Future trends

Most review articles have pointed out the potential of high pressure as a significant non-thermal alternative in food processing and preservation which allows better retention of food qualities such as colour, flavour and nutrient value. However, systematic quantitative data on its effectiveness and safety remain limited. However, the use of systematic kinetic studies has resulted in the development of inactivation models for some food spoiling enzymes and microorganisms (Sonoike et al., 1992; Hashizume et al., 1995; Ludikhuyze et al., 1998b; Weemaes, 1998; Van Loey et al., 1998; Indrawati, 2000; Reyns et al., 2000; Van den Broeck, 2000). As an example, Figure 17.1 shows a theoretical case study which combines data on pressure-temperature kinetics for some food quality-related enzymes (PPO, LOX, PME and ALP), microbial inactivation and chlorophyll degradation. In contrast to the various enzymes, the vegetative organisms follow a similar pattern, suggesting that enzymes are generally more resistant than vegetative microorganisms to pressure-temperature treatments. This model suggests that food quality-related enzymes may be more critical in defining optimal HP treatments. It can also be seen that at pressure-temperature combinations that result in sufficient inactivation of food-spoiling enzymes and microorganisms, total chlorophyll content is only slightly affected. This supports the view that nutritional and sensory quality is only minimally affected by pressure.

This kind of systematic kinetic approach provides a way forward for future research. Indeed, this kind of kinetic information on microbial and enzyme inac-tivation, together with more quantitative data on the effect of pressure on sensory and nutritional quality, is indispensable for regulatory approval (Food and Drug Administration (FDA) approval in the USA, Novel Food regulations in the EU).

Fig. 17.1 Simulated pressure-temperature combinations resulting in six log-unit reduction of microorganisms, 90% reduction of enzyme activity and 90% of chlorophyll loss after a treatment time of 15min: PPO (A); ALP (■); BSAA (O); pea LOX in situ (+); pea LOX in juice (♦); green bean LOX in situ (•); green bean LOX in juice (□); soybean LOX (►); PME (x); total chlorophyll content (—); yeast (A); Z. bailii (O); L. casei (-); E. coli (---).

Fig. 17.1 Simulated pressure-temperature combinations resulting in six log-unit reduction of microorganisms, 90% reduction of enzyme activity and 90% of chlorophyll loss after a treatment time of 15min: PPO (A); ALP (■); BSAA (O); pea LOX in situ (+); pea LOX in juice (♦); green bean LOX in situ (•); green bean LOX in juice (□); soybean LOX (►); PME (x); total chlorophyll content (—); yeast (A); Z. bailii (O); L. casei (-); E. coli (---).

The issue of toxic or allergenic compounds in pressure-treated food products also needs further investigation. Developments in these areas in the future would facilitate a larger scale industrial breakthrough of this new technology.

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