Changes in nanostructure of alkaline-soluble pectin in pear stored in pure oxygen.

The changes of nanostructure degradation of alkaline-soluble polyuronides(ASP) in pears(Pyrus bretschneideri Rehd cv. Huangguan) were examined during 30 days of storage in air(control) and pure oxygen at 2℃and 95%relative humidity.Qualitative and quantitative information of ASP polymers was determined by atomic force microscopy(AFM) on day 0,10 and 30.Results showed that the frequency of small width ASP increased in all treatments over storage time,but was higher in control,indicating pure oxygen treatment inhibited the degradation of ASP molecules and the aggregate separation.Widths of ASP chains consisted of three basic units with widths of 15.625,19.531 and 23.538 obtained from the AFM determination.These conclusions also revealed that parallel linkages or intertwists between the basic units are fundamental structural conformations of ASP molecules.