Kitniyot for Ashkenazim?

I have heard that under certain guidelines, the OU permits Kitniyot-derived products for Pesach, even for Ashkenazim; Can you please explain?

The minhag of Ashkenazim is to consider corn and all types of corn byproducts as kitniyot. Therefore, Ashkenazim will not eat corn syrup, corn alcohol or corn vinegar on Pesach. Yet Rav Belsky ruled that aspartame (an artificial sweetener commonly used in many diet products), although made from corn, may be used on Pesach. Aspartame is made by combining two amino acids (aspartic acid and phenylalanine). These amino acids are produced from corn through a fermentation process and neither one has a sweet taste. In fact, phenylalanine tastes bitter. Since the corn undergoes many steps during which it is fermented, reacted and then synthesized into a completely new molecule, we no longer view aspartame as a corn byproduct. This concept of losing halachic identity is known as “nishtaneh.” Although there is a disagreement among poskim as to whether one can rely on nishtaneh to permit non-kosher foods, and the OU does not permit that, Rav Belsky ruled that with regard to kitniyot, whose prohibition is only based on minhag, we are lenient.

The Gerald & Karin Feldhamer OU Kosher Halacha Yomis is dedicated to the memory of Rav Yisroel Belsky, zt"l, who served as halachic consultant for OU Kosher for more than 28 years; many of the responses in Halacha Yomis are based on the rulings of Rabbi Belsky. Subscribe to the Halacha Yomis daily email here.