Pectins, also known as pectic polysaccharides, are rich in galacturonic acid. Several distinct polysaccharides have been identified and characterised within the pectic group. The matrix portion of the composite is made of pectic polysaccharides. Their cell walls are composed chiefly of pectic substances on a rigid silica framework. The project resulted in four papers on pectic enzymes, one of which published in Nature. Pectic enzymes can sometimes be added to lessen the thickness of these solids.