Mayonnaise advise

Question

I am making vegan garlic mayonnaise at home using soy milk as an egg alternative. The taste is good on the day I make and bottle a batch. For some reason, however, after two days the mayo breaks up into curd in one bottle, and another bottle is bursting out and the mayo is fizzy. I'm not sure what could have gone wrong. Does anyone have any experience or knowledge on what happened, and how to fix it?

The ingredient I use: soy milk (slightly sweetened), Sunflower Oil, garlic, mustard, malt vinegar, agave syrup, pepper, salt, lemon juice, and a thickener (xantham gum).

Answer 1

The fizzing is a warning sign: There is unwanted life in your mayonnaise. The fizz indicates microbes - bacteria and/or yeasts - growing in your bottles. The fizz is likely CO₂, a byproduct of their digestive activities.

Any food with signs of unplanned and unknown fermentation processes is not safe and should be discarded.

You don’t mention any “sterilizing” or other preservation step and as you are using various raw ingredients, this was to be expected. Refrigeration can slow down the process, but won’t prevent it. A few days if refrigerated is the upper limit for a safe storage, but only if there are no signs of spoilage.

That said, I want to mention a second, rare but potentially lethal risk that your mayonnaise may contain: Botulism. Your ingredient list contains garlic and you are using it in an potentially anaerobic environment. (Your ingredient list doesn’t mention oil - that would create the classic “garlic in oil” scenario - but it’s almost certainly not acidic enough to be safe.) The danger of botulism is that it’s virtually unnoticeable for us humans. Unlike many spoilage processes, there is no smell or taste to warn us. And you won’t be cooking your mayonnaise, which could destroy the toxin. For garlic oil - and you can simply apply the same guideline in your case - the max storage time is a week in the refrigerator.

Answer 2

I did a search for a few vegan soy milk mayo recipes and the first three I found did not include the regular mayo rest period.

When making mayo with eggs, the acidic, fresh, mayo is allowed to sit at room temperature for a few hours to kill off some potential bacteria before refrigeration shuts everything down.

https://cooking.stackexchange.com/a/33331

First of all, the recommended period for this rest is around 8 hours not two days. Secondly, your risk of harmful bacteria is much lower as you are using processed ingredients instead of raw eggs. I would leave out the rest period altogether.

As for your results- As Stephie wrote, the bottle that was fizzing needs to be promptly discarded. Evidence of active bacterial action, unless you are intentionally fermenting, is a very very bad sign. Don't mess with it.

As for the other. Soy milk is fairly fragile; acidity and more so calcium can cause it to curdle into tofu. I wouldn't expect the acidity of the mayo itself to curdle the milk because there isn't that much milk and it is emulsified and thickened with gum. However, your curdled mayo is actually another sign of spoilage and you should throw it out.

In the future, to prevent this happening again, I would recommend simply not giving your mayo a chance to spoil and refrigerating it immediately. You might also experiment with using silken tofu instead of soy milk which, I've read, produces better results.