High-pressure treatment

Volume increases in wheat starch and potato starch granules during the compression and release phases were measured microscopically (Douzals et al, 1996a). Gelatinization of wheat starch began at pressures above 300 MPa and the largest increase in granule 

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A.I. Kolesnikov, A.M. Balagurov, I.O. Bashkin, V.K. Fedotov, V.Yu. Malyshev, G.M. Mironova, E.G. Ponyatovsky, A Real-Time Neutron Diffraction Study of Phase Transitions in the Ti-D System after High Pressure Treatment, J. Phys. Condensed Matter 5 5045 (1993). 

De Ancos, B., Gonzalez, E., and Cano, M.P., Effect of high-pressure treatment on the carotenoid composition and the radical scavenging activity of persimmon fruit purees, J. Agric. Food Chem., 48, 3542, 2000. 

Tarui, H., Murata, M., Tani, I. et al. (2001) Establishment and characterization of cell-free translation/ glycosylation in insect cell (Spodopterafrugiperda 21) extract prepared with high pressure treatment. Applied Microbiology and Biotechnology, 55 (4), 446 453. 

FDA regulation of, 21 578-579 gelatin in, 12 442 high pressure treatment of, 13 436 processed, 18 32-35 shipping containers for, 18 37 Food Quality Protection Act of 1996 (FQPA), 18 538-539 21 591 minor use pesticides under, 18-539-540 Food refrigeration, 21 558-566 importance of, 21 559 Food Safety and Inspection Service (FSIS), 13 17... 

Butz, P., Edenharder, R., Fernandez Garcia, A., Fister, H., Merkel, C., and Tauscher, B. (2002). Changes in functional properties of vegetables induced by high pressure treatment. Food Res. Int. 35, 295-300. 

High-pressure gelation could be an interesting new approach [16]. It has been shown that native starches can be gelatinised using high-pressure treatments... 

The self-assembly of caseins may be readily manipulated by processing methods that affect the integrity of native casein micelles and the character of the casein interactions in aqueous media. Examples of such procedures are (Dickinson, 2006) (i) acidification toward the isoelectric point (p/) (pH 4.6-4.8), leading to a neutralization of the net protein charge (ii) enzyme action, as exploited in the production of cheeses and fermented milks (iii) addition of divalent ions, especially, Ca2+ ions (iv) addition of sucrose or ethanol (v) temperature treatment and (vi) high-pressure treatment. 

We have seen earlier in this chapter how the self-assembly of casein systems is sensitively affected by temperature. Another thermodynamic variable that can affect protein-protein interactions in aqueous media is the hydrostatic pressure. Static high-pressure treatment causes the disintegration of casein micelles due to the dismption of internal hydro-phobic interactions and the dissociation of colloidal calcium phosphate. This phenomenon has been used to modify the gelation ability of casein without acidification as a consequence of exposure of hydrophobic parts of the casein molecules into the aqueous medium from the interior of the native casein micelles (Dickinson, 2006). High-pressure treatment leads to a reduction in the casein concentration required for gelation under neutral conditions, especially in the presence of cosolutes such as sucrose (Abbasi and Dickinson, 2001, 2002, 2004 Keenan et al., 2001). 

Figure 7.18 Protein-polysaccharide interactions in emulsions subjected to high pressure treatment (HPT). Influence of pH on average effective particle diameter d43 determined by static light scattering (Malvern Mastersizer) in emulsions (20 vol% soybean oil, 0.5 wt% p-lactoglobulin) prepared with untreated protein (open symbols) and high-pressure-treated (800 MPa for 30 min filled symbols) protein in the absence (O, ) and presence (A, ) of 0.5 wt% pectin. Reproduced from Dickinson and James (2000) with permission.

Dickinson, E., James, J.D. (2000). Influence of high-pressure treatment on p-lactoglob-ulin-pectin associations in emulsions and gels. Food Hydrocolloids, 14, 365-376. 

Galazka, V.B., Smith, D., Ledward, D.A., Dickinson, E. (1999). Complexes of bovine serum albumin with sulfated polysaccharides effects of pH, ionic strength and high pressure treatment. Food Chemistry, 64, 303-310. 

This method (ultra-high pressure treatment UHP) for the aseptic processing of food stuffs and other organic products still appears to be some way from extended application. 

In 1914, Bridgman described the coagulation of egg-white as a consequence of high hydrostatic-pressure treatment. In 1918 it seemed evident that all micro-organisms can be inactivated by a high-pressure treatment, just at room temperature, apart from those producing spores, and that each microbe requires individual and precise conditions to be inactivated. 

Later, Timson and Short started systematic experiments to test the resistance of bacterial spores, and tried to inactivate them completely to obtain a total sterilization. These authors studied the behaviour of spores under a high-pressure treatment with a long residence time at constant pressure in a range of temperature between - 25°C and 95°C. They noted the high insensitivity to pressure of the spores compared to vegetative forms [8]. 

In 1966, Lundgren [9] observed the existence of an optimum temperature for germination of spores, therefore Clouston and Willis [10, 11] deepened the process of germination and the inactivation of Bacillus pumilius under high-pressure treatment (HPT) and Wills [12] described the sensitivity of spores exposed to radiant energy. 

Effect of high-pressure treatment on Size-exclusion 66... 

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