Hibiscus sabdariffa L. calyces as a source of anthocyanins rich extracts to be used as a natural food colouring agente

Colour is the most important sensory perception when it comes to setting peoples expectations regarding the likely taste and flavour of food [l]. Since the consumers are more aware regarding the additives that are incorporated into food products, they have shown a preference for the consumption of natural additives over the artificial ones. This hás been one ofthe research lines ofthe scientific community, searching for natural additives to replace the artificial counterparts [2]. The present work studies the stability of an extract obtained from hibiscus calyces (Hibiscus sabdariffa L.), to test its possible use as a natural colourant in foods. The aqueous stability of the extract was monitored using the total anthocyanins content (TAC) as response (determined by HPLC-DAD) in function of time (t, 14 days), temperature (T, 4 to 70 °C), and pH (2 to 6). Aided by mechanistic/phenomenological models, the conditions favouring the stabilization ofthe extract were provided. The results obtained showed that the aqueous stability of the H. sabdariffa extracts was higher at lower pH values, shorter t values and T between 4 to 35 °C. However, certain new stable combinations of conditions were found, providing a wide range of conditions, in which the TAC ofH. sabdariffa extracts will remain stable at values of T within the range of50 to 70°C. Such facts, will help to understand how to incorporate stable natural extracts, rich in TAC, as natural colorant additives in food products, that may require strong processing conditions, such as bakery and dairy products. These results provide useful information for: i) potential industrial use offí. sabdariffa extract as alternative sources of natural additives rich in TAC; and ii) shelf-life calculations and TAC loss predictions at specific conditions of T and pH. Finally, the results obtained showed a certain agreement with previous reports regarding the stability of anthocyanin compounds, but providing a new alternative source.The authors are grateful to the Poundation tor Science and Technology (FCT, Portugal) and FEDER under Programme PT2020 for financiai support to CIMO (UID/AGR/00690/2013) and L. Barras contract; European Regional Development Fund (ERDF) through the Regional Operational Program North 2020, within the scope ofProject NORTE-01-0145-FEDER-023289 DeCodE and Mobilizing Project Norte-01-0247-FEDER-024479 ValorNatural*.