Animal Research International (2019) 16(1): 3162 – 3173 3162 IN VITRO STARCH DIGESTIBILITY OF BY - PRODUCTS OF SORGHUM STARCH EXTRACTION 1, 2 SOUILAH , Rachid , 1,3 BELHADI , Badreddine , 1 KHOUDJA , Elkhalil , 1 BEN EL AAKRI, Sara , 1 DJABALI , Djaffar and 1 NADJEMI , Boubekeur 1 Laboratoire d’Etudes et Développement des Technique s d’Epuration et de Traitement des Eaux et Gestion Environnementale, Département de Chimie, Ecole Normale Supérieure de Kouba , Algiers, Algeria. 2 Département de physique, Ecole Normale Supérieure, Laghouat, Algeria. 3 Département des sciences et techniques , Faculté de technologie, Université Amar Télidji, Laghouat, Algeria. Corresponding Author: Souilah , R. Département de Physique , Ecole Normale Supérieure de Laghouat , Algeria. Email: [email protected] Phone : +213551729980 Received: November 10, 2018 Revised: February 08, 2019 Accepted: February 1 5 , 2019 ABSTRACT The aim of the present study was to assess the nutritive value of by - products of sorghum starch extraction , as dietary starch from feed grains. Five by - products differing in their particle sizes and starch content s were collected . The mean values of fraction yields and starch contents , for first, second and third fraction of sorghum gluten feed were respectively 16 . 13 – 52 .63 % , 01. 97 – 44.08 % and 04 .9 9 – 56.75 % , while for sorghum gluten meal the values were 2 2. 27 – 71.13 % . The substrates from whole grain meal, prepared by dry milling, and from by - products differed in their in vitro starch digestion. The mean values for kinetic parameters ranged from 0.0066 to 0.0147 min - 1 for the rate constant ( k ) , from 53 .6 6 to 98.58 % for the starch hydrolysis at infinite time 3 3 ( C ∞ ) and from 6.06 ×10 to 8.47 × 10 % .min for the area under the hydrolysis curve (AUC) . Generally, a high digestibility of by - products of sorghum starch isolation with a great potential for sorghum in livestock and animal feed s are considered in this work . Keywords : Sorghum , Sta rch extraction, By - products , Starch digestion, Animal feed INTRODUCTION feed (G ö hl , 1981 ; Svihus et al. , 2005; Heu z é e t al. , 2015 ) , may find wider applications in the The w et - milling process is industrially used for food and non - food products (Wronkow ska , the separation of the main cereal components 2016) and can be used for ruminants, pigs, and involves physical, chemical and biochemical poultry and rabbi ts ( Wall and Paulis , 1978; G ö hl , operations . The s orghum starch produ ction by 1981 ; Hamid and El Zubeir , 1990; El Zubeir and wet milling process on industrial sca le has been Mustafa , 1992; Onifad e et al. , 1999 ). In this previously reviewed ( Eckh off and Waston , 2009) respect, v arious strategies have been suggested and the optimal condition has been investigated to improve feed v alues by increasing the in several laboratories (Yang and Seib , 1995; digestibility of both protein and starch . The Beta et al . , 2001; Higiro et al . , 2003; Pér ez Sira need to improve and optimize the efficiency of and Amaiz , 2004; Belhadi et al . , 2013). starch digestion in an important research The by - products are usually recombined focus es in the animal nutrition ( Selle et al., and dried to produce the sorghum bran, gluten 2010; Liu et al. , 2013 ) . feed , gluten meal and the germ meal. T hese The s tarch digestion is therefore crucial feed ingredients , largely used for the animal for the dietary energy of compound diets based ISSN: 1597 – 3115 ARI 2019 16(1): 3162 – 3173 www.zoo - unn.org Souilah et al. 3163 on cereals ( Wiseman , 2006 ). Several works ha s et al. ( 2001 ) and Belhadi et al . ( 2013) . A been conducted to investigate the starch schematic view of the procedure is presented in digestion kinetic from different ground grains by Fig ure 1. alpha - amylase ( Goñi et al ., 1997; Slaughter et al . , 2 001; Frei et al ., 2003; Hu et al ., 2004; Ezeogu et al ., 2005; Chung et al . , 200 6; Mahasukhonthachat et al . , 2010; Souilah et al. , 2014 ) . Various factors have been suggested as the cause of variation in the starch digestibility. Giuberti et al . (2014) and Z hu (2014) has reviewed the structure, physicochemical properties, modifications and uses of sorghum starch and the factors affecting the starch utilization in large food livestock . Lipids and proteins are the most abundant non - starch components in the feed ingredients that may affect t he physical state and susceptibility to amylo ly sis of starch in livestock ( Baldwin , 2001) , and grain processing conditions (e.g. milling, soaking, pelleting, extrusion , expanding and mixing) are a ffect ed on the alteration of c ereal Figure 1: Laborato ry small - scale schem e to grain starch, starch digestibility and utilization isolate starch from sorghum grains ( Theurer et al. , 1986; Mahasukhonthachat et al. , 2010; Al - Rabadi et al. , 2012; Koa et al. , 200 g of sorghum grain was steeped at 8 °C for 2017 ; Sopade, 2017 ). 24 h ours in 400 mL NaOH solution of The aim of the present study was to concentration 0.25 % (w/v) in a batch reactor assess the nutritive value of by - products (Beta et al . , 2001) . Steeped sorghum grains obtained after sorghum starch extraction, as were wet - milled by a grinder and mechanically dietary starch from fe ed grains. Small - scale sieved through 250 , 160 and 80 µm on a shaker laboratory steeping in NaOH , and wet - milling (Model RETSCH AS 200 Basic , France). Fractions process of starch extraction from sorghum that were held up by each sieve were washed whole grain was done . The fraction yield , starch with 75 mL of distilled water in order to recover yield and starch recovery in by - produc ts, starch more starch granules. According to the isolates were determined, and the kinetic of the termi nology used by Göhl ( 1981 ) , the b y - s tarch digestion in sorghum meal a nd by - products held up by the sieves 250 , 160 and 80 products w ere studied . µm were named sorghum gluten feed s (SGF) and labeled SGF 1 , SGF 2 and SGF 3 as first, MATERIALS AND METHODS second and third sorghum gluten fraction respectively. The filt rate was centrifuged at Materials Preparation: Four grain samples of 5,50 0× g, for 10 min utes using refrigerated local sorghum [ Sorghum bicolor (L.) Moench ] centrifuge (Jouan E96). After each cultivars were harve sted from Tidikelt region in centrifugation, the supernatant was eliminated the Algerian Sahara . Samples with white color and a top protein layer was sc rapped off and and non - tannin are labeled SB10AS , SB11AS, named sorghum gluten meal (SGM) . SB12FE and SB13FE . The sorghum grains were Approximately 2 – 3 litre of water process was cleaned and stored at 4 °C until use . The small - decanted a nd precipitate was dried in air oven scale laboratory steeping and wet - milling at 105 °C . The recovered dried precipitate was proce dure for isolation of starch from sorghum named steep liquor condensed gluten (SLCG ) . grains were performed as described by Pérez The starch slurry was dried overnight in oven at Sira and Amaiz ( 2004 ), Beta et al. ( 2000 ), Beta Animal Research International (2019) 16(1): 3162 – 3173 In vitro starch digestibility of sorghum by - products 3164 40 °C and recovered as dry starch isolate . The described elsewhere ( Goñi et al. , 1997 ; sorghum whole grains were ground to meal in Mahasukhonthachat et al. , 2010; Souilah et al. , IKA Labo r tech n ik A10 sample mill. The obtained 2014) . According to the perc entage of total meals were manually sieved over a 500 µm starch in each substra te, a mass of substrat e sieve. The milling characteristics of sorghum containing 300 mg of starch was weighed . The grain for wet - milling can be evaluated by masses were transferred in large tubes , to fraction yield , star ch yield and degree of which 25 mL of phosp hate buffer solution pH recovery. The fraction yield ( F Y % ) wa s 6.9 were added. To start starch hydrolysis, 5 ml calculated using equation 1 . of α - amylase (2 mg/m L ), type VI.B from porcine pancreas (A3172, Sigma - Aldrich) was added. ( % ) FY % = × 100 ( 1 ) The prepared mixture was incubated at 37 °C % for 3 h ours with constant shaking, aliquots of 0.2 ml were withdrawn at 0, 20, 40, 60, 90, Where m F = by - product fraction or starch 120, and 18 0 min utes, α - amylase was isolate mass in (g) , H F = by - product fraction or inactiva ted immediately by placing the tubes in starch isolate moisture , m g = sorghum grain boiling water bath for 5 min utes . Then, 2 .6 ml mass in (g) and H g = sorghum grain moisture. of 0.4 M sodium - acetate buffer solution ( pH The starch yi elds (SY % ) wa s calculated using 4.75), a nd 0.2 mL of an enzyme solution of equation 2 . amyloglucosidase from Aspergillus niger (3 260 U/mL, Megazyme, 9032 - 080 ) , 1 % (V /V) were ( % ) × ( % ) SY % = (2) added. In order to hydrolyze digested starch into glucose, the sample was incubated at 60 °C Where TS F = Total starch of fractions ( % ) . The d uring 45 min. Finally, the volume was adjusted degree of recovery ( D R % ) was calculated using with distilled water and glucose concentration in equation 3 . the digesta which was measured within the range ( 25 – 100 µg / m L) , using the oxidase - % pero xidase assay kits . DR % = FY % ( 3 ) % Modelling of Starch Digestograms: The Where TS g = Total starch of sorghum grain (% ). first - order exponential model in the kinetic study has been used to evaluate the starch hydrolysis Chemical Analysis: The m oisture content was or glycemic indices in the food and feed ( Goñi et determined according t o AACC methods 44 - 15A al.