Catalyzes xyloglucan endotransglycosylation (XET). Cleaves and religates xyloglucan polymers. Does not catalyze xyloglucan endohydrolysis (XEH). Probably involved in cell wall restructuring during fruit ripening and postharvest fruit softening. breaks a beta-(1->4) bond in the backbone of a xyloglucan and transfers the xyloglucanyl segment on to O-4 of the non-reducing terminal glucose residue of an acceptor, which can be a xyloglucan or an oligosaccharide of xyloglucan. Optimum pH is between 4.5-6.5. Loses activity rapidly when pH is lowered from 5 to 4. Expressed in fruit pulp. Expressed during fruit ripening (PubMed:23265513, PubMed:25849978). During storage, highest expression in fruits on day 12, decreasing sharply thereafter until end of storage (day 18) (PubMed:23265513). Expression is low in immature growing fruits, but increases significantly during the mature stage with the highest expression 120 days after full bloom. Expression in fruits is rapidly increased during storage at 25 degrees Celsius, with the highest expression on day 12, after which the expression decreases steadily until the end of storage (PubMed:25849978). In fruits, expression is greatly decreased by gibberellic acid (GA3) on day 12 of storage and by 1-methylcyclopropene (1-MCP) until day 12 of storage (PubMed:23265513). Expression in fruits is also decreased by low (0 degrees Celsius) temperature treatment throughout the storage (PubMed:25849978). Contains at least one intrachain disulfide bond essential for its enzymatic activity. Belongs to the glycosyl hydrolase 16 family. XTH group 1 subfamily.