Wheat gluten in extruded fish feed: effects on morphology and on physical and functional properties

Abstract

This article focuses on understanding the role of vital wheat gluten on the structural parameters of extruded fish feed and its correlation to the physical and functional properties. Gluten–soy protein concentrate blends with five gluten concentrations (0–200 g kg−1) were produced. An abrupt reduction in oil uptake was observed with the 200 g gluten kg−1 blend. Inclusion of gluten from 100 to 200 g kg−1 resulted in unacceptable product properties. Sinking of feed pellets with 0 and 50 g gluten kg−1 was 100%, whereas only 36% of pellets with 200 g gluten kg−1 sank. We suspect that this is due to a relationship between morphological structure and oil impregnation during coating of feeds. The addition of gluten at 200 g kg−1 gave a smoother and non‐porous outer surface. Pellets without gluten had a larger number of cells that were smaller than 200 μm (P < 0.05) compared with pellets with 100 and 200 g gluten kg−1. More spherical cell shapes (P < 0.01) and a compact structure were favoured in the presence of gluten. The closed porosity increased (P < 0.05), whereas interconnectivity between pores decreased (P < 0.01), with increasing gluten content from 0 to 200 g kg−1. The effects of the addition of gluten are probably related to the film‐forming properties of gluten.

Feed technological and nutritional properties of hydrolyzed wheat gluten when used as a main source of protein in extruded diets for rainbow trout (Oncorhynchus mykiss)

“…HWG also affected porosity of the extrudate and pellets in a different manner than the fish meal, as illustrated by increased diametric expansion by increasing dietary HWG to 25%, and the increased lipid loss following substitution of fish meal by HWG. Draganovic et al (2013) found that replacement of soy protein concentrate with wheat gluten resulted in decreased oil absorption capacity. In contrast to what was observed in this experiment where HWG replaced fish meal, Draganovic et al (2013) found that replacing soy protein concentrate by wheat gluten reduced lipid loss from extruded feed.…”

“…Draganovic et al (2013) found that replacement of soy protein concentrate with wheat gluten resulted in decreased oil absorption capacity. In contrast to what was observed in this experiment where HWG replaced fish meal, Draganovic et al (2013) found that replacing soy protein concentrate by wheat gluten reduced lipid loss from extruded feed. They ascribed the effect to gluten's causing larger cells with spherical cell shape and a more compact surface structure than did the soy protein concentrate.…”

Thoughts for the Future of Aquaculture Nutrition: Realigning Perspectives to Reflect Contemporary Issues Related to Judicious Use of Marine Resources in Aquafeeds

“…• Screw configuration affects pellet durability. Lin et al 1997;Sorensen et al 2002;Glencross et al 2010Glencross et al , 2012Morken et al 2011;Sorensen 2012;Draganovic et al 2013;Samuelsen et al 2013Samuelsen et al , 2014Oehme et al 2014 pelleted, sinking diets, but they are critical considerations for the commercial-scale manufacturing of extruded feeds. When testing new raw materials or formulations, nutrition researchers are encouraged to ask themselves-or, better yet, to ask extrusion scientists-questions such as "Can this formulation actually be extruded?…”

A combination of corn gluten and soybean meal as a substitute for fishmeal in diets of turbot (Scophthalmus maximusLinnaeus, 1758) in brackish water

“…An up to 52% blend of SBM, WGM and CGM (at a ratio of 42.6 : 42.6 : 14.7, respectively) (about 24 g) can be incorporated into juvenile turbot diets (Bonaldo et al., ). However, despite being a valuable protein source, WGM is still very expensive compared to other proteinous ingredients including FM (Gatlin et al., ) and a high (>10%) WGM incorporation leads to unwanted pellet extrusion characteristics (Draganovic et al., ). Therefore, testing alternative mixtures with limited WGM at certain levels would be expedient in diets of larger sized turbot compared with previous studies.…”