Limited nature of products considered kosher

Question

I was reading about the laws of bitul, though I've never learnt about them properly in any detail.

One example given in the book (An Artscroll book on kashrut) was that you can assume that a grocery store uses a knife only for watermelons... and that even if it's possible that the knife is not kosher, it would become so after a few cuts and the first few fruits cut would be nullified among the rest.

Based on the principles in this reasoning, why are some people extra stringent to avoid cholov stam milk and other products that are given kosher status by kosher lists but don't have a hechsher? It totally makes sense to me that you would want to avoid any possibility of contamination, but since it can apparently be nullified with a high enough quantity of the kosher ingredient (as would tend to be present), and since you can assume so much... what is the difference between the possibly non-kosher knife used to cut fruit and the machinery used to process something else? If it's heretical to say you can't eat actually non-kosher meat mixed in by accident with kosher meat in particular situations, then how is the extra caution necessary?

If there a factor of bitul only counting 'after the fact' so that you have to be cautious still with processes, why doesn't this apply in the case of the fruit from a grocery store? Is it because there more likelihood in the 'assumption' in that case? And if so, why the problem with cholov stam milk in the eyes of some people?

Answer 1

Some thoughts to consider.

• One is not allowed to mix up foods on purpose in order that they should become batel (nullified). For instance, if I have two pieces of Kosher meat and one piece of not-Kosher meat, I can't mix them up so that bittul would apply and I would have three pieces of edible meat. If I do this the law of bittul doesn't apply and all three pieces are considered forbidden for me to eat.

• Sometimes, arguments about if a certain food is kosher do not surround the laws of bittul. For instance, some say swordfish is kosher, while most differ. Some say the prohibition on eating new grain does not apply in the Diaspora, while most differ. Some say that adhesions on a cow's lung render the meat not kosher, while others differ. In these cases whether or not one accepts the product as kosher is independent of standards of supervision.

Answer 2

Cholov Akum is its own decree. In other words, it would have been completely kosher if not for the extra decree against it (like Pas Akum or Bishul Akum, which are intrinsically kosher yet there is a decree against consuming it).

The question is

1. Is Chalav Akum a decree "with a reason" which can be nullified if the reason doesn't exist (so that countries where Kosher milk is cheaper would not require supervision) - the opinion of the Pri Chadash or is it an intrinsic prohibition (such that one needs a Beis Din greater than the one that enacted the prohibition to cancel it)
2. Is government supervision considered "us seeing" (R' Moshe Feinstein) or not?

Source: http://rabbikaganoff.com/archives/1789