Optimization of the viability of Lactobacillus acidophilus and physico-chemical, textural and sensorial characteristics of flaxseed-enriched stirred probiotic yogurt by using response surface methodology

Abstract

Response surface methodology was applied to produce synbiotic yogurt containing Lactobacillus acidophilus and flaxseed with a high probiotic count and superior physicochemical and textural properties and desirable sensory attributes. The experiments were planned using the central composite design (CCD) with two independent variables: flaxseed concentration (0–4% w/w), and storage time (1–28 days). To assess yogurt, physicochemical, textural and sensory attributes were determined and optimised. The flaxseed concentration and storage time significantly affected the viability of the L. acidophilus and the texture and sensory attributes of yogurt. This study also demonstrated that the addition of flaxseed into the probiotic yogurt caused an increase in L. acidophilus growth (up to 8.82 CFU/mL) compared to the control sample (6.87 CFU/mL) and an enhancement in the yogurt's viscosity, hardness, cohesiveness, gumminess and water holding capacity (WHC) while a decrease in yogurt's syneresis and adhesiveness occurred. At the same time, high levels of flaxseed resulted in a reduction in the yogurt's desirable sensory attributes. In general, the results of the current study indicated the addition of 4% flaxseed into probiotic yogurt could result in a functional food product with 76.8% desirability that maintains suitable properties for approximately 13 days during refrigerated storage.