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, thus presenting 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.

Bioactivities of Kenaf Biomass Extracts: A Review

“…The study proposed that the reported radical scavenging activities are highly attributed to the total phenolic content and polysaccharide content of the extract. Other studies also reported likewise [11,12,34].…”

“…Moreover, the kenaf leaves can also be processed into tea that has functional values such as anti-diabetic properties. According to Goh, et al [11], the infusion of kenaf leaf tea with goji berries and red date tea (6:4) managed to exhibit hypoglycaemic effects by inhibiting the activity of the α-amylase enzyme. The study proposed that the mixture of both teas can work synergistically to disrupt the α-amylase enzyme, which plays a role in carbohydrate (starch, and glycogen) digestion (Figure 9).…”

“…Considering the large number of bioactive compounds extracted from kenaf, either from its leaves, seeds or flowers, this plant has the potential to be integrated into the food industry as functional foods that can offer health benefits. For example, it can be turned into a medicinal tea or healthy beverage whereby a pure kenaf tea, prepared from its dried powdered leaves, managed to show antioxidant activities [11]. Moreover, Ryu, et al [13] suggested kenaf flowers, which also have antioxidative capacity, can be a new source of edible flowers and food colourants.…”

“…For instance, oil that is extracted from kenaf seed has phytochemicals such as Vitamin E, sterol and polyunsaturated fatty acid that can help in combating cancer cells [7]. Even the simplest form of oral intake through tea that is made from kenaf leaves can help to minimise the risk of type-2 diabetes [11]. This proves that kenaf has the potential to be a natural source for plant-based medicine and food production.…”