Studies On The Effects Of Microencapsulation On The Physicochemical Properties And Stability Of Rose Residue Pigment

Rose(Rosa rugose)is a flower with high edible and medicinal value,but a large amount of flower residue is produced and wasted in rose essential oil industry.The extraction of edible natural pigment from rose residue and the microencapsulation of pigment to improve stability can not only improve the applied value of rose resource,but also reduce the cost of natural pigments development.In this study,rose residue was used as raw material for extraction,microencapsulation and characterization of natural pigment.The morphologies of the rose residue pigment and its microcapsules were evaluated by sensory evaluation and scanning electron microscopy.Physical properties such as moisture content,density,hygroscopicity,solubility and fluidity were determined.And chemical bonds were identified by Fourier infrared spectroscopy.Finally,the stability,degradation kinetics and gastrointestinal release characteristics were determined in terms of the retention rate of total flavonoids.The main conclusions were as follows.The natural pigment extracted from rose residue was initially identified as flavonoid according to ultraviolet absorption spectroscopy and chromogenic reaction.The extraction yield of rose residue pigment by aqueous two-phase extraction method was 11.58%,significantly higher than those by the aqueous acid extraction and alcohol extraction.Aqueous two-phase extraction separated the pigment and sugar,playing the role of preliminary purification.The recovery rate of pigment reached 93.70%in top phase.The purity of rose residue pigment was 79.20%after purification with macroporous resin AB-8.The rose residue pigment microcapsules were produced by spray drying.The highest encapsulation efficiency was at 84.25%when using maltodextrin as the wall material.Among composite wall materials,the combination of maltodextrin and gum arabic achieved the optimal encapsulation efficiency and sensory performance.The optimum conditions of microencapsulation process by response surface methodology were:total solid content 20%,ratio of core to wall material 5:1,and ratio of wall materials 4:1.The encapsulation efficiency of rose residue pigment reached 98.34�0.40%under the above conditions.The microcapsules loaded with rose residue pigment were shown as new phases by scanning electron microscopy and Fourier transform infrared spectroscopy,which proved the formation of pigment microcapsules.The pigment microcapsules were light pink and slightly sticky powders,and the particles were fine and uniform with no impurities.The recovery solution was dark orange,homogeneous and stable without agglomeration,which was close to the solution before spray drying.The microcapsules were single spherical particles,and the particles size became larger after spray-drying,which was among 1?10 ?m.The surface of microcapsules was intact without cracks or holes,except some wrinkles.The surface of microcapsule with composite wall materials appeared smoother indicating the better performance.The moisture content of the microcapsules was about 4%,only 1/3 of the counterparts of unembedded pigment.The density of the microcapsules was about 0.5 g/mL,about 2.5 times that of the unembedded particle.The hygroscopicity and fluidity of the microcapsules decreased while the solubility increased slightly.Rose residue pigment was not resistant to light and heat,and sensitive to oxygen and pH,while microencapsulation could significantly improve the stability of pigment.At the storage temperatures of 4?,25? and 37?,the degradation of total flavonoids in rose residue pigment and microcapsules were consistent with the first-order reaction kinetics model,and the degradation rate constant(k)increased as the increase of storage temperature.The k value of pigment microcapsules was far below that of umembedded pigment,and the half-life increased significantly,indicating that microencapsulation could stabilize the rose residue pigment and extend its shelf life.The combination of maltodextrin and gum arabic as an encapsulant showed the lowest degradation rate and the longest half-life.During the digestion of the simulated gastrointestinal tract,the release rate of flavonoid pigments in the microcapsules was significantly reduced,especially that with composite wall materials,indicating that the microcapsules had a sustained release effect.