Fabrication And Characterization Of Macadamia Oil Powders Based On Macadamia Protein Isolate/Chitosan Hydrochloride Complex Polymer

Macadamia protein isolate（MPI）is a natural,green,biocompatible,and sustain-able food grade ingredient with high nutritional value which mainly extractd from the kernel residues of macadamia nuts.And there is very scarce research focus on its application in the preparing of food emulsions and spray-dried oil powders.Based on this urgent requirements,the aim of present study was to investigate the optimum conditions for preparing the MPI/chitosan hydrochloride（CHC）non-covalent complexes and the primary interactions between two biopolymers in the formation of MPI/CHC complex.The storage ability of the complex polymer was also determined.After that,this paper further explored the potential of MPI/CHC complex in the stabilization of oil-in-water（O/W）emulsions and fabrication of macadamia oil powders.The main results were as follows:1.MPI is most likely to form the soluble complex with CHC by electrostatic attraction and hydrogen bond under the mass ratio of 5:1（MPI:CHC）at pH 4.5,which has been proved the optimal experiment condition by varying the the mass ratio of MPI-to-CHC and pH of solutions.Besides,the complex polymer has aslo shown the good storage ability in that there is still no obvious precipitation or other undesirable phenomena after storage for 7 days at ambient temperature.Moreover,the MPI/CHC（5:1）complex could also efficacious reduce the interfacial tension between the oil and aqueous phase which maintain its value about 4 mN/m.2.The O/W emulsions could be successfully prepared by utilizing the MPI/CHC complex as only bioemulsifier at the condition of high speed shearing.And when both biopolymers initially complexed in the absence of an oil phase,which will only be added at the end of the emulsification process could produce the fine emulsions with samllest droplet size and good storage ability.Furthermore,the mean droplet size(D_3,2,D_4,3)of O/W emulsions decreased gradually with the increase of complex concentration（c）or the reduction of oil volume fraction（φ）and then fluctuate at a certain value.Instead,the zeta（ζ）-potential of the complex appeared independent of variation in the c andφ.Nevertheless,the storage stability and centrifugal stability of the O/W emulsion were always promoted in pace with the elevation of c andφ.In addition,the O/W emulsion also exhibiting the typical pseudoplastic fluid properties,and the gel-like structures,its yielding stress were also enhanced with the increase c andφ.Beyond that,the emulsion has weak resistance to the enhancement of NaCl concentration in aqueous phase（<20 mM）,and displayed the preferable stability at pH 4.5 or 6.5.3.The capacity of MPI/CHC complex along with maltodextrin（MD）as the wall system for producing the macadamia oil powders was aslo investigated preliminary.The final results indicate that the optimal core-wall ratio was 1:3 when prepare the spray-dried oil powders.Besides,the addition of CHC would heighten the viscosity of macadamia oil emulsion,and its elevation in content improved the storage stability of the emulsion in a certain range as well.However,the emulsifying effect of wall material system on oil droplets decreases significantly when the content of CHC is too high,then the storage stability declined subsequently.In terms of powder properties,the addition of CHC had no significant effect on the humidity of the powder,but could significantly improve its solubility,wettability and decrease its flowability（p<0.05）.Furthermore,the wall material system which consist of MPI/CHC 5:1 and MD has exhibited the best rehydration stability,encapsulation efficiency and oxidative stability.