Improve the quality of bog bilberry juice by controlling the inoculation pH and timing ofLactobacillus plantarum

Abstract

Quality changes to bog bilberry juice at different pH levels (pH 2.67 and 3.60) during a 14‐day Lactobacillus plantarum (L. plantarum B7 and L. plantarum C8‐1) inoculation process was investigated in terms of changes in reducing sugars, amino acids, biogenic amines, total anthocyanins, total phenolic content, and juice color. Results showed that bacterial strains grew better in the pH adjusted juice (pH 3.60), and L. plantarum B7 was less able to utilize reducing sugar than L. plantarum C8‐1 in both pH conditions during the entire inoculation process. Most amino acids and biogenic amines decreased at this level, while the γ‐aminobutyric acid increased in the juice after inoculation. Malic acid and amino acids were consumed faster in the juice to yield a high level of lactic acid. The total anthocyanin content in the juice was reduced, whereas no significant alteration was observed in the total phenolic content after inoculation. The juice showed an increase in the L* value but a decrease on the a* value, with the b* value approaching 0. The adjusted pH juice displayed a higher L* value but lower a* and b* values after inoculation. Multivariate analyses indicated that the pH value and the inoculation time played key roles in altering the quality of the juice after inoculation, while the strain effect was mainly observed in the pH adjusted juice. Our results provide useful information on how to improve the quality of low pH berry juice by inoculating L. plantarum. Novelty impact statement The results indicate that the quality of juice could be improved by controlling the inoculation conditions and time of Lactobacillus plantarum. The paper provides useful information on how to improve the quality of low pH berry juice by inoculating L. plantarum.