Effect of Steaming on Cell Wall Chemistry of Potatoes (Solanum tuberosum Cv. Bintje) in Relation to Firmness

Abstract

The aim of this work was to investigate the heat-induced changes in cell wall polysaccharides of potato in relation to texture. Potatoes (Solanum tuberosum cv. Bintje) were subjected to a time course of steaming (95 °C) with and without a preliminary low-temperature heat treatment (50 °C, 3 h). Cell wall material was prepared and extracted sequentially with water, NaCl, trans-1,2-cyclohexanediamine-N,N,N‘,N‘-tetraacetic acid, sodium salt (CDTA), and Na2CO3 to leave a residue. These were analyzed for their carbohydrate compositions, their degree of methyl esterification, and the molecular size of selected soluble polysaccharides. Steaming caused the tissues to soften. This was accompanied by an increase in DMSO- and water-soluble pectic polysaccharides and a concomitant decrease in the CDTA, Na2CO3-soluble, and residual pectic polysaccharides. In contrast to many vegetables, low-temperature preheating failed to reduce steaming-induced softening, but resulted in a general reduction in the degree of methyl esterification of cell wall pectic polymers and a decrease in the cooking-induced modification to all pectic fractions. Preheating was effective, however, if potato tissues were presoaked in dilute CaCl2. The role of Ca2+-cross-linked polymers in tissue firmness is discussed. Keywords: Cell walls; texture; potatoes and processing