Effect of water activity on extractable polyphenols and some physical properties of Hibiscus sabdariffa L. calyces (original) (raw)
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Plant Science Today
The calyx of the roselle plant (Hibiscus sabdariffa L.) has been extensively studied for its anthocyanins. Roselle calyces are exceedingly perishable, making the process of drying and extracting them without sacrificing quality quite difficult. Similarly, there are several commercial drying procedures available, each with its own set of benefits and drawbacks on nutritional and physicochemical qualities in the final product. The goal of this study was to examine the effects of sun, oven and freeze drying on the physicochemical and nutritional properties of roselle calyx. The antioxidant (%RSA), total anthocyanin content (TAC) and their HPLC identification, physicochemical as well as proximate composition were determined. The results showed that freeze drying increased the drying rate significantly and retained the antioxidant activity (32 mg/100 g QE) then fresh calyx, sun and oven drying, freeze-dried calyx also have higher TAC (176.9 mg/l) than sun and oven dried calyx, the HPLC a...
African Journal of …, 2010
Water extract of the calyces of Hibiscus sabdariffa Linn (Malvaceae) is used widely as a food additive and refreshing drink with proven medicinal benefits, which are attributed to its phytochemical constituents. Relevant physicochemical and stability studies have been carried out on the freeze-dried and formulated samples of aqueous extract of the calyces of H. sabdariffa. The phytochemical constituents, moisture sorption characteristics and the effect of extract concentration, light and pH on the color of the extract were determined. The stability of the anthocyanins contained in the extract and the thermal characteristics of the freeze-dried extract were also evaluated. The dye solution which has hot-pink color and a pH of 2.1 ± 0.6 contained flavonoids, glycosides, sterols, balsams, phenols, monosaccharides, free reducing and combined reducing sugars. The extract solution also showed colour and light transmittance responsiveness to changes in pH. Fourier transform infrared (FTIR)spectra and the diffraction scanning thermograms show the degradation effect of light on the extract. The dry samples of the extract showed higher photo-stability relative to the solutions. The isothermal moisture sorption profile of the powdered freeze-dried extract and the formulated granules showed characteristic sigmoidal curves corresponding to Type 2 and 5 isotherms respectively. The aqueous extract of the calyces of H. sabdariffa generally showed high light and pH sensitivity and positive tests for the presence of some active secondary plant metabolites that are probably responsible for its claimed health benefits.
Scientific Conference Proceedings, 2012
Antioxidant capacity, phytochemicals, phyto-nutrients and bioactive compounds, have all become buzzwords in the growing market for natural health food-products and speciality juice drinks. The main objective of this study was to determine the bioactive compounds in the calyces of Hibiscus sabdariffa L. and evaluate its functional potential hence provide an incentive to production, processing and consumption of roselle in Kenya where it is not widely cultivated and utilized. Proximate composition was determined using established AOAC methods. Antioxidant activity (AA) color degradation index (CDI) and were carried using 1-1 diphenyl picryl hydrazyl radical (DPPH) and hunters color meter respectively. HPLC, UV-visible spectrophotometer and atomic absorption spectrophotometer (AAS) were used to determine water soluble vitamins (WSV), total polyphenolic content (TPC) and mineral composition respectively. Product formulations were done and their consumer acceptability determined based on a 9-point hedonic. It was found that the properties of roselle extract before and after pasteurization included pH of 3.88 ± 0.00 and 3.42 ± 0.01, total acidity (as malic acid) of 2.24 ± 0.00 and 2.24 ± 0.03 %, total phenolic contents of 6.06 ± 0.18 and 5.82 ± 0.01 mg/g roselle extract, respectively. The antioxidant activities using DPPH assay with ascorbic acid standard, expressed as EC50 (Efficient Concentration) were 230.01 ± 2.40 and 235.34 ± 0.79 μg/ml, respectively. Iron and calcium were content was 8.59 ± 0.31 and 14.83 ± 0.60 mg/100g respectively. After sensory analysis, the pure roselle drink was generally more acceptable in taste, flavor, aroma, consistency and overall characteristics with an average overall score of 7.6 out of 9 in comparison with Rosela orange drink, rosella apple drink and rosella melon drink. These properties give roselle the potential as a functional ingredient in beverage manufacture and other applications such as utilisation in polymeric natural color development. Roselle can also be applied in the food industry for manufacture of red wine and roselle fruit flavored preserves, thus exhibiting great potential in commercial application in the food and pharmaceutical industry. More studies for in-vivo properties of Roselle extracts are however needed, to further substantiate the health claims of roselle extract in human nutrition.
Effect of particle size on the antioxidant and color properties of Hibiscus sabdariffa extracts
Roselle (Hibiscus sabdariffa) calycesextracts possess sometherapeutic effects; one of them is the antioxidant capacity. Color of Roselle extracts is mainly due to anthocyanins, which are responsible of the red-purple color and much of their antioxidant capacity (AC). The aim of this research was to evaluate the influence of the average particle size (APS), type of solvent, and extraction time (ET) on color and antioxidant properties of Roselle extracts. Color properties, AC, and efficient concentration (EC50) were evaluated according to a 2x3x3 factorial design: two APS (0.55±0.016 and 0.97±0.034 mm), three solvents (distilled water, 2% citric acid, and 50% ethanol), and three ET (30, 45, and 60 min). The extraction process was conducted at 50°C using a solid:liquid ratio of 1:10. The extracts obtained with an APS of 0.97 mm weremore luminous(43.6±2.8) and redder (61.8±1.0) than extracts from powder of 0.55 mm:41.1±3.4 and 60.3±2.2, respectively. Extracts obtained with distilled water and 2% citric acid solution presented adeep red color. The alcoholic extracts showed a red-purple color. The AC was higher in acid extracts, followed by the alcoholic and aqueous extracts:105.6±7.3, 93.8±5.6, and 83.2±12.1 mg equivalents of Trolox/100 mL, respectively. The EC50 was better for the alcoholic extracts (13.4±1.0 mg of extract) than for the other extracts. The inhibition of DPPH was similar in the alcoholic (80.2±2.9%) and acid(82.1±2.1%) extracts in comparison to the aqueous extracts (74.1±5.2%). Increasing the ET from 30 to 60 min, the antioxidant capacity decreased from 97.3±10.1 to 90.7±12.0 mg equivalents Trolox/100mL. An extraction of chemicals of Roselle calyces with 50% ethanol or 2% citric acid (2%), at 50°C for 30 to 45 min, may deliver an extract with good color and functional properties to be used for preparing products such as powders, capsules or concentrates.
Roselle Calyces Particle Size Effect on the Physicochemical and Phytochemicals Characteristics.
The effect of average particle size (APS), type of solvent, and extraction times (ET) on the physicochemical (moisture, pH, total soluble solids (TSS), titratable acidity, color, water activity (aw), density), and phytochemical (total anthocyanins and phenols content)propertiesin Hibiscus sabdariffa (Roselle) calyces was analyzed. The phytochemical properties evaluation was performed using a factorial design 2×3×3: two APS (median diameters, d50, of 0.55 ± 0.016 (fine powder) and 0.97 ± 0.034 (ground powder) mm), three solvents (water, 2% citric acid, and 50% ethanol) and three ET (30, 45, and 60 min). All extractions were performed at 50 °C. The APS was determined by sieve analysis using Tyler sieves of different number of mesh. Regarding physicochemical properties, no significant differences (p > 0.05) were observed in moisture content, pH, and titratable acidity; however, the 0.55 mm fine powder (FP) of Hibiscus calyces had lower aw(0.37±0.01) and higher TSS (5.53±0.05%) than the 0.97 mm ground powder (GP). The extracts obtained fromGP showed a deeper red color than those of FP. The best combination of independent variables, in order to obtain the highest concentration of anthocyanins (451.4±28.1 mg/100 g d.s.) and total phenols (2016.2 ± 159.8 mg/100 g d.s.) were APS of 0.55 mm, 50% ethanol, and ETof 30 min. Keywords: Hibiscus sabdariffa, average particle size, phytochemicals, anthocyanins, phenolic compounds
Emirates Journal of Food and Agriculture
Hibiscus sabdariffa L. is a plant from tropical climates, which produces, among other products, deep red calyces used to prepare refreshing drinks. The high humidity (85-87%) of the calyces at the time of harvest must be reduced to about 12% for handling and storage. The aim of the work was to evaluate the effect of the dehydration method of the calyces (sun drying, SD; air-drying, AD, at three temperatures: 50, 60 and 70 ºC) of three varieties of Hibiscus sabdariffa L. on the quality of their aqueous extracts. The quality was measured as a function of color), and chemical variables (titratable acidity, TA, total soluble phenols, TSP; total anthocyanins content TAC, and organic acids). The varieties used were Negra Quiviquinta (NQ) with dark red calyces, UAN-9 with light red calyces, and UAN-16, with white calyces. The dehydration method affected the quality of the extracts. The SD was the one that most affected the color and chemical variables. The color of the extracts was darker ...
International journal of food science, 2018
The utilisation of roselle ( L.) calyx as a source of anthocyanins has been explored through intensive investigations. Due to its perishable property, the transformation of roselle calyces into dried extract without reducing their quality is highly challenging. The aim of this work was to study the effect of air temperatures and relative humidity on the kinetics and product quality during drying of roselle extract foamed with ovalbumin and glycerol monostearate (GMS). The results showed that foam mat drying increased the drying rate significantly and retained the antioxidant activity and colour of roselle calyces extract. Shorter drying time was achieved when higher air temperature and/or lower relative humidity was used. Foam mat drying produced dried brilliant red roselle calyces extract with better antioxidant activity and colour qualities when compared with nonfoam mat drying. The results showed the potential for retaining the roselle calyces extract quality under suggested dryi...
Antioxidant and Physicochemical Properties of Hibiscus Sabdariffa Extracts from Two Particle Sizes
The effect of average particle sizes (APS: 0.45 and 1.01 mm), solvent types (ST: distilled water, 2% citric acid solution, and 50% ethanol), and extraction times (ET: 40, 50, and 60 min) on the physicochemical properties, antioxidant capacity, and half maximal effective concentration (EC50) in calyces of Roselle (Hibiscus sabdariffa) was analyzed. The extracts obtained with distilled water and 2% citric acid solution had an intense red color which purities (C) were 78.5 ± 2.3 and 79.8 ± 2.2, respectively. The alcoholic extracts showed a dark red color (C = 75.9 ± 1.8). The alcoholic (820.2 ± 73.7 mg Trolox equivalents (TE)/100 g dry calyces) and acid extracts (773.34 ± 53.0 mg TE/100 g dry calyces) showed higher antioxidant capacity than the aqueous extracts (673.24 ± 116.0 mg TE/100 g dry calyces). The EC50 value was better for the alcoholic extracts, followed by the 2% citric acid extracts and finally by the aqueous extracts (13.4 ± 1.0, 14.9 ± 1.0, and 17.2 ± 1.2 mg of extract, respectively). According to results, the best antioxidant properties were achieved using an APS of 0.45 mm, 50:50% ethanol:water ratio, and ETs of 30 or 45 min.
Hibiscus sabdariffa L. Extract: Characterization (FTIR-ATR), Storage Stability and Food Application
Emirates Journal of Food and Agriculture
The objective was to evaluate the extract stability of hibiscus in different conditions and the food application. Anthocyanins (TA), phenolic compounds (TP) and color, at: 4 and 25 °C, presence or absence of light, pH stability and FTIR were evaluated. Gelatin developed with hibiscus extract was submitted to sensory analysis. Light and temperature factors affected the stability of TP and TA throughout the storage. Higher stability was observed at 4 ºC and absence of light (in relation to TA and TP respectively, 3% and 26% losses were observed in this condition against 43% and 39% at 25 °C with light). Regarding pH, it was observed that pH change affected the absorbance and color in the hibiscus extract. Finally, the hibiscus extract, when added at the highest concentration into gelatin, was the most accepted by tastes, and scored 7 (like moderately) for color and global acceptance.