Effect of defatted soybean flour on the flavour of extruded mixtures with wheat flour

Abstract

Mixtures of wheat semolina, 5% glucose and 0-30% defatted soybean flour were used for the preparation of extruded samples using a pilot plant single screw extruder, maximum temperature being 140°C. The browning reactions were only moderate, the intensities of the trichromatic a* coordinate increased, and some changes were observed in chroma and the odour difference ∆E*. The sensory acceptability improved by increasing the content of soybean flour, the odour intensity increased, and some changes were observed in the sensory profile. Volatile substances were isolated using a SPME procedure, and the volatiles were separated using a Fisons GLC 8000 apparatus equipped with a mass spectrometer. Among the flavour active volatiles, pyrazines were the most prominent class of compounds, especially methyl and ethyl substituted derivatives. Pyrrole and furan substituted pyrazines were found only in small amounts because of the low extrusion temperature. Other furan and pyrrole derivatives had a lesser effect on flavour because of their relatively low amounts. Aldehydes, fatty acids, ketones, and other aliphatic derivatives contributed only a little to the resulting flavour. Compared to the mixtures of semolina and glucose only, the additions of defatted soybean flour moderately increased the number of substituted pyrazines detected in the extruded mixtures but increased substantially the pyrazine fraction in the total peak area. Among furan derivatives, 2-furancarboxaldehyde, 2-furanmethanol and 5-methyl-2-furyl alcohol belonged to the most prominent derivatives. Among other compounds, acetic acid, butyrolactone and maltol should be mentioned.Keywords: extrusion; flavour; pyrazines; soybean flour; wheat flour 230 Vol. 20, Czech J. Food Sci.pyrroles, and pyrazines was enhanced by the addition of reducing sugars and by the addition of amino acids. The results were previously published in greater detail (FA-ROUK MANSOUR et al. 2000MANSOUR et al. , 2001. Both reducing sugars and free amino acids are efficient precursors of Maillard reactions. Furan derivatives and maltol originate from sugar degradation products during extrusion cooking (RIHA & HO 1996) but pyrazines are the main sensory active products of Maillard reactions (YOO & HO 1997). Their content is higher in rye bread than in wheat bread (SCHIEBERLE & GROSCH 1987). Pyrazines, which possess very strong roasted bread crust and even burnt flavour notes, were isolated from bread (ROTHE 1974;RIHA & HO 1996;SCHIEBERLE & GROSCH 1984; OSNA-BRUGGE 1989). BALTES and BOCHMANN (1987) isolated many (more than 200) pyrazines from heated model mixtures of amino acids and sucrose as obtained at a temperature corresponding to that of coffee roasting.Similar processes occur during the extrusion cooking of cereal products (LUNDGREN et al. 1991/92). Under mild extrusion conditions used in our experiments, the production of volatile heterocyclic substances was much less intensive than in the course of model experiments or traditional baking. The number of oxygen and nitrogen cont...

Na+ and Cl− induce differential physiological, biochemical responses and metabolite modulations in vitro in contrasting salt-tolerant soybean genotypes

“…In the present study, among the metabolites, aldehydes and furans such as benzeneacetaldehyde, 2-furan-carboxaldehyde, 2-furancarboxaldehyde 5-methyl-, phenyl acetaldehyde, and 2-furanmethanol were found in salt-stressed calli. Some of these metabolites were previously observed in soybean due to lipid oxidation, degradation, and sugar dehydration (Pokorny et al 2000;Lee and Ahn 2009). The present results showed that, under different salt treatments, soybean callus synthesized aldehydes and alcohol.…”