Title : Effect of dried beetroot, tomato and kale powders on the physicochemical and sensory properties of yogurt
Abstract:
The aim of this study was to evaluate the effect of adding dried vegetable powders from beetroot (Beta vulgaris L.), tomato (Solanum lycopersicum L.) and kale (Brassica oleracea var. sabellica) at levels of 0.2%, 0.5% and 1.0% on the physicochemical and sensory properties of fermented yogurts, as well as their changes during storage. The vegetable powders were obtained by convective drying and added to milk prior to fermentation. Analyses were performed after 1, 7 and 14 days of refrigerated storage. The physicochemical parameters determined included pH, titratable acidity, viscosity, degree of syneresis, color parameters (L*, a*, b*), total antioxidant activity, vitamin C, lycopene and β-alanin. Volatile compound profiles were assessed using an electronic nose (e-nose) system combined with multivariate data analysis. In addition, a sensory evaluation covering appearance, texture, odor, taste and overall acceptability was conducted.
The results showed that both the type and concentration of vegetable powder, as well as storage time, significantly affected the properties of the yogurts. Prolonged storage resulted in a further decrease in pH and an increase in titratable acidity, with more pronounced changes observed in samples containing 1.0% vegetable powders. Viscosity increased during storage, particularly in yogurts supplemented with beetroot and kale powders. Color changes intensified with storage time, with tomato powder providing the greatest color stability. Sensory evaluation indicated that yogurts containing 0.2% and 0.5% vegetable powders and stored for 7 days achieved the highest consumer acceptability, whereas a decline in sensory scores was observed after 14 days of storage, especially in samples with 1.0% kale powder.
The findings suggest that dried beetroot, tomato and kale powders can be successfully used as functional ingredients in yogurt, with an optimal addition level of up to 0.5%, ensuring desirable physicochemical and sensory quality during 14 days of refrigerated storage.
Research financed by the Ministry of Science and Higher Education of Poland as part of the targeted subsidy "Research network of natural science universities for the development of the Polish dairy sector - research project" (SUP-RIM) (MEiN/2023/DPI/2866).
