Brown spot in my sake batch

Please advise O Great Sake Brewers!

I was finishing up a large batch of sake (8 cups dry rice) and about a week before pulling, I turned the jug to notice a large brown spot in the rice. I periodically checked the smell throughout the fermentation to see if it was off, but it smells sweet and magical. I was hoping someone might know what this is, if it is bad - like botulism bad or just some random fluke. I am attempting pasteurization in case it is ok or this kills weird bacteria, but if it is a wasted batch, I am ok dumping it before poisoning myself or friends.

If the brown spot has no hair on it and it looks more like the rice sludge is just changed color rather than something growing on it then it sounds like oxidation. If your yeast pooped out too early and did not survive the long cold fermentation spell of Sake brewing then that may be the case. Just strain and press the Sake like normal and once it is cleared with finnings and bottled or if you like it cloudy like Mirin then make sure to heat pasteurize each bottle. It should be fine. If you are just cold crashing and trying to clear without finnings I would use a Camden tablet crushed up mixed in after the Sake lees are pressed to help prevent further oxidization.

Thank you! That is what it appeared to be - it was all subsurface and in the sake liquid. That is a relief!

I will continue on with it - I appreciate the input!