Ultra-high pressure treatment effects on polysaccharides and lignins of longan fruit pericarp

Longan fruit pericarp was subjected to ultra-high pressure treatment. The yields of water-soluble polysaccharides, alkali-soluble polysaccharides and cellulose were comparatively analysed before and after ultra-high pressure treatment. A negative relationship was observed between pressure and water-soluble polysaccharide yield. The lowest yield (6.4 ± 0.6 mg/g) was obtained at 500 MPa. No significant differences (P > 0.05) in alkali-soluble polysaccharide and cellulose yields was found between the ultra-high pressure-treated and non-treated samples (control). Furthermore, a similar phenomena was observed for cellulose. The degrees of hydrolysis (DH) of control and 500 MPa-treated cellulose were 26.6% and 29.4%, respectively, and there was a significant difference (P < 0.05) between them. The degradation and oxidation of lignins were analysed using high performance liquid chromatography, and four main peaks appeared. A comparative profile suggested that ultra-high pressure treatment could not result in a change in the lignin composition.