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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.

In this study, flaxseed was used as a functional ingredient in yogurt formulations. The goal of this study was to produce prebiotic yogurt supplemented with flaxseed and investigation of its texture and sensory properties. Yogurt samples containing 0–4 flaxseed was produced and stored at refrigerator (4–5°C) for 28 days. Textural properties were determined by texture analysis, and sensory characteristics were assessed by 26 trained panelists. Addition of flaxseed to yogurt samples increased the hardness, gumminess, chewiness, cohesiveness, and springiness values in produced yogurt samples. However, adhesiveness level was reduced in a sample enriched with flaxseed. By increasing flaxseed concentration, the color of samples was significantly different than the control sample; L* value was diminished and a* and b* value increased. Sensory scores including taste and mouthfeel, appearance, and overall acceptance showed reduction trend in samples containing a high level of flaxseed. In general, results showed that the addition of 2.63 flaxseed into yogurt samples lead to produce functional food with satisfactory texture, sensory characteristics that sustained these properties until 17.17 days after cold storage. © 2019 The Authors. Food Science & Nutrition published by Wiley Periodicals, Inc.