Extruded flaxseed meal enhances the nutritional quality of cereal-based products

Key Findings

Flaxseed is a source of high-quality protein containing a number of essential amino acids. Lysine is the limiting amino acid in flaxseed and can be complimented by cereal and legume proteins. The objective of this study was to characterize the composition of extruded flaxseed meal compared with ‘raw’ flaxseed and to evaluate the nutritional quality of two fortified cereal based food products by biological and chemical indexes. Among non-essential amino acids, Glu was present in the largest amount in raw flaxseed, followed by Asp and Arg, Gly and Ser and, Ala and Pro, and no significant differences with extruded flaxseeds were found. Regarding essential amino acids, Leu was the most predominant, followed by Val, Thr, Lys, Ile, and then Met + Cys, His, and Tyr. Trp was the amino acid present in the lowest amount and extrusion did not cause significant differences. The results confirmed the stability of amino acids to extrusion conditions. Animal studies using the EFM diets showed biological value (BV) was fair (80) while true digestibility (TD) was low (73) possibly due to the high dietary fiber. The protein content of cereal bars was moderate (17.6 %) as was fiber (11.3 %).

Abstract

Human consumption of flaxseed is increasing due to its health benefit properties and extrusion processes can enhance its nutritional quality. Extruded flaxseed meal (EFM) obtained in a pilot plant was characterized and incorporated in flour mixes and cereal-based bars to demonstrate its nutritious usefulness. Amino acid content was not affected by extrusion and, despite lysine was the limiting amino acid, the chemical score (CS) was 83 %. Thiamin and riboflavin decreased slightly as consequence of extrusion, phytic acid did not change and trypsin inhibitor activity was undetectable. Proximate composition and nutritional quality determined by biological and chemical indexes were compared among EFM, flour mixes (FM) and cereal bars (CB). They presented high protein levels (26, 20 and 17 %, respectively), good biological value (BV) (80, 79 and 65, respectively), acceptable true protein digestibility (TD) (73, 79 and 78, respectively), and high dietary fiber (33, 20.5 and 18 %, respectively). The ratio of n6:n3 for CB was within the WHO/FAO recommendations. These results open a new venue for the usefulness of nutritious/healthy extruded flaxseed flours into ready-to-eat cereal-based products with improved nutritional quality.