Abstract
Emulsions of peanut and soy proteins, including their major components (arachin, conarachin, glycinin and β−conglycinin), were prepared by ultrasonication (300 W, 20 min) at a constant protein concentration (4%, w/v) and oil fraction (30%, v/v). These emulsions were then induced by CaCl2, transglutaminase (TGase) and glucono-δ-lactone (GDL) to form emulsion gels. The optimum coagulant concentrations were obtained for peanut and soy protein-stabilized emulsion gels, such as CaCl2 (0.15 and 0.25 g/dL, respectively), TGase (25 U/mL) and GDL (0.3% and 0.5%, w/v, respectively). For the CaCl2-induced emulsion gels, the hardness of the β−conglycinin gel was the highest, whereas that of the conarachin gel was the lowest. However, when TGase and GDL were used as coagulants, the strength of the conarachin emulsion gel was the best. For the GDL-induced emulsion gels, microstructural analysis indicated that the conarachin gel showed more homogeneous and compact structures. The gelation kinetics showed that the storage modulus (G′) of all the GDL-induced emulsions increased sharply except for the arachin-stabilized emulsion. The interactive force nature varied between conarachin and arachin emulsion gels. This work reveals that peanut conarachin could be used as a good protein source to produce emulsion gels when suitable coagulants are selected.
Highlights
Emulsion gels have a certain mechanical strength filled with emulsion droplets
We found that compared with highpressure homogenization, the peanut protein emulsion prepared by the ultrasonic method had improved strength and microstructure after gelation [4]
In the case of soy protein isolate (SPI), peanut proteins isolate (PPI), β−conglycinin and conarachin emulsion gels, their G0 values gradually increased with increasing frequency, indicating that these emulsion gels are mainly formed through noncovalent “physical crosslinks”, which are breakable or deformable [31]
Summary
Emulsion gels have a certain mechanical strength filled with emulsion droplets. They can be used as fat substitutes or as delivery systems to embed bioactive substances to improve chemical stability [1,2]. Emulsion gels with whey protein isolate at the interface had the highest gel strength (fracture stress and storage modulus), followed by the gels with sodium caseinate, soy protein isolate (SPI), lactoferrin at the interface [11] Peanut proteins are another important plant protein in addition to soybean proteins, but compared with soybean proteins, the functional properties of peanut proteins are far from being explored, which has seriously limited the applications of peanut proteins in the food industry. Some structural and functional properties of peanut protein components have been revealed by the above work, little has been studied regarding the preparation and characterization of arachin/conarachin-stabilized emulsion gels. Emulsions of peanut and soy proteins, including their components, were prepared by ultrasonic methods, and the emulsions were further induced by salt (CaCl2 ), TGase and acid (glucono-δ-lactone, GDL) to form emulsion gels. This study will promote the understanding of the physical properties of peanut and soybean protein-based emulsion gels induced by various coagulants
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