Influence of Calcium Lactate on the Fate of Spoilage and Pathogenic Microorganisms in Orange Juice

Calcium lactate is used by the beverage industry as a source of calcium to fortify fruit juice. The objective of this study was to evaluate the influence of various concentrations of calcium lactate on the fate of pathogenic and spoilage microorganisms in orange juice. Commercial nonfortified orange juice was supplemented with calcium lactate at a concentration equivalent to 0, 5, 10, 15, 20, 25, or 30% dietary reference intake. The pH of each fortified juice was adjusted to 3.6 or 4.1. The prepared juice samples were inoculated separately with a three-strain mixture of salmonellae, a three-strain mixture of spoilage yeasts, and three single strains of spoilage bacteria including Alicyclobacillus acidoterrestris, Lactobacillus plantarum, and Lactobacillus sake. The contaminated juice was stored at 4 and 10°C, respectively, for 6 to 7 weeks and assayed once a week for populations of salmonellae, spoilage yeasts, or spoilage bacteria. The results indicated that A. acidoterrestris was inhibited in all juice stored at 4°C and low-pH juice stored at 10°C. The bacterium, however, was able to grow at 10°C in the high-pH juice with calcium lactate concentrations equivalent to 0 and 5% dietary reference intake. The cells of L. sake declined and eventually died off in low-pH juice stored at 4 and 10°C and in high pH stored at 4°C. But the organism flourished at 10°C in the high-pH juice containing 0, 10, and 20% dietary reference intake of calcium lactate. The populations of L. plantarum remained approximately stable in low- as well as in high-pH juice stored at both 4 and 10°C. While inhibited at 4°C, the spoilage yeasts grew at 10°C. Salmonellae died off in all juice stored at 4°C and in low-pH juice stored at 10°C. However, they persisted in the high-pH juice stored at 10°C except in the samples that contained 20 to 30% dietary reference intake of calcium lactate.