Application of ultrasonication at different microbial growth stages during apple juice fermentation by Lactobacillus plantarum: Investigation on the metabolic response.

Affiliation

Wang H(1), Tao Y(2), Li Y(1), Wu S(1), Li D(1), Liu X(3), Han Y(4), Manickam S(5), Show PL(6).
Author information:
(1)College of Food Science and Technology, Nanjing Agricultural University, Nanjing 210095, Jiangsu, China.
(2)College of Food Science and Technology, Nanjing Agricultural University, Nanjing 210095, Jiangsu, China. Electronic address: [Email]
(3)INRAE, UMR408, Sécurité et Qualité des Produits d'Origine Végétale
(SQPOV), F-84000 Avignon, France.
(4)College of Food Science and Technology, Nanjing Agricultural University, Nanjing 210095, Jiangsu, China. Electronic address: [Email]
(5)Petroleum and Chemical Engineering, Faculty of Engineering, Universiti Teknologi Brunei, Bandar Seri Begawan, BE1410, Brunei Darussalam.
(6)Department of Chemical and Environmental Engineering, Faculty of Science and Engineering, University of Nottingham Malaysia, Jalan Broga, Semenyih 43500, Selangor Darul Ehsan, Malaysia.

Abstract

In this work, low-intensity ultrasonication (58.3 and 93.6 W/L) was performed at lag, logarithmic and stationary growth phases of Lactobacillus plantarum in apple juice fermentation, separately. Microbial responses to sonication, including microbial growth, profiles of organic acids profile, amino acids, phenolics, and antioxidant capacity, were examined. The results revealed that obvious responses were made by Lactobacillus plantarum to ultrasonication at lag and logarithmic phases, whereas sonication at stationary phase had a negligible impact. Sonication at lag and logarithmic phases promoted microbial growth and intensified biotransformation of malic acid to lactic acid. For example, after sonication at lag phase for 0.5 h, microbial count and lactic acid content in the ultrasound-treated samples at 58.3 W/L reached 7.91 ± 0.01 Log CFU/mL and 133.70 ± 7.39 mg/L, which were significantly higher than that in the non-sonicated samples. However, the ultrasonic effect on microbial growth and metabolism of organic acids attenuated with fermentation. Moreover, ultrasonication at lag and logarithmic phases had complex influences on the metabolism of apple phenolics such as chlorogenic acid, caffeic acid, procyanidin B2, catechin and gallic acid. Ultrasound could positively affect the hydrolysis of chlorogenic acid to caffeic acid, the transformation of procyanidin B2 and decarboxylation of gallic acid. The metabolism of organic acids and free amino acids in the sonicated samples was statistically correlated with phenolic metabolism, implying that ultrasound may benefit phenolic derivation by improving the microbial metabolism of organic acids and amino acids.