In order to get high quality proteins from herring by-products,suitable for human consumption, it is important to choose the righttechnological process as well as the optimal process conditions.We tested two different processes, and concluded that the thermalextraction of herring by-products is a better technological choicecompared to hydrolysis, when it comes to the amount and qual-ity of separated oil and color of soluble protein powders. Neitherthe seasonal variations in raw material, nor enzymes used in theprocess, influenced the color of hydrolysates, but time and temper-ature of the processes can be an important tool for controlling thecolor. No significant differences were observed, between bitternessof hydrolysates and stick water samples, by comparing samplesobtained from two different seasons, but both process conditionsand the enzymes used play an important role for the formationof bitterness. Insoluble fractions had significantly higher proteinefficiency ratio compared to soluble fractions, but no significantdifferences were obtained by comparing fractions after differentprocessing.