The present invention relates to a process for selectively removing undesired oligosaccharides from aqueous mixtures such as plant processing waste products, including soy whey and other vegetable wheys, using an ultrastabilized large pore, hydrophobic zeolite Y. The resulting solution, which contains isoflavones and digestible sugars such as glucose, fructose and sucrose, can serve as the basis for a nutritious new product.