Safe to leave mashed fruit for 2-3 days?

[RossClement]

I would like to make my own fruit syrups for making soft drinks. The simplest recipes I've found are those on "The Foody" website. E.g. this one:

http://thefoody.com/drinks/strawberrysyrup.html

However, all their fruit syrup recipes (including the blackberry one which I'd like to try in season) say to leave the mashed fruit, covered, in a cool dark place for 2-3 days. Is this really safe? Wouldn't the fruit start to "ferment"?

[cedarblue]

i'd have thought so - is anything added to the fruit at the mashed stage? do you think the possible fermentation is necessary to the syrup making??