Biological Properties of VHF‐ and Microwave‐Heated Soybeans

Biological Properties of VHF‐ and Microwave‐Heated Soybeans ABSTRACT Whole soybeans at natural moisture levels were heated by varied exposures to dielectric heating at frequencies of 42 and 2450 MHz. The minimum energy absorbed (MEA) was calculated from temperature‐elevation and moisture‐loss data. Because the heating rates were different at the two frequencies, plots of various biochemical properties against temperature or exposure time revealed an apparent frequency dependence. This dependence on frequency disappeared, however, when the MEA value was substituted as the independent variable. Chemical and biochemical analyses revealed that dielectric heating at natural moisture levels should be as efficient as commonly practiced moist “toasting” in improving the nutritional value of soybeans. Trypsin inhibitor activity was reduced to a low level, indicating that maximum nutritional quality had been reached. Protein solubility and dispersibility, but not urease activity, can be used as indicators of trypsin inhibitor inactivation by dielectric heating. Indications were obtained that MEA values, or perhaps even moisture loss, might be used as an index of trypsin inhibitor inactivation. Lipoxygenase‐inactivated samples of improved flavor were produced by the dielectric heating treatments. Some treated samples with low trypsin inhibitor and lipoxygenase activities still retained relatively high peroxidase activities that may be advantageous for bleaching effects. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Food Science Wiley

Biological Properties of VHF‐ and Microwave‐Heated Soybeans

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Publisher
Wiley
Copyright
Copyright © 1981 Wiley Subscription Services, Inc., A Wiley Company
ISSN
0022-1147
eISSN
1750-3841
D.O.I.
10.1111/j.1365-2621.1981.tb15371.x
Publisher site
See Article on Publisher Site

Abstract

ABSTRACT Whole soybeans at natural moisture levels were heated by varied exposures to dielectric heating at frequencies of 42 and 2450 MHz. The minimum energy absorbed (MEA) was calculated from temperature‐elevation and moisture‐loss data. Because the heating rates were different at the two frequencies, plots of various biochemical properties against temperature or exposure time revealed an apparent frequency dependence. This dependence on frequency disappeared, however, when the MEA value was substituted as the independent variable. Chemical and biochemical analyses revealed that dielectric heating at natural moisture levels should be as efficient as commonly practiced moist “toasting” in improving the nutritional value of soybeans. Trypsin inhibitor activity was reduced to a low level, indicating that maximum nutritional quality had been reached. Protein solubility and dispersibility, but not urease activity, can be used as indicators of trypsin inhibitor inactivation by dielectric heating. Indications were obtained that MEA values, or perhaps even moisture loss, might be used as an index of trypsin inhibitor inactivation. Lipoxygenase‐inactivated samples of improved flavor were produced by the dielectric heating treatments. Some treated samples with low trypsin inhibitor and lipoxygenase activities still retained relatively high peroxidase activities that may be advantageous for bleaching effects.

Journal

Journal of Food ScienceWiley

Published: May 1, 1981

References

  • Rapid improvement in nutritional quality of soybeans by dielectric heating
    Borchers, Borchers; Manage, Manage; Nelson, Nelson; Stetson, Stetson
  • Study of a lipohydroperoxide breakdown factor in soy extracts
    Gini, Gini; Koch, Koch

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