Study On The Extraction,characteristics,and Microbial Utilization Of Purple Corn Cob Pigment

Purple corn is one of the important source of natural anthocyanin pigments in plant world.It has high dietary value as well as nutritional value.The maize grain, corn cob and husk of Yuezijin purple corn,which is cultivated by Guangdong Academy of Agricultural Sciences,all have a high content of pigment.The by-product-purple corn cob has a higher pigment than maize grain.The development and utilization potential of purple corn cob is great .The present study of pigments extracted from purple corn cob is lack.Therefore,study on the extraction,purification,properties,composition, application of purple corn cob pigment is of great significance.Firstly,study was made on extracting anthocyanins from purple corn cob. The effects of different reagents,concentrations,extraction time,pH value,ratio of material to solvent,extraction temperature on yield were discussed.Box-Behnken center-united experiment design and response surface methodology were used to optimize the extraction technology of anthocyanins of purple corn cob.Data was analyzed using Design expert.The optimum extraction conditions were: the concentration of ethanol 80%,the extraction time 2h,the pH value 2.2, the ratio of material to solvent 13.5,the extraction temperature 58.9℃.Secondly,The method for purification of purple corn pigment by macroporous resin was studied.The results showed that X-5 resin was the best for purification of purple corn pigment.The optimum purification conditions are as follows:pH of crude extraction 1.5,concentration 0.971 mg/ml,its flow rate 5 ml/min;pH of 50% ethanol is the optimum eluent for desorpting purple corn pigment,and its optimal flow rate is 0.5 ml/min.Under the optimized technical conditions mentioned above,the resin X-5 has the saturation adsorption amount of 36.63 mg/ml(wet resin).The colour value of purified purple corn pigment is 19.66 times as much as that of unpurified one.Thirdly,effect of illumination,temperature,pH value,antiseptic,metallic ions, oxidant and reductant and some food materials on the stability of purple corn anthocyanin were investigated. The results indicated that: illumination and temperature affected the stability of purple corn anthocyanin distinctly.According to Arrhenius equation,purple corn anthocyanin degradation fits the first-order rate reaction under light irradiation.The purple corn pigment should be preserved out of light;Purple corn anthocyanin degradation fits the first-order rate reaction under 40-80℃thermal treatment.The thermal degradation activity ( E0) is16037 kJ/mol.The degradation fits the second-order rate reaction under 100℃thermal treatment.The best pH value to keep purple corn anthocynin is 2 to 3;Sodium benzoate,sorbic acid,sodium ion,aluminum ion and potassium ion have little effect on the stability of purple corn cob anthocyanin;Calcium ion will decrease absorbance of purple corn cob pigment significantly;Hydrogen peroxide,sodium sulfite,vitamin C both will decrease absorbance of purple corn cob pigment in a certain range; Different food materials have different effects on the stability of purple corn anthocyanin.Fourthly,Paper chromatography (PC), ultraviolet-visual spectrum(UV) and infrared spectrum(IR) were used to study the red pigment from Purple corn cob. Three components were separated by paper chromatography and were identified by paper chromatography as well as ultraviolet-visual spectrum and infrared spectrum. The three major components of pigment are likely to Cyanidin-3-glucoside, Peonidin-3-glucoside and Pelargonidin-3-glucoside which are anthocyanins.Lastly,microbial treatment was carried out on purple corn cob. A better microbial effect can get if microbial treatment was done as follows: The initial moisture content of purple corn cob is 70%, The additive amount of sugar is 5%, The pH value of the additive solution is 5, The additive amount of Haixing microbial agent is 0.25g/kg.During the microbial process,there was only a small loss of purple corn cob pigment.In the end of the fermentation the loss rate of purple corn cob pigment was only 86.18%.