Replacing fish meal with untreated and enzymatically treated torula yeast (Cyberlindnera jadinii) affects pelleting die flow resistance and physical properties of the feed pellets
Among novel feed ingredients, yeast has gained significant importance. Fishmeal typically provides superior feed conversion ratios (FCR) in farmed aquatic organisms compared to most alternative ingredients. However, published data suggests that the yeast Cyberlindnera jadinii is a promising alternative. This study demonstrates that replacing fishmeal with torula yeast, either untreated or treated with protease and endo-exo 1.3-{beta}-glucanase, reduces feed material resistance in the pelleting die during pellet discharge. It also investigates how enzyme-treated yeast affects pellet quality. Experiment 1 examined changes in flow resistance and pellet quality when fishmeal was replaced by yeast. Experiment 2 assessed the impact of enzyme-treated yeast on pellet flow resistance and physical quality. Results showed a significant increase in flow resistance in diets with 20% yeast and enzyme-treated yeast. The tensile strength of pellets with 20% yeast increased in both experiments. Pellets with 10%, 20%, and 100% yeast exhibited aquaphobic behavior compared to those without yeast, which benefits feed consumption, reduces wastage, and supports sustainable feed manufacturing. However, pellets with 10% and 20% enzyme-treated yeast showed lipophobic behavior, which is less ideal during post-production processes. Enzymatic treatment reduced underwater swelling of pellets with 10% and 20% yeast. Minimal enzymatic hydrolysis is recommended to lower underwater disintegration. The longitudinal surface roughness of pellets decreased with enzyme-treated yeast, with pellets containing 20% treated yeast showing the lowest surface roughness.