Inactivation of Listeria monocytogenes in Black Mulberry (Morus nigra) Juice

Fresh black mulberry juice is well known as a good source of antioxidant. In this study, survival and growth of Listeria monocytogenes in black mulberry juice were determined. The influences of the incubation temperature, time, pH value, and acid adaptation response of the test microorganism on the antilisterial effects of the different dilutions of juice samples were investigated. The survival and growth of L. monocytogenes were periodically determined by enumeration over 7 days. No viable cells were detected after 2 days incubation at 37C in all un-neutralized juice samples. However, it took 7 days for neutralized samples. Acid adaptation increased the survival of L. monocytogenes in un-neutralized mulberry juices. It was detected that the black mulberry juice has antimicrobial components which correlated with the concentration used. In conclusion, the black mulberry juice has antilisterial effect, but storage conditions should be considered for safety production of fresh black mulberry juice.

Practical Applications

Nowadays, nonthermally processed, raw, and/or natural foods gain popularity because of their rich nutritive effects and positive contributions to health. However, the numbers of the cases of foodborne diseases related with consuming fresh fruit juice are increasing. Refrigeration is the most preferred method for the safety of nonprocessed, fresh fruit juice. However, Listeria monocytogenes which is one of the most important pathogens in fresh juices could survive and even grow during refrigeration and causes listeriosis. Detection of growing and survival pattern of L. monocytogenes in black mulberry juice during different storage conditions is important for food industry to produce and offer safe products. The results of the study are also important to predict the microbiological safety of the similar acidic fruit juices.