Microbiological assay with Lactobacillus plantarum for detection of adulteration in orange juice.

A microbiological assay has been developed to help detect adulteration in orange juice. Under standard assay conditions with diluted orange juice, the growth of Lactobacillus plantarum is proportional to the concentration of juice in the assay mixture. Imitation orange beverages did not support growth. Growth was also independent of the normal levels of common beverage ingredients such as sugar, acids, butylated hyroxyanisole, and orange oil. Commercial orange juices reconstituted from concentrates from various sources were assayed by the microbiological procedure, and the variability of results (coefficient of variation 24%) was about the same as or slightly lower than that for many of the other constituents used to estimate adulteration.