Mechanistic insights into structural evolution of goji berry (Lycium barbarum L.) during pulsed vacuum drying...

The textural formation mechanism of goji berry (Lycium barbarum L.) during pulsed vacuum drying (PVD) was investigated using multiscale approach integrating low-field nuclear magnetic resonance (LF-NMR), transmission electron microscopy (TEM), X-ray diffraction (XRD), rheological analyses, etc. Results indicated non-uniform moisture migration and transition in water transport pathways during PVD. Textural and rheological alterations were associated with pectin depolymerization and subsequent matrix densification. The progressive loss of cell membrane integrity was observed, as evidenced by ten-fold increase in malondialdehyde content. Concurrent modifications in cell wall polysaccharides (cellulose, hemicellulose, and pectin) revealed the crucial roles of pectin methyl esterase (PME) and polygalacturonase (PG) in facilitating the accumulation and transformation of chelator soluble pectin (CSP) from both water-soluble pectin (WSP) and Na2CO3-soluble pectin (NSP). These findings provide fundamental insights into the structural and mechanical evolution of berry during PVD, offering theoretical foundation for optimizing industrial dehydration processes to improve product quality.