MSc Ulla Holopainen-Mantila has characterized in her doctoral thesis the formation of barley grain structure and the main storage proteins called hordeins under growth conditions typical to Northern Europe. In addition, the effects of the grain structure on end use properties in milling as well as in hydration and modification during malting were demonstrated.
Barley (Hordeum vulgare L.) is a globally important grain crop. The composition and structure of barley grain is under genotypic and environmental control during grain development, when storage compounds, mainly starch and protein, are accumulated. Grain structure plays a significant role in barley processing quality. Today, barley is mainly exploited as feed or as a raw material for malt production, but the use of barley as a food ingredient is increasing.
In this study, the longer photoperiod typical to latitudes in Southern Finland was shown to influence the hordein deposition during grain filling both at the tissue and subcellular level. Furthermore, the observed hordein localization was linked to improved, faster hydration of grains at the beginning of malting. Thus, the results suggest that the growing environment affects the end-use properties of barley and that especially the northern growing conditions have a positive impact on barley processing quality. Moreover, the role of the subaleurone region in barley grain was found to be significant with respect to end use quality.
The influence of sulphur application on hordein composition in the Northern European growing conditions was demonstrated for the first time in this doctoral thesis. Compounds poor in sulphur served as nitrogen storage pools when the sulphur application rate was lower than 20 mg S / kg soil. The current study also showed that even when sulphur is sufficiently available in field conditions, the hordein composition may react to sulphur application. The observed sulphur responses were in accordance with those reported earlier for hordein composition. This indicates that the more intensive growth rhythm induced in northern growing conditions does not alter greatly the effect of sulphur on grain composition.
The doctoral thesis of Ulla Holopainen-Mantila confirmed that the main grain components: starch, protein and β-glucan, influence grain processing properties including milling, hydration and endosperm modification. However, their influence on endosperm texture (hardness or steeliness), which also affects the performance of barley grains in these processes, cannot be directly derived or estimated on the basis of the grain composition. The results obtained suggest that hordeins should also be taken into account in the evaluation of the processing behaviour of barley grains.
Public examination on 20 March
The public examination of the doctoral dissertation of Ulla Holopainen-Mantila is held in University of Helsinki, Faculty of Biological and Environmental Sciences on 20 March at 12. The address is Biokeskus 2, auditorium 1041, Viikinkaari 5, Helsinki. The title of the dissertation is "Composition and structure of barley (Hordeum vulgare L.) grain in relation to end uses". Opponent is Prof. Giuseppe Perretti, University of Perugia (Italia).
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