There has been a lot of interest in Roselle (Hibiscus sabdariffa L.), called Bissap in Senegal, hibiscus recently because of consumer interest in nutraceutical products. However, beverages made from hibiscus have a short self-life due to anthocyanin and flavor degradation. The purpose of our study was first to assess the impacts of water, extraction procedure and origin on the anthocyanins of hibiscus extracts and secondly, to examine the impacts of freeze-drying on the anthocyanins and the volatiles compositions of hibiscus extracts. For the first experiment, a 2x3 factorial design was used with hibiscus calyces from Senegal and Egypt for the factor origin, distilled water and reformulated Dakar (Senegal) water for the second factor water, and then cold and hot extraction procedures were applied. For the second experiment, Senegalese hibiscus was extracted with hot and cold water and one part of each extract was freeze-dried. For both objectives, a ratio of 1:15 w/v (1 kilogram of calyces for 15 liters of water) were used. The time-temperature was 98°C / 30 min for hot and 22°C / 4 hours for cold extractions. The anthocyanins were determined using high performance liquid chromatography (HPLC). And the volatiles were measured using headspace-solid phase microextraction and gas chromatography-mass spectrometry (HS-SPME-GCMS). Origin and temperature as well as their interaction had significant effects on the anthocyanin contents, with respective p-values of 0.0036 and 0.0025 and 0.0002. Freeze-drying showed no effect on the anthocyanins in cold extracts. In contrast, a significant difference between the hot extract and its freeze-dried product was observed with a p-value of 0.0013. For the flavor compounds, the aroma profiles were different between cold and hot extracts and their instant powders. Globally the results of this study can help in the optimization when processing hibiscus derivatives. / MSLFS

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. / Doctor of Philosophy / Hibiscus is a plant native to the tropics. Two types of hibiscus plants exist: red and white; both have been used in traditional medicine, in cooking and for making beverages. Both share the following characteristics: sour taste, pleasant natural flavor, refreshing properties, and high content of elements such as dietary fiber and antioxidants that promote health. Hibiscus calyces are reported to have potential to retard early aging, fight against inflammation, and reduce metabolic risk factors (diabetes, obesity, and high blood cholesterol). Fiber acts as prebiotic in the human gut and therefore facilitate bowl movement. Hibiscus calyces are consumed in the forms of tea, juice, smoothies, jam and marmalade and are highly appreciated by consumers. However, despite these attributes and possible uses, the whole calyces' byproducts, spent calyces, are discarded after obtaining the juice from the whole calyces. They are considered as a waste product. As hibiscus is mostly produced and mainly known in places like India and Africa, we were interested in learning about American consumers knowledge and perception of hibiscus products. The purpose of this work was to evaluate the spent calyces' major components and investigate American consumers' knowledge of hibiscus. Red and white hibiscus were obtained from Senegal. Nutrients in spent calyces obtained from cold or hot aqueous extraction of each type of hibiscus was determined. The waste calyces obtained from both hibiscus types contain significant amounts of fiber, sugars, acids, anthocyanin pigments and other phenolic compounds. Phenolic compounds were idenuutified and many are known to have positive effects on health. Many aroma compounds were present in the waste product as well. The results revealed that most American consumers were familiar with and had consumed hibiscus products before. They were most interested in teas followed by juice. Taste was the prime reason why they consume hibiscus products then health properties. participants` willing to pay (WTP) did not increase after they were provided with information on hibiscus health benefits. Hibiscus spent calyces could be used for new food products manufacturing as they can add value to our diet and help consumers stay healthy. The findings can help in the promotion of hibiscus products consumption and commercialization and in reducing food waste.

No description available.