Impact of malolactic fermentation with Lactobacillus plantarum on volatile compounds of sea buckthorn juice

Abstract

Malolactic fermentation using sea buckthorn (Hippophaë rhamnoides) juice as raw material was performed with six different strains of Lactobacillus plantarum. Increasing juice pH from 2.7 to 3.5 or adapting cells to low pH (i.e., acclimation) prior to inoculation allowed malolactic fermentation with all tested strains. Moreover, reducing pH of the growth medium from 6 to 4.5 with l-malate had little or no impact on biomass production. Volatile profile of sea buckthorn juice was analyzed with HS-SPME–GC–MS before and after fermentation. A total of 92 volatiles were tentatively identified and semi-quantified from sea buckthorn juice, majority of which were esters with fruity odor descriptors. Esters and terpenes were decreased in both inoculated and control juices during incubation. Microbial activity increased the levels of acetic acid (vinegar like), free fatty acids (cheese like), ketones (buttery like), and alcohols with fruity descriptors. Conversely, aldehydes associated with “green” aroma were decreased as a result of fermentation. Juices fermented with DSM 1055 had the highest acid and alcohol content, while fermentation with DSM 13273 resulted in the highest content of ketones. Compared to inoculation with other strains, fermentation with strains DSM 16365 and DSM 100813 resulted in rapid malolactic fermentation, less production of volatile acids, and lower loss of esters and terpenes important for natural sea buckthorn flavor.

Changes of Volatile Flavor Compounds in Sea Buckthorn Juice during Fermentation Based on Gas Chromatography–Ion Mobility Spectrometry

“…In addition to the flavors mentioned above, according to our sensory evaluation and the relative content of volatile compounds in Table 1 , the ethyl octanoate (threshold: 1.00 × 10 −4 mg/kg) and the ethanol (threshold: 2900 mg/kg) might be contribute to the sweet odor. After fermentation, the flavors of the sea buckthorn juice were mainly esters and alcohols, which is consistent with the relevant literature [ 14 , 48 ]. In contrast to the GC–MS method (solid phase microextraction–gas chromatography–mass spectrometry), (E)-2-Hexenyl acetate and propyl acetate were detected via GC–IMS [ 2 , 14 , 48 ].…”

“…After fermentation, the flavors of the sea buckthorn juice were mainly esters and alcohols, which is consistent with the relevant literature [ 14 , 48 ]. In contrast to the GC–MS method (solid phase microextraction–gas chromatography–mass spectrometry), (E)-2-Hexenyl acetate and propyl acetate were detected via GC–IMS [ 2 , 14 , 48 ].…”

“…They appeared or increased significantly in the samples after 24 h of fermentation. The formation of the sea buckthorn flavor compounds was related to amino acid metabolism, fatty acid metabolism, malolactic fermentation, β-carotene degradation, and so on, among which some intermediates are produced [ 2 , 14 , 55 ].…”

“…Fermentation can produce some functional substances during metabolism, which is beneficial to improve the quality of fruit juice and produces a strong aroma [ 11 , 12 ]. It has been reported that fermentation can significantly improve the antioxidant capacity, as well as the phenols and aroma components, of fruit juices [ 13 , 14 , 15 , 16 , 17 ]. Schubertová et al reviewed the effect of malolactic fermentation on the organic acids and polyphenols of sea buckthorn fruit juice.…”

Co‐fermentation metabolism characteristics of apple vinegar with Acetobacter pasteurianus and Lactobacillus plantarum

“…The effects of the cell‐free supernatant, extracellular polysaccharide, and various lactic acid concentrations of L. plantarum on the growth characteristics of A. pasteurianus are presented in Figure 3. The growth of A. pasteurianus was determined by its optical density at 600 nm (Markkinen et al, 2021). Compared with the control group, which underwent the pure fermentation process with A. pasteurianus , the cell‐free supernatant had a positive effect on the growth of A. pasteurianus and increased the accumulation of organic acids.…”