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 / Roselle (<i>Hibiscus sabdariffa</i> L.), called Bissap in Senegal, is an annual shrub of tropical countries, locally used as a nutritious functional beverage. It has been associated with many health benefits and is also used in many industrial applications, hence its growing interest among entrepreneurs. However, beverages made from hibiscus have a short selflife due to degradation of anthocyanins and flavors. The purpose of our study was first to assess the impacts of water, extraction procedure and origin on the anthocyanins of hibiscus extracts. Senegal and Egypt hibiscus were used to prepare beverages with distilled water and reformulated Dakar (Senegal) water with cold and hot extraction temperature. Secondly, we examined the impact of freeze-drying on the anthocyanins and the volatile compositions of hibiscus extracts. Senegalese hibiscus was extracted in hot and cold conditions one part of each extract was freeze-dried. The result of this investigation show that origin and extraction temperature have significant effects on the anthocyanins contents. As expected, freeze-drying as no effect on the anthocyanins for cold extract. In contrast, significant differences were seen between the hot extract and its freeze-dried products. The aromas profiles were different when comparing cold and hot extracts to their respective instant powders as well as between the hot and cold extracts. The results of this study show freeze-dried hibiscus has volatiles and anthocyanins similar to non dried, suggesting that freeze drying is an option for stabilizing hibiscus.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/88756 |
| Date | 05 October 2016 |
| Creators | Ndiaye, Oumoule |
| Contributors | Food Science and Technology, O'Keefe, Sean F., Duncan, Susan E., Cisse, Ben Mady |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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