Studies On Characteristics Of The Moso Bamboo Hemicelluloses-based Emulsifier

As consumers question the safety of synthetic emulsifiers,the demand for natural plant polysaccharide emulsifiers is increasing.Hemicelluloses-based materials can be used to stabilize oil-in-water food emulsions because of their physical and chemical properties.Currently,most studies are still limited to spruce galactoglucomannans（GGM）,and other types of hemicelluloses-based emulsifiers are rarely reported at home and abroad.Hemicelluloses-based emulsifiers are obtained through extraction methods and modification of alkaline-extracted hemicelluloses to prepare oil-in-water emulsions.Emulsifying stability was investigated by measuring droplet particle size distribution and size,Zeta potential,particle size distribution image,and emulsion stability.It provided theoretical support for the application of hemicelluloses-based materials in food emulsifiers.This study may contribute to choosing appropriate hemicelluloses-based emulsifiers for application in the food and beverage industries.First,after the moso bamboo are crushed,dewaxed,and dried for pretreatment,the hemicelluloses（H_L and H_H）were obtained from the dewaxed bamboo and the delignified bamboo（holocellulose）by hot water extraction,respectively.The results showed that H_L has higher lignin and protein content than H_H.Further study on the emulsifying properties of two different hemicellulose compositions,the results showed that the emulsifing stability of H_L increased first and then weakened with the increase of concentration.The emulsifing stability of H_L was the best when the concentration was 1.5 wt%.The droplet size distribution curve of H_L and H_H emulsions moved to the direction of large droplets with the increase of storage time.The droplet distribution image showed that the H_H emulsions had severe flocculation and H_L performed well.Subsequently,hemicelluloses were extracted from the pretreated bamboo material using high-concentration alkaline solution（10 wt%KOH）.Hemicelluloses were fractionated with 45%,60%and 75%ethanol solutions to obtain xylan-based emulsifiers（H₁,H₂ and H₃）.The molecular weight,lignin and protein content decrease accordingly,and the emulsifying stability decreases accordingly for H₁,H₂ and H₃.The results showed that droplet size distribution was standard normal distribution within a certain concentration range of H₁ and H₂,concentrated particle size distribution,strong electrostatic effect,and it showed good emulsification performance.The emulsifing stability of H₁,H₂ and H₃ was the best when the concentration was 1.0 wt%.With the increase of storage time,the droplet size distribution curve of the three emulsions moved to the direction of large droplets and emulsifying stability of H₁,H₂,and H₃decreased sequentially.Finally,hemicelluloses were extracted from the pretreated moso bamboo material using low concentration alkaline solution（3 wt%KOH）,and Octenyl succinate anhydride modified xylan（OSA-XH）was prepared by reacting xylan-based hemicellulose and octenyl succinic anhydride（OSA）using triethylamine as a catalyst in DMSO system.Through lots of experiments,we determined that reaction time（2 h）,reaction temperature（40℃）and n_osa/n_xylan=4:1,to obtain the maximum degree of substitution（DS=1.24）of OSA-XH.Studies have shown that the higher the degree of substitution,the stronger the emulsion stability.OSA-XH and common emulsifier GA were used to prepare emulsion under the same conditions.OSA-XH showed similar emulsion stability to GA.With the increase of the concentration,the average particle diameter of the emulsion formed by OSA-XH gradually decreased,and then it tended to be slow.When the concentration was 0.85 wt%,The emulsifing stability of OSA-XH emulsified emulsion reached the best.