Plasma-activated water regulates water distribution to resist softening of goji berries

Abstract

This study’s objective was to investigate the application of plasma-activated water (PAW) for treating goji berries and assess its effectiveness in preventing softening during storage. This objective was achieved by analyzing the water distribution and content of goji berries during storage using low-field nuclear magnetic resonance (LF NMR) and magnetic resonance imaging (MRI). The findings showed that PAW treatment shortened the relaxation time of T22 and T23, making the consistency of water freedom or binding degree of the four water environments in the treated goji berries higher compared with the control group. Furthermore, the PAW-treated group’s vacuolar and cell wall water contents were 4.532% and 86.544% at the late storage period; these values were all higher compared with the control group’s values. PAW treatment delayed the decrease of the goji berries’ vacuolar and cell wall water contents, reduced water loss, and regulated the water dynamic balance. In addition, the PAW treatment of goji berries increased the absorption peak of pectin at 1420 and 1735 cm−1, delayed the degradation of cell wall substances, and inhibited the deformation and damage of the cell wall structure; this resulted in a substantially higher pectin content compared with the control group (P < 0.05). Furthermore, the PAW-treated group’s polysaccharide content, hardness, and frangibility were 92.53 mg/g, 22.94 N, and 16.68 N respectively at the late storage period; these values were all higher compared with the control group’s values. The study’s results demonstrated that the PAW treatment of goji berries improves hardness and frangibility, reduces gumminess, and maintains texture characteristics, water content, and nutrients, especially polysaccharides, thereby delaying the softening process during storage.