The impact of extraction time on the quality of herbal teas
Keywords: bioelectric Vincent method, chemical composition, herbs, sensory evaluation
AbstractThe research was done at Aleksandras Stulginskis University (Vytautas Magnus University Agriculture Academy since 2019) in 2015–2016. Tea blends were made from naturally occurring herbs and berries. The berries for blends were lyophilized and the medicinal plants were dried. The tea blends were filled with water at 90°C and extracted for 15 and 30 min, the infusions were filtered and then analysed. The purpose of the research was to determine the biochemical parameters and organoleptic properties of tea infusions extracted at different times using conventional and holistic research methods. The amount of soluble solids, vitamin C, titratable acidity, pH, redox potential, specific electrical conductivity and energy value (P) of the products were determined in the tea infusions. The values of the tea infusions colour coordinates (L*, a*, b*) were determined and sensory analysis was performed. The research results showed that the amounts of soluble solids and vitamin C were greater in the tea infusions extracted for 15 min than those in the infusions extracted for 30 min. After extraction for 30 min, the titratable acidity of the tea infusions also decreased. The pH values were higher for the tea infusions extracted for 15 min, whereas the values of redox potential and electrical conductivity were higher for the tea infusions extracted for 30 min. All tea infusions extracted for 15 min were characterized by a lower energy value (P) and are therefore more suitable for human organism. During extraction over a longer period (30 min), the colour of the tea infusions became richer. The colour, smell and taste of the tea infusions extracted for 30 min were scored higher by sensory evaluation.