Development of sustainable fish farming is relevant for meeting the growing seafood consumption. In light of the global protein shortage, the use of high quality protein ingredients in fish feeds should be reduced. The nutritional quality of novel protein sources which currently have a lower quality requires the upgrading through existing or novel processing techniques, to enable their application in fish feeds. The latter requires knowledge on key chemical and physical properties of pre-processed ingredients and their effect/relationship with processes that determine protein digestion in fish.
In this interdisciplinary project, knowledge from the fields of food chemistry/processing and fish nutrition is integrated. The project is built up of several parts: (1) identification of key components (i.e., indicators) in processed hydrolysates of feather meal and soybean meal (with a focus on feather meal); (2) their effect on in vivo digestion in fish; (3) the effect of critical processing condition on protein digestion, using the identified key components; and (4) the effect of feed matrix on in vivo and in vitro protein digestion. In the first part, different hydrolysates will be produced under a wide range of process conditions. These hydrolysates will be screened for the presence of key components presumed to be relevant. Next, a selection of these hydrolysates with wide ranges in the key components will be assessed regarding their in vivo protein digestion in fish in order to determine the essential key components/markers. These key markers will then be used to study the impact of pre-processing condition on the quality of feather meal hydrolysates. Finally, the in vivo digestion of “good” quality hydrolysates will be studied in relation to the ingredient matrix of the fish feed. Measurements will focus on in vitro and in vivo protein digestion of hydrolysates. Peptides in collected samples will be analysed and quantified by state-of-the-art UHPLC-MS. Trout is the species studied.