Effects of different washing and precipitating solutions on sugar content, cytotoxicity, chemical structure and prebiotic potential of pistachio hull polysaccharide

Pistachio hull contains water-soluble polysaccharides with prebiotic potential. In polysaccharide extraction, ethanol is commonly used to remove impurities and precipitate polysaccharides. This study compared the efficiency and safety of different washing and precipitating materials to identify a cost-effective method to produce polysaccharides. The extracted polysaccharides were ethanol washed and ethanol precipitated (EWEP), methanol washed and methanol precipitated (MWMP), chemical washed and ethanol precipitated (CWEP), and chemical washed and methanol precipitated (CWMP). Bases on our results, using chemical compounds in washing stage led to a 50% decrease in the amount of extracted polysaccharide. The FT-IR analysis results, probiotic stimulation growth, and cytotoxicity assay showed no difference between the MWMP and EWEP polysaccharides (p > 0.05). The residual methanol, microstructure morphology, monosaccharide composition and antimicrobial activity of MWMP polysaccharide were also measured. We indicated that methanol is a safe, efficient and cost-effective agent for removing impurities and precipitating water-soluble polysaccharides. Further studies are required to explore the physical, chemical and functional characteristics of MWMP polysaccharide.