Transglutaminase-Induced Polymerization of Pea and Chickpea Protein to Enhance Functionality.

Pulse proteins, such as pea and chickpea proteins, have inferior functionality, specifically gelation, compared to soy protein, hindering their applications in different food products, such as meat analogs. To close the functionality gap, protein polymerization via targeted modification can be pursued. Accordingly, transglutaminase-induced polymerization was evaluated in pea protein isolate (PPI) and chickpea protein isolate (ChPI) to improve their functionality. The PPI and ChPI were produced following a scaled-up salt extraction coupled with ultrafiltration (SE-UF) process. Transglutaminase (TGase)-modified PPI and ChPI were evaluated in comparison to unmodified counterparts and to commercial protein ingredients. Protein denaturation and polymerization were observed in the TG PPI and TG ChPI. In addition, the TGase modification led to the formation of intermolecular ß-sheet and ß-turn structures that contributed to an increase in high-molecular-weight polymers, which, in turn, significantly improved the gel strength. The TG ChPI had a significantly higher gel strength but a lower emulsification capacity than the TG PPI. These results demonstrated the impact of the inherent differences in the protein fractions on the functional behavior among species. For the first time, the functional behavior of the PPI and ChPI, produced on a pilot scale under mild processing conditions, was comprehensively evaluated as impacted by the TGase-induced structural changes.

Innovative method for analysis of safranal under static and dynamic conditions through combination of HS-SPME-GC technique with mathematical modelling.

INTRODUCTION: Saffron (Crocus sativus L.) is a well-known spice which is used as the colourant and flavouring agent in food products. Safranal could act as an indicator for saffron grading, authentication and adulteration, as well as for quality evaluation of saffron flavoured products; since it is the main odourant and the most aroma-active compound of saffron. OBJECTIVES: Firstly, determination of the optimum static conditions for safranal extraction through headspace solid-phase micro-extraction combined with gas chromatography (HS-SPME-GC) technique. Secondly, safranal measurement in different saffron flavoured products under the optimised static conditions. Thirdly, elucidation of the method efficiency for safranal measurement under non-equilibrium conditions for a saffron drink sample. METHODS: Different equilibrium times, pH and salt concentrations were applied on aqueous solutions of safranal. Accordingly, the optimised static conditions were determined for safranal extraction through HS-SPME-GC approach using polydimethylsiloxane (PDMS) fibre. RESULTS: Under static conditions, a linear response was obtained for standard curve within the safranal concentration range of 0.08-30 ppm, with R2 = 0.9999. The limits of detection and quantification were 0.04 and 0.08 ppm, respectively. Despite the fact that safranal peak area was an efficient parameter for quantifications under static conditions; its poor reproducibility was proved under dynamic conditions for the saffron drink sample. This observation necessitated application of kinetic studies on real food samples. CONCLUSIONS: Safranal extraction was successfully performed from aqueous matrices through HS-SPME-GC, under static conditions. Mathematical modelling resulted in kinetic parameters that improved the efficiency of safranal measurement under dynamic conditions, using PDMS fibre.

Binding of safranal to whey proteins in aqueous solution: Combination of headspace solid-phase microextraction/gas chromatography with multi spectroscopic techniques and docking studies.

The objective of this work was to study molecular binding of safranal to whey proteins by taking advantage of headspace solid-phase microextraction combined with gas chromatography (HS-SPME/GC), fluorescence and circular dichroism (CD) spectroscopies, and docking studies. The results of HS-SPME/GC indicated that bovine serum albumin (BSA) had the highest affinity toward safranal, with binding constant of 3.196 × 103 M-1. Also, binding strength was reduced in the order of α-lactalbumin (α-Lact), whey protein isolate (WPI), and ß-lactoglobulin (ß-Lg). Although there was a good agreement between results of HS-SPME/GC and fluorescence spectroscopy regarding the safranal binding site on whey proteins, the order of their binding affinity toward safranal was not consistent for both techniques. According to docking studies, conformational alterations in secondary and tertiary structures of whey proteins induced by safranal association resulted from hydrophobic interactions and hydrogen bonds.

Effect of drying methods on the structure, thermo and functional properties of fenugreek (Trigonella foenum graecum) protein isolate.

BACKGROUND: Different drying methods due to protein denaturation could alter the functional properties of proteins, as well as their structure. So, this study focused on the effect of different drying methods on amino acid content, thermo and functional properties, and protein structure of fenugreek protein isolate. RESULTS: Freeze and spray drying methods resulted in comparable protein solubility, dynamic surface and interfacial tensions, foaming and emulsifying properties except for emulsion stability. Vacuum oven drying promoted emulsion stability, surface hydrophobicity and viscosity of fenugreek protein isolate at the expanse of its protein solubility. Vacuum oven process caused a higher level of Maillard reaction followed by the spray drying process, which was confirmed by the lower amount of lysine content and less lightness, also more browning intensity. ΔH of fenugreek protein isolates was higher than soy protein isolate, which confirmed the presence of more ordered structures. Also, the bands which are attributed to the α-helix structures in the FTIR spectrum were in the shorter wave number region for freeze and spray dried fenugreek protein isolates that show more possibility of such structures. CONCLUSION: This research suggests that any drying method must be conducted in its gentle state in order to sustain native structure of proteins and promote their functionalities. © 2017 Society of Chemical Industry.

A comparison of chemical, structural and functional properties of fenugreek (Trigonella foenum graecum) protein isolates produced using different defatting solvents.

This study showed defatting solvents including hexane, diethyl ether, chloroform, ethanol and acetone, due to their influence on protein denaturation and structure, have considerable effect on the amino acid composition, thermal characterizations, surface and functional properties of fenugreek protein isolate. FTIR analysis while confirmed the presence of secondary structures in all fenugreek protein isolates, showed differences in these structures. Hexane and diethyl ether resulted in comparable coagulated protein percentage, interfacial tension, emulsifying properties, surface hydrophobicity, Td and SDS-PAGE profile in fenugreek protein isolates. The lowest surface tension in fenugreek protein isolate produced from ethanol defatted flour was in accordance with its considerable foaming properties. Maximum Td and ΔH were observed in fenugreek protein isolate obtained from acetone defatted fenugreek flour. The highest amounts of hydrophobic and charged hydrophilic amino acids in fenugreek protein isolate produced from hexane and acetone defatted fenugreek flours respectively, were in accordance with the polarity of the applied defatting solvents. Thermograph and coagulated protein percentage confirmed that chloroform caused the lowest thermal stability in fenugreek protein isolate.

Fenugreek (Trigonella foenum graecum) seed protein isolate: extraction optimization, amino acid composition, thermo and functional properties.

BACKGROUND: With increasing demand for new protein sources, research on plant protein extraction and evaluation of the functional properties of protein isolates is necessary. In this study, pH and NaCl concentration, as two parameters affecting protein extraction of fenugreek seed, was investigated and the condition of fenugreek protein isolate (FPI) extraction was optimized using response surface methodology. RESULTS: FPI had significantly (P< 0.05) higher protein and essential amino acid content (891.00 and 387.41 g kg(-1) , respectively) compared with soy protein isolate (SPI). FPI was rich in Asp and Glu, confirming the presence of bands in the acidic region (30-39 kDa) of its electrophoretic pattern. Differential scanning calorimeter thermography of both FPI and SPI showed two peaks with high denaturation temperature, confirming the presence of high protein content and hydrophobic amino acids. Protein solubility, foaming capacity, foam stability and emulsion stability of FPI were higher than SPI; moreover, both FPI and SPI showed pH-dependent protein functionalities. CONCLUSION: Fenugreek seed protein extraction was optimized by control of pH and NaCl concentration. FPI could be used as a protein source with remarkable functional properties.