Browsing by Subject "rye"

Nitrogen leaching is the main cause of nitrogen loss from Finnish agricultural soils. Nitrogen leaching can exceed 20 kg/ha/year. The Finnish waters and the Baltic Sea are affected by nitrogen leaching due to that nitrogen increases algae blooming. Studies have shown that the loss of nitrogen can be decreased by cultivating catch crops. Nitrogen leaching can in some cases be decreased by up to 90 %. In Finland catch crops are seldom grown. Catch crops are thought to be too costly and time consuming. The aim of this study was to investigate how efficiently winter wheat, rye and winter turnip rape function as catch crops and what effect the preceding crops of fallow, barley and peas have on autumn sown crops, with regard to nitrogen levels. A three year-long field experiment was established in 2010 at Viikki research farm in Helsinki. Winter wheat, rye and winter turnip rape were cultivated as catch crops; the preceding crops were fallow in 2010-2011 and barley and pea in 2011-2012. In 2012 winter wheat, rye and winter turnip rape were cultivated with fallow, peas and barley as preceding crops. In this study the soil’s mineral nitrogen content was measured before sowing in autumn and in spring. In 2010-2011 the soil’s mineral nitrogen content was also measured after harvest. The nitrogen content of the plants was measured in autumn. The seed quality and the seed yield were also measured. In autumn 2011 the mineral nitrogen content of the soil was higher after barley than after peas. However, there was more mineral nitrogen after cultivating fallow, compared to peas and barley in autumn 2012. The loss of mineral nitrogen between autumn 2010 and spring 2011 was slight. The nitrogen loss was greatest where winter turnip rape was cultivated, due to the plant’s high nitrogen assimilation. Winter turnip rape accumulated much more nitrogen than rye and winter wheat, whereas rye accumulated more nitrogen than winter wheat in 2010 and 2011. Mineral nitrogen loss between autumn 2011 and spring 2012 was high, over 80 % of the nitrogen was lost due to heavy rainfall and a mild winter.

The literature review deals with the composition of rye flour and the significance of en-zymes and sourdough in rye flour processing. The operational principles of twin screw extruders, the extrusion of grain based materials and the formation of aroma during grain based extrusion are also reviewed. The aim of this study was to determine the influence of the amount of powered rye sourdough and extrusion cooking parameters on the structure and properties of rye extrudate. Three process parameters were varied: content of rye sourdough powder, process temperature during the final stages of extrusion and revolution speed of the extruder's screws. A Box-Behnken's experimental design was used with 3 levels of dried sourdough powder content (0, 20 and 40%), 3 screws revolution speeds (200, 350 and 500 rpm) and 3 exit temperatures (120, 150 and 180°C). Feed rate was set at 4.0 kg/h and the moisture of the feed was 17.4%. A total of 15 experiments were perfomed. Pasting properties, acidity, acid value and D- and L-lactic acid concentration of full grain rye flour, dried rye sourdough flour and ground extrudate powder were determined. Acetic acid concentration of dried rye sourdough powder was also determined. Moisture content, expansion, texture, bubble sizes and colour of extrudate were determined. Extrusion cooking produce very different types of rye extrudates and the effect of process parameters on structure of extrudate was significant. When the pressure at the die was 30–40 bar, structure of extrudates were porous. Freeze dried extrudates were harder than extru-dates stored for one day at room temperature. Young's modulus decreased with increasing screws speed and processing temperature. Extrudate’s expansion increased as a function of increased revolution speed of screws and decreased processing temperature. As the content of dried sourdough increased, the bubble sizes of extrudate increased and also yellow (a) and red (b) colour and acidity of extrudates became stronger. Lightness (L) was statistical significantly higher when temperature was higher. As expected, the concentration of D- and L-lactic acid increased with increasing dried sourdough content. Decreased content of dried rye sourdough and slower revolution speed of screws increased cold peak viscosity signifi-cant. Peak and hold viscosities increased with slower revolution speed of the screws and decreased content of dried sourdough. Final viscosity and setback value increased signifi-cantly with slower revolution speed of the screws. The optimal extrudate, which was crispy and had a good flavour, was obtained when the content of dried sourdough powder was 20%, revolution speed of the screws was 500 rpm and processing temperature was 120°C.