Research On Effects Of Copigmentation With Phenolic Acid And Microencapsulation On Stability Of Anthocyanins In Red-fleshed Apple

Red-fleshed apples with bright red are cultivated widely in Xinjiang Autonomous Region of China.They are rich in anthocyanins,which are good sources of natural edible pigment with a great potential value.Red-fleshed apples are too tart to be eaten raw and mainly used in food ingredients.However,anthocyanins are easy to be affected by lihting and heating which can lead to sediment and fading during processing and storage.'NO.1 Zihong' red-fleshed apple is taken as experimental material in present article.The methods of copigmentation and microencapsulation are used to protect anthocyanins and their influence on stability is investigated.The main results of this study were:1.Ultrasonic-ass isted method was used to extract anthocyanins in the flesh and skin of "NO.1 Zihong" red-fleshed apple.pH differential method was adopted to determine the total content of red-fleshed apple anthocyanins(268.6 mg kg-1 in fresh weight).HPLC was employed and results showed that "NO.1 Zihong”red-fleshed apple mainly consists of cyanidin-3-galactoside,cyanidin-3-arabinoside and cyanidin-3-glucoside,and cyanidin-3-galactosidase accounted for the largest proportion(75.34%).2.The powder of anthocyanins from 'NO.1 Zihong' red-fleshed apple was dissolved in a buffer solution with pH=3.0 and the copigmentation effect and stability of caffeic acid,ferulic acid,chlorogenic acid and gallic acid were evaluated under the condition of heating,light exposure,oxidation and adding metal ions(Fe3+).The main results were listed as follows:(1)At the concentration of 0.01 mol/L,caffeic acid,ferulic acid,chlorogenic acid and gallic acid all showed evident copigmentation,which leaded to the phenomena of hyperchromic effect and the bathochromic shift in varying degrees(5-11 nm);(2)After anthocyanins were heated in water-bath for one hour,chlorogenic acid and gallic acid showed the best protection effect,which was better than caffeic acid and ferulic acid;(3)Under natural lighting,the half-life of anthocyanins solution without copigments was less than 7 days,while the stabilities of anthocyanins with phenolic acids as copigments increased evidently(P<0.05)and the half-life of anthocyanins with chlorogenic acid was increased by 170.87%;(4)After being oxidized by 0.1%H2O2 forone hour,the content of anthocyanins in control group decreased to 38.39%,however,the retention rate of treatment groups with caffeic acid,ferulic acid,chlorogenic acid and gallic acid were 57.95%,63.10%,59.95%and 48.81%,respectively,which were significantly higher than control group(P<0.05);(5)The solution of Fe3+ with concentration of 2.5x10-4-1×10-3 mol·L-1 had an adverse effect on anthocyanins color and the stability of anthocyanins with gallic acid as copigments was the highest.3.As for the experiments of encapsulation,microcapsules were prepared with Arabic gum and malkodextrin(m:m=3:2)as the wall material and anthocyanins or anthocyanins-caffeic acid as core.Two drying processes,spray drying and vacuum freeze drying,were used to produce microcapsules with red-fleshed apple anthocyanin.The microcapsule samples made by spray drying were numbered as A1(without caffeic acid)and A2(with caffeic acid);the microcapsule samples produced by vacuum freeze drying were numbered as B1(without caffeic acid)and B2(with caffeic acid).The main results were demonstrated as follows:(1)The moisture content of Al,A2,B1 and B2 were 4.43%,4.81%,3.90%and 3.73%respectively and the microcapsule ratio of A1,A2,B1 and B2 were determined as 96.84%,93.85%,94.07%and 95.80%separately;(2)the particle mean diameter of these four groups were all around 300 nm and there was no obvious difference(P>0.05);all microcapsules were negatively charged while the charge quantity of freeze drying samples were obviously higher than that of spray drying samples(P<0.05);(3)Spray drying samples appear round particles with different size and the surface was bumpy while the shape of freeze drying samples were flake-like or blocky with pores;(4)The results of FTIR spectra analysis showed that microencapsulation had no obvious influence on the functional groups of original anthocyanins and the characteristic absorption bands of these four group were almost the same.(5)The microencapsulation of red-fleshed apple anthocyanins can significantly(P<0.05)improve the stability under the condition of heating,lighting and oxidation and the best processing procedure was first copigmentation and then microencapsulation;different drying processes had no obvious influence on the stability under the condition of heating,lighting and oxidation.In conclusion,the red-fleshed apples anthocyanins were very unstable in adverse condition,such as heating,lighting and oxidation.Both copigmentation and microencapsulation significantly improved the stability of red-fleshed apple anthocyanins,and combined with two methods showed super effect to protect the anthocyanins.