Sensory profile and consumer preference of novel probiotic yoghurt enriched with orange sweet potato (<I>Ipomoea batatas</I>)

Abstract

Due to increased consumer demand for appealing healthy foods, there is a rising global trend of developing nutritious commercial yoghurts with attractive sensory attributes. The success of formulating a food product is dependent not only on improving human health systems but also its palatability. Yoghurts fortified with plant-based foods (fruits and spices) have been acceptable in the market, but there are minimal products with vegetables and root crops such as orange sweet potato. The present study evaluated the sensory profile and consumer preference of novel probiotic yoghurts enriched with provitamin A (beta carotene) rich orange sweet potato (OSP). Milk was fermented using commercial mixed probiotic yoghurt starter cultures [Christian Hansen, Denmark, ABT 12 with Lactobacillus acidophilus (LA-5), Streptococcus thermophilus (TH-4) and Bifidobacterium animalis subsp. lactis (BB12)]. The resulting yoghurts were enriched with purees from two different varieties of OSP tubers (Tainung or SPK 004) at 15 and 25 % (w/v)  concentrations. Sensory profiling of the formulated yoghurt was conducted using 9 trained panelists at University of Reading, Sensory Science Center, UK. Consumer acceptability of the formulated yoghurts was assessed by scoring questionnaire with 5 modality  attributes using 9-point hedonic scale while intent to purchase by 5-point hedonic scale at Karatina community, Kenya. The panelists  reported 26 quantitative descriptive sensory attributes significantly different (p<0.01) between the fortified yoghurts and control yoghurt (no OSP) with Tainung variety scoring highest in specks, orange colour, powdery appearance, mouthfeel, and after taste  (starchy and musty). Consumer preferences records from four different demographic cohort groups (n=120) aged 6–65 years and of different socioeconomic status, showed high overall mean liking hedonic scores of 5-8 out of 9.0 for the modalities (appearance, colour,
odour, taste and texture) in all the fortified yoghurts, with significant differences (p<0.05) between the two varieties and concentration of the OSP purees, but no difference within the cohorts. The purchase intent score varied significantly (p<0.05) between both yoghurt samples and the study community cohorts, with Op puree enriched sweetened yoghurts recording the highest value. The study demonstrated that probiotic yoghurts enriched with nutritious OSP purees have unique sensory attributes that are acceptable to consumers but preference differed based on variety of OSP and concentration of the fortifying purees.

Key words: Orange sweet potato, Probiotic yoghurt, sensory profile, Consumer acceptability, Fortification