Combined effect of mild pretreatment and fungal fermentation on nutritional characteristics of canola meal and nutrient digestibility of processed canola meal in rainbow trout

Authors: ALHOMODI, AHMAD - South Dakota State University; KASIGA, TOM - South Dakota State University; Berhow, Mark; BROWN, MICHAEL - South Dakota State University; GIBBONS, WILLIAM - South Dakota State University; KARKI, BISHNU - South Dakota State University

Submitted to: Journal of Food and Bioproducts Processing
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/4/2022
Publication Date: 3/9/2022
Citation: Alhomodi, A.F., Kasiga, T., Berhow, M.A., Brown, M.L., Gibbons, W.R., Karki, B. 2022. Combined effect of mild pretreatment and fungal fermentation on nutritional characteristics of canola meal and nutrient digestibility of processed canola meal in rainbow trout. Journal of Food and Bioproducts Processing. 133: 57-66. https://doi.org/10.1016/j.fbp.2022.03.002.
DOI: https://doi.org/10.1016/j.fbp.2022.03.002

Interpretive Summary: This study characterized the use of water washing and fungal culture fermentation pretreatment of defatted canola seed meals as an ingredient in fish feed meals. Canola is a major oilseed crop, and the seed meal that remains after oil extraction has an excellent protein composition for animal feed applications. However, there are anti-nutritional factors such as glucosinolates, phytic acid, and high fiber that limit its use in animal feed. In this study, HECM was washed with water to improve its protein composition and remove anti-nutritional factors. During wash step significant amount of anti-nutritional factors were removed providing a washed meal with higher levels of proteins and amino acids. Fermentation of washed canola meal with fungal cultures, similar to the preparation of yogurt, resulted in higher protein and amino acid content when compared to the uninoculated controls. Based on these findings, pretreatment with mild water washing and/or fermentation enhances the nutritional availability in canola meal. These results provide insight for the development of new uses of canola meal for food and feed products with improved nutritional characteristics.

Technical Abstract: The effects of mild pretreatment with fungal fermentation on the nutritional characteristics of hexane extracted canola meal (HECM) was examined. HECM is a by-product of canola oil extraction process and has restricted use in animal diets due to the presence of high levels of antinutritional factors (ANFs) and limited digestibility resulting in low nutrient availability. In this study, HECM was washed with water at different solid loading rates (SLR) to remove soluble ANFs. During wash step significant amount of soluble carbohydrates and glucosinolates were removed from the HECM which yielded washed meal with higher levels of proteins and amino acids when compared to the raw HECM. A protein digestibility test was conducted using Rainbow trout with feed that had 30% of fish meal replaced with washed HECM. The studies showed that the experimental meal exhibited higher protein digestibility than raw HECM. Fermentation of washed HECM and raw HECM with single and mixed cultures of Aureobasidium pullulans, Neurospora crassa and Aspergillus niger resulted in higher protein and amino acid content when compared to the uninoculated controls. Additionally, different strains under single and mixed culture fermentations exhibited varied reduction in the ANFs. Based on these findings, pretreatment with mild water washing and/or fermentation enhances the nutritional availability in HECM.