Aqueous extract of Gracilaria birdiae (Plastino & Oliveira) as a texture modifier in fermented milks

Abstract

This study evaluated the physicochemical characteristics of Gracilaria birdiae and the effects of aqueous extract of this seaweed on the physicochemical, microbiological and textural features of milk fermented with a mixed culture of Streptococcus thermophilus, Lactobacillus acidophilus and Bifidobacterium animalis subsp. lactis. The seaweed powder contained 68.61 g 100 g−1 dietary fibre and the seaweed aqueous extract was composed of 2.44 g 100 g−1 total solids. The seaweed did not inhibit the growth of cultured microorganisms and all fermented milk assays achieved similar microbial viability and acid production after 5 h at 37 °C. Nonetheless, the microbial viability tended to be above 9 log cfu ml−1 in the assays added to G. birdiae even after 2 h of fermentation, with increased acid production at this period compared to the products without seaweed. When the seaweed extract was compared to gelatin as a texture modifier, the effect of G. birdiae was higher than the animal hydrocolloid. Moreover, the interaction effect of these two ingredients was about a half that of the seaweed alone. The desirability function showed that similar texture parameters obtained for the final product prepared using gelatin at 0.4 g 100 g−1 would be obtained using only G. birdiae at 0.3 g 100 g−1.