Quantitative Analysis of Ginger Maturity and Pulsed Electric Field Thresholds: Effects on Microstructure and Juice's Nutritional Profile

Abstract

This study used fresh (young) and old (mature) ginger tissues as model systems to investigate how plant maturity modulates the response to pulsed electric field (PEF), a non-thermal processing technology. Specifically, the influence of tissue maturity on dielectric behavior and its downstream effect on juice yield and bioactive compound extraction was systematically evaluated. At 2.5 kV/cm, old ginger exhibited a pronounced dielectric breakdown effect due to enhanced electrolyte content and cell wall lignification, resulting in a higher degree of cell disintegration (0.65) compared with fresh ginger (0.44). This translated into a significantly improved juice yield of 90.85% for old ginger, surpassing the 84.16% limit observed in fresh ginger. HPLC analysis revealed that the extraction efficiency of 6-gingerol and 6-shogaol increased from 1739.16 to 2233.60 µg/g and 310.31 to 339.63 µg/g, respectively, in old ginger after PEF treatment, while fresh ginger showed increases from 1257.88 to 1824.05 µg/g and 166.43 to 213.52 µg/g, respectively. Total phenolic content (TPC) and total flavonoid content (TFC) also increased in both tissues, with OG-2.5 reaching 789.57 µg GAE/mL and 336.49 µg RE/mL, compared with 738.19 µg GAE/mL and 329.62 µg RE/mL in FG-2.5. Antioxidant capacity, as measured by ABTS^•+ and DPPH^• inhibition, improved more markedly in OG-2.5 (37.8% and 18.7%, respectively) than in FG-2.5. Moreover, volatile compound concentrations increased by 177.9% in OG-2.5 and 137.0% in FG-2.5 compared with their respective controls, indicating differential aroma intensification and compound transformation. Structural characterization by SEM and FT-IR further corroborated enhanced cellular disruption and biochemical release in mature tissue. Collectively, these results reveal a maturity-dependent mechanism of electro-permeabilization in plant tissues, offering new insights into optimizing non-thermal processing for functional food production.

Keywords: cell disintegration; ginger maturity; juice yield; nutritional profile; pulsed electric field.

Figure 1

Total phenolic content (a) and total flavonoid content (b) of fresh and old ginger (juice) treated with PEF. Different letters above the data points indicate statistically significant differences (p < 0.05) among treatments.

Figure 2

Total flavanols (a) and condensed tannin contents (b) of fresh and old ginger (juice) treated with PEF. Letters above the data points denote significant differences among treatments (p < 0.05).

Figure 3

DPPH^• inhibition of FG (a) and OG (b); ABTS^•+ inhibition of FG (c) and OG (d); and metal chelation potential (e) of FG and OG treated with PEF. Letters above the data points indicate significant variation (p < 0.05).

Figure 4

SEM images of FG and OG slices treated with PEF at different intensities.

Figure 5

Cell disintegration degree (Z) of FG and OG treated with PEF. Different letters represent significant differences across treatments (p < 0.05).

Figure 6

FT-IR spectra of FG (a) and OG (b) juice treated with PEF.

Figure 7

6-, 8-, 10-Gingerol and 6-, 8-, 10-shogoal contents in FG and OG treated with PEF (2.5 kV/cm). Different letters indicate statistically significant differences (p < 0.05) among treatments.