Thermal Food Processing

562 Thermal Food Processing: New Technologies and Quality Issues
TABLE 17.13
Chemical and free amino acid components of pressure
autolytic extract (PAE), fish sauce (Nampla) and soy sauce
17.8 CONCLUSIONS
The softening of vegetables and browning occurring during thermal processing
were suppressed by pressure. Pressure might also have the capability of inhibiting
an off-flavor and discoloration, and reducing viscosity during thermal
treatment. Another important function of thermal treatment is pasteurization
and sterilization of foods to provide consumer safety. It is, however, difficult
to kill microorganisms by pressure, because some microorganisms survived at
pressures above 500 MPa, while others died below 300 MPa. Bacterial spores
were considerably inactivated by thermal treatment combined with pressure,
though a few spores survived. Thus, the use of pressure for inactivating microorganisms
is effective, but there are still some problems to resolve. Finally, two
innovative techniques of pressure treatment combined with mild heating were
introduced. One is to use the combination of pressurization at 80 MPa and mild
heating at 42°C to allow easy shucking of oysters without the need of hands.
A key to shucking oysters is temperature. The other is the autolysis of unsalted
fish protein under pressurization. This technique can be a new way for producing
a good-quality autolytic extract in an extremely short period without any addition
of salt.
ACKNOWLEDGMENTS
PAE Nampla Soy sauce
pH 6.6 5.4 5.4
NaCl (%) 0.6 20.9 13.6
T-N (%) 2.62 1.74 1.41
F-N (%) 1.42 1.06 0.74
F-N/T-N 0.54 0.61 0.45
Amino acids (%)
Glu 1.47 1.22 1.23
Ala 1.00 0.78 0.79
Asp 0.88 0.84 0.19
Leu 1.27 0.67 0.72
Lys 1.24 0.87 0.30
The authors are indebted to Dr. Kenji Namba, Hiroshima University, for discussion
and valuable suggestions about the studies carried out in Section 17.7. The
authors are also grateful to Mrs. Y. Aoyama, Y. Shigeta, S. Tanimoto, S. Yamauchi,
and K. Kakugawa for their help across the board.