Effect of using kefir in the formulation of traditional Tarhana

Abstract Tarhana is known as a fermented cereal product made traditionally from wheat flour and yoghurt. As a novelty, kefir was used as substitute for yoghurt in tarhana production partially and completely to investigate the effects on fermentation activity, nutritional, sensory and rheological properties of tarhana. Addition of kefir increased the fermentation activity as raise in acidity values was observed compared to tarhana samples prepared with yoghurt. Regarding dry tarhana samples, the highest acidity degree, protein, ash and phenolic contents were detected in samples prepared with 100% kefir. Counts of LAB groups (M17 and MRS agar) of tarhana enriched with 100% kefir was higher than that of other tarhana samples during the fermentation period. Moreover, kefir affected the scores of sensory properties of tarhana soups. Tarhana soups prepared with kefir gave the highest scores for mouth feel, odour and consistency attributes. Tarhana soup prepared with 50% yoghurt and kefir showed the lowest viscosity probably due to synergistic effect on starch hydrolysis by bacterial population from both ingredients. These results suggest that replacement of yogurt with kefir in the formulation of Tarhana may enhance some properties of the soup.摘要 塔赫纳（Tarhana）是一类以小麦粉与酸奶为传统原料制备的发酵谷物制品。本研究创新性地将开菲尔部分或完全替代酸奶应用于塔赫纳生产，以探究其对塔赫纳发酵活性、营养品质、感官特性及流变学性质的影响。实验结果显示，与仅以酸奶制备的塔赫纳样品相比，添加开菲尔可提升发酵活性，表现为酸度值升高。针对干燥塔赫纳样品，采用100%开菲尔制备的样品其酸度、蛋白质、灰分与酚类物质含量均为最高。在整个发酵周期内，添加100%开菲尔的塔赫纳样品中，乳酸菌类群（M17与MRS琼脂）的菌落数均高于其余样品组。此外，开菲尔对塔赫纳汤品的感官评分存在影响：以开菲尔制备的塔赫纳汤在口感、气味与稠度属性上得分最高。采用50%酸奶与50%开菲尔制备的塔赫纳汤粘度最低，这一现象可能源于两种原料所含菌群对淀粉水解的协同作用。上述研究结果表明，在塔赫纳配方中以开菲尔替代酸奶，可提升该汤品的部分品质特性。