Effect of pretreatment methods on the sensory and nutritional properties of a yoghurt-like product made from tiger nuts (Cyperus esculentus L.)

Aim: Underexploited local plant resources, such as tiger nuts, have significant nutritional potential. Tiger nuts can be used to produce a plant-based yoghurt that would enable people suffering from lactose intolerance to enjoy its benefits. This study aimed to evaluate the sensory acceptability, physicochemical, and nutritional properties of a yoghurt-like product made with tiger nuts pretreated by various methods (soaking, drying, roasting, boiling, and germination). Methods: Six types of vegetable yoghurt were produced from the milk obtained after different pretreatment methods (soaking, germination, roasting, drying, and boiling) of tiger nuts. A control sample was made of untreated tiger nuts. Nutritional analyses were carried out using conventional methods. Quantifying bioactive and antinutrient compounds was conducted via spectrophotometry and titration methods. Physicochemical analysis of samples was also carried out. A consumer preference test was conducted using an untrained panel. Results: Yoghurt samples made with tiger nuts, pretreated through roasting, showed the best sensory characteristics and overall acceptability. Drying of tiger nuts resulted in a significantly higher energy value, as did the protein content (5.46%) in the germinated yoghurt and the fibre content (2.80%) in the boiled yoghurt. Syneresis and water holding capacity decrease slightly during all the pretreatment methods applied. With regards to bioactive compounds, phenolic compounds [393.39 mg GAE (gallic acid equivalent)/100 g DM (dry matter)] were more abundant in the yoghurt whose seeds were boiled, while the content of alkaloids [1,178.08 mg QE (quinine equivalent)/100 g DM] was higher in the products made with roasted tiger nuts. Roasting and germination were respectively the most effective pretreatment methods for the reduction of the amount of phytate and saponin. Conclusions: Production of yoghurt with roasted tiger nuts appears to be the best option in terms of its sensory attributes and its nutritional properties. Its consumption will contribute significantly to improving the nutrient and bioactive compounds intake for those suffering from lactose intolerance.