Effect of pectin modification based on the fermentation by lactic acid bacteria on drying characteristics and texture of apples.

This study combined the modification of pectin by fermentation and the drying characteristics of fermented apples to evaluate the effect of fermentation pre-treatment on the formation of dried apple texture. The results showed that lactic acid bacteria altered the pectin content of water-soluble pectin, simultaneously, P. ethanolidurans significantly increased the esterification degree of sodium carbonate-soluble pectin (55.17 %). The significant increase of Sugar ratio 3 in water-soluble pectin (49.62 % and 50.38 %) and sodium carbonate-soluble pectin (15.22 % and 11.71 %) indicated that L. brevis and P. ethanolidurans could enhance the branching degree of rhamnogalacturonan I structure in these two fractions. Furthermore, L. coryniformis induced water-soluble pectin and sodium carbonate-soluble pectin to transform into linear conformation. In addition, L. brevis and P. ethanolidurans promoted polygalacturonase activity, L. coryniformis and P. ethanolidurans promoted pectinesterase activity, while L. brevis and L. coryniformis inhibited β-galactosidase activity. The drying characteristics results showed that fermentation could improve the drying rate in the later stage of drying. Moreover, the apples fermented by L. brevis had a uniform large pore structure and the highest crispness value (28 ± 4) after drying. These results revealed that fermentation altered the branching and conformation of pectin, thereby affecting the drying quality of apples.