Hydrostatic pressure treatment

Patel, H. A., Singh, H., Anema, S. G., and Creamer, L. K. (2006). Effects of heat and high hydrostatic pressure treatments on disulfide bonding interchanges among the proteins in skim milk. /. Agric. Food Chem. 54, 3409-3420. 

In high-pressure applications these are two main trends of research high hydrostatic pressure treatment (2000-7000 bar) and supercritical CO2 treatment. In both cases the aim is to inactivate the micro-organisms in order to protect and preserve foods, and so to prolong their shelf-life. 

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. 

Mertens, B. Hydrostatic pressure treatment of food equipment and processing. New Methods of Food Preservation, G.W. Gould, ed., Blackie Academic and Professional, Great Britain, p. 135,1995. 

The effects of pressure on organic systems are known since the 19 century from qualitative experiments. The effects of high hydrostatic pressure treatment on the inactivation of microorganisms were reported 100 years ago by Hite. On 1899, Hite uses pressure for milk preservation. On 1914, Bridgman notices that egg white looks cooked after pressure treatment. Though it is not intuitive, proteins also unfold with pressure. 

The efficiency of hydrostatic pressure treatment may be enhanced by applying it in combination with mild temperature (30°C-50°C) and/or with bacteriocin (Trujilo et al., 2002 Devlieghere et al., 2004). Examples of commercialized products treated by high hydrostatic pressure are fruit juices, jams, sauces, and sliced cooked ham (Trujillo et al., 2002). 

Narisawa et al. (2008) demonstrated that protein fractions of skimmed milk provided protection against injury and inactivation of E. coli by high hydrostatic pressure treatment. The protective effect was found to increase with an increase in the concentration of protein in skimmed milk. Ramaswamy et al. (2009) indicated that casein and lactose present in milk were the major contributors for pressure protection of E. coli in milk during high-pressure treatment. Fat content in milk (0%-5%) had no significant influence on the destruction, however (Figure 5.13). 

Dede, S., Alpas, H., and Bayindirli, A. 2007. High hydrostatic pressure treatment and storage of carrot and tomato juices Antioxidant activity and microbial safety. Journal of the Science of Food and Agriculture 87 773-782. 

Kural, A.G. and Chen, H. 2008. Conditions for a 5-log reduction of Vibrio vulnificus in oysters through high hydrostatic pressure treatment. International Journal of EoodMicrobiology 122 180-187. 

Narisawa, N., Fumkawa, S., Kawarai, T., Ohishi, K., Kanda, S., Kimijima, K., Negishi, S., Ogihara, H., and Yamasaki, M. 2008. Effect of skimmed milk and its fractions on the inactivation of Escherichia coU K12 by high hydrostatic pressure treatment. International Journal of Food Microbiology 124 103-107. 

Sainz, C.B., Younce, F.L., Rasco, B., and Clark, S. 2009. Protease stability in bovine milk under combined thermal-high hydrostatic pressure treatment. Innovative Food Science and Emerging Technologies 10 314-320. 

Polydera, A.C., Stoforos, N.G., and Taoukis, P.S. 2005b. Effect of high hydrostatic pressure treatment on post processing antioxidant activity of fresh Navel orange juice. Food Chem. 91,495—503. 

Li, H., Zhu, K., Zhou, H., Peng, W, 2012. Effects of high hydrostatic pressure treatment on allergenicity and structural properties of soybean protein isolate for infant formula. Food Chem. 132, 808-814. 

PTR-TOF-MS was also used to probe the effect of heat and high hydrostatic pressure treatment of milk base in the presence or absence of a transglutaminase protein and how it influences the flavor development of yoghirrt [86]. The influence of pig diet on the VOC profile of dry-cirred Iberian ham was examined with differences foimd in aldehydes, ketones, and srrlfur-corrtaining compotmds [87]. 

Bauer BA, Wiehle T, Knorr D. 2005. Impact of high hydrostatic pressure treatment on the resistant starch content of wheat starch. Starch/Starke 57 124-133. 

The third and perhaps most important class of water repellents consists of materials appHed to the surface of concrete for above-grade stmctures or others where water pressure on the concrete is small. This iacludes damp-proofing ia which treatments cannot be subjected to continuous or even intermittent hydrostatic pressure (83). Repellents that may be used are oils, waxes, soaps, resias, and siUcon-based systems (84). 

Chen, H., Hoover, D. G., and Kingsley, D. H. (2005). Temperature and treatment time influence high hydrostatic pressure inactivation of feline calicivirus, a norovirus surrogate. /. Food Prot. 68, 2389-2394. 

FIG. 4 Effects of varying raw material treatments prior to osmotic dehydration on moisture (MC) and solid (SC) content expressed on initial dry matter (idm). Potato slices, high hydrostatic pressure (Rastogi et al., 2001) carrot slices, PFE (Rastogi et al., 1999) bell pepper disks, PFE (Ade-Omowaye et al., 2002b) and apple slices, edible coatings (Lenart and Dabrowska, 1998). 

Rastogi, N.K., Angersbach, A., and Knorr, D. 2000b. Synergistic effect of high hydrostatic pressure pre-treatment and osmotic stress on mass transfer during osmotic dehydration. J. Food Engineer. 45, 25-31. 

High hydrostatic pressure (HHP) processes have been used mainly for sauces or seafood and proven effective at reducing microbial populations without adverse effects on product quality (Considine et al., 2008 Brinez et al., 2006). HHP treatment causes bacterial inactivation by damaging the cell membrane, which affects membrane permeability and intracellular enzyme inactivation and possibly ruptures the plant cell wall (Kniel et al.,... 

Kniel, K. E., Shearer, A. E., Cascarino, J. L., Wilkins, G. C., and Jenkins, M. C. (2007). High hydrostatic pressure and UV light treatment of produce contaminated with Eimeria acervulina as a Cyclospora cayetanensis surrogate.. Food Prot. 70,2837-2842. 

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). 

Most of the features of the theoretical treatment of bubble motion are present in the treatment that considers the water incompressible and neglects gravity effects. We quote from Cole (Ref 1, Chapt 8) The simplest approximation to the true motion of the bas bubble is the one in which it is assumed that the motion of the surrounding water is entirely radial and there is no vertical migration. In this approximation, which has been discussed by a number of writers, the hydrostatic buoyance resulting from differences in hydrostatic pressure at different depths is neglected. It is thus assumed that at an infinite distance from the bubble in any direction the pressure has the same value as the initial hydrostatic pressure P0 at the depth of the charge... 

Treatment in autoclaves was also used in earlier years to reduce the viscosity of collodion cotton intended for the manufacture of varnishes. For the same purpose, a water slurry of nitrocellulose may be boiled under hydrostatic pressure in tubes, as a continuous process. These methods are discussed in detail in the chapter devoted to the manufacture of collodion cotton for varnish production. 

The results are not very different for the two techniques, as recent studies on Escherichia coli have demonstrated [2] a treatment with CO2 with a contact time of 15 min, an operating pressure of 150 bar, and constant temperature of 35°C, leads to the same microbial reductions as a treatment with a hydrostatic pressure of 3000 bar at the same temperature. 

Nowadays, supercritical C02 is used in numerous technological processes for the production or treatment of new materials. Among others, the food industry is seeking new alternative techniques to protect and preserve foods. The use of C02, a non-inflammable, atoxic, relatively inexpensive gas, under supercritical conditions, could become relevant in this field. In fact, it has been demonstrated that the effect of microbial inactivation, assuring healthy food preservation is already consistent at more moderate pressures (lower than 200 bar) than those employed by traditional hydrostatic-pressure HPT methods. 

In experiments with cultured cells it has been shown that osteocytes, but not periosteal fibroblasts, are extremely sensitive to fluid flow, resulting in increased prostaglandin as well as nitric oxide production [104, 105], Three different cell populations, namely osteocytes, osteoblasts, and periosteal fibroblasts, were subjected to two stress regimes, pulsatile fluid flow and intermittent hydrostatic compression [104], Intermittent hydrostatic compression was applied at 0.3 Hz with a 13-kPa peak pressure. The pulsatile fluid flow was a fluid flow with a mean shear stress of 0.5 Pa with cyclic variations of 0.02 Pa at 5 Hz. The maximal hydrostatic pressure rate was 130 kPa/sec and the maximal fluid shear stress rate was 12 Pa/sec. Under both stress regimes, osteocytes appeared more sensitive than osteoblasts, and osteoblasts more sensitive than periosteal fibroblasts. However, despite the large difference in peak stress and peak stress rate, pulsatile fluid flow was more effective than intermittent hydrostatic compression. Osteocytes, but not the other cell types, responded to 1 hour pulsatile fluid flow treatment with a sustained prostaglandin E2 upregula-... 

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