The influence of oxidizing agents on water extracts of rye flour

• Published in: Food hydrocolloids Vol. 27; no. 1; pp. 72 - 79
• Main Authors: Buksa, Krzysztof, Nowotna, Anna, Ziobro, Rafał, Gambuś, Halina, Kowalski, Stanisław
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.05.2012; Elsevier
• Subjects: Ascorbic acid; Biological and medical sciences; Cross-linking; Crosslinking; enzyme activity; Flour; Flour water extract; Food additives; Food industries; Fundamental and applied biological sciences. Psychology; gels; General aspects; gluten; hydrogen peroxide; oxidants; Oxidation; pentosans; Peroxidase; Polymers; Proteins; Rye; Rye flour; Viscosity; Flour water extract; Oxidation; Cross-linking; Rye flour; Water; Extract; Flour
• ISSN: 0268-005X; 1873-7137
• DOI: 10.1016/j.foodhyd.2011.08.014

The main constituents of rye flour extracts are proteins and pentosans. After cross-linking under the action of oxidizing agents those components are able to bind much more water than in their native (prior to modifications) state. As a consequence rheological properties of extract are changed. It was observed that kinematic viscosity of water extract of rye flour decreases rapidly with time. The reason for this behavior could be high enzymatic activity of flour extract. It was also found that the addition of hydrogen peroxide in the absence of additional peroxidase (which is naturally present in 1:9 or 1:1 water extracts of flour) causes the greatest increase in viscosity, due to the cross-linking of soluble polymers. Moreover after the addition of H 2O 2 to water extracts strong gels were obtained, which were characterized by tan  δ = 0.5 (tan  δ < 1). Moreover G′ was independent of frequency, which also suggests cross-linking of the pentosans. The addition of ascorbic acid, which is known to act preferably on gluten proteins, to 1:9 or 1:1 flour extracts had only a little effect on viscosity. In this case the values of tan  δ = 0.9 were close to 1, which is typical for a weak gel. The application of inactivated rye flour extract, containing mainly proteins and pentosans, proved stronger effect of H 2O 2 in comparison to ascorbic acid on polymer cross-linking, but only after the addition of peroxidase. The gel obtained with H 2O 2 and peroxidase was also characterized by low tan  δ = 0.4. The results indicate, that pentosans are the main subject of cross-linking reactions in rye flour water extracts. [Display omitted] ► Effects of cross-linking agents on viscosity of rye flour extracts were examined. ► Viscosity of untreated water extract of rye flour decreased rapidly in time. ► The addition of H 2O 2 to rye flour extracts caused the highest increase of viscosity. ► The addition of ascorbic acid to fresh flour extracts had only a little effect on viscosity. ► Extract concentration and amount of oxidizing agents had an impact on its viscosity.