Journal of Agriculture and Food Research (Dec 2021)
In vitro bioactive properties of the tamarind (Tamarindus indica) leaf extracts and its application for preservation at room temperature of an indigenous roselle (Hibiscus sabdariffa)-based drink
Abstract
“Foléré” is an indigenous roselle-based drink produced in the Northern part of Cameroon for commercial purposes; however, its poor hygienic quality and short shelf-life are over time harmful for consumers' health and producers’ incomes. In the context of increasing concern on the safety of chemical additives and at the sight of the side effects of heat treatments on food quality, natural techniques of preservation are receiving a particular attention. Hence, the effects of tamarind leaf extracts on the physicochemical attributes and microbial quality of the “foléré” beverage through storage were assessed. Firstly, phytochemical and antimicrobial properties of 4 extracts (aqueous, hexane, ethanolic, and acetone) were studied, then the 2 most active extracts were selected. The beverage was prepared using the hot water technique, the nectar obtained was mixed with extracts, and both physicochemical and microbiological parameters of the blended “foléré” samples were investigated for 5 days at room temperature during which the stability and shelf-life of the samples were evaluated. Ethanolic and acetone extracts showed the highest total polyphenol (9.25 ± 0.02 mg of PE/g and 18.64 ± 0.02 mg of PE/g) and flavonoid (94.11 ± 0.01 mg of QE/g and 138.42 ± 0.07 mg of QE/g) contents. Acetone extract exhibited by far the best antimicrobial activity against both bacteria and fungi tested. This antimicrobial activity of extracts against Bacillus cereus (r = 0.969; p < 0.05), Bacillus subtilis (r = 0.978; p < 0.05), Aspergillus sp. (r = 0.952; p < 0.05) were positively and significantly correlated to the flavonoids content. A total of 4 and 12 bioactive compounds were identified in ethanolic and acetone extracts, with oleic acid as one of the most relevant compounds in both extracts. The use of these extracts in the “foléré” beverage reduced the total aerobic count and was more effective with the use of acetone extract, because it prevented significant changes in the physicochemical as °Brix. The formulated “foléré” samples were still palatable until the 5th day as compared to control samples stored at room temperature which were spoilt after a day of storage. This study suggests that the tamarind leaf extracts might help to upgrade quality and shelf-life of the indigenous beverages.
