Influence of phenolics in finger millet on grain and malt fungal load,and malt quality

Phenolic type, fungal load, germinative energy (GE) and malt quality of finger millet grain types of varied kernel colour and phenolic content were analysed, to determine if phenolics in finger millet grain influence its malt quality. The fungal load (total fungal count (TFC) and infection levels) of the unmalted grain and malt were negatively correlated (p < 0.05) with total phenolics (TP) and amount of phenolic type (condensed tannins, anthocyanins and flavan-4-ols). High-phenol finger millet types had much higher malt quality than the low-phenol types, with respect to diastatic power (DP), and α- and β-amylase activities. GE, DP and α-amylase activity were positively correlated with TP and amount of phenolic type (p < 0.05) and negatively correlated with TFC (p < 0.01). Phenolics in finger millet grain influence its malt quality positively by contributing to attenuation of the fungal load on the germinating grain.     

Multiple molecular forms of finger millet subtilisin and amylase inhibitors

Nine varieties of finger millet (Eleusine coracana Gaertn) including a wild form were screened for proteinase and α-amylase inhibitory activities. Subtilisin inhibitory activity was present in all the varieties examined and was highest in the wild form, while the cultivated varieties had more trypsin inhibitory activity. Isoelectric focusing of a 60% ammonium sulphate fraction of the wild form, before and after complexing with subtilisin, showed multiple forms of subtilisin inhibitors one of which was also active against trypsin. Isoforms of finger millet subtilisin inhibitors were isolated from the ammonium sulphate fraction by ion exchange chromatography on DEAE-Sephadex followed by SP-Sephadex chromatography. Copurification of trypsin and α-amylase inhibitory activities with subtilisin inhibitory activity was observed during cation exchange chromatography. PAGE analysis revealed them to be charge isomers with pI in the range 5·5–6·0. SDS–PAGE gave an estimate of 12 000 mol wt for each of them. Finger millet subtilisin inhibitors were more active on bacterial proteinases than on bovine trypsin and chymotrypsin.     

龙爪稷多酚超声辅助双水相提取工艺及其抗氧化活性研究

采用超声辅助乙醇-硫酸铵双水相体系提取龙爪稷多酚,以多酚得率为指标,采用单因素试验和响应面分析法优化提取工艺。结果表明,超声辅助双水相提取龙爪稷多酚的最优提取工艺为:乙醇体积分数41%、硫酸铵浓度0.3g/mL、超声温度42℃、超声时间29 min、液料比60:1(mL/g),在该工艺条件下,龙爪稷多酚的得率为319.15mg/100g;龙爪稷多酚有较强的体外抗氧化活性,其总还原能力、清除DPPH自由基能力、清除羟自由基能力分别达到同浓度VC的91.84%,96.79%,89.03%。     

Composition and enzyme inhibitory properties of finger millet (Eleusine coracana L.) seed coat phenolics: Mode of inhibition of α-glucosidase and pancreatic amylase

Inhibitors of alpha glucosidase and pancreatic amylase play a vital role in the clinical management of postprandial hyperglycemia. Although, powerful synthetic inhibitors are available, natural inhibitors are potentially safer. Phenolic compounds from the millet seed coat were extracted with acidified methanol and characterised by HPLC and ESI-MS. These phenolics showed strong inhibition towards α-glucosidase and pancreatic amylase and the IC₅₀ values were 16.9 and 23.5 μg of phenolics, respectively. The enzyme kinetic studies, using Michaelis–Menton and Lineweaver–Burk equations, indicated that, in the presence of millet phenolics, the Michaelis–Menton constant (K_m) remained constant but the maximal velocity (V_max) decreased, revealing a non-competitive type of inhibition. The study indicated the therapeutic potentiality of millet phenolics in the management of postprandial hyperglycemia.     

不同溶剂提取穇子多酚的抗氧化性及对龙眼保鲜作用的研究

本文采用不同溶剂提取穇子多酚,并对其抗氧化性和保鲜作用进行了研究。结果表明：穇子多酚消除DPPH自由基的能力大于BHT接近Vc;还原能力接近BHT与Vc;低浓度条件下对羟基自由基的清除能力均低于BHT与Vc,高浓度时则接近BHT。经过穇子多酚处理的龙眼果实在可滴定酸含量方面优于茶多酚和Vc处理组,在失重率、腐烂率、Vc含量、还原糖和总糖含量方面接近于茶多酚和Vc。整体而言,穇子多酚都表现出较好的抗氧化活性和保鲜作用,其中以酸性乙醇提取的效果最好。可作为天然保鲜剂进行进一步开发与利用。     

Evaluation of antioxidant and antimicrobial properties of finger millet polyphenols (Eleusine coracana)

Phenolic acids from finger millet (Eleusine coracana) milled fractions (whole flour, seed coat, 3%, 5% and 7%) were isolated and their antioxidant and antimicrobial properties were evaluated. Acidic methanol extracts from seed coat to whole flour were rich in polyphenol content and were found to be stable up to 48 h at pH 4, 7, and 9 as studied by ultraviolet spectroscopy. Diadzene, gallic, coumaric, syringic and vanillic acids were identified as major phenolic acids from the extracted phenolics. Diadzene content was highest in concentration in the 5% flour. The reducing power of seed coat extract was significantly (p < 0.05) higher than that of whole flour extract. Antioxidant activity (AA) as determined by the β-carotene–linoleic acid assay indicated that the AA was highest in seed coat extract (86%), whilst at the same concentration it was only 27% in the whole flour extract. The seed coat extract showed higher antimicrobial activity against Bacillus cereus and Aspergillus flavus compared to whole flour extract. From these observations, it can be inferred that the polyphenols are responsible for the microbial activity of the millet and the results indicate that potential exists to utilise finger millet seed coat as an alternative natural antioxidant and food preservative.     

Characterization of purified xylanase from finger millet (<Emphasis Type="Italic">Eleusine coracana-</Emphasis>Indaf 15) malt

Xylanase (E.C. 3.2.1.8) was purified to apparent homogeneity from 96 h finger millet (Eleusine coracana, Indaf-15) malt by a three step purification procedure via ammonium sulphate fractionation, DEAE-cellulose ion exchange and Sephadex G-75 gel permeation chromatographies with a recovery of 4.0% and fold purification of 60. Xylanase, having a molecular weight of 29 ± 2 kDa was found to be monomeric on SDS-PAGE. pH optimum of the enzyme was found to be in the range of 5.0–5.5. The activation energy was 25 kJmol⁻¹. Xylanase showed maximum stability at 35 °C in a pH range of 5.0–6.0. K _m and V _max of purified xylanase were found to be 0.2% and 4.5 μmol min⁻¹, respectively. Metal ions such as Ca²⁺, Mg²⁺, Mn²⁺, Cu²⁺, Fe²⁺, Ag²⁺ and Ni²⁺ enhanced xylanase activity at 5 mM concentration. p-chloromercuribenzoate, citric, oxalic and boric acids inhibited the enzyme in concentration dependent manner. The mode of action of xylanase was found to be “endo” as determined by the analysis of products liberated from larchwood xylan by ESI-MS and H¹NMR. In vitro studies using Bifidobacterium and Lactobacillus sp. confirmed the prebiotic activity of the xylo-oligosaccharides.     

Fusarium verticillioides from finger millet in Uganda

Finger millet (Eleusine coracana) is a subsistence crop grown in Sub-Saharan Africa and the Indian Sub-continent. Fusarium species occurring on this crop have not been reported. Approximately 13% of the Fusarium isolates recovered from finger millet growing at three different locations in eastern Uganda belong to Fusarium verticillioides, and could produce up to 18,600?µg/g of total fumonisins when cultured under laboratory conditions. These strains are all genetically unique, based on AFLP analyses, and form fertile perithecia when crossed with the standard mating type tester strains for this species. All but one of the strains is female-fertile and mating-type segregates 13:20 Mat-1:Mat-2. Three new sequences of the gene encoding translation elongation factor 1??α were found within the population. These results indicate a potential health risk for infants who consume finger millet gruel as a weaning food, and are consistent with the hypothesis that F. verticillioides originated in Africa and not in the Americas, despite its widespread association with maize grown almost anywhere worldwide.     

Effect of finger millet (Eleusine coracana, Indaf-15) malt esterases on the functional characteristics of non-starch polysaccharides

Acetic acid esterase (AAE) (E.C 3.1.1.6) and ferulic acid esterase (FAE) (E.C 3.1.1.73) cleaves the acetyl groups substituted at O-2/O-3 of the xylan backbone and feruloyl groups substituted at 5′–OH group of arabinosyl residues, respectively of arabinoxylans. These enzymes modulate the functional properties of cereal arabinoxylans such as viscosity, foam stabilization and gelling. In the present study, water-soluble non-starch polysaccharides (WSPs) from ragi, wheat flours were isolated, and their functional characteristics were studied in the presence of purified esterases. Relative viscosities of the enzyme treated WSPs were marginally less than the untreated ones. Untreated WSPs from wheat and ragi were found to stabilize the thermal disruption of protein foams compared to the esterase treated ones. AAE treated WSPs of wheat and ragi showed increased gelation while FAE treated ones showed slight decrease in comparison with their respective controls. Xanthan gum (XG), which was deacetylated by purified AAE, showed improved gelation (ratio of relative viscosities for 0, 1 and 2 h of control and enzyme treated blend is 1:1.16, 1:1.35 and 1:1.20, respectively) when blended with locust bean gum (LBG).     

Finger millet polyphenols: Optimization of extraction and the effect of pH on their stability

Finger millet, one of the minor cereals, is known for several health benefits and some of the health benefits are attributed to its polyphenol contents. Investigations of suitable solvents for extraction of polyphenols and their stability, during changes of pH and temperature, were carried out. Histochemical examination of the millet kernels, and also analysis of the seed coat and the endosperm fractions of the millet for the polyphenol contents, revealed that nearly 90% of the polyphenols were concentrated in the seed coat tissue. In view of that, the polyphenol contents of the seed coat fraction of the millet were extracted with different polar and non-polar solvents, and it was observed that 1% HCl–methanol was very effective for extraction of the millet polyphenols. Accordingly, the polyphenols were extracted with acidic methanol and the polyphenols obtained were examined for pH and temperature stability. The phenolic contents (6.4 ± 1.0%) of the extract remained constant at highly acidic to near neutral pH (6.5) but decreased gradually to 2.5 ± 0.3% as the alkalinity increased to pH 10. The increase in pH resulted in precipitation of some of the extracted matter, and this increased from 4 ± 0.5% to 40 ± 3% of the extracted matter, as the pH increased from 1 to 10. But, the polyphenol contents of the extract were stable to the changes in the temperature of the extract. Fractionation of the polyphenols extracted by high performance liquid chromatography (HPLC) showed that the analytes were derivatives of benzoic acid (gallic acid, proto-catechuic acid, and p-hydroxy benzoic acid) and cinnamic acid (p-coumaric acid, syringic acid, ferulic acid and trans-cinnamic acid). However, in a highly alkaline condition (pH 10) of the extract, only gallic acid and proto-catechuic acid were detected.     

发芽对糜子酚类化合物及抗氧化活性的影响

探讨了发芽时间对糜子中酚类化合物含量、存在形式及抗氧化活性的影响。将经过表面灭菌的糜子种子放入25℃,相对湿度95%的人工气候箱中避光发芽6 d,每天取样,测定其中酚、黄酮含量及抗氧化指标（DPPH、ABTS、FRAP、ORAC）的变化。结果显示,从发芽2 d起,酚、黄酮含量及各项抗氧化指标明显增高。发芽6 d后,内糜8号总酚、总黄酮含量分别为发芽前的5.9和1.9倍,西农10-04号则分别为发芽前的4.6和1.9倍,抗氧化能力均显著增强（p<0.05）。此外,发芽4 d后芽中总酚、总黄酮含量及抗氧化能力显著高于（p<0.05）相应种子。总酚、总黄酮与抗氧化能力间均显示出极强的相关性,其中以总黄酮与FRAP相关性最高（r=0.985）。研究表明,发芽是一种有效提高糜子中酚类化合物含量及抗氧化活性的加工方式。      

Effect of processing on starch fractions in different varieties of finger millet

The effect of processing on starch fractions in finger millet (ragi) was studied in a standardized system and convenience mixes. In raw varieties, rapidly available starch (RDS) was 8.3% to 11.1% with slowly digestible starch (SDS) of 26.4% to 35.3%, and total available starch (TAS) 39–53%. The changes in the SDS and TAS were statistically significant. Puffing resulted in an increased RDS and decreased SDS. The changes were more prominent in hill grown varieties as compared to base varieties. Resistant starch (RS) ranged from 0.9% to 1.0% among raw varieties and decreased during puffing. The effect of puffing on gelatinisation of ragi flour was investigated, MR-1 variety showed a single phase transition with gelatinisation temperature of 64 °C, the same was found to be absent in puffed flour reflecting the gelatinisation during puffing. RS formation was influenced by the processing methods, increased during pressure cooking and roasting while dietary fiber increased during cooking and both decreased in all other processing methods. However, its implication in the convenience mix has shown that other ingredients also play a role in the RS content.     

Functional and tableting properties of acetylated and oxidised finger millet (Eleusine coracana) starch

The functional and tableting properties of native (NaFM) and chemically modified (by acetylation, AcFM; and oxidation, OxFM) finger millet starches were investigated. The tablet formation properties of the starches were assessed by Heckel and Kawakita analysis. The swelling power and solubility of the starch increased with increase in temperature with AcFM having the highest swelling power, while OxFM had the highest solubility. X‐ray diffractometry showed that the starches had the characteristic ‘A’ pattern with strong peaks at 3.78, 4.37, 4.87, and 5.17 Å. Chemical modification causes rupture of some starch granules as revealed by the Scanning Electron Micrograph. Chemical modification also leads to improved gelatinisation profile, with reduction in ΔH_gel from 9.64 J/g (NaFM) to 3.88 J/g (AcFM) and 8.76 J/g (OxFM). The bulk density and Hausner's ratio increased after chemical modification of the starch. Chemical modification reduced the mean yield pressure, P_y (Heckel analysis) but increased the deformability P_k (Kawakita analysis) of the starch compacts. Chemical modification also increased the crushing and tensile strength of the starch compacts, but lowered its disintegration time and friability.     

Changes in carbohydrates, proteins and lipids of finger millet after hydrothermal processing

Finger millet was soaked, steamed and dried to prepare hydrothermally processed millet, followed by decortication to prepare decorticated millet. The physicochemical properties and carbohydrate, protein and lipid profiles of control and processed millet were determined. The carbohydrates were fractionated to amlypectin and amylose equivalent fractions using gel permeation chromatography. The non-starch polysaccharides were isolated and their alditol acetyl derivatives were characterized by gas chromatography (GC). The proteins were extracted using different solvents and the total proteins were fractionated using SDS-PAGE. The ether extractable lipids were esterified and fractionated through GC. Hydrothermal processing decreased the amylopectin fraction and increased the amylose equivalent portion of the starch. Decortication further lowered the first fraction and increased the second fraction. A decrease in cold, hot water soluble and hemicellulose-B fractions and an increase in pectic polysaccharides, hemicellulose-A and cellulosic fractions were observed as a result of hydrothermal processing. Decortication significantly reduced the total non-starch polysaccharides specifically the cellulose fraction. Hydrothermal processing decreased the overall extractability of proteins by 50% but decortication increased it to 80%. It was observed that hydrothermal treatment did not change the gross nutrients composition of finger millet but for their profile. Decortication of hydrothermally processed millet caused significant changes in the nutrient contents and also in their profiles.     

Optimization of stress medium enhance hydroxyl radical inhibition by water-soluble protein from germinated millet

A growth-promoting medium was developed to enhance the production of a hydroxyl radical inhibitory water-soluble protein from germinated millet. The single factor test indicated that H₂O₂ plays a key role in the inhibition activity. An optimal medium composition, consisted of H₂O₂, gibberellin, Protamex and Tween-40, was achieved using statistical experimental designs. A fractional factorial design was applied to determine the key factors that affected the hydroxyl radical scavenging activity, and a central composite experimental design and response surface methodology were used to optimize those factors, respectively. A second-order polynomial prediction equation was obtained, that could determine the effects of H₂O₂ and Protamex on the response. It was found that a low concentration of H₂O₂ and Protamex could enhance the inhibition of hydroxyl radicals. The optimal medium composition for growth-promoting was as follows: H₂O₂ 1.56 mL/100 mL, gibberellin 0.2595 mg/L, Protamex 0.25 mg/mL and Tween-40 0.7 mL/100 mL. With the optimal medium, the highest hydroxyl radical inhibition (58.16%) was achieved.     

Hydrothermal treatments of Finger millet (Eleusine coracana) starch

The effect of hydrothermal treatments on the properties of Finger millet starch was investigated. Finger millet was modified by heat-moisture treatment, HMT at 100 °C, 16 h; 20% moisture level (MHT-20), 25% moisture level (MHT-25) and 30% moisture level (MHT-30) and annealed, ANN at 50 °C for 48 h (MAN). Results of the pasting characteristics shows that MNS and MAN were indicative of type ‘B’ starch which is characteristic of normal cereal starches, while HMT starches were Type ‘C’ which is characteristics of cross-linked or legume starches. MNS belonged to the type ‘A’ pattern of cereal starches. X-ray diffractometry studies (XRD) show that MNS gave strong peaks centered at 23.5, 20.3, 18.2, 17.15, and 15.15 Å, while HMT and ANN starches retained the typical ‘A’ pattern. Scanning electron microscopy (SEM) studies show that the shape and surface characteristics of the starches were irregular, polygonal-shaped granules, with less than 1% cavity or ruptured granules. Modification did not affect the appearance. All the starches swell as the temperature increased in the order MNS>MAN>MHT-20>MHT-25>MHT-30, and solubilized at different rate in the following order: MHT-30>MHT-20>MHT-25>MAN>MNS. The gelation profile of the starches ranged from 4 to 8% (w/v), while its oil and water absorption capacity ranged from 1.90 to 2.50 and 2.75 to 3.25 g/g, respectively.     

Quality characteristics of biscuits prepared from finger millet seed coat based composite flour

Finger millet seed coat is an edible material and contains good proportion of dietary fibre, minerals and phytochemicals. The seed coat matter (SCM) forms a by-product of millet milling, malting and decortication industries and can be utilised as composite flour in biscuit preparation. The SCM from native, malted and hydrothermally treated millet contained 9.5–12% protein, 2.6–3.7% fat and 40–48% dietary fibre, besides 3–5% polyphenols and 700–860 mg/100 g of calcium. The biscuits prepared using the composite flour were of crisp texture and exhibited breaking strength of 1480–1690 g compared to control biscuits (1560 g). The biscuits were of mild grey colour (ΔE = 40–50) and exhibited higher protein, dietary fibre and calcium contents. The sensory evaluation of the biscuits indicated that 10% of SCM from native and hydrothermally processed millet and 20% from malted millet could be used in composite biscuit flour.     

Starch hydroxyalkylation: Physicochemical properties and enzymatic digestibility of native and hydroxypropylated finger millet (Eleusine coracana) starch

Starch was isolated from finger millet (Eleusine coracana) and it was etherified with propylene oxide to produce hydroxypropylated derivative. The specific specie used in this study is African finger millet known as jeero. The yield of starch obtained from finger millet on dry weight basis was 52.4%. Progressive increases in molar substitution (MS) were observed as the volume of propylene oxide added to the reaction medium increased. The X-ray pattern of native finger millet starch conforms to the ‘A’ diffraction pattern characteristics of cereal starches. Prominent peaks were observed at around 2θ=15°, 17°, 18° and 23° and weaker peaks at around 2θ=20° and 26°. No pronounced differences were observed between the diffractograms of native starch and the hydroxypropyl derivatives. Hydroxypropylation improved the free swelling capacities of the native starch at all temperatures studied (30–90 °C). Turbidity of unmodified finger millet starch paste increased progressively as the days of storage increased. Turbidity reduced remarkably after hydroxypropylation and reduction in turbidity was observed as the MS of the modified starches increased. Hydroxypropylation reduced pasting temperature, increased peak viscosity but reduced setback value. In addition, hydroxypropylation reduced percentage syneresis of the unmodified starch. Retrogradation properties monitored with differential scanning calorimetry reveals that starch retrogradation reduced reasonably after hydroxypropylation. Carbon 13 NMR spectroscopy reveals that hydroxypropylation took place predominantly on carbon 6 on the anhydroglucose unit (AGU).     

Iron fortification of finger millet (Eleucine coracana) flour with EDTA and folic acid as co-fortificants

Fortification of staple foods with iron is a feasible strategy to enhance the intake of this mineral. In the present investigation, finger millet flour was explored for its suitability as a vehicle for fortification with iron. Ferrous fumarate and ferric pyrophosphate were added at levels that provided 6 mg of iron per 100 g of the flour, and both were found to be equally effective. Inclusion of EDTA and folic acid, along with the iron salts, significantly increased the bioaccessibility of iron from the fortified flours. The fortified flours were stable up to a period of 60 days. There was a decline in the bioaccessible iron content in the flour fortified with ferric pyrophosphate after 30 days of storage. Heat processing of the flours improved the bioaccessibility of iron from the unfortified and fortified flours. Fortification with iron did not affect the bioaccessibility of the native zinc from the flours.     

Prebiotic potential of xylooligosaccharides derived from finger millet seed coat

The present study deals with the enzymatic production of xylooligosaccharides (XOS) from water-soluble xylan (WSX) extracted from finger millet CO9 seed coat and the evaluation of its prebiotic potential. The yield of XOS was 72%, when the WSX of the finger millet seed coat was treated with commercially available xylanase of Thermomyces lanuginosus. The XOS obtained when analyzed using high-performance liquid chromatography–evaporative light scattering detector (HPLC-ELSD) indicated a degree of polymerization (DP) of 2 and Electro Spray Ionization Mass Spectra (ESI-MS) revealed xylobiose as the major sugar. The presence of β-glycosidic linkages of XOS was identified by Fourier Transform Infrared Spectrometer (FTIR) and Nuclear Magnetic Resonance (NMR) studies. The XOS exhibited an antioxidant activity of 75% and prebiotic efficacy. Prebiotic activity in the presence of probiotic strains was strain specific and differences in the prebiotic activity score (PAS) between strains were evident. The cell-free supernatant of Lactobacillus plantarum grown on the XOS from finger millet seed coat showed strong antibacterial activities against four pathogenic microorganisms compared with commercial XOS. Finger millet seed coat represents an abundant and alternative source for the extraction of xylan and its use for prebiotic XOS production.