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. 2025 May 21;14(10):1833.
doi: 10.3390/foods14101833.

Moderate Ohmic Field Modification of Okara and Its Effects on Physicochemical Properties, Structural Organization, and Functional Characteristics

Zhongwen Cao  1   2 , Chengcheng Xie  1   2 , Cheng Yang  2   3 , Xingyu Liu  1   2 , Xiangren Meng  1   2
Affiliations

Moderate Ohmic Field Modification of Okara and Its Effects on Physicochemical Properties, Structural Organization, and Functional Characteristics

Zhongwen Cao et al. Foods. .

Abstract

This study employed ohmic heating to investigate its impact on the physicochemical properties, structural organization, and functional characteristics of okara. Ohmic heating was applied with different field strengths and holding times. After moderate ohmic treatment, the water-holding capacity, oil-holding capacity, and swelling capacity of okara increased by 51.11%, 88.89%, and 43.64%, respectively. The microstructure and secondary structure were improved. The total sugar and soluble dietary fiber content were enhanced. The levels of active substances such as total flavonoids and total phenols significantly increased, leading to improved antioxidant capacity. The properties of okara were influenced by the field strength and holding time. This study provides new insights for the processing and development of okara, particularly in the application of functional foods.

Keywords: functional foods; modification; ohmic heating; okara.

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Conflict of interest statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Figure 1
Figure 1
OH Schematic Diagram: (a) control computer, (b) alternating current variable-frequency power supply, (c) control cabinet, (d) heating chamber, (e) thermocouples, (f) control panel of alternating current variable-frequency power supply, and (g) control panel of control cabinet. OH: Ohmic heating.
Figure 2
Figure 2
Total sugar content of okara after WH and OH treatments. UT: untreated okara, WH: water heating, OH: ohmic heating. Numbers 3, 6, and 9 represent incubation for 3, 6, and 9 min; 0, 40, 45, and 50 represent field strengths of 0, 40, 45, and 50 V/cm. The different letters represent significant differences among all groups (p < 0.05).
Figure 3
Figure 3
Content of SDF in okara after WH and OH treatment. UT: untreated okara, WH: water heating, OH: ohmic heating. Numbers 3, 6, and 9 represent incubation for 3, 6, and 9 min; 0, 40, 45, and 50 represent field strengths of 0, 40, 45, and 50 V/cm. The different letters represent significant differences among all groups (p < 0.05).
Figure 4
Figure 4
The TFC of okara before and after WH and OH treatments. TFC: total flavonoid content, UT: untreated okara, WH: water heating, OH: ohmic heating. The numbers 3, 6, and 9 represent incubation for 3, 6, and 9 min; 0, 40, 45, and 50 represent field strengths of 0, 40, 45, and 50 V/cm. The different letters represent significant differences among all groups (p < 0.05).
Figure 5
Figure 5
The TPC of okara after WH and OH treatments. TPC: total phenolic content, UT: untreated okara, WH: water heating, OH: ohmic heating. The numbers 3, 6, and 9 represent incubation for 3, 6, and 9 min; 0, 40, 45, and 50 represent field strengths of 0, 40, 45, and 50 V/cm. The different letters represent significant differences among all groups (p < 0.05).
Figure 6
Figure 6
The DPPH radical scavenging and ABTS radical scavenging abilities of okara after WH and OH treatments. UT: untreated okara, WH: water heating, OH: ohmic heating. The numbers 3, 6, and 9 represent incubation for 3, 6, and 9 min; 0, 40, 45, and 50 represent field strengths of 0, 40, 45, and 50 V/cm. The different letters represent significant differences among all groups (p < 0.05).
Figure 7
Figure 7
The Fourier-transform infrared spectra of okara after WH and OH treatment. UT: untreated okara, WH: water heating, OH: ohmic heating. The numbers 3, 6, and 9 represent incubation for 3, 6, and 9 min; 0, 40, 45, and 50 represent field strengths of 0, 40, 45, and 50 V/cm. (a) Fourier-transform infrared spectra of UT and WT. (b) Fourier-transform infrared spectra of UT and OH40. (c) Fourier-transform infrared spectra of UT and OH45. (d) Fourier-transform infrared spectra of UT and OH50.
Figure 7
Figure 7
The Fourier-transform infrared spectra of okara after WH and OH treatment. UT: untreated okara, WH: water heating, OH: ohmic heating. The numbers 3, 6, and 9 represent incubation for 3, 6, and 9 min; 0, 40, 45, and 50 represent field strengths of 0, 40, 45, and 50 V/cm. (a) Fourier-transform infrared spectra of UT and WT. (b) Fourier-transform infrared spectra of UT and OH40. (c) Fourier-transform infrared spectra of UT and OH45. (d) Fourier-transform infrared spectra of UT and OH50.
Figure 8
Figure 8
The microstructure of okara after WH and OH treatment. UT: untreated okara, WH: water heating, OH: ohmic heating. The numbers 3, 6, and 9 represent incubation for 3, 6, and 9 min; 0, 40, 45, and 50 represent field strength of 0, 40, 45, and 50 V/cm. The square in images emphasizes the pores of okara.
Figure 9
Figure 9
Correlation analysis among various parameters of okara after ohmic heating modification. WHC: water-holding capacity, OHC: oil-holding capacity, SC: swelling capacity, TFC: total flavonoid content, TPC: total phenolic content, SDF: soluble dietary fiber. ‘*’ indicates a significant difference (p < 0.05).
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