This is a bit of a strange question, but may a small amount of soap or detergent be placed in the water when cooking with sous vide? Is the vacuum effective enough to prevent any taste of soap from entering the food contents? Thank you
This depends on the bag used. Most zip style bags are not impermeable. Whether or not a soap flavor or aroma molecule is large enough to permeate is something I do not know. However, as suggested in the conversation above, you can use a vacuum sealer, and the appropriate bags (more impermeable) to seal a bag within a bag. I think you would be good to go in this scenario.
I'd be concerned with two things here.
First of all, I'd be concerned that some soap might contaminate the food product without you knowing about it. If it's a low enough concentration of soap that it would not cause significant harm to ingest, this isn't a big concern; on the other hand, I might be inclined to use something other than actual soap that is able to accomplish the purpose here if that is possible - for example, a mild bleach solution (I've also seen "pool shock" suggested) might be safer. Do some research on whatever you add to make sure it's actually okay for this purpose. If your purpose is to remove bacteria, this is probably your best bet.
Second, I'd be concerned with odors from the soap affecting the food being cooked. Even if the soap never contacts the food, the odors that make the soap smell good are much more likely to affect things in my experience. If you do use soap, use an odorless soap (something like original (blue) Dawn, no endoresement suggested).
If you can edit the question to provide more of an explanation as to why you're asking it (you mention Kosher laws, but not the specific issue you're trying to address) you may get a better answer.
If you really want to be sure, then use a retort bag to vacuum seal the food. The retort bag is not gas permeable so you don't have to worry about any soap aromas affecting the food.
Retort bags are usually made from multi layer laminated plastic sheeting designed specifically to be gas impermeable and heat resistant.