The Preparation And Aroma Stability Research Of Citral Pickering Emulsion

Citral is one of the most important flavor compounds in fresh juice,which contributes to a strong,pleasant and lemon-like aroma with very high consumer acceptance.Unfortunately,it is chemically unstable,and degrades rapidly at low pH and oxidative environment.This limited its extensive application in food industries.In this research,we applied Pickering emulsion stabilized with polysaccharide particles to encapsulate citral and protect it from degradation in acidic environment.Thus the aroma stability of citral was improved.First,the polysaccharide particles were modified and the selected polysaccharide particles were chitosan,cellulose and starch.Chitosan was modified with sodium tripolyphosphate(TPP)by ionic crosslinking and formed chitosan-sodium tripolyphosphate(CS-TPP).Microcrystalline cellulose(MCC)was dissolved and regenerated by concentrated phosphoric acid and formed regenerated cellulose(RC).Waxy maize starch(WMS)was modified with octenyl succinic anhydride(OSA)and formed octenyl succinic anhydride modified waxy maize starch(OSA-WMS).Then the Pickering emulsion stabilized with the above modified polysaccharide particles were prepared by high-shear rotor homogenizer.The ratio of polysaccharide particles and their modified reagents were optimized by the size,morphology and appearance of the Pickering emulsions.Results shown that the obtained Pickering emulsion had high stability when the ratio of CS to TPP was 5:5(w/w),the ratio of concentrated phosphoric acid to MCC was 50:1(v/w)and the ratio of OSA to WMS was 3:100(w/w).Three groups of Pickering emulsion stabilized with different concentrations of the above optimal modified polysaccharide particles were prepared.And the size,size distribution,microstructure and appearance of the Pickering emulsions were studied.Besides,the stabilization mechanism of the Pickering emulsions were discussed.Results shown that the size of the Pickering emulsions decreased as the concentrations of the modified polysaccharide particles increased,and the stability of the Pickering emulsion enhanced.Moreover,the Pickering emulsions were spherical and without aggregation and demulsification.The Pickering emulsions had high stability when the concentration of CS-TPP was 0.6%(w/v),the concentration of RC was 0.8%(w/v)and the concentration of OSA-WMS was 1.5%(w/v).CLSM revealed the absorption of the modified polysaccharide particles on the oil-water interface.The particles prevented the aggregation of the droplets,thus stabilizing the Pickering emulsions.After the concentration of the modified polysaccharide particles were optimized,the aroma stability of citral in the Pickering emulsions was analyzed by gas chromatography(GC).Results showed that the Pickering emulsion could protect citral from degradation effectively compared with the control.And the contents of 4-isopropyltoluene,4-methylacetophenone and p-cresol were decreased.In the Pickering emulsion stabilized by CS-TPP(the concentration of CS-TPP was 0.6% w/v),the retention of citral was 52.34%,58.11% in the Pickering emulsion stabilized by RC(the concentration of RC was 0.8% w/v)and 62.23% in the Pickering emulsion stabilized by OSA-WMS(the concentration of OSA-WMS was 1.5% w/v),while the retention of citral was 0.98% in the control.In comparison,the aroma stability of citral in the Pickering emulsion stabilized by OSA-WMS was the highest.Finally,the stability mechanism of citral in the Pickering emulsion was studied combined with the molecular structure of the modified polysaccharide particles.The modified polysaccharide particles were amphiphilic,the hydrophilic group of the particles connected with water phase,the hydrophobic group connected with oil phase.Thus isolated citral from the acid environment,enhancing the aroma stability of citral.