Quality of cow milk set yoghurt stabilized with native sweet potato (ipomoea batatas l.) starch extracted using different methods

Abstract

Gelatin extracted from animal tissues is widely used to stabilize set yoghurt. However, there is an increased consumer preference for plant-based stabilizers, such as starch, over animal-based gelatin in yoghurt products. The properties of starch depend on the extraction method and affect the quality of the final product. Therefore, this study investigated the quality of cow milk set yoghurt stabilized with sweet potato (Ipomoea batatas L.) starch (SPS) extracted using three different methods. Sweet potato tubers (3 kg) were washed, peeled and divided equally into 3 lots. Starch was extracted by blending each lot separately with distilled water (1:1) (SPS1), 1M NaCl (1:1) followed by centrifugation at 2200 rpm/15 min (SPS2), and distilled water (1:1) followed by centrifugation at 2200 rpm/15 min (SPS3). Experimental yoghurts (3% fat, 7% sugar) were prepared using gelatin (Control), SPS1 (T1), SPS2 (T2) and SPS3 (T3) as the stabilizer at the rate of 0.5% (w/w) and arranged according to completely randomized design with 3 replicates. The physicochemical and functional properties of SPS and yoghurt and the sensory attributes of yoghurt were investigated using standard methods. Data were analyzed with SPSS software (ver. 25) employing the analysis of variance (ANOVA) procedure followed by Tukey’s test for mean separation, while sensory data using the Friedman non-parametric test. SPS1 had the highest water absorption capacity of 0.780±0.002 mg/g and was significantly (p<0.05) different from SPS2 and SPS3, while pH was significantly (p<0.05) higher in SPS2. Moisture content in SPS produced with different methods was in the agreeable range (12.73±0.05 to 16.74±0.03%) and significantly (p<0.05) different with the starch extraction method. Swelling power and solubility of SPS were increased with the increase of temperature from 50°C to 80°C. Compared to the control, yoghurt manufactured using SPS showed significantly lower (p<0.05) water holding capacity except in T2, while spontaneous whey syneresis was not detected in any of the treatments. The colour of the yoghurts was not affected by the stabilizers used except the b* value. Sensory evaluation revealed no differences between the treatments, indicating the possibility of using SPS extracted using the methods mentioned as a stabilizer in the production of set yoghurt, which is comparable to gelatin.