Nutritional Value of Spent Hibiscus Calyces and Assessment of Consumers' Knowledge and Perception of Hibiscus Products for the Promotion of their Consumption

Hibiscus calyces have anti-inflammatory effects, reduce metabolic risk factors, and act as a prebiotic in the human gut. Bioactive compounds in hibiscus include dietary fiber, polyphenols and vitamins and hibiscus calyces have a well appreciated flavor. Preparation of juice from hibiscus is done using hot or cold aqueous maceration procedures. When hibiscus beverages are made, the remaining biomass, the spent calyces, is discarded. Little information is available on the composition of the spent calyces. To determine whether the spent calyces have potential value, it is important to evaluate the composition of major bioactive elements and other potentially valuable components like aromas. The overall goal of this work was to determine if hibiscus spent calyces have components that would be of nutritional value, and to investigate consumer interest in hibiscus consumption in the U.S. The first objective was to measure the contents of sugar, fiber, anthocyanins, other phenolics, vitamin C, and organic acids (hibiscus/garcinic, citric, succinic, fumaric acid) in spent calyces. The second objective was to identify and quantify flavor compounds in the spent calyces. The third objective was to assess American consumers knowledge and perception of hibiscus products. Cold and hot aqueous extractions were carried out on whole calyces of red and white hibiscus using a calyces:water ratio of 1:15. The spent calyces were freeze-dried and analyzed for sugar, fiber, anthocyanins, total phenolics, vitamin C, organic acids and flavor compounds and compared to whole calyces. Soluble and insoluble dietary fiber were measured using sequential enzymatic digestion and gravimetric filtration according to the AOAC method. HPLC was used to determine sugars, anthocyanins and vitamin C, acids. UPLC to identify polyphenols and GCMS with SPME to identify and quantify aroma compounds. Results of the survey show that most of the American consumers who participated in this study have consumed hibiscus products before and were aware of the health attributes of hibiscus products. The most liked products were tea and juices. Main reason for hibiscus consumption was in order: taste, health, flavor, and trend. The health statement provided to the participants of the survey did not affect their willingness-to-pay (WTP) for hibiscus beverages. Spent calyces contained significant amounts of sugars, anthocyanins, total phenolic, organic acids, vitamin C, dietary fiber, and aroma compounds. More fiber was found in the spent calyces than in the raw ones; volatiles profile and phenolics profile were similar to those of the raw calyces. These important nutritional compounds make hibiscus spent calyces useful as a functional ingredient in food products or for producing nutraceutical products. Use of spent calyces will increase value of hibiscus products benefit to both consumers and industrials and help reduce economic and environmental issues related to food waste management.