436 The nutrition handbook for food processo instrumentation. Different types of high pressure vessels can be distinguished, 1.e (i)'monobloc vessel(a forged constructed in one piece);(ii)multi layer vessel consisting of multiple layers where the inner layers are pre-stressed to reach pressure or(iii)wire wound vessel cons sisting of pre-stressed vessels formed by winding a rectangular spring steel wire around the vessel. The use of monobloc vessels is limited to working pressures up to 600 MPa and for high pressure application above 600MPa, pre-stressed vessels are used. The position of high pressure vessels can be vertical, horizontal or tilting depending on the way of processing(Mertens and Deplace, 1993; Zimmerman and Bergman, 1993 Galazka and Ledward, 1995; Mertens, 1995: Knorr, 2001) 21.4 Commercial high pressure treated food products With regard to the large-scale application of high pressure technology in the food industry, a problem still to be solved today is the improvement of the economic feasibility, i.e. the high investment cost mainly associated with the high capital cost for a commercial high pressure system. The cost of a vessel is determined y the required working pressure/temperature and volume. Furthermore, once technically and economically feasible processes have been identified, one needs to evaluate whether the unique properties of the food justify the additional cost and to what extent consumers are willing to pay a higher price for a premium ity produc High pressure technology is unlikely to replace conventional thermal pro- tood g, because the second \echnique is a well-established and relatively cheap food preservation method. Currently, the reported cost range of high pressure processes is 0. 1-0.2S per litre(Grant et al, 2000) whereas the cost for thermal treatment may be as low as 0.02-0.04$ per litre. However, the technology offers commercially feasible alternatives for conventional heating in the case of novel food products with improved functional properties which cannot be attained by conventional heating Today, several commercial high pressure food products are available in Japan, Europe and the United States. A Japanese company, Meidi-Ya, introduced the first commercial pressure treated product(a fruit-based jam) on the market in April 1990, followed in 1991 by a wide variety of pressure-processed fruit yoghurts, fruit jellies, fruit sauces, savoury rice products, dessert and salad dress ings(Mertens and Deplace, 1993). Recently, there were more than 10 pressure treated food products available in Japan. In Europe, fruit juice was the first commercially available high pressure product in France followed by a pressurised delicatessen style ham in Spain and pressurised orange juice in the United Kingdom. In the United States, high pressure treated guacamole has been launched on the commercial market. In addition, pressure treated oysters and hummus are commercially available. A list of commercially available pressurised food products in Japan, Europe and the United States in the last decade is sum- marised in Table 21.1instrumentation. Different types of high pressure vessels can be distinguished, i.e. (i) ‘monobloc vessel’ (a forged constructed in one piece); (ii) ‘multi layer vessel’ consisting of multiple layers where the inner layers are pre-stressed to reach higher pressure or (iii) ‘wire-wound vessel’ consisting of pre-stressed vessels formed by winding a rectangular spring steel wire around the vessel. The use of monobloc vessels is limited to working pressures up to 600 MPa and for high pressure application above 600 MPa, pre-stressed vessels are used. The position of high pressure vessels can be vertical, horizontal or tilting depending on the way of processing (Mertens and Deplace, 1993; Zimmerman and Bergman, 1993; Galazka and Ledward, 1995; Mertens, 1995; Knorr, 2001). 21.4 Commercial high pressure treated food products With regard to the large-scale application of high pressure technology in the food industry, a problem still to be solved today is the improvement of the economic feasibility, i.e. the high investment cost mainly associated with the high capital cost for a commercial high pressure system. The cost of a vessel is determined by the required working pressure/temperature and volume. Furthermore, once technically and economically feasible processes have been identified, one needs to evaluate whether the unique properties of the food justify the additional cost and to what extent consumers are willing to pay a higher price for a premium quality product. High pressure technology is unlikely to replace conventional thermal pro￾cessing, because the second technique is a well-established and relatively cheap food preservation method. Currently, the reported cost range of high pressure processes is 0.1–0.2 $ per litre (Grant et al, 2000) whereas the cost for thermal treatment may be as low as 0.02–0.04 $ per litre. However, the technology offers commercially feasible alternatives for conventional heating in the case of novel food products with improved functional properties which cannot be attained by conventional heating. Today, several commercial high pressure food products are available in Japan, Europe and the United States. A Japanese company, Meidi-Ya, introduced the first commercial pressure treated product (a fruit-based jam) on the market in April 1990, followed in 1991 by a wide variety of pressure-processed fruit yoghurts, fruit jellies, fruit sauces, savoury rice products, dessert and salad dress￾ings (Mertens and Deplace, 1993). Recently, there were more than 10 pressure treated food products available in Japan. In Europe, fruit juice was the first commercially available high pressure product in France followed by a pressurised delicatessen style ham in Spain and pressurised orange juice in the United Kingdom. In the United States, high pressure treated guacamole has been launched on the commercial market. In addition, pressure treated oysters and hummus are commercially available. A list of commercially available pressurised food products in Japan, Europe and the United States in the last decade is sum￾marised in Table 21.1. 436 The nutrition handbook for food processors