The effect of high hydrostatic pressure on the structure of whey proteins-guar gum mixture.

The effect of high hydrostatic pressure (HHP) on the structural properties of whey protein concentrate (WPC) and guar gum mixture has been investigated at pH 5. WPC (6 % w/v) and guar gum (0.25 % w/v) mixture was freeze dried after adjusting pH and treated at different pressure levels (0-600 MPa) for 0-30 min. The solubility of treated powders decreased significantly (p < 0.05) as treatment time and pressure levels increased. Thermal analysis showed an increase in denaturation temperature after HHP treatment at 600 MPa. A more crystalline structure was observed in samples treated with 600 MPa for 20 and 30 min. With increasing pressure and time, particle size of the samples increased and the highest particle size was belonged to sample treated at 600 MPa for 30 min (759.66 nm). SEM results exhibited that by applying the pressure, irregularity of shapes and particle size increased while the apparent cracks decreased. FTIR results indicated that HHP treatment changed shift in bond and peak intensity. As reported in the current study, the application of HHP treatment as a green physical technology on protein-polysaccharide mixture could be used to improve interaction of protein and polysaccharide.

A study on the structural, physicochemical, rheological and thermal properties of high hydrostatic pressurized pearl millet starch.

Starch in native form has limited application due to functional and physicochemical characteristics. To overcome these limitations, starch can be modified by non-thermal technologies such as high hydrostatic pressure (HHP). This study investigates high-pressure-induced gelatinization and the effect of this process on the structural, functional, morphological, pasting, thermal, physical and rheological properties of millet starch. The suspension of millet starch and water was pressurized at 200, 400 and 600 MPa for 10, 20 and 30 min to modify the starch in terms of structure, morphology, some physicochemical and rheological properties. Swelling strength and starch solubility decreased as a result of treatment with HHP. All treatments caused to increase in water holding capacity of the starch (from 0.66 % for native starch to 2.19 % for 600 MPa-30 min). Thermal analysis showed a decrease in gelatinization temperature and enthalpy of gelatinization and the pasting properties showed a decrease in the peak viscosity after HHP treatment. In addition, HHP treatment caused to increase in the hydration ability of starch by creating porosity and gaps in the granule surface and increasing the specific surface area. HHP application resulted in an increase in the peak time and pasting temperature and a decrease in breakdown and peak viscosities, final viscosity and setback viscosity in comparison with native starch of millet. The starch sample treated with 600 MPa for 30 min had the lowest syneresis and retrogradation ability. Increasing pressure and the time led to an increase in the elastic nature of the starch samples. According to the results, it is possible to increase usage area of starches in the food industry by improving its technological with HHP. This green physical technology can influence the quality parameters of starch, which can provide benefits for product machining and economic purposes.

Effects of high hydrostatic pressure on the rheological properties and foams/emulsions stability of Alyssum homolocarpum seed gum.

The ability to modify food and increase the shelf life by enhanced stability using nonthermal process is of interest to many food companies. Here, we investigate the effects of high hydrostatic pressure (HHP), as a nonthermal process, at various pressure levels (200, 400, and 600 MPa for 30 min) on the functional properties of aqueous dispersions of Alyssum homolocarpum seed gum (AHSG). In this regard, the rheological properties, foam stability, and emulsion stability of the HHP-treated gums were analyzed and compared. Dynamic oscillatory test indicated that the HHP-treated gums had more gel-like behavior than viscous-like behavior (storage modulus > loss modulus) at designated pressures. When AHSG was treated by HHP, both elastic (G') and viscous (G″) moduli were increased compared to the native AHSG. The native- and HHP-treated gums exhibited a shear-thinning (pseudoplastic) behavior. Furthermore, the pressure levels have a significant effect on consistency coefficient, flow behavior index, and yield stress (p < .05) of AHSG. The results showed that the HHP-treated gums lead to improve the foam and emulsion stability of AHSG. Finally, we assume that HHP-treated AHSG improves texture in the food materials.