Incorporation of Lactobacillus delbrueckii subsp lactis (CIDCA 133) in cold-set gels made from high pressure-treated soybean proteins

The ability of freeze-dried high pressure-treated soybean proteins to form cold-set gels and their aptitude to act as a protective matrix to Lactobacillus delbrueckii subsp lactis strain CIDCA 133 were evaluated. Gels were obtained by dispersing denatured soybean protein isolates (SPI) in water or in a lactobacilli suspensions, and further incorporation of calcium. When SPI were dispersed in water, ordered, adhesive, and with high water holding capacity gels were obtained at a calcium concentration of 0.015 mol L−1. Increase in calcium concentration to 0.020 mol L−1 increased elastic modulus (small deformation rheology) and maximum force (texture profile) and made gels become opaque. When protein concentration was 90 g L−1, and denaturation of SPI was carried out at 600 MPa gels with higher values of elastic modulus were obtained as compared with those from gels denatured at 400 MPa. After dispersing denatured SPI in lactobacillus suspensions the gels were turbid and with a pink-like color. Elastic modulus and tan δ of gels prepared in lactobacilli suspensions were higher than those dispersed in water, revealing that matrix was modified by lactobacilli presence. The lactobacilli included in these cold-set gels survived better than in coagulated milk to a modeled gastric challenge. Moreover, bacteria remained viable without damaging the matrix during a 28-days storage at 4 °C. The high soybean protein concentration would be responsible for lactobacilli protection. Our results suggest that SPI cold-set gels may be used as carriers for lactobacilli protecting them from the effect of simulated gastric juice and enabling their incorporation in functional foods.