The use of HPLC for quality prediction of South African wheat cultivars

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Date
2004-11
Authors
Meintjes, Gisela Diana
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Publisher
University of the Free State
Abstract
English: The primary aim of this study was to determine whether size-exclusion high performance liquid chromatography (SE-HPLC) could be used for quality prediction of South African wheat cultivars. · A bread cultivar, a cracker cultivar and two soft wheat cultivars were used in this two-year experiment. · Protein extracts of wheat flour were analysed by SE-HPLC. · SDS was used for the first protein extraction step, and the rest of the proteins were extracted by sonication. · The SE-HPLC method fractionated the storage proteins (both SDS-soluble and SDS-insoluble) into four distinct peaks of decreasing molecular size range, representing mainly larger polymeric proteins (mainly HMW-glutenins), smaller polymeric proteins (mainly LMW-glutenins), larger monomeric proteins (mainly gliadins), and smaller monomeric proteins (mainly albumins and globulins). · The wheat samples were also analysed for a total of 11 important quality characteristics. · Relationships between the amount and size-distribution of polymeric and monomeric proteins and flour quality properties were established. · The influence of different nitrogen (N) treatments on protein fractions and quality characteristics was also determined by SE-HPLC.The results showed that both the genotype and N-treatments had a significant influence on quality characteristics. · However, the genotype (cultivar effect) had a more significant influence on the protein fractions and quality characteristics than the N-treatments. · The total amounts of N applied during the treatments had a more significant eff ect on protein fractions and quality characteristics than later N-applications (N applied during the flag leave stage). · The SDS-soluble and SDS-insoluble polymeric proteins were found to be equally important in quality prediction. · The hard wheat cultivars were characterised by an increase of polymeric protein as opposed to monomeric protein. · The polymeric proteins (glutenins) were strongly positively correlated with dough strength properties, such as alveograph P/L ratio and alveograph strength. · The large monomeric proteins, which are mainly gliadins, were positively associated with the soft wheat cultivars, and had a consistently significant negative effect on quality characteristics, such as falling number (FLN), vitreous kernels (VK), alveograph P/L ratio and alveograph strength. · The large monomeric proteins showed positive correlations with single kernel weight (SK weight), single kernel diameter (SK diameter) and breakflour yield (BFLY). · SE-HPLC provided a simple and an objective test for measuring the relative size-distributions of wheat storage proteins. · SE-HPLC also proved to be very usefull in predicting quality.
Afrikaans: · Die hoofdoel van die studie was om te bepaal of SE-HPLC aangewend kan word vir kwaliteitsbepaling van Suid-Afrikaanse koring kultivars. · ‘n Broodkoring kultivar, ‘n kultivar vir cracker produksie en twee sagte koring kultivars is ontleed gedurende hierdie twee jaar eksperiment. · SE-HPLC is gebruik om prote ïen ekstrakte van die meel ontleed. · SDS is gebruik tydens die eerste ekstraksie prosedure. Die SDSonoplosbare proteïene was daarna met behulp van sonifisering geëkstraheer. · The SE-HPLC metode het die bergingsproteïene (beide SDS-oplosbare en SDS-onoplosbare) in vier duidelike fraksies verdeel volgens hul molekulêre gewig. Die vier fraksies (of pieke) het bestaan uit groter polimeriese proteïene (hoofsaaklik hoë molekulêre gewig gluteniene), kleiner polimeriese proteïene (hoofsaaklik lae molekulêre gewig gluteniene), groter monomeriese proteïene (hoofsaaklik gliadiene) en kleiner monomeriese proteïene (hoofsaaklik albumiene en globuliene). · Die koringmonsters is getoets vir 11 belangrike kwaliteitseienskappe. · Die verwantskappe tussen die hoeveelhede en grootte-verspreiding van polimeriese en monomeriese proteïene en kwaliteitseienskappe is bepaal. · Die invloed van verskillende stikstofbehandelings op die proteïenfraksies en kwaliteitseienskappe is vasgestel met behulp van SE-HPLC. · Die resultate het getoon dat beide die genotipe en die verskillende stikstofbehandelings gelei het tot betekenisvolle verskille in die kwaliteitseienskappe. · Die effek van die genotipe of kultivar op die proteïenfraksies en kwaliteitsei enskappe was egter baie belangriker en duideliker as die effek van die verskillende stikstofbehandelings. · Die totale stikstof-hoeveelhede wat toegedien is, het meer betekenisvolle resultate getoon as latere stikstoftoedienings. · Die SDS-oplosbare en SDS-onoplosbare polimeriese proteïene was ewe belangrik in die voorspelling van koringkwaliteit. · Die harde korings was gekenmerk deur ‘n verhoogde polimeriese:monomeriese proteïen -verhouding. · Die polimeriese proteïene (gluteniene) was sterk gekorreleer met deegsterkte en kwaliteitseienskappe soos alveogram P/L verhouding en alveogram sterkte. · Die groter monomeriese proteïene (gliadiene) was positief geassosieer met die sagte kultivars en het betekenisvol negatief gekorreleer met kwaliteitseienskappe soos valgetal, glasagtige korrels, alveogram P/L verhouding en alveogram sterkte. · Die groter monomeriese proteïene het positiewe korrelasies getoon met korrel-massa, korrel -deursnee en breekmeel. · SE-HPLC was ‘n relatief eenvoudige en objektiewe metode om die grootte-verspreiding van bergingsproteïene te bepaal. · SE-HPLC was ook baie effektief vir die voorspelling van koringkwaliteit.
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Keywords
Dissertation (M.Sc. (Plant Sciences))--University of the Free State, 2004, Wheat -- South Africa, Wheat -- Quality -- South Africa, Monomeric proteins, Polymeric proteins, SE-HPLC, Baking quality, Plant proteins -- Analysis, High performance liquid chromatography
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