Mitigation of apricot quality loss and waste during high-temperature processing via sonication and electric field pretreatments

Abstract

This study systematically evaluated the sequential application of 2% CaCl₂ soaking, sonication (150–300 W, 2–5 min), and pulsed electric field (PEF; 1.5–3.0 kV cm⁻¹, 30–90 min) pretreatments on firmness retention, weight loss, and bioactive compounds in apricot pieces prior to blanching at 85 °C for 3 min, employing a response surface methodology (RSM) design encompassing 27 treatments (T1–T27) alongside controls (C1: blanching only; C2: CaCl₂ + sonication; C3: CaCl₂ + PEF). Conventional blanching (C1) reduced firmness to 0.23 N (baseline) and incurred 20% weight loss, while the optimized treatment T10 (200 W/3 min sonication + 1.5 kV cm⁻¹ 30 min PEF) enhanced post-blanching firmness to 0.3335 N, achieving 45% retention (p < 0.05 vs. C1; superior to C2: 20%, C3: 27%), and curtailed weight loss to 9% (55% reduction). Firmness peaked at moderate sonication/PEF intensities but declined under extreme conditions due to over-permeabilization, with RSM plots revealing significant quadratic interactions (r = 0.92; firmness-weight loss). Bioactive retention in T10 surpassed C1, yielding a total polyphenol content (TPC) of 14.9 ± 0.8 mg GAE per g DW (19% higher), a total flavonoid content (TFC) of 6.6 ± 0.4 mg CE per g DW (25% higher), DPPH scavenging of 54 ± 4.0% (20% higher), and a total anthocyanin content (TAC) of 3.4 ± 0.2 mg C3G per g DW (36% higher; ANOVA, Tukey's HSD, p < 0.05), outperforming single pretreatments and correlating strongly with firmness (r = 0.88; TPC-firmness). Fourier-transform infrared spectroscopy (FTIR) confirmed intensified pectin cross-linking (1730 and 1620 cm⁻¹) and preserved glycosidic bonds in T10. The enhanced textural stability in T10 was further attributed to PME mediated demethylation of pectin, facilitating Ca²⁺–pectin cross-linking and strengthening the middle lamella structure, while X-ray diffraction (XRD) indicated elevated relative crystallinity (28.2% vs. 19.1% in C1), underpinning synergistic Ca²⁺-mediated pectin stabilization, cavitation enhanced impregnation, and electroporation driven uniformity against thermal degradation. These findings demonstrate combined pretreatments as a viable strategy to mitigate blanching-induced quality loss in apricot pieces, enhancing process yield, texture, and nutritional value for sustainable stone fruit processing.