Effect of Starter Culture and Fermentation Time on Anti-inflammatory Properties of Fermented Soymilk

MARTINEZ-VILLALUENGA, CRISTINA; TORINO, MARIA INES; FRIAS, JUANA; VIDAL-VALVERDE, CONCEPCION

Gdansk

Conferencia; Euro Food Chem XVI Conference: Translating food chemistry into health benefits; 2011

Fermentation with highly proteolytic strains of lactic acid bacteria (LAB) is considered a successful strategy to produce bioactive peptides from different food substrates (1). The anti-inflammatory potential of soy peptides obtained by enzymatic proteolysis has been demonstrated in cell based models (2). Therefore, fermented soy-based products might be considered to prevent chronic inflammation which predisposes individuals to several degenerative diseases (3, 4). This study evaluated the effect of starter cultures and fermentation time on anti-inflammatory activities of soymilk. For these purpose, four soymilk fermentation trials were performed using 1% inoculum (v/v) of both, commercial (CECT LAB strains) and indigenous bacteria. These last ones included Gram positive-catalase negative rod- and coccus-shaped strains isolated from spontaneously fermented soymilk. Starter 1 (control starter) only contained Streptococcus thermophilus CECT 986 and Lactobacillus delbrueckii subsp. lactis CECT 372 in a 1:1 ratio. Starter 2, 3 and 4 also included Lactobacillus acidophilus CECT 903, indigenous rod or indigenous coccus, respectively. Inoculated soymilk was fermented at 42ºC until final pH 5.0 ± 0.2 (FpH) and also during 24 h (F24). Bacterial counts (CFU/ml), pH and titratable acidity (TTA, ºD) as well as the anti-inflammatory potential of fermented soymilk were examined. The anti-inflammatory activity was determined as the inhibition of NO production in LPS-induced RAW264.7 macrophages. Starter cultures showed similar acidifying activity and the soymilk pH fell down to 5.07 in 4.5 h (FpH) and the TTA was 37 ºD. By lengthening the incubation (F24), pH reached values of 3.83-3.97, while TTA ranged between 77 ºD (starter 2) and 110 ºD (starter 4). Differences in viability were observed for starter cultures. Indeed, total LAB population increased 1.5 - 2.0 log units from inoculation (to about 106 CFU/ml) in all fermentations, but it remained stable until F24 only for starter 2 and 3. Extract from non-fermented but chemically acidified soymilk (negative control) did not show anti-inflammatory activity. However, FpH soymilk extracts exhibited a noticeable inhibition (28-58%) of NO production in LPS-activated macrophages. Longer fermentation time up to 24 h resulted in higher inhibition of NO in LPS-induced macrophages treated with F24 soymilk extracts (44-71%). Indigenous soybean rod- and coccus-shaped strains improved (P≤0.05) the anti-inflammatory activity of  both FpH and F24 soymilk extracts. In conclusion, indigenous soybean strains enhanced anti-inflammatory potential of fermented soymilk which might be further enhanced by extending the fermentation time. References (1)     Korhonen H, Pihlanto, A. Int. Dairy J., 16, 945-960. (2)     Martinez-Villaluenga C, Dia VP, Berhow M, Bringe NA, de Mejia EG. 2009. Mol. Nutr. Food Res., 53, 1007-1078. (3)     Sastre M, Klockgether T, Heneka MT. 2006. Int. J. Dev. Neurosci., 24, 167–176. (4)     Sell H, Eckel J. 2009. Proc. Nutr. Soc., 68, 378–384.