Preparation Of Sunflower Heads Pectin-Fe(Ⅲ) And Its Properties

Sunflower heads contain 18～24%low methoxyl pectin,they possess remarkable biological and functional properties.Sunflower heads pectin as the systems for the carry of functional elements and exerts the bioactivity.This study aimed to obtain optimum conditions of preparation pectin and pectin–Fe（III）,physicochemical properties,and the structure was determined and characterized.The pectin–Fe（III）was investigated via in vivo and vitro assays.The main research contents and results were as follow:Extraction of sunflower heads pectin from fresh sunflower heads by subcritical water extraction.The effect of extraction time,pressure,temperature,liquid solid ratio on the pectin yield was studied.The maximum yield of pectin was optimized using response surface methodology.Its physicochemical properties,structure and thermal stability were investigated.Influence order of the extraction factors from the most to the least significant was liquid solid ratio,temperature and pressure.The yield（6.57%）of pectin was maximized at pressure 8 bar,temperature 120?C and liquid solid ratio 7 m L/g.The molecular weight,galacturonic acid and degree of esterification were found to be 11.5 k Da,82%,and 17.7%,respectively.Pectin represented obvious polysaccharide structure and good thermal stability.Pectin-Fe（III）was prepared by sunflower heads pectin and Fe Cl₃.The effects of trisodium citrate,temperature and p H value on Fe content of pectin–Fe（III）.The optimum conditions were obtained by single factor and response surface methodology.The physicochemical properties were analysed.The optimum conditions were temperature 80°C,p H 8,ratio of sodium citrate to pectin 2,the iron content of pectin–Fe（III）reached 20.07%.p H value had the greatest influence on the Fe content of pectin–Fe（III）,followed by temperature and ratio of sodium citrate.Pectin–Fe（III）was reddish brown powder and water solubility.There were no free iron ions in the aqueous solution of pectin–Fe（III）.The molecular weight and total carbohydrate were 12.7 k Da and 47.81%,respectively.The fucose,rhamnose,arabinose,galactose,glucose,mannose,galacturonic acid and glucuronic acid contained 0.5%,2.25%,4.6%,5.5%,4.0%,0.8%,82%and 0.8%,respectively.The structural and thermal properties using fourier-transform infrared spectroscopy,proton nuclear magnetic resonance,ultraviolet–visible spectroscopy,X–ray diffraction,X–ray photoelectron spectroscopy and thermogravimetric analyser.The reduction,release of Fe from simulated gastric fluid and intestinal fluid,antioxidant properties of pectin–Fe（III）were investigated.These results showed that pectin-Fe（III）exhibitedβ–Fe OOH structure.Pectin-Fe（III）suggested higher thermal stability than pectin.Fe³⁺in the pectin–Fe（III）could be reduced to Fe²⁺was ascorbic acid in the p H range of 3–12.The iron release was 0 and 96.5%in simulated gastric fluid and simulated intestinal fluid,respectively,which indicated that the pectin–Fe（III）possessed good gastric tolerance and higher bioavailability.Pectin–Fe（III）exhibited scavenging activities of DPPH and ABTS radicals,which were weaker than pectin.This study provided theoretical basis and technical support for the further development and utilization of sunflower heads pectin and the relationship between pectin structure and function.Pectin–Fe（III）exhibited excellent water solubility,good chemical stability and good gastric tolerance.Therefore,pectin–Fe（III）could be exploited as a new iron fortifier in the market.It has remarkable application value and will bring huge economic benefits.