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There are few studies applying pulsed electric field (PEF) on solid foods in databases. Egg white protein (EWP) was subjected to PEF for elucidating mechanism of changes in molecular structure of enzymes and protein components for solid foods. Determination of free and total sulfhydryl groups, ultraviolet (UV) spectroscopy, infrared (IR) spectroscopy, and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) were used to compare EWP before and after PEF treatment. The results showed that the amount of free sulfhydryl increased while that of total sulfhydryl decreased after PEF exertion. PEF did not change the SDS-PAGE patterns visibly and no shift in maximum absorption wavelength but intensity could be observed in UV spectra of EWP. IR spectra of EWP were subjected to Gaussian multi-component peak modeling for molecular secondary structure analyses. Either the voltage of the PEF ( P < 0.01) or the residence time of the sample ( P < 0.05) significantly decreased the relative portion of α-helices while increased that of β-sheets in EWP, and impact could also be seen in respect of contents of β-turns and random coils in amide I region of EWP and its fractions. The results are of reference values to potential applications of PEF on solid foods. [ABSTRACT FROM AUTHOR]

Pulsed electric field (PEF) was applied to moisture-preconditioned canola seeds to evaluate the effect on oil yield. The effect of PEF on functional and structural properties of canola protein left over after oil extraction were also examined in albumin and globulin fractions obtained at optimal conditions for oil yield. Generally, PEF pretreatment significantly improved (P < 0.01) the following functional properties of canola protein and its fractions: solubility, water-holding capacity, emulsibility, emulsion stability, oil-holding capacity, foamability, and foam stability. Infrared spectrometry revealed that the secondary structure of the protein changed upon PEF, as shown by changes in the proportions of α-helices, β-sheets, and β-turns in the amide I region. An increased amount of free sulfhydryl groups and surface hydrophobicity suggested alterations in tertiary structure as well. PEF caused the formation of new protein aggregates with low molecular mass, demonstrated by sodium dodecyl sulfate polyacrylamide gel electrophoresis and changes in the number of total sulfhydryl groups. [ABSTRACT FROM AUTHOR]

Pulsed electric field (PEF) is promising in food industry in modifying properties of materials. The influences of PEF pretreatment on hydrolysis, texture, multi-scale and semi-crystalline lamellar structure, thermal properties, and flavor of rice were investigated with two special treatments for high and low contents of slowly digestible starch and resistant starch, using enzymatic hydrolysis, scanning electron microscopy, differential scanning calorimetry, X-ray diffractometry, small angle X-ray scattering, attenuated total-reflection Fourier-transform infrared spectrometry, texture profile analysis, and gas chromatography-mass spectrometry (MS)-MS. Upon PEF pretreatment, the starch hydrolysis degree and glycemic index of cooked rice increased slightly; the hardness, springiness, cohesiveness and chewiness of cooked rice increased significantly (P < 0.05). PEF reduced the integrity of cell structure, altered the gelatinization enthalpy, relative crystallinity degree, semi-crystalline layered structure of rice lightly, without obviously changing the diffractive pattern type of rice grains. PEF pretreatment caused decrease of phenols and ketones and increase of acids and aldehydes in cooked rice. • Pulsed electric field (PEF) significantly affected texture of cooked rice. • PEF significantly enhanced starch hydrolysis and increased glycemic index of cooked rice. • PEF significantly changed composition of volatile compounds of rice. [ABSTRACT FROM AUTHOR]

Highlights • Effect of PEF on structural properties of starches type A, B, and C investigated. • Polarized light microscopy, XRD, ATR-FTIR, SSNMR, SAXS, GPC used. • Effect of PEF on structure and in vitro digestibility of starch patterns revealed. Abstract Effect of pulsed electric field (PEF) on the structural properties of representative starches with different crystalline type, wheat starch for type A, potato starch for type B, and pea starch for type C, were investigated with polarized light microscopy (PLM), X-ray diffractometry (XRD), attenuated total internal reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, solid-state nuclear magnetic resonance (SSNMR) spectroscopy, small-angle X-ray scattering (SAXS), and gel permeation chromatography (GPC) to understand whether PEF could be applied directly in starchy foods. The results showed that PEF could change the structure of all three types of starch, especially potato starch; the birefringence, represented by Maltese cross in polarized microscopic observation changed slightly; XRD and SSNMR spectra demonstrated PEF did not change the crystalline type of starch granules. However, relative crystallinity variations happened at some points of electric field intensity (EFI). Increasing with the EFI, a bigger variation of R 1045/1022 happened in potato starch than in wheat starch and pea starch, as illustrated by ATR-FTIR. Significant influences of PEF on the scatter structure and fractal dimension of self-similar structures were observed for wheat starch and potato starch, but not for pea starch. The GPC suggested that molecular weight distribution changed for all the three starches. And in vitro tests showed that PEF changed significantly (P < 0.05) the digestibility of starches, especially wheat starch and potato starch. [ABSTRACT FROM AUTHOR]

Pulsed electric field (PEF) was efficient in inactivating lipase in wheat grains. To understand the modification in wheat components, the functional, rheological, and structural properties of vital wheat gluten (VWG) were evaluated after PEF treatment. The results showed that the PEF parameters, electric field intensity (EFI), pulse frequency, pulse width, and material residence time significantly (P < 0.01) affected the solubility, water-holding capacity, oil-holding capacity, foaming capacity, foam stability, and emulsion stability to different extents. The transition temperature and denaturation enthalpy of gluten protein decreased significantly (P < 0.01). The elastic modulus, viscous modulus, tanδ of the wet gluten protein, and the apparent viscosity of VWG changed slightly; however, they changed significantly (P < 0.05) with the increase in EFI. Larger EFIs resulted in a more homogeneously condensed and evenly distributed wet gluten pore. The proportion of α-helices and β-sheets had decreased and increased with the increase in EFI, respectively, while the proportion of random coils changed insignificantly (P > 0.05). The amount of free and total sulfhydryl increased and decreased significantly (P < 0.01) with an increase in EFI, respectively. Surface hydrophobicity was significantly reduced (P < 0.01). • Pulsed electric field (PEF) was applied to dry wheat gluten powder. • Functional, rheological and structural properties were investigated. • PEF showed significant actions on gluten protein properties to different extent. [ABSTRACT FROM AUTHOR]

Rice accounts for more than half the global population as staple food with starch predominating the major component. The effect of pulsed electric field (PEF) on thermal, paste and digestible properties, morphology, and hierarchical structure of rice starch in solid state was investigated. Upon PEF treatment, the gelatinization enthalpy (Δ Η) of starch decreased, the retrogradation value of starch paste decreased slightly; and the rapid digestible starch (RDS) increased, the slowly digestible starch (SDS) decreased and the resistant starch (RS) changed slightly. PEF might act on the outer structure of starch granules, slightly changed the molecular structure of rice starch by rearranging the short-range structure and damaging the amorphous and crystalline structure. Pearson correlation analysis suggested that molecular weight of amylopectin, Δ Η and digestibility were strongly dependent on the electric field strength; the changes in multi-scale structure was closely related to those in properties of PEF. The improvement of digestibility of rice starch might be attributed to the disruption of starch granule surface as evidenced by SEM observation and the rearrangement of multi-scale structures of rice starch induced by PEF. • PEF can modulate the properties and multi-scale structures of rice starch. • M w of amylopectin, ΔΗ and digestibility changes depending on the EFI input. • The digestibility improvement attributes to rearrangement of starch structures. [ABSTRACT FROM AUTHOR]