The infusion of goji berries and red dates ameliorates the overall qualities of kenaf leaves tea

Abstract

Kenaf (Hibiscus cannabinus) is an industrial crop in Malaysia, and especially used as a source for composite wood. Kenaf leaves as a by-product of the plantation can be consumed as food due to its high nutritional value. Kenaf leaves have high antioxidant properties, thus are suitable to be made into herbal tea. However, its flavour is considered sour, and becomes a challenge for product development. The main objective of the present work was to evaluate the physicochemical and functional (ascorbic acid content, calcium content, and anti-diabetic) properties of kenaf leave tea (KLT) with 0, 60, and 100% kenaf leaves used. KLT was prepared by steaming and drying the kenaf leaves, followed by sieving. Then, the powder was mixed with distilled water at 1% (w/v). Another portion of red dates and goji berries tea (RGT) was prepared by boiling the red dates:goji berries:water at 1:2.5:28.5 ratio. Two portions of tea were infused using 60% KLT and 40% RGT. Results showed that a 100% KLT (positive control) was always highest in terms of total phenolic content (TPC) and total flavonoid content (TFC). The antioxidant activities were positively correlated with DPPH and ABTS scavenging activities, and ferric reducing antioxidant power (FRAP). Contrary, the negative control (0% KLT) showed the highest α-amylase inhibitory effect. The present work also evaluated the acceptance of consumers using the Hedonic sensory test among 50 panellists with balance male and female candidates. Since 100% KLT extract was in low pH values (2.17 ± 0.26), 60% KLT infused with goji berries and red dates gained the highest consumers' acceptance. Therefore, as a compromise between sensory and functional properties, a maximum of 60% KLT was a suitable formulation for the consumers