Preparation Of Proanthocyanidin Microcapsules And Its Performance Study

Proanthocyanidins are now internationally recognized as effective natural antioxidants,with an antioxidant capacity 20 times that of vitamin C and 50 times that of vitamin E.However,proanthocyanidins exhibit some properties that may limit their industrial application and are susceptible to oxidative hydrolysis or ring-opening degradation during processing and storage by temperature,light,p H,oxygen,redox agents,metal ions,etc.,resulting in a reduction of their physiological activity.Microcapsules are often used to encapsulate unstable active substances such as polyphenols to enhance their stability and physiological activity,and there are few studies on the preparation of microcapsules by the sharp-pore method,and the single sodium alginate as the wall material has poor mechanical properties.stability,antioxidant activity and slow release performance of proanthocyanidins.The results of the study are as follows:（1）Based on the single-factor experiment and the screening experiment（Plackett-Burman,PB）,the effects of five factors on the embedding rate were investigated:wall-to-core ratio,mass fraction of sodium alginate solution,mass fraction of carboxymethyl cellulose solution,mass fraction of calcium chloride solution and embedding time.The optimal conditions for the preparation of proanthocyanidin microcapsules by the sharp pore method were optimized using response surface experiments,and the optimal conditions for the preparation of proanthocyanidin microcapsules were the core-to-wall ratio of 1:3,the mass fraction of sodium alginate solution of 2.0%,the mass fraction of carboxymethyl cellulose solution of 1.50%and the mass fraction of calcium chloride solution of 3.0%.The embedding rate of proanthocyanidins was 93.57%.This method has high microencapsulation rate,mild conditions,and is simple and feasible.（2）The properties and structures of the prepared proanthocyanidin microcapsules were characterized.The particle size of lyophilized microcapsules was 0.82 mm=820μm<1000μm,which is within the applicable particle size range of microcapsules.The morphological observation showed that the wet proanthocyanidin microcapsules were rounded and smooth without trailing and sticking,and the lyophilized microcapsules were observed to be intact solid particle structure;the color difference analysis of the microcapsules showed that there was a difference in the color difference before and after the embedding of proanthocyanidin,and the proanthocyanidin after the embedding became brighter but to the extent of reddish-brown.The difference between the microcapsules prepared with carboxymethyl cellulose and sodium alginate as the wall material and those prepared with single sodium alginate was found that the mechanical properties of the microcapsules prepared with the composite wall material were improved;the thermogravimetric analysis of the microcapsules proved that the microencapsulation enhanced the storage stability of procyanidins,and the procyanidins were successfully loaded,The results of spectral analysis indicated that proanthocyanidins were successfully encapsulated.（3）The stability of proanthocyanidins microcapsules was investigated.Different p H,temperature and light were used to treat proanthocyanidins and their microcapsules,and the higher retention rate of proanthocyanidins in microcapsules was found by comparing the retention rate of proanthocyanidins between them,indicating that microencapsulation of proanthocyanidins is an effective means to enhance the acid and alkaline resistance,heat resistance and light resistance of proanthocyanidins.retention of proanthocyanidins than single proanthocyanidins in a 28-d storage experiment;The adverse effect of different metal ions(Na⁺,Zn²⁺,Mg²⁺,K⁺,Ca²⁺,Fe²⁺,Fe³⁺)on the stability of proanthocyanidins in microcapsules was much less than that of single proanthocyanidins,indicating that microcapsules can maintain the stability of proanthocyanidins in metal ion solutions to some extent;by analyzing the effect of common food additives（potassium sorbate,sodium benzoate,citric acid,sodium bisulfite）on the stability of proanthocyanidins in microcapsules,it was found that the retention of proanthocyanidins in microcapsules was higher compared with that of single proanthocyanidins,indicating that microcapsules can significantly enhance the stability of proanthocyanidins against food additives.（4）Antioxidant activity and in vitro release studies of the prepared proanthocyanidins microcapsules were performed.By measuring the scavenging ability of microcapsules on DPPH radicals,ABTS radicals and hydroxyl radicals as well as the magnitude of ion reduction ability,it was found that microcapsules had slightly stronger antioxidant activity than single proanthocyanidins,i.e.microencapsulation would not adversely affect the antioxidant activity of proanthocyanidins;in vitro simulated digestion experiments were conducted on microcapsules and single proanthocyanidins,and it was found that the cumulative release rate of proanthocyanidins from microcapsules The cumulative release rate of proanthocyanidins in microcapsules was always significantly lower than that of single proanthocyanidins,which proved that microencapsulation of proanthocyanidins could significantly improve the slow-release effect of proanthocyanidins;The release rate curves of microcapsules at different p H（4,6,8）and temperature（4℃,25℃,37℃）were fitted with Avrami’s formula to study the release characteristics of microcapsules under different conditions,and it was found that the microcapsules fit well with the formula,and the release response of microcapsules under temperature and p H conditions were between the diffusion-limited kinetic response and the primary kinetic response except 25℃.By comparing the release rate constants of microcapsules,it was proved that microcapsules could be stored relatively stably at 4℃and p H 4,respectively.