Heat-Induced Gelation of Pea Legumin:  Comparison with Soybean Glycinin

Abstract

Gel network formation of pea legumin (8.4% on a protein basis, pH 7.6) was monitored via dynamic rheological measurements. Gelation was performed in the absence and presence of the thiol-blocking reagent N-ethylmaleimide, at different rates of heating and cooling. Overall, it was shown that pea legumin gel formation was not effected by changes in the heating rate, and the two differently heated samples were unaffected by the addition of 20 mM NEM, which indicated that disulfide bonds were not essential within the network strands of these legumin gels. However, slowly cooling the legumin samples caused disulfide bonds to become involved within the network; this was observed by a large increase in gel strength that was then substantially reduced when repeating the sample in the presence of NEM. These experiments were repeated with soybean glycinin in order to determine whether a common model for gel formation of legumin-like proteins could be built, based upon molecular reasoning. The two proteins were affected in the same way by changes in the conditions used, but when applying a procedure of reheating and recooling the gel networks responded differently. Pea legumin gel networks were susceptible to rearrangements that caused the gels to become stronger after reheating/recooling, yet glycinin gel networks were not. It was concluded that the same physical and chemical forces drove the processes of denaturation, aggregation, and network formation. Each process can therefore be readily targeted for modification based upon molecular reasoning. Pea legumin and soybean glycinin gel networks had structurally different building blocks, however. A model of gelation aimed at texture control therefore requires additional information.

Functional Properties and Oxidative Stability of Flaxseed Oil Microencapsulated by Spray Drying Using Legume Proteins in Combination with Soluble Fiber or Trehalose

“…These observations are consistent with other studies which showed that pea protein isolate formed a paste instead of a rigid gel (Adebiyi and Aluko 2011). O'Kane et al (2004) stated that pea protein forms more unstructured gels than soy protein and thus their gelling properties are not as good as those of soy.…”

Gelation properties of salt-extracted pea protein isolate induced by heat treatment: Effect of heating and cooling rate

“…In the study of O'Kane, Happe, Vereijken, Gruppen, and van Boekel (2004), heating rate did not affect gel formation with pea legumin. However, it was observed that slower cooling of the legumin samples increased the gel strength.…”

“…They suggested that slow cooling could maintain the protein in its unfolded state for a longer time, slowing down the reactivity of the exposed residues, and enabling more optimal arrangement to occur, prior to interactions between proteins. Since hydrogen bonds are favored at low temperature and it has been confirmed that one of the main forces involved in promoting gel structure of pea legumin protein is the hydrogen bonds (O'Kane et al, 2004), it can be speculated that the hydrogen bond formation is enhanced at slower cooling rate resulting in stronger gels. O' Kane et al (2004) also indicated that under a slower cooling rate (1°C/min heating and 0.2°C/min cooling) hydrophobic interaction and disulfide bond are involved in formation of gel structure of pea legumin protein.…”

Impact of Legume Flour Addition on Pasta Structure: Consequences on Its In Vitro Starch Digestibility

“…49 Heat denaturation of legume protein would involve the exposure of hydrophobic residues, protein aggregation by intermolecular hydrophobic interaction and agglomeration of aggregates into a network structure. 25,50 The addition of legume flour also had an impact on the starch fraction. In the intermediate and central regions of pasta strand, legume starch granules could be differentiated from durum wheat starch by their different sizes and shapes.…”