Question: Is vegan food already offered to the deceased suitable for eating?
Answer: The idea that post-offered food is unhealthy is not true. If not fit for eating, many who eat it should know this by now by falling sick on record. However, if exposed for long, check that it has not turned bad due to the weather.
For more peace of mind, you can recite the Buddha’s name (Āmítuófó) ten times before eating, to ask for blessings, to ensure the food is alright, so as to not waste it. (Out of reverence, do not offer post-offered food to the Triple Gem.)
Related Article:
Can We Eat Food After Offering At Shrines?
https://thedailyenlightenment.com/2015/05/can-we-eat-food-after-offering-at-shrines