Problem with mold growing on sake rice

[Dehitay]

I just failed my first attempt at making sake. I washed, soaked, cooked, and cooled the rice. Then I added the kouji yeast and mashed it together, threw the mash into a muslin bag, put the bag in a jar, and covered it. This was about a week ago. I decided to open the jar to check on the progress and there's mold growing on top of the rice.

I'm not sure what I did wrong and I don't want to try again just to have the same thing happen. Is there anything I can do to stop this from happening again? The kouji yeast is more expensive than regular yeast. Should I add water to the top of the rice after putting it in the jar or something? Is the likely problem that I failed to sanitize something properly? I could really use some advice to avoid repeating the mistake.

 

[NosArtur]

What color was the mold? White and slightly fuzzy, like velvet, or some other color? Did it look something like this?

The image is of koji. Koji is the mold that breaks down the rice so that the yeast can metabolize the sugars. Not sure how you can make sake without mold.

 

[Dehitay]

What color was the mold? White and slightly fuzzy, like velvet, or some other color? Did it look something like this?

The image is of koji. Koji is the mold that breaks down the rice so that the yeast can metabolize the sugars. Not sure how you can make sake without mold.

It is white and fuzzy, but it also has a lot of green areas in it as well. I've never actually seen what the rice in sake looks like during or after the fermentation process. I had assumed it mostly stays the same with maybe some discoloration. Is this normal?