Preparation Of ρ-Coumaric Acid And Xylooligosaccharide And Analysis Of Flavors From Corn Cob

Corn cob is agricultural waste with tremendous yield and low utilization, most of it is discarded and part of it used as fuel or feed, p-coumaric acid is a functional ingredient at a level of 2% higher in corn cob, which crosslinks with the cell wall polysaccharide or lignin. The aim of this research is to extract p-coumaric acid and xylooligosaccharide from the corn cob. The main results were as follows:1 Preparation ofp-coumaric acid from corn cobThe preparation technology for p-coumaric acid includes:alkaline extraction, ultrafiltration, decolorization of the filtrates, adsorption using anion exchange chromatography, desorption, second decolorization, concentration, crystallization. The optimal technology parameters were descibed in detail as follows.(1) Alkaline extractionOne part of corn cob was extracted using 15 parts of 2% of sodium hydroxide (w/v) at 25℃for 12h; under this condition,2.52%of p-coumaric acid was released.(2) Ultrafiltration and decolorization of the filtrateThe extracts mentioned above were filtrated using a 200-mesh nylon cloth, the filtrates were ultrafiltrated using the membrane with 10000 Da molecular cutoff.2.5%(w/v) of HC-303 activated charcoal was added into the filtrates and stirred at 25℃for 40min; this decoloration process proved to remove 64.25% of the pigments in the ultrafiltrates.(3) The adsorption technologyOne volume of D201 anion exchange resin was added into 25 volume of the decolored ultrafiltrate and stirred at 25℃for 120min; under this condition,92.43% of p-coumaric acid was adsorbed.(4) The desorption technology6 bed volume of eluents (ethanol, water and HCl in a ratio of 65:31:4) was used to desorb p-coumaric acid from the resin at 25℃for 120min, under this condition,95.37% of p-coumaric acid were adsorbed.(5) The second decolorization1.0%(w/v) of HC-303 activated charcoal was added into the desorption liquid and stirred at 25℃for 30min; this decoloration process proved to reservate 66.31% of p-coumaric acid in the desorption liquid.(6) Concentration and crystallizationThe decolorized eluents was concentrated to remove ethanol, crystal was collected by filtration.HPLC analysis showed that p-coumaric acid has a yield of 0.98% on the basis of dry corn cob and the purity of the product reached 98.4%.2 The optimal technology for praparation of XOsThe concentrates after ultrafiltration were washed using 6 volumes of water and then neutralized with HC1.20g/L of Pentopan Mono BG CN was added into the concentrates with pentosan concentration at 48.4g/L and reacted at pH5.0,60℃for 6 h. Under this condition, 6.95g/L of reducing sugars and 16.75 mg/mL of total soluble sugars were produced; the average degree of polymerization for oligosaccharides was 2.41.After purified, the oligosaccharide syrup contained 11.2% of oligosaccharide.3 The analysis of flavors in the corn cobHeadspace-Solid phase microextraction (HS-SPME) coupled to gas chromatography-mass spectrometry (GC-MS) was used to analyze flavor compounds in the corn cob. The results showed that 20 volatile flavor compounds in the cob and the predominant flavor compounds were C4～C9 volatile carbonyl compounds, esters, alcohols, aromatics, furans, acids and hydrocarbons compounds, of which the molecular weights distribution were at a range of 80～140, all of those compounds showed synergistic effect on formation special flavor of sweet corn in the corn cob. 4 Rapid determination of feruloylated oligosaccharidesFeruloylated oligosaccharides were respectively prepared from wheat bran, corn cob, and corn bran by enzymic hydrolysis and their rapid determination method was estabolished, and the accuracy of the method was verified by HPLC. The results showed that, after purification by Amberlite resin chromatography to remove the non-ferulic acid bound oligosaccharides, the dural wavelength-spectrophotometry (345nm,375nm) method could effectively determine the content of ferulic acid bound to the oligosaccharides; Combined with the determination of reducing sugars after acidolysis, it could be precisely quantitatively determine the total content of feruloylated oligosaccharides, the content of the bound ferulic acid and oligosacchrides respectively.