Abstract: The present invention provides a method for adjusting the yield and purity of a proteinase inhibitor extract from plant tissue, preferably potato tubers. The extraction and isolation of the proteinase inhibitor from potatoes begins with the addition of an organic acid, preferably formic acid, and a salt, preferably sodium chloride, to raw potatoes. The mixture is subjected to process steps to extract soluble proteins. The extract is subjected to heat treatment at an adjusted temperature and adjusted duration whereby purity of the proteinase inhibitor is enhanced by heating at a relatively high temperature for a relatively short duration and whereby yield of the proteinase inhibitor is enhanced by heating at a relatively low temperature for a relatively long duration. If the removal of soluble protein impurities that are not denatured during the heat treatment step is desired, ultrafiltration is used. By adjusting the cycles of filtration, purity of the proteinase inhibitor can be adjustably selected.

Abstract: A method for preparing a product of a protein and carotenoid. The carotenoid is added to a solvent. A source of metal ions and a source of proteins is added. The protein and carotenoid product is extracted from the solution in order to demonstrate binding of the lutein to the proteins. The protein and carotenoid product is substantially soluble in water and increases the ability to add the carotenoid to water-based systems, such as foods, beverages, and personal care products. The protein and carotenoid products are particularly suited for use in human supplements where it is desired to add both the protein and the carotenoid to the diet.