Variability in the Technological Production and the Effects on the Physicochemical Property of “Foléré”: An Indigenous Nonalcoholic Drink Manufactured From the Reddish Purple Calyx of Hibiscus sabdariffa

Foléré beverage is a non-alcoholic concoction prepared from the reddish-purple dried calyx of Hibiscus sabdariffa. Despite being a nutritive and functional beverage, its production remains empirical, often characterized by unstable pH and short shelf life. The objective of this study was to evaluate the effects of the technological processing on the pH of foléré beverage using a Box–Behnken design. The Box–Behnken design was used to design the experiment and to determine the best combination of the hibiscus calyx, water, fruit pulp extract, and sugar needed to achieve the pH of 2.5. The experimental data were fitted to generate the second-order polynomial model and analysed using an appropriate statistical test. The crude extracts of tamarind fruit pulp were analysed to determine their phytochemical contents and antioxidant activities; meanwhile, the UHPLC-MS/MS was used to elucidate and identify the non-volatile bioactive compounds of the extract with the highest antioxidant activities. The phytochemical contents and antioxidant activities of the hydro-ethanolic and aqueous extracts varied significantly (p < 0.05). The hydroethanolic extract registered the highest polyphenol (51.72 ± 0.5 mgGE/g) and flavonoid (22.85 ± 0.26 mgQE/g) contents as well as the DPPH scavenging activity (80.81% ± 0.81%) and FRAP activity (57.19 ± 8.4 mgTE/g). The UHPLC-MS/MS analysis of the hydro-ethanolic extract revealed the presence of seven flavonoid derivatives and two organic acids. Furthermore, the volume of water, amount of sugar, fruit pulp extract, and calyx significantly affected the pH of the foléré beverage, and a 1:40 (w/v) calyx-to-water ratio, 20 mg/mL fruit pulp extract, and 16% sugar were needed under optimum conditions to attain the pH of 2.5. This study provides a standardised manufacturing scheme that could upgrade the production of foléré beverages to the semi-industrial level.