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Comparative study of the functional properties of lupin, green pea, fava bean, hemp, and buckwheat flours as affected by pH.

Raikos V, Neacsu M, Russell W, Duthie G - Food Sci Nutr (2014)

Bottom Line: In this study, the effect of pH on the functional properties of lupin, green pea, fava bean, hemp, and buckwheat flours was investigated and compared with wheat flour.Wheat, green pea, buckwheat, and fava bean were more capable of forming firm gels compared with lupin and hemp, as indicated by least gelling concentrations (LGCs).Depending on the application, flour functionality may be effectively tailored by pH adjustment.

View Article: PubMed Central - PubMed

Affiliation: Natural Products Group, Rowett Institute of Nutrition and Health, University of Aberdeen AB21 9SB, Scotland, UK.

ABSTRACT
The demand for products of high nutritional value from sustainable sources is growing rapidly in the global food market. In this study, the effect of pH on the functional properties of lupin, green pea, fava bean, hemp, and buckwheat flours was investigated and compared with wheat flour. Functional properties included solubility, emulsifying and foaming properties, gelling ability, and water holding capacity (WHC). All flours had minimal solubility at pH 4 and their corresponding values increased with increasing pH. Emulsifying properties were improved at pH 10 for all samples and emulsion stability showed a similar trend. Increasing pH in the range 4-10 enhanced the foaming properties of the flours, particularly buckwheat and hemp. Wheat, green pea, buckwheat, and fava bean were more capable of forming firm gels compared with lupin and hemp, as indicated by least gelling concentrations (LGCs). The ranking of the water binding properties of the different types of flours were lupin>hemp>fava bean>buckwheat>green pea>wheat. Results indicate that underutilized flours from sustainable plant sources could be exploited by the food industry as functional food ingredients or as replacements of wheat flour for various food applications. Depending on the application, flour functionality may be effectively tailored by pH adjustment.

No MeSH data available.


Effect of pH on creaming stability of oil-in-water emulsions (lupin) standing at room temperature for 24 h.
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fig03: Effect of pH on creaming stability of oil-in-water emulsions (lupin) standing at room temperature for 24 h.

Mentions: The emulsification process depends on the ability of proteins to adsorb rapidly at the oil–water interface where they form a strong, viscoelastic film around the oil droplets. This offers a degree of protection against any destabilizing mechanisms (Pearce and Kinsella 1978). Denaturation and partial unfolding of protein molecules upon adsorption at the interface with appropriate hydrophobic and hydrophilic orientation is critical for emulsion formation and stabilization (Carvalho et al. 2006). In the present study, the emulsifying ability and stability of all flour dispersions increased with increasing pH (Table2) despite marked differences in protein concentrations (Table1). Furthermore, as revealed by the migration pattern of SDS-PAGE, the protein composition of the different flours differs to a great extent (Fig.2). The lanes corresponding to lupin and green pea contain higher number of bands compared to the other samples. The intensity of the protein bands is also indicative of the protein concentration and results are in agreement with the macronutrient composition of the flours. Lanes 2 (wheat) and 7 (buckwheat) appear to have less protein compared to all other lanes. Thus, both qualitative and quantitative differences in protein content are expected to contribute to the emulsifying properties of each flour sample. In agreement with other studies, emulsifying ability and stability was highest at pH 10 and followed a similar pattern to the observed pH-dependent solubility (Adebowale and Lawal 2004; Sridaran et al. 2012). Solubility affects the ability of protein molecules to diffuse fast and adsorb at the interface. Such enhanced emulsifying properties at alkaline pH may also arise from the dissociation and partial unfolding of globular proteins. Resulting exposure of hydrophobic amino acid residues consequently increases the surface activity and adsorption at the oil and water interface (Nir et al. 1994). The pH-driven effect on emulsion stability had an impact on the creaming rate of the samples, which was noticeably lower at pH 10 (Fig.3). Wheat and lupin were the least promising emulsifying agents, whereas buckwheat and hemp had the highest emulsifying ability and stability indices at pH 10. Although adequate protein concentration is a prerequisite for emulsion formation and stabilization, the type of protein is also critical in terms of the reduction in the interfacial tension and the formation of a protective layer around the oil droplet (Prinyawiwatkul et al. 1993). This is reflected in lupin flour, which although has the highest protein content (400 g kg−1) shows poor emulsifying properties. Not all protein molecules are as effective as emulsifiers and this is deduced from the significant differences in the emulsifying activity and stability indices of the flours analyzed in this study.


Comparative study of the functional properties of lupin, green pea, fava bean, hemp, and buckwheat flours as affected by pH.

Raikos V, Neacsu M, Russell W, Duthie G - Food Sci Nutr (2014)

Effect of pH on creaming stability of oil-in-water emulsions (lupin) standing at room temperature for 24 h.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4256586&req=5

fig03: Effect of pH on creaming stability of oil-in-water emulsions (lupin) standing at room temperature for 24 h.
Mentions: The emulsification process depends on the ability of proteins to adsorb rapidly at the oil–water interface where they form a strong, viscoelastic film around the oil droplets. This offers a degree of protection against any destabilizing mechanisms (Pearce and Kinsella 1978). Denaturation and partial unfolding of protein molecules upon adsorption at the interface with appropriate hydrophobic and hydrophilic orientation is critical for emulsion formation and stabilization (Carvalho et al. 2006). In the present study, the emulsifying ability and stability of all flour dispersions increased with increasing pH (Table2) despite marked differences in protein concentrations (Table1). Furthermore, as revealed by the migration pattern of SDS-PAGE, the protein composition of the different flours differs to a great extent (Fig.2). The lanes corresponding to lupin and green pea contain higher number of bands compared to the other samples. The intensity of the protein bands is also indicative of the protein concentration and results are in agreement with the macronutrient composition of the flours. Lanes 2 (wheat) and 7 (buckwheat) appear to have less protein compared to all other lanes. Thus, both qualitative and quantitative differences in protein content are expected to contribute to the emulsifying properties of each flour sample. In agreement with other studies, emulsifying ability and stability was highest at pH 10 and followed a similar pattern to the observed pH-dependent solubility (Adebowale and Lawal 2004; Sridaran et al. 2012). Solubility affects the ability of protein molecules to diffuse fast and adsorb at the interface. Such enhanced emulsifying properties at alkaline pH may also arise from the dissociation and partial unfolding of globular proteins. Resulting exposure of hydrophobic amino acid residues consequently increases the surface activity and adsorption at the oil and water interface (Nir et al. 1994). The pH-driven effect on emulsion stability had an impact on the creaming rate of the samples, which was noticeably lower at pH 10 (Fig.3). Wheat and lupin were the least promising emulsifying agents, whereas buckwheat and hemp had the highest emulsifying ability and stability indices at pH 10. Although adequate protein concentration is a prerequisite for emulsion formation and stabilization, the type of protein is also critical in terms of the reduction in the interfacial tension and the formation of a protective layer around the oil droplet (Prinyawiwatkul et al. 1993). This is reflected in lupin flour, which although has the highest protein content (400 g kg−1) shows poor emulsifying properties. Not all protein molecules are as effective as emulsifiers and this is deduced from the significant differences in the emulsifying activity and stability indices of the flours analyzed in this study.

Bottom Line: In this study, the effect of pH on the functional properties of lupin, green pea, fava bean, hemp, and buckwheat flours was investigated and compared with wheat flour.Wheat, green pea, buckwheat, and fava bean were more capable of forming firm gels compared with lupin and hemp, as indicated by least gelling concentrations (LGCs).Depending on the application, flour functionality may be effectively tailored by pH adjustment.

View Article: PubMed Central - PubMed

Affiliation: Natural Products Group, Rowett Institute of Nutrition and Health, University of Aberdeen AB21 9SB, Scotland, UK.

ABSTRACT
The demand for products of high nutritional value from sustainable sources is growing rapidly in the global food market. In this study, the effect of pH on the functional properties of lupin, green pea, fava bean, hemp, and buckwheat flours was investigated and compared with wheat flour. Functional properties included solubility, emulsifying and foaming properties, gelling ability, and water holding capacity (WHC). All flours had minimal solubility at pH 4 and their corresponding values increased with increasing pH. Emulsifying properties were improved at pH 10 for all samples and emulsion stability showed a similar trend. Increasing pH in the range 4-10 enhanced the foaming properties of the flours, particularly buckwheat and hemp. Wheat, green pea, buckwheat, and fava bean were more capable of forming firm gels compared with lupin and hemp, as indicated by least gelling concentrations (LGCs). The ranking of the water binding properties of the different types of flours were lupin>hemp>fava bean>buckwheat>green pea>wheat. Results indicate that underutilized flours from sustainable plant sources could be exploited by the food industry as functional food ingredients or as replacements of wheat flour for various food applications. Depending on the application, flour functionality may be effectively tailored by pH adjustment.

No MeSH data available.