No abstract

. 1999. Measuring polyphenol oxidase activity in a wheat breeding program. Can. J. Plant Sci. 79: 507-514. High levels of polyphenol oxidase (PPO) have been associated with discoloration of end-use products of wheat, especially certain noodle types. Two whole-seed methods of measuring PPO, one based on 10 mM tyrosine as substrate and the other on 90 mM catechol, were examined and modified to determine their potential as screening tools in large-scale breeding programs. Thirteen spring wheat and two spring triticale genotypes were used to compare the methods. Both methods could measure PPO on individual seeds. All genotypes displayed large seed-to-seed variation for PPO with both substrates. The mean coefficient of variation for the PPO values of individual seeds within genotypes was 39% with tyrosine and 34% with catechol. Furthermore, the PPO values of individual seeds within genotypes were not normally distributed for most genotypes. Identifying genotypes with incremental improvements in PPO would probably require measurement of 70-100 seeds. Approximately 50% of the catecholase activity was associated with the water extract after soaking seeds for 16 h, while all of the tyrosinase activity was still associated with the seed, suggesting that different enzymes are responsible for oxidizing tyrosine and catechol in wheat. While the 10 mM tyrosine assay was nondestructive and allowed plants to be generated from seeds low in PPO, 90 mM catechol reduced germination to less than 20%. Reducing the catechol to 30 mM improved germination to 85%, did not substrate-limit the reaction, and reduced the health risk associated with the assay. Spectral and kinetic differences between the assays were also considered. . Des niveaux élevés de polyphénol oxydase (PPO) ont été associés avec la coloration anormale des produits du blé, en particulier certains types de nouilles. Deux méthodes de mesure sur le grain entier utilisant comme substrat, l'une un milieu à 10 mM de tyrosine, l'autre à 90 mM de catéchol, étaient comparées puis modifiées pour déterminer leur utilité comme outil de triage dans les grands programmes de sélection génétique. Treize génotypes de blé de printemps et deux de triticale de printemps étaient utilisés pour comparer les deux méthodes. Chacune de ces dernières a permis de mesurer la PPO sur des grains individuels. Dans les deux substrats tous les génotypes manifestaient de fortes variations de la PPO d'un grain à l'autre. Le coefficient moyen de variation des valeurs PPO à l'intérieur d'un même génotype était de 39 % avec la tyrosine et de 34 % avec le catéchol. En outre, pour la plupart des cultivars étudiés, ces valeurs ne suivaient pas une distribution normale. L'identification de génotypes possédant des valeurs PPO plus élevées demanderait probablement un échantillon de 70 à 100 grains. Approximativement 50 % de l'activité catécholasique était associé à l'extrait aqueux obtenu par trempage des grains pendant 16 h, alors que l'activité de la tyrosinase était encore entière-ment associée avec le grain, f...

Background and objectives The conventional method for determining oil absorption capacity (OAC) in pulse ingredients involves mixing a sample with excess oil, centrifuging the dispersion, and then calculating the amount of oil absorbed. However, there are issues associated with the conventional method such as loss of the less dense materials through oil decanting process and reabsorption of oil by samples after centrifugation. Therefore, the objective of this work was to develop a method that could eliminate those concerns for determining OAC. Findings A method for measuring OAC of flours or protein concentrates/isolates derived from pulses and soybeans was developed. The new method involved mixing 0.5 g sample with 1.5 ml canola oil intermittently for 20 min, centrifuging the inverted sample tubes at 600 ×g for 25 min, and measuring the amount of oil absorbed per gram of dry sample. Comparing to the conventional method, the new method used a lower sample to oil ratio (1:3 g/ml), and each test tubes were centrifuged upside down in an apparatus at a lower centrifugal force (600 ×g). A syringe barrel was used in the apparatus to hold a filter paper in place to prevent sample materials from draining out with the excess oil during centrifugation. Test efficiency increased due to combining steps of centrifugation and oil draining in the new method. Differences in OAC values determined by the new method were exhibited from various pulse and soybean materials. Conclusions Amounts of oil absorbed by flours and protein concentrates/isolates from pulses and soybeans could be measured by the new method without accounting for the extra free oil trapped in the samples. The new procedure showed good within‐laboratory reproducibility. More samples could be tested with the new method due to its simplified procedure. Flours and protein concentrates/isolates from pulses and soybeans with different OAC values could be separated from each other using the new method. Significance and novelty The method developed was simple and reliable and could be applied to a variety of pulse and soybean ingredients.

Background and objectives: Air classification is a physical process based on particle size and density used to separate pulse flours into protein and starch concentrates. Little information is available on how variety and crude protein content affect physicochemical and functional properties of the air-classified yellow pea proteins. The objective of this work was to investigate the effect of flour protein content on particle size (PS), yield, protein separation efficiency (PSE), composition, anti-nutritional factors, and functionality of the air-classified protein concentrates derived from commercially grown yellow pea varieties.Findings: Pea protein concentrates obtained from high-protein flours had lower PS, PSE, starch, insoluble and total dietary fiber (IDF and TDF), sucrose, raffinose, and stachyose, but higher protein, foaming capacity (FC), and foaming stability (FS) at 30-120 min than that from low-protein flours. Crude protein of the pea flours had no significant effect on yield, ash, soluble dietary fiber (SDF), phytic acid (PA), trypsin inhibitor activity (TIA), water-holding capacity (WHC), oil absorption capacity (OAC), and oil emulsion capacity (OEC) of the corresponding protein concentrates. Among pea varieties, PS, yield, starch, IDF, TIA, sucrose, oligosaccharides, and FS at 30 min of the protein concentrates varied significantly but their PSE, protein, ash, SDF, PA, WHC, OAC, OEC FC, and FS at 10, 60-120 min remained similar.Conclusions: Air classification is better suited to using high-protein pea flour due to low oligosaccharides, high-protein concentration, and foaming properties of resulting protein fractions compared to concentrates derived from low-protein peas. However, lower PSE could be a concern due to presence of more small starch particles in the high-protein pea samples. Significance and novelty:This study showed the relationships between flour protein content and characteristics of the air-classified protein concentrates from yellow peas and identified areas for improvement.