Caracterization of starches of sorghum and pearl millet cultivated in the Algerian Sahara

Starches of sorghum (Sorghum bicolor (L.) Moench) and pearl millet (Pennisetum glaucum (L.)) cultivated in Tidikelt (In Salah) and Ahaggar (Tamanrasset), were the subject of a characterization study. The approach consists of the isolation of starches, the determination of physico-chemical and functional properties and the study of enzymatic hydrolysis modification. The starches with a rate ranging from 63.1 to 66.8 % were isolated according to the alkaline method. The purity of the obtained starches is satisfactory (91.4-96.7 %).However the extraction yield remains average (59.1-61.2 %). The physical properties (color, shape and size of the granules), chemical composition (moisture, starch and amylose) and rheological properties (solubility, swelling power and viscosity) of the isolated starches were determined. Important results were obtained highlighting interesting functional properties of these starches. Indeed, the average diameter of native starches granules had reached 18 and 10µm for sorghum and pearl millet respectively. These values are lower than those of others regions cultivars and close to those of corn and cassava. The amylose content (23.0 and 27.1 %) revealed that the analyzed cereals are normal varieties. The analysis of viscosity showed a very high peak viscosity that is reached rapidly. The DSC analysis has revealed higher gelatinization temperatures, attributed to high maturity temperatures. The X-rays diffraction patterns show the type A characteristic of cereals and allowed deducing the relative degrees of cristallinity. The kinetic studies of hydrolysis showed that the sorghum and pearl millet starches present susceptibility for hydrolysis in presence of fungal, bacterial and human amylases. However, this susceptibility varies according to the treatment used with the integral grinding (flour) and to enzyme source. The experimental conditions allowing to enzymatic hydrolysis reactions of isolated starches to follow the Michaelis-Menten model were determined and kinetic constants (KM and Vmax) were calculated. The HPAEC-PAD profiles of oligosaccharides in sorghum starches hydrolysates were determinated for highlight the amylases activities. The study demonstrated the potential of sorghum and pearl millet starches and considers their applications and bioprocessing.Les amidons de sorgho (Sorghum bicolor (L.) Moench) et de mil perlé (Pennisetum glaucum (L.)) cultivés dans les régions du Tidikelt (In Salah) et de l’Ahaggar (Tamanrasset) ont fait l’objet d’une étude de caractérisation. L’approche suivie a consisté à isoler les amidons, à déterminer leurs propriétés physicochimiques et fonctionnelles et à étudier leur modification par hydrolyse enzymatique Les amidons présents avec un taux de 63,1 à 66,8 %, ont été isolés selon la méthode alcaline. La pureté des amidons obtenus est satisfaisante (91,9-96,7 %). Cependant, les rendements d’extraction restent moyens (59,1-61,2 %). Les propriétés physiques (couleur, forme et taille des granules), la composition chimique (teneur en humidité, amidon et amylose) et les propriétés fonctionnelles (solubilité, pouvoir de gonflement et viscosité) des amidons isolés ont été déterminées. Des résultats importants ont été obtenus, mettant en évidence des propriétés physicochimiques spécifiques de ces amidons. En effet, la taille moyenne des granules natifs est de18 et 10 µm respectivement pour le sorgho et le mil. Ces valeurs sont plus faibles que celles des amidons de cultivars d’autres régions. La taille est voisine de celle des amidons de maïs et de manioc. La teneur en amylose comprise entre 23,0 et 27,1 % a révélé que les céréales analysées sont des variétés normales. L’analyse du comportement à l’empesage a montré une viscosité au pic très importante atteinte rapidement. L’analyse calorimétrique a révélé des températures de gélatinisation élevées dues aux hautes températures de croissance. Les diffractogrammes aux rayons X présentent le type caractéristique des céréales et ont permis de déduire les degrés de cristallinité. Les études cinétiques d’hydrolyse ont montré que des amidons isolés présentent une susceptibilité à l'hydrolyse en présence des amylases pures d'origine fongique ou bactérienne. Cependant, cette susceptibilité diffère selon le prétraitement préconisé pour la mouture intégrale et selon le type d’enzyme. Les conditions expérimentales, permettant aux réactions d’hydrolyse enzymatique des amidons isolés d’obéir au modèle de Michaelis-Menten ont été déterminées et ont permis de calculer les valeurs des constantes cinétiques (KM et Vmax). Les profils de maltooligosaccharides contenus dans les hydrolysats d’amidon de sorgho ont été déterminés par HPAEC-PAD afin de définir le mode d’action des amylases. L’étude a permis de montrer les potentialités des amidons de sorgho et de mil perlé et d’envisager leurs applications et leur bioconversion

HPAEC-PAD profiles of maltooligosaccharide produced by hydrolysis of sorghum starches using amylases from various sources

peer reviewedStarches isolated from white and pigmented sorghum (Sorghum bicolor (L.) Moench) were used to determine enzymatic activity of starch hydrolysis by fungal (Aspergillus Oryzae) and bacterial (Bacillus Subtilis) α-amylase and oligosaccharides profiles of hydrolysate was determinate in same conditions by High Performance Exchange Anion Chromatography with Pulsed Amperometric Detection (HPEAC-PAD). Pure starches from potato, amylose and amylopectin were used for comparison. Oligosaccharide compositions ranging from glucose (DP1) to maloheptaose (DP7) as well as the significantly effect of α-amylase source and starch structure were determined

Nutritional quality of some landraces of pearl millet Pennisetum Glaucum grown in hyperardi ecosystem

Pearl millet Pennisetum glaucum is the most widely grown type of millet considered as secondary cereal. The center of biodiversity is in the Sahel zone of West Africa. It's known to be well adapted to drought, low soil fertility, and high temperature. Pearl millet is an important food across the Sahel. It is a main staple in a large region of Nigeria, Niger, Mali and Burkina Faso. India is the largest producer of pearl millet. The Sahara of Algeria which is a hyper arid region bordering the Sahel countries include many landraces. The aims of this study were to determinate the nutritional value of grains from some landraces of pearl millet. The protein, starch, fat, fiber, soluble sugar and minerals contents were obtained. An important interest was given to starch, as energetic source, so the ratio of amylose and amylopectin and some of its properties as rheological and thermal properties were determinate and showed interesting values comparatively to those given by previously studies done on pearl millet grown in different ecosystems. Pearl millet grains are gluten free and rich in starch, protein and minerals; it exhibits interesting applications in food and health, especially for celiac, anemic and cardiac patients and it is recommended for children growth. The grain components and their properties can present a competitive potential to satisfy specific, technological and nutritional needs for target market. Conservation and use of genetic diversity of millet in farming systems are at the heart of important issues, including food self-sufficiency

Kinetic of Sorghum starches bioconversion using various a-amylases

Industrial enzymology is an important branch of biotechnology. Enzymes offer alternative ways of making products previously made using conventional chemical. Originally, acid conversion was used to produce glucose syrups but today alpha-amylase are used to hydrolyze starches. Corn starches are the most useful industrially despite that Sorghum (Sorghum bicolor (L.) Moench) starches exhibit interesting properties. These properties show variability according to genotype and influence the digestibly of starch in the presence of amylases. The aim of this research is to determine the susceptibility of isolated starches from different cultivars of sorghum cultivated in hyper arid ecosystems of the Sahara of Algeria to the bioconversion using pure α-amylases and so to study the influence of the genotype of sorghum on the liquefaction and saccharification which respectively produce dextrin and reducing sugars. Many authors have reported that properties of starch as amylose content, solubility affect the starch behaviour during the enzymatic hydrolysis as well as mechanism of action of amylases. Starches sorghum were isolated and purified in the laboratory from white and pigmented seeds of cultivars from Algeria (In Salah), and United States of America. Some of their characteristics were determined. Amylases used were from fungal and bacterial sources (α-amylase from Aspergillus oryzae α-amylase from Bacillus subtilis), which possess an important hydrolysis activity. The kinetic studies of enzymatic catalysis had allowed to identify of optimum operating conditions and to calculate enzymatic activities. We also highlight the influence of genotype on starch bioconversion. Indeed, the composition and concentrations of maltoolisaccharides obtained after amylase hydrolysis were determined using HPAEC-PAD and results of profiles show differences according the sources of starch and amylase. This study is of great importance to consider industrial bioconversion of starches to produce oligosaccharides syrups

Morphological and thermal properties of starches isolated from white and pigmented sorghum landraces grown in hyper arid regions

The starches were isolated from white and red sorghum, predominant cultivars in the Sahara of algeria. Morphological, thermal properties and amylose content of isolated starches were examined. The determination of these proprties is relevant to the comprehension of starch and starch-based foods digestibility in order to direct them towards the specific applications in food and non food sectors

Isolation and chemical characterization of pearl millet starches from Algeria

Starch is the most important carbohydrate in the human diet. Depending on botanical origin and genetic background, starch has different chemical structures, and so different functional properties. Native starch constitutes a key ingredient in numerous food and chemical applications as well as its modified products. The word production reaches 60 million tons with an average growth rate of 2,4 %. Industrially, Starch is isolated from corn, wheat and potato. Pearl millet grain cultivated in the Algerian Sahara present 59, 8 -68, 8 % of starch so we focused on isolation and characterization of this starch. For that, four (4) cultivar samples of pearl millet were collected from In Saleh, Tamanrasset (Algeria) and Agadez (Niger) regions and starch was isolated using modified alkaline method. The isolated starches were pure (93 – 97%). Some physicochemical and functional properties as granules size, thermal and rheological properties were determined. Pearl millet starches exhibit unique properties. Indeed, it has a high gelatinization temperature (75°C) and very high viscosity (4872 cP) compared to starches of pearl millet growing in other ecosystems and other botanical sources (corn, wheat ...). These properties makes them suitable for applications in cosmetic and pharmaceutical industries as powders, in food as Thickener and texturizing, and in chemistry industries as thin, resistant and biodegradable films for embedding or encapsulation