ISSN 1330-9862 original scientific paper (FTB-2783) Cell Wall Metabolism of Two Varieties of Ber (Ziziphus mauritiana Lam.) Fruit During Ripening Praduman Yadav 1 *, Sunil Kumar 2 , Veena Jain 3 and Sarla P. Malhotra 3 1 Plant Biochemistry and Quality Control Laboratory, Directorate of Oilseeds Research, Hyderabad-500030, Andrapradesh, India 2 Central Institute of Post Harvest Engineering and Technology, Abohar-152116, Punjab, India 3 Plant Biochemistry and Molecular Biology Laboratory, Department of Biochemistry, CCS Haryana Agricultural University, Hisar-125004, Haryana, India Received: April 1, 2011 Accepted: July 21, 2011 Summary Two ber varieties differing in their shelf lives (Umran, 8 to 9 and Illaichi, 4 to 5 days) were analyzed for cell wall components, cell wall degrading enzymes and their isoenzyme profile at immature green, mature green, turning colour, ripe and overripe stages of ripen- ing. Cellulose and pectin contents decreased during ripening in both varieties. This decrease was accompanied by a corresponding increase in pectin methylesterase, polygalacturonase and cellulase. The increase in the activity of pectin methylesterase was about 20- and 10- -fold, that of polygalacturonase about 8.4- and 5.7-fold, and of cellulase 5.5- and 4.4-fold in Umran and Illaichi, respectively. The basal level of activities of all these enzymes was higher at all the stages of ripening in Illaichi variety, having short shelf life, as compared to Um- ran, with long shelf life. This was further confirmed by the intensity of isoenzyme bands of these enzymes. The isoenzyme profile also revealed that two isoenzymes of each, pectin methylesterase and polygalacturonase, and one of cellulase could be considered as iso- enzymes responsible for the softening of cell wall during ripening and could be potential targets for manipulation to delay softening during ripening. Key words: cellulase, cellulose, isoenzymes, pectin, pectin methylesterase, polygalacturonase Introduction Fruits constitute a commercially important and nu- tritionally indispensable food commodity. Being part of a balanced diet, fruits play a vital role in human nutri- tion by supplying the necessary growth-regulating fac- tors essential for maintaining normal health. However, they in general contain a very high percentage of water, and exhibit a relatively high rate of metabolic activity, which makes them highly perishable commodities with short shelf life. Moreover, developing countries includ- ing India lack the efficient system of transportation and storage of these horticultural crops and suffer from the postharvest losses of about 30 % of total production, amounting to a monetary loss of 8880 million US dollars per annum (1). Ber, a tropical fruit tree species belonging 467 P. YADAV et al.: Ber Fruit Cell Wall Metabolism During Ripening, Food Technol. Biotechnol. 50 (4) 467–472 (2012) *Corresponding author; E-mail: praduman1311@gmail.com to the family Rhamnaceae, is very popular among con- sumers due to its high nutritive value and comparative- ly lower market price. It is a hard tree, which can thrive well under adverse climatic conditions. However, due to perishable nature and poor shelf life of the fruit, high postharvest losses are the major constraints in develop- ing ber fruit industry. Development of practical solutions to these postharvest problems requires detailed under- standing of biochemistry and molecular biology of fruit ripening process, which is a genetically programmed and highly coordinated physiological event of organ trans- formation from unripe to ripe stage. During ripening, many biochemical changes including synthesis and deg- radation of pigments, conversion of starch to sugars, pro- duction of volatiles and hydrolysis of cell wall compo-