Changes in cell wall neutral sugar composition related to pectinolytic enzyme activities and intra-flesh textural property during ripening of ten apricot clones.

The changes of texture and cell wall characteristics of apricot were investigated in ten clones at two maturity stages. Fruit firmness, cell wall composition and enzyme activity of three apricot flesh zones were analysed. The AIS (alcohol-insoluble solids) were characterised by high amounts of uronic acid (179-300 mg g-1 AIS) and relatively high amounts of cellulosic glucose (118-214 mg g-1 AIS). The methylesterification degree varied significantly among the different clones ranging from 58 to 97 in Ab 5 and Mans 15 respectively. Conversely to zones firmness, enzymatic activity was higher in pistil followed by equatorial and peduncle zones. The ripening effect has been observed in firmness evolution according to enzymatic activity. This correlation allowed a classification of clones depending on softening. Among studied clones, Ab 5, Marouch 16, Mans 15 and Cg 2 were less influenced by softening and have the advantage of a technological valorisation for the processing industry.

Cell wall polysaccharides degradation and ultrastructure modification of apricot during storage at a near freezing temperature.

The effects of near freezing temperature (NFT) storage at -1.9 °C on cell wall degradation of 'Shushanggan' apricot was studied comparing to 0 °C and 5 °C storage. Our results indicated that NFT storage strongly inhibited the solubilization of Na2CO3-soluble pectin and cellulose, by the suppression of cell wall modifying enzymes (polygalacturonase, ß-Galactosidase, pectin methyl esterase and cellulase) and related genes expressions. The loss of side chains was the main modification in CDTA (Cyclohexane-diamine-tetraacetic Acid)-soluble pectin during storage and made the main contribution to the softening of apricot, while the loss of side chain was suppressed by NFT storage. Microscopic observation showed that NFT storage delayed the degradation of pectin fraction and protected cell wall structure from loosing. This study proves that NFT storage is an effective technology to suppress the cell wall polysaccharides degradation and ultrastructure modification of apricot.