Effect of diammonium phosphate (DAP) on fermentation dynamics in fruits from non-fertilized meadow orchards

The fermentation characteristics of five apple and five pear varieties from non-fertilized meadow orchards (“Streuobstwiesen”) was studied. While some varieties fermented without problems, some varieties showed sluggish and stuck fermentation with high residual sugar concentration at the end of the fermentation period. A potential reason for these fermentation problems could be a poor nitrogen supply. The effect of diammonium phosphate (DAP) supplementation on the fermentation dynamics was studied over two consecutive years, with 200.0 mg/L DAP added on day 0 or day 3 of fermentation. DAP effectively prevented stuck fermentations and accelerated sluggish fermentations. In particular, in the 2021 harvest, early DAP addition reduced the fermentation time by up to 6 days. The studied pear varieties indicated a greater demand for additional nitrogen compared to apple mashes. In general, nutrient addition proved beneficial for yeast cell growth of all ten fruit mashes. These findings suggest that the correct use of DAP could enhance the fermentation process in fruit mashes with low nutrient supply, which might be crucial for producing high-quality distillates from meadow orchard fruits.