| The strategy of the conception, stemming from current adoption of new foodingredient (fibers) technology in response to consumer desirability on a new source offood ingredient in the market has motivated our current study as an interest toresearchers/industrialists to upgrade and/or add value to the existing ingredients.The purpose of this study was to develop suitable technologies for producing a novelfood ingredient of dietary fibers from white and yellow foxtail millets; and upgradingagricultural products to enhance their potential use as functional food ingredients for foodapplication and improve the quality of new food product.The results of this study showed that yellow seed had higher macronutrients (protein,carbohydrate, starch, total fiber, insoluble and soluble fibers) compared to white. Theantinutrient (tannin) was in trace for both millets. Other nutrients such as (amino acids,minerals, and vitamins) were high in white than yellow millet, whereas the same level ofthe sugar was observed in both millets. Remarkably, a weak variation is observed in thesoluble sugar after treatment with H2SO4at different concentrations.The functional and structural characteristics of the fibers from foxtail millets extractedwith water and phosphate buffer at different temperatures (60,90, and120°C), showedthat the effects of temperatures and solvents used during extraction of the fibers haveinfluenced the results. Fiber yields were decreased in deproteinized samples whendecreased temperature, whereas increased in defatted samples at low temperatures.However, this trend was not observed among the monosaccharides, for whichsequential variation was found in both treatments, respectively. The water absorptioncapacity (WAC) and oil absorption capacity (OAC) increased with temperature forinsoluble fiber, except those of the phosphate buffer, for which WAC and OACdecreased and did not follow the variation of temperatures. WAC and OAC variedirregularly at high temperatures for both treatments insoluble and soluble fibers, and hadhigher values when compared to insoluble fibers. Viscosity increased as increasedtemperature for water at60°C and buffer120°C in both millets. The similar trend wasobserved of the color measurement where decreased l,(a), and b values, as increasedtemperatures. Scanning electron microscopy confirmed progressively the effects (erosiveaction) on fibers caused by treatment of solvents, and elucidated the differences at60and120°C. Since fiber is senescent and lignified plant tissue, in vitro digestion changed theparticle appearance, but the structural matrix and water binding capacities weremaintained throughout. The extraction and fractionation of insoluble fibers from foxtail millet seeds, and theresults showed that neutral detergent insoluble fibers (NDIF) were high for white andyellow foxtail millets. The white samples yielded15.44%,11.56%, and27.00%as therespective insoluble, soluble, total dietary fibers that of the yellow offered97%,15.91%,and27.88%as in that order. White foxtail millet had the highest total hemicellulose(52.8%) content followed by yellow foxtail (50.34%). Cellulose and lignin were (32.41%and31.34%) and (2.89%and3.07%) for white and yellow respectively. The pectinsubstances were estimated to be lowest in both samples. Glucose uptake was varied from12.43%to98.22%for purified insoluble material-white (PIM-W) and those for purifiedinsoluble material-yellow (PIM-Y) from14.36%to98.57%, and the increase wasdependent on both glucose and sample concentrations.Several solvents (water, ethanol, methanol, propanol, and acetone) were employed tooptimize the polyphenol extraction from both varieties of foxtail millet’s insoluble fibers.Acetone had the maximum concentration of extracted antioxidant followed by methanoland propanol, while the minimum concentrations were found in water and ethanol. Thetotal polyphenol was the highest in acetone followed by propanol and methanol. Totalflavonoid was measured in trace for all solvents except propanol and acetone which didnot give any results. The results showed that both insoluble fibers extracts were differedin their capacities to quench2,2-dyphenyl-1-pykril-hydrazy (DPPH) and2,azino-bis[3-ethylbenzothiazoline-6-sulfonic acid]diammonium salt (ABTS+) radicals from0to60min running. Trolox equivalent against ABTS+was also measured. No correlation wasobserved between TP and radical scavenging capacities for DPPH and ABTS+.Insoluble fibers were isolated from both white and yellow seeds and evaluated for theirhypoglycemic effects by In vitro studies. The hypoglycemic effects of these fibers werecompared with that of commercial soy insoluble fiber (SIF). The results revealed thatwhile glucose adsorption capacity (GAC) of all samples showed only traces atconcentration of10μmol, the GAC was high in SIF compared to both white foxtailinsoluble fibers (WFIF) and yellow foxtail insoluble fiber (YFIF), as the glucoseconcentration was elevated from25mol to200mol. Glucose diffusion and retardationindex were nearly the same between YFIF and WFIF but were lower than that of SIFafter1h dialysis. Finally, the hypoglycemic effects of YFIF and WFIF were found to beable to absorb glucose as well as retard glucose diffusion and inhibit-amylase activity.Results obtained from in vitro kinetic study showed that SIF had high reducing power(RP), but no different to that of YFIF, while WFIF thus comparable to RP value of SIF.The cholesterol binding capacity (CBC) at pH2and pH7were differed for all insolublefibers, and the higher values were noted in pH7for SIF followed by YFIF and WFIF had low value; similar trend was observed in ferrous ion chelating with different insolublefiber fractions.The extracted starch had appreciable content of amylose and the amylopectin waspositively reported, but showing only the traces of its presence. The microstructure of thestarch granules seemed to have similar characteristics and showed little swelling at lowertemperature as observed under optical microscopy with same granule sizes (20μm), whileincreased the length, the structure of the starch granules changed to birefringent andshowed the characteristics “Maltese cross” pattern under polarized light withconsiderable faint hilmus. The size of the granules also changed to (50μm), in order toprovide their resistant starches by several in vitro studies. The rapid Visco-Analyzer(RVA) pasting characteristics indicated that paste viscosity, hot past viscosity increased,and cool past viscosity decreased, whereas pasting temperature increased for commercialcorn starch (CCS), white foxtail millet starch (WFS), and yellow foxtail millet starchy(FS). The CCS had low hot paste viscosity than WFS and YFS, due to its low amylosecontent. The resistant starch (RS) was significantly high in defatted and low in boiledsamples, respectively. In vitro kinetic study revealed important effects of the starchdigestibility, and were fast with high amylose but slow with low amylose content. |
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