Many other recipes for kiwi sorbet also add some lemon juice. I simply do not think that is necessary.
If you do not mind using raw eggs, you may want to add a whipped-up egg white to the sorbet base just before churning - this will improve consistency, particularly if the sorbet is going to spend some time in the freezer. I must admit, however, that I've never added egg white to this particular sorbet - if it freezes too hard, I cut out a piece of the sorbet with a knife (!) and, possibly, soften the block in the micro-wave oven for about 20 seconds or so;-)