Corn gluten meal (CGM) is a high protein (60% crude protein), highly digestible feed ingredient widely used in diets for salmonids, however its use has been related to reduction in muscle pigmentation possibly due to pigment interaction. Therefore, laboratory scale and in vivo trials were conducted to reduce pigment level in CGM and to assess its effect on fish muscle pigmentation, respectively. In the first chapter, a bench-scale study was carried out to investigate factors that affect bleaching of carotenoids in CGM, using white soy flake flour (WSFF) as a lipoxygenase (LOX) source. Plackett-Burman and Box-Behnken designs were used to screen and optimize factors, respectively. Furthermore, a 12-week growth trial was conducted in order to assess the effects of dietary regular and pigment bleached CGM on growth and muscle pigmentation of rainbow. In the second chapter, a 24-week growth trial was carried out in order to assess the effects of increasing levels of CGM on growth and muscle pigment deposition in rainbow trout. In the third chapter, a bench-scale (10 g) corn wet milling procedure was used to assess the bleaching of carotenoids from CGM during steeping. Studies from this thesis confirmed the negative effects of CGM on fillet pigmentation and highlighted the need for evaluation of muscle quality traits such as colour in response to inclusion of new feed ingredients. Furthermore, this thesis gives insight on how to reduce pigments from corn gluten meal using cost-effective and practical bleaching approaches.