Abstract: An inventive method and a device for the biotechnological reduction of sugar substances in fruit educts for the purpose of obtaining low-sugar fruit products characterized by enzymatic and/or fermentative reaction processes. Said method is characterized by a closed-loop control process, by means of which the pH value in the low-sugar fruit product is adjusted to a predetermined higher value, as compared to the pH value in the fruit educt, in such a way that during the reduction of the sugar substances by at least 30% by weight to less than 40% by weight, the pH value is increased between 0.6 and 1.0 pH units; or that during the reduction of the sugar substances by at least 40% by weight to less than 50% by weight, the pH value is increased between 0.7 and 1.1 pH units; or that during the reduction of the sugar substances by at least 50% by weight to less than 65% by weight, the pH value is increased between 0.8 and 1.