations showed that addition of CUR caused no negative effect on noodle quality and was determined to be sensory acceptable. The minimum inhibitory concentration of CUR against B. cereus and E. coli was 0.125 and 0.5 mg/ml, respectively. The growth curve revealed that CUR presented good antibacterial effect against both bacteria. The leakage of intracellular substances, cell viability, and bacterial morphology change after CUR treatment confirmed the destructive effects of CUR on plasma membrane integrity. These results indicated that CUR had the potential to be applied as a natural preservative for controlling the growth of spoilage microorganisms and extending the shelf life of millet fresh noodle.