Dietary fibre and cell-wall polysaccharides in the fruits of Japanese quince (Chaenomeles japonica)

The dietary fibre in the fruits of 12 genotypes of Japanese quince (Chaenomeles japonica) and 1 genotype of flowering quince (Chaenomeles speciosa) were prepared using two different methods: the alcohol insoluble solid (AIS) preparation; and the Association of Official Analytical Chemists (AOAC) method for total as well as for soluble and insoluble fibre. The two methods resulted in similar but significantly different estimates. No interaction was revealed between the methods and the genotypes studied. For content of total dietary fibre, three main groups could be distinguished: a group containing a low amount of fibre (three genotypes, 28–30 g/100 g dry matter), a group containing a medium amount of fibre (nine genotypes, 30–36 g/100 g dry matter) and an isolated genotype (Chaenomeles speciosa) that contained a considerable amount of fibre (38 g/100 g dry matter). The amount and the nature of monomeric sugars in the constitutive polysaccharides of the fibres were determined after total hydrolysis of the AIS or the total dietary fibre (TDF). The fibre contained mostly pectic and cellulosic polysaccharides. Analysis of the fibre from different parts of the fruits of two genotypes showed that they differed in their proportion of constituent polysaccharides (cellulose, hemicelluloses and pectic polysaccharides).