Improvement of pearl millet (Pennisetum glaucum (l.) r. br) prolamin extractability: Chromatographic separation, characterization and functional properties

The major protein fraction in pearl millet is prolamin the alcohol soluble fraction called pennisetin. Researches on the factors affecting pennisetin extraction and on its functional properties are still very scant. In this paper, the effect of temperature, reducing agents (β-mercaptoethanol, dithiothreitol or sodium metabisulfite) and sodium hydroxide on pennisetin extraction was assessed.
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Improvement of pearl millet (Pennisetum glaucum (l.) r. br) prolamin extractability: Chromatographic separation, characterization and functional propertiesIMPROVEMENT OF PEARL MILLET (Pennisetum glaucum (L.) R. BR) PROLAMIN EXTRACTABILITY:CHROMATOGRAPHIC SEPARATION, CHARACTERIZATION AND FUNCTIONAL PROPERTIESRafika Bibi1,2, Hind Mokrane1*, Khaled Khaladi1,2, Houria Amoura1Address(es): Prof. Hind Mokrane, PhD.1 Laboratoire des produits bioactifs et de valorisation de la biomasse, Ecole Normale Supérieure, B.P. 92, 16050 Vieux-Kouba, Algiers, Algeria, phonenumber:00213555253835.2 Département des sciences de la matière, Université Alger 1 Benyoucef Benkhedda, Algiers, Algeria.*Corresponding author: hind.mokrane@g.ens-kouba.dz or mokraneh2017@gmail.com https://doi.org/10.15414/jmbfs.3674ARTICLE INFO ABSTRACTReceived 5. 9. 2020 Pearl millet is a gluten free cereal resistant to drought, diseases and pests. The major protein fraction in pearl millet is prolamin theRevised 18. 5. 2021 alcohol soluble fraction called pennisetin. Researches on the factors affecting pennisetin extraction and on its functional properties areAccepted 28. 5. 2021 still very scant. In this paper, the effect of temperature, reducing agents (β-mercaptoethanol, dithiothreitol or sodium metabisulfite) andPublished 1. 10. 2021 sodium hydroxide on pennisetin extraction was assessed. Samples were characterized by protein and amino acid (AA) analysis, SDS- Page and reversed phase high-performance liquid chromatography (RP-HPLC). Pennisetin was extracted with high protein purity (90.1%) from pearl millet grain flour (PMF) using 70% aqueous ethanol containing 1% sodium metabisulfite and 0.2% sodiumRegular article hydroxide at 60°C. SDS-Page confirmed pennisetin extraction and showed three subunits corresponding to the 27-, 22- and 12 kDa- pennisetins. The percentage of essential amino acids in pennisetin (68.55%) was higher than that in PMF (41.64%). The hydrophobic character of pennisetin was confirmed by the presence of 45.49% of hydrophobic amino acids. Functional properties of pennisetin and PMF were investigated. Compared to PMF, pennisetin exhibited comparable oil and water binding capacities and higher foaming capacity and emulsifying activity index but with lower emulsion stability. Pennisetin functional properties were similar or lower relatively to common used proteins of wheat, sorghum, rice or peanut. Excluding water, oil binding and foam capacities, all the functional properties of pennisetin and PMF were significantly different (p≤0.05).The findings suggest increasing the use of pennisetin and PMF as nutritional and health promoting agent for vegans and celiac patients. Keywords: Pearl millet, Effect of solvent, Pennisetin extraction, RP-HPLC, Functional propertiesINTRODUCTION type, reducing agent type and sample-to-solvent ratio (De Brier et al., 2015; Gessendorfer et al., 2010; Hamaker et al., 1995; Nałęcz et al., 2017; Park andPearl millet [Pennisetum glaucum (L) R. Br.] is an important cereal crop Bean, 2003; Redant et al., 2017). To date only few studies have been conductedclassified sixth in term of consummation after wheat, rice, maize, barley and on the factor affecting pearl millet proteins extractability. Chandna and Mattasorghum. Mostly it is grown in the arid and semi-arid tropics of south Asia, sub- (1990) characterized the seed protein extract of eight pearl millet lines by SDS-Saharan Africa, China, Russia and Latin America (Bora et al., 2019; Ranasalva Page and two dimensional electrophoresis. Later, Marcellino et al. (2002)and Visvanathan, 2014; Sarita, 2016). Pearl millet is a drought-resistant crop reported the use of 55% aqueous isopropanol containing ß-ME to extractwith short growing season and good resistance to diseases and pests (Sarita, pennisetins and characterized them by SDS-Page, bidimensional gel2016). This gluten free cereal contains higher levels of essential amino acids electrophoresis, MALDI-TOF/MS and RP-HPLC. In a similar study, Ricks(AA) than maize, rice, wheat and sorghum particularly methionine, cysteine and (2007) adapted a method used for zein extraction to isolate pennisetin in a singlelysine (Akinola et al., 2017; ...