Modifications in cell wall composition after cold storage of calcium-treated strawberry (Fragaria x ananassa Duch.) fruit

Strawberry (Fragaria x ananassa Duch.) is a highly perishable fruit, and storage life may be less than a week. In this work, chemical changes to cell wall polymers were characterised in calcium-treated strawberry fruit I day after removal from storage at 3degreesC for 10 days. Cell walls were extracted sequentially in order to fractionate soluble, ionically-bound (CDTA-soluble), covalently-bound (Na2CO3-soluble), and matrix (KOH-soluble) polysaccharides. Calcium treatments delayed fruit ripening only slightly, but improved resistance to fungal attack without being detrimental to external appearance. Application of calcium helped retain higher levels of ionically-bound pectins and contributed to maintaining structural integrity of cell walls, probably as a consequence of calcium deposition in pectin polysaccharides. Preservation of cell wall and middle lamella structure by applied calcium was related to higher uronic acid and sugar contents in the CDTA-soluble fraction, reflecting slowed down dissolution of cell walls and lengthened commercial life for treated fruit. (C) 2004 Elsevier B.V. All rights reserved.