**Author details**

338 Chromatography – The Most Versatile Method of Chemical Analysis

**11. Final considerations** 

**List of abbreviation** 

be isolated and its minimal length estimated. Under controlled conditions, acid hydrolysis of RG-I gives a fraction of intermediate molar mass that is rich in GalA and Rha. The neutral side

RG-II was first isolated from cell walls using enzymatic treatment. The structure of RG-II was investigated using a combination of enzymatic and controlled acid hydrolysis. Using

The products from chemical and enzymatic hydrolysis are further fractionated by chromatographic techniques and structurally characterized. Usually, ion-exchange and size exclusion chromatography are used to fractionate the segments of pectic chains produced in the partial hydrolysis. The recovery of oligosaccharides with low degree of polymerization greatly facilitates the structural studies. Elucidation of the sequence of glycosyl units with the methods current available is only possible for oligosaccharides. This approach allowed the identification of xylogalacturonan in the modified hairy region of apple pectin [50].

One of the steps in the structural analysis of pectins is the determination of the glycoside linkages. Methylation analysis is one of the main tools to determine glycosydic linkages of polysaccharides and their oligomers. In this procedure, the free hydroxyl groups of pectins or their oligosaccharides are methylated. Then, the partially methylated material is hydrolysed and submitted to reactions to afford volatile derivatives. The products from this procedure are separated and analyzed using the chromatographic method of GC-MS [51].

Due to the need in recent years to seek alternatives that meet sustainable development, polysaccharides have emerged as source of sustainable products for fuel, food, materials and medicine. In this context, pectin is found in all higher plants and can be obtained from renewable sources. Although nowadays, commercial pectin is usually derived from citrus peel or apple pomace, other by-products from agroindustry can be used for pectin isolation. However, pectin preparations from non-traditional sources with a set of properties for specific applications require complete structural elucidation of the polymers. Chemical and enzymatic modification of pectins can be used to obtain new functionalities and again, an understanding of pectin fine structure–function relationships is required. Considerable progress has been made in the elucidation of the fine structure of pectin mainly due to the progress of chromatographic and spectroscopic methods; however a better understand is necessary in order to be able to design pectins for specific industrial or biological applications either by chemical modification or genetic engineering. At the moment, apple

pectin remains a well suited option for different applications.

FAO Food and Agriculture Organization

HG Homogalacturonan RG-I Rhamnogalacturonan I

chemical fragmentation, four oligosaccharides from side chains were obtained [42].

42].

chains are quickly hydrolysed to form low molar mass oligosaccharides [49;

Maria Helene Giovanetti Canteri *Federal Technological University of Paraná, Ponta Grossa, Paraná, Brazil* 

Alessandro Nogueira and Gilvan Wosiacki\* *State University of Ponta Grossa, Av. General Carlos Cavalcanti, Ponta Grossa, Paraná, Brazil* 

Carmen Lúcia de Oliveira Petkowicz *Federal University of Paraná, Curitiba, Paraná, Brazil* 
