Development of High-Protein Oat for the Feed and Food Industry

Abstract: Oats are an excellent source of high-quality proteins, with a favourable amino acid composition. Oat proteins therefore have greatpotential to complement existing animal and plant protein sources, especially if the protein content could be increased. In this thesis,high-protein oat lines were identified and characterised. More than a thousand individual lines in a mutagenised oat population(Targeting Induced Local Lesions in Genomes (TILLING) population) were screened for total protein using an elemental particleanalyser. This identified 230 lines with a seed protein content of 15% protein or higher. Belinda, the original variety from which themutagenised population was constructed, had approximately 12%, and the most protein-rich line had 24%.The amino acidcompositions for 31 of the high-protein lines were determined by various methods, and the contents of essential amino acids (EAA)were evaluated according to the FAO/WHO amino acid recommendations. This showed that several of the high-protein linescontained sufficient levels of EAAs, although there was some variability in the amounts of nutritionally limiting amino acids. Severallines had higher EAA levels than Belinda. Five of the high-protein oat lines were selected for asymmetric flow field-flow fractionation(AF4) analysis. In all experiments the AF4 instrument was connected to an online multi-angle light scattering (MALS) and ultraviolet(UV) detection system. Greater variation was found in the quantity of soluble proteins in the different high-protein lines than in Belinda,and a few lines had clearly elevated levels of globular proteins. Sodium-dodecyl sulphate polyacrylamide gel electrophoresis (SDSPAGE)also revealed that the increase in protein in the high-protein lines was mainly due to an increase in the globulin fraction. Theeffect of heat treatment on the soluble protein content in oat groats was also evaluated, using the AF4 system and amino acidanalysis. The results showed that the total amount of soluble protein was reduced by 50%, mainly due to a reduction in amino acidsassociated with albumin and water soluble prolamins. An attempt was made to increase protein content by nitrogen fertilisation, andeffects on grain quality were also analysed using avenin protein of Belinda oat cultivars grown or developed under various fields andin the greenhouse as a reference. Results showed that excess nitrogen fertilisation (≥ 100 kg/ha) increased total protein percentagein Belinda and high-protein oat lines. Furthermore, oat lines grown under field conditions showed differences in avenin proteins whencompared to the corresponding lines grown in the greenhouse, as analysed by SDS-PAGE gel electrophoreses. This may explainthe differences in protein levels in cultivars grown under different environmental conditions. Crosses were performed between the sixlines with the highest protein levels and the original non-mutated Belinda variety from which the mutagenised population was derived.The F1 hybrid seeds were grown in a greenhouse, and self-pollinated and individual seeds from the F2 offspring were analysed. Thisshowed that the high-protein character was stably inherited. To test this further, the 15 high protein lines were amplified in severaldifferent plots in the field and the protein content was again determined in seeds harvested at the end of the season. This confirmedthe stability of the high-protein character. Total dietary fibre (TDF), ß-glucan and lipid levels were also measured in the selected lines.The analysis showed that the values for these components were normally distributed around the original level in Belinda, i.e. therewas no positive or negative correlation between fibre, ß-glucan, lipid and high protein content. In conclusion, the high-protein oatlines, identified here from an oat mutagenised population, proved to be phenotypically stable in the field and produced high-qualityproteins. When developed further, the resulting cultivars will be very valuable for future use in the food and feed industry. Total dietaryfibre, especially soluble and insoluble fractions andβglucans, is high in these lines, which is another important benefit in the use ofhigh-protein oat lines for food applications. Since oats in general give good yields and quality, especially in the Nordic countries, thelines presented here have potential to become a new source of vegetable proteins and will enable the development of novel foodproducts based on oat.