What substance is used in sour mashing to enhance fermentation?

The substance used in sour mashing to enhance fermentation is backset from previous distillation. Sour mashing is a technique in whiskey production where a portion of the mash from a previous distillation is added to the new mash. This process introduces lactic acid bacteria along with additional nutrients that are beneficial for yeast activity. As a result, backset helps to create a slightly acidic environment that promotes fermentation and contributes to the overall flavor profile of the final spirit.

Moreover, the use of backset can improve the consistency and stability of the fermentation process, as it helps maintain the pH levels conducive to yeast activity. This leads to more efficient fermentation and can enhance the complexity of the whiskey being produced.

While fresh yeast, water, and molasses can all play roles in fermentation processes, they do not specifically align with the unique characteristics provided by backset in the sour mashing technique.