The Effect of High‐Pressure Microfluidization Treatment on the Foaming Properties of Pea Albumin Aggregates

International audienceThe effect of dynamic high-pressure treatment, also named microfluidization, on the surface properties of thermal pea albumin aggregates (AA) and their foaming ability was investigated at pH 3, 5, and 7. The solubility of albumin particles was not affected by the increase in microfluidization pressure from 70 to 130 MPa. Particle charge depended only on the pH, whereas protein surface hydrophobicity was stable at pH 5, decreased at pH 3, but increased at pH 7 after microfluidization treatment and with the applied pressure. Surface tension of AA measured at air/water interface was favorably affected by the microfluidization treatment at each pH preferentially due to size reduction and increased flexibility of protein particles. The foaming capacity and stability of AA depended on the pH conditions and the microfluidization treatment. The high-pressure treatment had little influence in foaming properties at acidic pHs, probably related to a more compact form of AA at these pHs. At neutral pH, the foaming properties of pea AA were strongly influenced by their surface properties and size associated with significant modifications in AA structure with microfluidization. Changes in albumin aggregate characteristics with pH and microfluidization pressure are also expected to modulate other techno-functional properties, such as emulsifying property. Practical Application Albumins are known for their interesting nutritional values because they are rich in essential amino acids. This fraction is not currently marketed as a protein isolate for human consumption, but can be considered as a potential new vegetable protein ingredient. This document demonstrated that heat treatment or dynamic high-pressure technology can control the foaming properties of this protein for possible use in expanded foods

Native-state pea albumin and globulin behavior upon transglutaminase treatment

International audienceThe behavior of pea albumin (Alb) and globulin (Glob) in their native state upon microbial transglutaminase (MTGase) treatment was studied. Only Glob was able to form a gel, at up to a 10% (w/w) concentration, with a minimum gelling concentration of 6% (w/w), and with a cross-linking degree of 25%. The most affected Glob subunits were convicilin (71 kDa), vicilins (55, 50, and 35 kDa), and legumin acidic subunit (40 kDa). In contrast, the legumin basic subunit (20 kDa) and vicilins of molecular weight less than 20 kDa remained mostly intact in all studied conditions. The cross-linking degree of Alb was 12%, which was not sufficient to form MTGase-induced gel. Major albumin polypeptide (PA2 26 kDa) was not affected by the MTGase concentration or by pH variation. Pea Alb and Glob in their native state were ranked as poor and moderately good substrates for MTGase, respectively, and unfolding them by thermal or chemical denaturation could be an interesting way to improve the efficiency of cross-linking

1H NMR Spectroscopy As Tool To Study Transglutaminase Crosslinking Of Pea Globulin

Skiathos Island, GREECE - 30 May - 02 June 2013International audienceA new method based on NMR spectroscopy was developed to detect the G-L (GlutamylLysine) isopeptide bonds formed by the enzymatic transglutaminase reaction. Because of thecomplexity of NMR signals of proteins due to their structures, the method was first developedon a model system (glutamine and lysine) to simplify the detection of the G-L residue. Andthen, the results were applied on the real protein matrix (pea globulin). MTG treatment ofmodel system led to the appearance of a new resonance on NMR spectrum which isoriginated probably from the ε-methylene protons of lysine residues covalently linked toglutamine. The comparison between NMR spectra of MTG-treated and untreated pea globulinwith MTG-treated model system permitted to identify the G-L isopeptide signal. The G-Lisopeptide signal is also observed in the NMR spectra of native pea globulin (untreated whichMTG), indicating that the isopeptide is naturally present in pea proteins. However, thesuperimposition of NMR spectra of MTG-treated and untreated pea globulin shows a higherintensity of G-L isopeptide signal for MTG-treated samples. The increased signal intensityevidences the enzymatic reaction and permits to quantify the G-L isopeptide

Monitoring of transglutaminase crosslinking reaction by 1H NMR spectroscopy on model substrates

International audienceA new method based on 1H NMR spectroscopy was developed for monitoring transglutaminase crosslinking reaction with model molecules (CBZ-Gln-Gly and N-α-acetyl-lysine). The transglutaminase reaction led to the appearance of new resonances on NMR spectrum as well as significant decrease in others. The new observed resonances, originated from newly formed ɛ-(γ-glutamyl)lysine isopeptide bonds, evidence the enzymatic reaction and allow to quantify the ɛ-(γ-glutamyl)lysine fragment. Moreover, the decrease in resonance intensity, originated from lysine, permit to determine the crosslinking degree. These results obtained by 1H NMR spectroscopy can be used as an alternative method to LC–MS, reducing drastically the analysis time from 7 days to 2 h