Novel Applications of High Pressure Processing

Fish Protein Gels HPP can be used to produce new surimi products. In surimi processing, the sarcoplasmic proteins are removed by thorough washing since they do not form gels when heated. However, if sarcoplasmic proteins are pressurized at over 300 MPa, they will coagulate and can be incorporated into surimi and related products. Pressure-induced gels have been reported to have a springy texture similar to that of prepared sausages. Studies using various hydrocolloids (for example, various gums, alginates, and carrageenans) showed that the main difference was due to the process (pressure, temperature, time) under which the gels were produced. When gels were produced under high pressure with moderate heating, the resulting gels were very elastic and light, with high water holding capacities. Gels produced under high pressure at cold temperatures possessed high puncture test properties (breaking deformation, breaking force) and high cohesiveness and water holding capacity. In contrast, gels produced by heating at atmospheric pressure exhibit low cohesiveness, high lightness and yellowness, high adhesiveness and hardness. The combined systems (pressure treatments and ingredients) present a new potential for surimi type products. Muscle Appearance and Texture When red and white muscle fish are pressurized, the muscle tissue becomes opaque similar to boiling or grilling with increasing pressures and holding times. Therefore the fish obtains the characteristics of a cooked, rather than a fresh product. This color change may not be perceived by consumers as desirable. Both red and white muscle tissues become lighter with increasing hydrostatic pressures. The redness in red muscle fish decreases with increasing hydrostatic pressures, however, the yellow color is not affected by various pressure treatments. Similar color effects have been observed when Alaska pollock surimi was pressurized up to 500 MPa. There is a general toughening/hardening of the muscle tissue when 101 MPa of pressure is applied. The upper limit for maintaining or enhancing tissue hardness is the application of 203 MPa for 10 minutes. Beyond this point, the tissue becomes softer. The hardening of fish muscle is not generally considered an undesirable effect, however, softening could be a problem with fish having soft muscle tissues.