Effect of bath temperature and soaking time on the dynamics of water holding capacity of everlasting pea-wheat extrudates
 
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Engineering and Cereals Technology Department, University of Agriculture, Skromna 8, 20-704 Lublin, Poland
 
Int. Agrophys. 2007, 21(3): 241–248
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ABSTRACT
The paper presents the results of a study on the effect of soaking time and water bath temperature on the dynamics of hydration of everlasting pea-wheat extrudates. The extrudates were produced with variable raw materials composition; the shares of the leguminous material (everlasting pea whole meal) and cereal material (wheat whole meal) were 35, 50 and 65%, respectively. Other variable factors applied included three levels of raw material moisture, of 18, 21 and 24%, and two profiles of extruder barrel temperature distribution - 90/120/150/140/130°C and 110/140/180/ 170/130°C. The study of the process of extrusion was conducted by means of a twin-screw extrusion-cooker type 2S-9/5, using a die of diameter of 3x6 mm and screw rotation speed of 75 r.p.m. It was demonstrated that the adopted ranges of process parameters permit stable operation of the extruder and obtainment of good quality products. As samples with a high content of legumes are difficult to hydrate, a study of the dynamics of water absorption by those extrudates was performed. It was shown that increase in the soaking time up to 90 min resulted in unsatisfactory improvement of the amount of water absorbed by the tested samples of everlasting pea-wheat extrudates. Also examined was the effect of varied water temperature at constant soaking time of 15 min. When the water temperature was increased from 20 to 70-80°C, the amount of water absorbed by all the tested extrudates increased, irrespective of their raw material composition and of the process parameters. Further increase of water temperature resulted in a drop of the water holding capacity in all of the samples analysed.
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