ABSTRACT. Rendered proteins are well suited for animal nutrition applications, but due to their insolubility, inhomogeneity, and the presence of non‐protein substances, they are difficult to utilize in other applications. In an attempt to overcome these obstacles to utilization, three types of rendered proteins [meat and bone meal (MBM), feather meal (FM), and blood meal ( BM)] were partially defatted and then hydrolyzed to varying extents using calcium hydroxide or one of three enzymatic treatments, in 4‐ or 6‐L batches. After centrifugation, filtration, and spray drying, these hydrolysates were analyzed for changes in physical and chemical properties that relate to their potential utility. In all cases, the proportion of organic matter solubilized increased along with hydrolysis duration, although the molar mass distribution of the hydrolysis product only had a weak dependence on hydrolysis duration; the soluble material consisted of very small peptides at all time points. Alkalihydrolysis was not effective in yielding a product low in ash;