Antioxidative Properties of Fermented Soymilk Using Lactiplantibacillus plantarum LP95

Abstract

In recent times, there has been a growing consumer interest in replacing animal foods with alternative plant-based products. Starting from this assumption, for its functional properties, soymilk fermented with lactic acid bacteria is gaining an important position in the food industry. In the present study, soymilk was fermented with Lactiplantibacillus plantarum LP95 at 37 °C, without the use of stabilizers as well as thickeners and acidity regulators. We evaluated the antioxidant capacity of fermented soymilk along with its enrichment in aglycone isoflavones. The conversion of isoflavone glucosides to aglycones (genistein, glycitein, and daidzein) was analyzed together with antioxidant activity (ABTS) measurements, lipid peroxidation measurements obtained by a thiobarbituric acid reactive substance (TBARS) assay, and apparent viscosity measurements. From these investigations, soymilk fermentation using Lp. plantarum LP95 as a starter significantly increased isoflavones' transformation to their aglycone forms. The content of daidzein, glycitein, and genistein increased after 24 h of fermentation, reaching levels of 48.45 ± 1.30, 5.10 ± 0.16, and 56.35 ± 1.02 μmol/100 g of dry weight, respectively. Furthermore, the antioxidant activity increased after 6 h with a reduction in MDA (malondialdehyde). The apparent viscosity was found to increase after 24 h of fermentation, while it slightly decreased, starting from 21 days of storage. Based on this evidence, Lp. plantarum LP95 appears to be a promising candidate as a starter for fermented soymilk production.

Keywords: Lactiplantibacillus plantarum; fermentation; functional food; isoflavones; soymilk.

Figure 1

Viable cell count (log CFU/mL) of Lp. plantarum LP95 (continuous line) and pH values (dashed line) during the fermentation of soymilk at 20 °C (red line), 28 °C (green line), and 37 °C (blue line). Error bars indicate the standard deviation of the means (n = 3).

Figure 2

Viable cell count (log CFU/mL) of Lp. plantarum LP95 (blue line) and pH values (orange line) during soymilk fermentation (37 °C; 24 h) and fermented soymilk storage (4 °C; 49 days). Error bars indicate the standard deviation of the means (n = 3).

Figure 3

Viscosity curves of soymilk during fermentation using Lp. plantarum LP95 as a starter at 37 °C (A) and fermented soymilk during storage at 4 °C (B) at different times: viscosity (η) as a function of the shear rate ($\dot{\gamma }$).

Figure 4

Apparent viscosity at 50 s⁻¹ of soymilk during fermentation using Lp. plantarum LP95 as a starter at 37 °C (A) and fermented soymilk during storage at 4 °C (B) at different times. All values are expressed as the mean ± standard deviation (n = 3). Different lowercase letters in each bar indicate significant differences (p < 0.05).

Figure 5

Variations in TEAC expressed as mg Trolox Eq./100 g D.W. (A) and TBARS expressed as µg MDA Eq./100 g D.W. (B) in soymilk during fermentation using Lp. plantarum LP95 as a starter. All values are expressed as the mean ± standard deviation (n = 3). Different lowercase letters in each bar indicate significant differences (p < 0.05).