What is the main challenge posed by low levels of mould growth during sake fermentation?

The main challenge associated with low levels of mould growth during sake fermentation stems from the insufficient production of enzymes necessary for converting starches into fermentable sugars. The key player in this process is the mould Aspergillus oryzae, which is crucial for saccharification—the conversion of starch to sugar. If mould growth is low, the quantities of enzymes like amylase may not be adequate, limiting the effective breakdown of starches.

As a result, if the enzymes are not produced in sufficient quantities, there may be a risk that the yeast runs out of available sugars to ferment. This can halt fermentation prematurely, preventing the production of alcohol and leading to a sake that is lower in alcohol content and potentially lacking in complexity. Therefore, adequate mould growth is essential to ensure there are enough enzymes for sugar conversion and a successful fermentation process.