Influence of Lactic Acid Bacterium Strains on Changes in Quality, Functional Compounds and Volatile Compounds of Mango Juice from Different Cultivars during Fermentation

Abstract

The effects of lactic acid fermentation using Lactiplantibacillus plantarum 75 (L75), Leuconostoc pseudomesenteroides 56 (L56) and its combination (L56 + 75) on the quality, bioactive and volatile compounds of mango juices (MJ) from three cultivars (‘Peach’, ‘Sabre’ and ‘Tommy Atkins’) were investigated. Fermented and unfermented MJ were evaluated for LAB growth, physicochemical parameters, volatile compounds, antioxidants activities (DPPH, ABTS, FRAP methods), total phenolic content (TPC) and sensory properties. The unfermented juices served as a control. Twenty-four-hour fermentation was ideal for MJ based on LAB growth profiles. Generally, titratable acidity, TPC, FRAP, DPPH and ABTS scavenging activities significantly increased with fermentation by the L75 strain and were highest in the L75-fermented ‘Sabre’ MJ, while L75-fermented ‘Peach’ MJ had higher ABTS activity (p < 0.05). In contrast, the L56 strain enhanced β-carotene retention, with improved colour properties in L56-fermented ‘Peach’ MJ. Fermentation with L75 in ‘Sabre’ and ‘Peach’ MJ aided the synthesis of new volatile compounds (alcohols, esters, ketones and aldehydes). A PLS-DA scatter plot showed two clusters separating the ‘Peach’ and ‘Sabre’ mango juice fermented with L75 from the rest. Based on the variable importance of the projection value (VIP) scores, pentadecane, 8-hexyl and butyl isobutyrate were shown as marker candidates to distinguish ‘Peach’ and ‘Sabre’ MJ fermented with L75 from the other treatments, whereas ethyl octanoate and isobutyl acetate differentiated the ‘Sabre’ MJ fermented with L75 from the other treatments. ‘Sabre’ and ‘Peach’ MJ fermented with L75 and L56 could provide antioxidants, meeting the recommended daily requirements for ascorbic acid and carotenoids in adults and teenagers. Hence, lactic acid fermentation of these local cultivars is a way to benefit consumers.

The Bioaccessibility and Antioxidant Activities of Fermented Mango Cultivar Juices after Simulated In Vitro Digestion

“…As described by Cele et al [ 6 ], the Folin–Ciocalteu assay was used to determine the total phenolic content of the MJs. A 200-µL aliquot of digested fraction was mixed with a 1000 µL diluted Folin–Ciocalteu reagent.…”

“…Carotenoid profiles of MJs digests (20 mL) in 150 mL tightly sealed tubes were extracted with acetone: hexane (1:1) containing 0.1% BHT incubated overnight in the dark as described by Moloto et al [ 17 ] and Cele et al [ 6 ]. The residue was rinsed with 5 mL volumes of the extraction solvent and centrifuged (Model Hermle Z326k, 153 Hermle Labortechnik, Wehingen, Germany) at 3000× g for 5 min at 5 °C.…”

“…Antioxidant power was determined by combining 10 mmol/L TPTZ (2,4,6-tris(2-pyridyl)-1,3,5-triazine) dissolved in 40 mM HCl with 20 mM FeCl 3 in a 1:1:10 ratio having 20 mM acetate buffer (pH 3.6) [ 6 ]. A 0.1 g of freeze-dried MJs digest was reconstituted in 80% methanol, and to 20 µL of the digest, 150 µL FRAP reagent was added in a microtitre plate and incubated for 10 min.…”

“…Aside from the role of carotenoids as antioxidants in preventing some diseases related to oxidative stress, the high level of carotenoids in mango fruit makes it a good choice for treating vitamin A deficiency [ 5 ]. Moreover, mango juices hold the potential to meet the Recommended Dietary Allowance (RDA) requirements of carotenoids for different classes of the population [ 6 ].…”

“…Extensive studies have been conducted on mango fruits and juices; however, limited information exists on the bioactive compounds contained in indigenous South African mango cultivars. Our previous study reported the preservation of ascorbic acid, carotenoids, phenolic compounds, and antioxidants after 24 h fermentation of indigenous mango cultivar juices with select Lactic acid bacteria (LAB) strains [ 6 ]. Similarly, Mapelli-Brahm et al [ 7 ] had earlier reported the potential of fermentation in improving the retention and bioaccessibility of the carotenoids in fruits and vegetables, while Wang et al, [ 8 ] confirmed this observation in ultrasonic pre-treated fermented mango juice after lactic acid bacteria fermentation.…”