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Osita Sunday Nnyigide,오유나,송형용,박은경,최수형,현규 한국유변학회 2017 Korea-Australia rheology journal Vol.29 No.2
This paper reports the effects of urea on the heat-induced gelation of bovine serum albumin (BSA), which was studied by the tube inversion method, rheological measurements, and small-angle neutron scattering (SANS). An increase in the urea concentration accelerated the rate of gelation because the protein molecules have already been unfolded to some extent during sample preparation in the urea solution. In addition, the BSA solution in the presence of urea underwent a sol-gel-sol transition during the time sweep test at a constant temperature of 80oC. On the other hand, the BSA solution without urea turned into a hard and brittle gel that did not return to the solution state during isothermal heating at a constant temperature of 80oC. Aggregation and re-bonding of the denatured and unfolded protein chains led to gel formation. Urea added to the protein denatures its tertiary and secondary structures by simultaneously disrupting the hydrogen bonds, hydrophobic interactions, and altering the solvent properties. Furthermore, urea induces thermoreversible chemical interactions in BSA solutions leading to the formation of a gel with dynamic properties under these experimental conditions.
The rheological properties and gelation kinetics of corn starch/bovine serum albumin blend
Osita Sunday Nnyigide,현규 한국유변학회 2020 Korea-Australia rheology journal Vol.32 No.1
The rheological properties and gelation kinetics of corn starch (CS)/bovine serum albumin (BSA) blends were investigated using the mass ratio of [CS]/[BSA] of 0, 0.5, 1, 2, and 3. The results from the temperature ramp and time sweep tests within linear viscoelastic regime showed a decrease in the gelation temperature (Tgel) and gelation time (tgel) of the BSA with increasing the mass ratio of [CS]/[BSA]. A significant decrease in the Tgel and tgel occurred at 5 wt.% BSA with [CS]/[BSA] = 3, where about 12℃ and 11 min drops in the Tgel and tgel were recorded. At the molecular scale, the decrease in the Tgel and tgel with increasing the mass ratio of [CS]/[BSA] was attributed to the breaking down of hydrogen bonding sites in the CS molecules with increasing temperature, and thereby allowing the hydroxyl group to engage in intermolecular hydrogen bonding with the BSA polar amino acid residues. The hydrogen bonding in addition to other noncovalent forces appeared to strengthen the microstructure of the CS/BSA gel as confirmed by the dynamic frequency sweep test. The frequency sweep test also showed that the value of the storage modulus (G') at [CS]/[BSA] = 3 was about 10 to 103 orders of magnitude larger than its value recorded for the pure BSA. Kinetically, the gelation process was well modelled by the temperature dependency of reaction rate constant as represented by the Arrhenius equation. If interpreted in terms of the energy required to attain the gel state, the addition of CS reduced the gel activation energy (Ea) to 153.90 kJ/mol as against the original value of 268.55 kJ/mol that was observed for the BSA without CS.
Nnyigide Osita Sunday,현규 한국유변학회 2023 Korea-Australia rheology journal Vol.35 No.4
The main objective of food rheology is to identify food structure and texture by rheological measurements, thereby reducing the requirement for sensory analysis in evaluating food products. However, determining food texture and structure exclusively from rheological measurements can be challenging because of the complicated composition and structure of food, as well as the complexities of factoring in the changes that occur during food mastication. This article provides a comprehensive review of the current experimental, computational and machine learning techniques used in food rheology to probe the structure and texture of food products. The textural attributes and structural information that can be inferred from each measurement technique is discussed and recent studies that carried out the measurements are highlighted. Also presented in this review are the recent progress in the experimental techniques and challenges.