Letteratura scientifica selezionata sul tema "Hibiscus sabdariffa – Transformation"

The present study aims at valorizing the stem of Hibiscus sabdariffa, a by-product of agriculture in Benin. This natural resource, abundant in tropical countries, including Benin, was until now considered as a biodegradable waste and treated as such. However, it possesses adsorption properties that can be exploited through its transformation into activated carbon for various uses, including water pollution control. For this purpose, activated carbon has been developed from Hibiscus sabdariffa stems chemically impregnated with phosphoric acid. The pseudo second-order model predicts the kinetics of phenol adsorption on the activated carbon produced. The thermodynamic study of the adsorption process of phenol shows that it is exothermic and spontaneous with an ordered structure on the surface of the material.

The utilisation of roselle (Hibiscus sabdariffa 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 drying conditions.

The reaction parameters for the graft co-polymerization of efficient Butyl acrylate (BA) monomer onto Hibiscus sabdariffa (Roselle) stem fiber were optimized and used to further explore the additive effect of methyl acrylate (MA), vinyl acetate (VA) and styrene (Sty) on percentage grafting, properties and the behavior of the fiber, in binary vinyl monomeric mixtures. The graft co-polymers were characterized by XRD, TGA, DTA, SEM and FTIR techniques and evaluated for physico-chemical changes like moisture absorption, swelling behavior, dye uptake studies and chemical resistance against 1N NaOH and 1N HCl. With increase in percentage grafting the percentage crystallinity, crystallinity index, and hydrophylicity were reduced whereas there was an increase in physico-chemico-thermal resistance, hydrophobicity, miscibility with organic solvents as a result of morphological transformation in these fibers. These modified graft copolymers were then used as reinforcement in phenol-formaldehyde polymer matrix as reinforcement and evaluated mechanically for modulus of elasticity, modulus of rupture, stress at the limit of proportionality and hardness. The composites reinforced with grafted fiber had better strength than raw fiber reinforced composites and phenoplast.

Hibiscus sabdariffa is a tropical plant with red calyxes whose anthocyanins, phenols, and antioxidant activity make it attractive to consumers both from a nutritional and medicinal standpoint. Its seasonality, perishability, and anthocyanin instability, led to the setup of stabilization methods comprising drying and powdering. However, its properties can often be altered during these stabilization processes. Treatments such as dehumidified-air-drying, infrared drying, and oven-drying, and their combination showed better quality preservation. Moreover, powder production enables superior biomolecule extractability which can be linked to a higher bioaccessibility. However, the required temperatures for powder production increase the bioactive molecules degradation leading to their antioxidant activity loss. To overcome this issue, ambient or cryogenic grinding could be an excellent method to improve the biomolecule bioavailability and accessibility if the processing steps are well mastered. To be sure to benefit from the final nutritional quality of the powder, such as the antioxidant activity of biomolecules, powders have to offer excellent reconstitutability which is linked to powder physicochemical properties and the reconstitution media. Typically, the finest powder granulometry and using an agitated low-temperature reconstitution media allow for improving anthocyanin extractability and stability. In this review, the relevant physicochemical and processing parameters influencing plant powder features from processing transformation to reconstitution will be presented with a focus on bioactive molecules and antioxidant activity preservation.

Two studies were conducted to explore the utilization of rosolle seed meal (RSM) as a feedstuff in small ruminant feed. In study one, the effect of processing methods on the proximate compositions, mineral contents and anti-nutritional factors of roselle seed were evaluated. Four different processing methods were evaluated as treatments, T1 = was control (untreated roselle seed), T2 = fermented roselle seed, T3 = hot water treated roselle seed, and T4 = lye water treated roselle seed. The prepared samples were subjected to laboratory analysis. In the second study, feeding trial was conducted to assess the performance of grazing red Sokoto bucks supplemented with diets containing processed roselle seed meals. Four experimental diets were formulated using wheat offal, sorghum husk, rice husk, salt, bone meal and processed RSM (T1= Untreated RSM; T2 = Fermented RSM; T3 = Hot water treated RSM and T4 = Lye water treated RSM) as treatments. The bucks were supplemented the diets for 84 days, after six hours grazing in a 50 hectares' rangeland daily. Sixteen red sokoto bucks, four bucks per treatment with average weight of 11.69±0.32kg were used in a completely randomized design, water was provided ad libitum. Data were generated on feed intake, weekly weight changes and feed conversion ratio. Results obtained in study one indicated that processing methods had no significant (P>0.05) effect on the proximate compositions of resolle seed except on ether extract and dry matter contents. The mineral compositions of the roselle seed obtained showed that there were significant (P<0.05) differences in the values of Potassium (K), Sodium (Na) and Copper (Cu). Lye water treated roselle seed (T4) was statistically superior to others in terms of K and Na, while fermented roselle seed (T2) was statistically superior in Cu. The result obtained in the analysis of anti- nutritional factors revealed that all the parameters were significantly (p<0.05) different. The values of tannin, saponin, Pytate, cyanide and oxalate ranged from 0.38-0.87mg/g, 13.21- 22.57mg/g, 33.13-50.79mg/g, 6.51-10.34mg/g and 2.12-4.36mg/g respectively. Results from the second study showed that there was significant (P<0.05) difference in the mean values of total weight gain, average feed intake and total feed intake. In conclusion, processing methods substantially reduced the effect of anti-nutritional factors in roselle seed which can serve as a good source of feedstuff for small ruminant production. Also, supplementation of roselle seed meal can significantly improve the performance of goats without any detrimental effect. Deux études ont été menées pour explorer l'utilisation de la farine de graines de rosolle (le 'RSM') comme aliment dans l'alimentation des petits ruminants. Dans la première étude, l'effet des méthodes de traitement sur les compositions immédiates, les teneurs en minéraux et les facteurs anti-nutritionnels de la graine de roselle ont été évalués. Quatre méthodes de traitement différentes ont été évaluées comme traitements, T1 = était témoin (graine de roselle non traitée), T2 = graine de roselle fermentée, T3 = graine de roselle traitée à l'eau chaude et T4 = graine de roselle traitée à l'eau de lessive. Les échantillons préparés ont été soumis à une analyse en laboratoire. Dans la deuxième étude, un essai d'alimentation a été mené pour évaluer les performances des mâles Sokoto rouges au pâturage complétés par des régimes contenant des farines de graines de roselle transformées. Quatre régimes expérimentaux ont été formulés en utilisant des abats de blé, des balles de sorgho, des balles de riz, du sel, de la farine d'os et du 'RSM' transformé (T1 = le 'RSM' non traité ; T2 = le 'RSM' fermenté ; T3 = le 'RSM' traité à l'eau chaude et T4 = le 'RSM' traité à l'eau de lessive) comme traitements. Les mâles ont été nourris pendant 84 jours, après six heures de pâturage quotidien dans un pâturage de 50 hectares. Seize mâles sokoto rouges, quatre mâles par traitement avec un poids moyen de 11,69 ± 0,32 kg ont été utilisés dans une conception complètement aléatoire, de l'eau a été fournie ad libitum. Des données ont été générées sur la consommation alimentaire, les changements de poids hebdomadaires et le taux de conversion alimentaire. Les résultats obtenus dans la première étude ont indiqué que les méthodes de traitement n'avaient pas d'effet significatif (P> 0,05) sur les compositions proches de graines de résolle, sauf sur l'extrait d'éther et la teneur en matière sèche. Les compositions minérales de la graine de roselle obtenues ont montré qu'il y avait des différences significatives (P <0,05) dans les valeurs de Potassium (K), Sodium (Na) et Cuivre (Cu). La graine de roselle (T4) traitée à l'eau de lessive était statistiquement supérieure aux autres en termes de K et de Na, tandis que la graine de roselle fermentée (T2) était statistiquement supérieure en Cu. Le résultat obtenu dans l'analyse des facteurs anti- nutritionnels a révélé que tous les paramètres étaient significativement différents (p <0,05). Les valeurs de tanin, saponine, pytate, cyanure et oxalate variaient respectivement de 0,38 à 0,87 mg / g, 13,21 à 22,57 mg / g, 33,13 à 50,79 mg / g, 6,51 à 10,34 mg / g et 2,12 à 4,36 mg /g. Les résultats de la deuxième étude ont montré qu'il y avait une différence significative (P<0,05) dans les valeurs moyennes du gain de poids total, de la prise alimentaire moyenne et de la prise alimentaire totale. En conclusion, les méthodes de transformation ont considérablement réduit l'effet des facteurs anti-nutritionnels dans les graines de roselle qui peuvent servir de bonne source d'alimentation pour la production de petits ruminants. En outre, la supplémentation en farine de graines de roselle peut améliorer considérablement les performances des chèvres sans aucun effet néfaste.

Different reaction parameters for the graft copolymerization of butyl acrylate ontoHibiscus sabdariffafiber were optimized. Graft copolymers thus obtained were subjected to characterization using XRD, TGA, DTA, SEM and FTIR techniques and were evaluated for physio-chemical changes in the behavior. The percentage crystallinity and crystallinity index were found to decrease with increase in grafting while there was reduction in moisture absorption and increase in chemical, thermal resistance of the graft copolymers.

The paper deals with characterisation and evaluation of the transformations in waste biomass Hibiscus sabdariffa stem fibre on graft copolymerisation with ethyl acrylate (EA) and butyl acrylate (BA) monomer, using a ceric ammonium nitrate–nitric acid initiator system. Different reaction parameters, such as temperature, time, initiator concentration, monomer concentration, and pH, were optimised to obtain the maximum graft yield. The graft copolymers thus formed were characterised by FTIR, SEM, TGA, DTA, and XRD techniques. The swelling behaviour of graft copolymers in different solvents was studied and screened for dye uptake behaviour in 0.1% gentian violet dye. With increase in percentage grafting, the percentage crystallinity, crystallinity index, and moisture absorption were found to decrease, whereas the chemical resistance (against 1N HCl and 1N NaOH), thermal resistance, and solubility in organic solvents were found to increase.

To investigate the potential of Hibiscus sabdariffa var. altissima (Thai kenaf) biomass as a feedstock for bioethanol production, Thai kenaf bark and core were pretreated at a moderate temperature with different phosphoric acid (H3PO4) concentrations. It was revealed that there was a higher glucan content in the Thai kenaf bark (57.97% ± 0.36%) compared with that in the core (43.10% ± 0.15%). The H3PO4 pretreatment resulted in a reduction in the lignin content and total removal of hemicellulose. This exposed the cellulose to attack by cellulase enzymes and resulted in an increased enzymatic digestibility. A high glucose concentration (GC; 7.02 g/L) and hydrolysis efficiency (HE; 95.79%) were achieved with 75% H3PO4 for the bark after 72 h of enzymatic hydrolysis. However, these values were not that different from those of the 70% H3PO4-pretreated bark (6.89 g/L and 95.43%, respectively). Nevertheless, the Thai kenaf core pretreated with 75% H3PO4 recorded a higher GC (6.30 g/L) and HE (91.67%) after 72 h of enzymatic hydrolysis. The scanning electron microscopy and X-ray diffraction analyses revealed the destruction of the surface structure and an increase in the porosity and crystallinity index of the Thai kenaf biomass, which corresponded to an increased enzymatic digestibility.

L'Hibiscus sabdariffa (hibiscus) est une plante dont les calices comestibles, contiennent des polyphénols et des molécules d'anthocyane qui sont à la fois des composés antioxydants et responsables de leur couleur rouge attrayante pour le consommateur. Ces particularités constituent un fort potentiel santé qui répond aux demandes actuelles du marché et un atout économique pour les industries. Cependant, cette plante tropicale et saisonnière dont les calices riches en eau, sont très périssables, sensibles à l'humidité et à la chaleur, et les molécules d'intérêt (anthocyanes) sont thermosensibles et instables en milieu aqueux. Dans ce contexte, la transformation des calices en poudre permet, en plus d'optimiser le coût du transport et l'espace de stockage, de stabiliser les calices en assurant une longue durée de conservation du produit, de faciliter l'accessibilité aux biomolécules et donc à ses bienfaits pour la santé, ceci, à condition que le procédé soit maîtrisé. L'un des meilleurs moyens de préserver les propriétés nutritionnelles d'origine (teneur en anthocyanes, activité antioxydante) des calices est d'obtenir des produits peu transformés ou « minimally processed products » en combinant le séchage à l'étuve (contrôlé), le broyage et le fractionnement par tamisage. Ce procédé a été étudié dans ce travail et les propriétés physicochimiques (granulométrie, forme, structure, porosité, proportion de fibre, teneur en anthocyanes, activité antioxydante) et fonctionnelles des poudres (écoulement, reconstitution, extractibilité des biomolécules) ont été systématiquement évaluées dans un but de formulation de boisson. L'intérêt d'un tel procédé est la facilité de sa mise en œuvre, applicable à tous végétaux, la facilité d'usage de la poudre, l'amélioration de la disponibilité et l'accessibilité des biomolécules. Ce travail a permis d'identifier l'impact du séchage solaire et du broyage sur les propriétés physicochimiques des poudres, ces dernières impactant directement les propriétés fonctionnelles. La substitution du séchage solaire par le séchage contrôlé à l'étuve et un fractionnement par tamisage supplémentaire après le broyage ont permis d'améliorer les propriétés fonctionnelles des poudres. Ces propriétés singulières des poudres ainsi obtenues, ont permis de distinguer des applications qui leur sont propres
Hibiscus sabdariffa (hibiscus) is a plant with edible calyxes containing polyphenol and anthocyanin molecules that are both antioxidant compounds and responsible for their attractive red color for consumers. These particularities constitute a good health potential that meets the current market demands, and an economic potential for industries. However, this tropical and seasonal plant whose water-rich calyxes are highly perishable, sensitive to humidity and heat, and whose the interesting molecules (anthocyanins) are heat-sensitive and unstable in aqueous medium. In this context, the calyx transformation into powder allows, besides optimizing the transport cost and storage space, to stabilize the calyxes by ensuring a long product shelf-life, and to improve the biomolecule accessibility. This allows to benefit to its health assets provided that the process is controlled. One of the best ways to preserve the calyx original nutritional properties (anthocyanin content, antioxidant activity) is to obtain minimally processed products by combining controlled oven-drying, grinding and fractionation by sieving. This process was studied in this work and the powder physicochemical properties (particle size and shape, structure, porosity, fiber proportion, anthocyanin content, antioxidant activity) and functional properties (flowability, reconstitution, biomolecule extractability) were systematically evaluated for drink formulation. The interest of such a process is the ease of its implementation applicable to all plants, the powder ease of use, the improvement of the biomolecule availability and accessibility. This work allows identifying the impact of sun-drying and grinding on the powder physicochemical properties, the latter impacting the functional properties. The substitution of sun-drying by controlled oven-drying and an additional fractionation by sieving preceded by grinding allowed improving the powder functional properties. These powder functional properties were singular and allowed to distinguish specific applications for each powder type (fine or coarse powders)

Providing food, clothing, shelter, and medicine, plants have played a critical role in human existence for millennia. The utilization of roselle (Hibiscus sabdariffa L.) calyx as a source of anthocyanins has been studied through rigorous investigations. Due to its perishable feature, the transformation of roselle calyces into dried without decreasing in their quality is highly difficult. This research was aim to determine effect various drying techniques of roselle sun, oven and freeze drying. Antioxidant, phenolic, flavonoids and anthocyanin content were determined. The studies revealed that freeze drying retained the antioxidant qualities, rate of drying increased significantly than oven and sun drying. It is concluded in other to retain the roselle calyces extract quality freeze drying methods should be employed.