The Construction Of OSA Starch-based Nanocarriers And The Application In Curcumin Encapsulation

Curcumin is a hydrophobic polyphenol compound derived from plants,which has many physiological functions such as anti-oxidation,anti-inflammatory,anti-cancer and so on.However,the low water solubility,poor stability,sensitivity to environmental conditions,and low oral bioavailability of curcumin severely limit its further development and application in the fields of food,medicine,etc.Therefore,designing a scientific and ideal carrier for encapsulation is the core of solving the problem.The construction of nanocarriers provides a new idea for functional factor encupsulation and delivery systems designing.Starch as a natural polymer carrier,has lots of advantages such as wide range of source,low cost,ideal biocompatibility,safety and non-toxicity,easy modification of molecular structure and so on.To improve the water solubility,dispersibility and stability of curcumin,waxy maize starch(WMS)was selected as the raw material,then esterification with octenyl succinic anhydride(OSA)and combined with pullulanase treatment to prepare OSA-debranched starch(OSD).The OSD-curcumin nanocomposites were constructed through self-assembly;the effects of OSD with different degrees of substitution(DS)on the encapsulation effciency,stability and release of curcumin were investigated,and the encapsulation mechanism was explored.The main contents are as follows:Firstly,OSD with different DS were prepared,starch-based nanocarriers were constructed successfully,and the structures were characterized.In this paper,the effects of enzymatic hydrolysis conditions on particle size,polydispersity,DS and amylose content were investigated.The effect of molecular structure of OSD on the digestibility and thermodynamic properties of the carrier were explored.The results showed that debranching significantly reduced the relative molecular weight of OSA starch.OSD was mainly composed of short side chains,long side chains and incompletely debranched amylopectin;the particle size was 120.97 nm,the Zetapotential was-30.47 m V,indicated the OSD nanoparticles had good stability;the crystal structure of OSD was type B.Esterification and debranching increased the resistant starch content to 32.10%,which proved that OSD was suitable for preparing starch-based nanocarriers and encapsulation the functional factors.Secondly,OSD and curcumin were used for the preparation of nanocomposites,the encapsulation efficiency,loading capacity and particle size were considered as the inspection indicators,determined the optimal preparation process.When the mass ratio of curcumin/OSD was 1:40,the encapsulation efficiency reached more than 82%,the loading capacity was higher than 20 μg/mg,and the particle size was below 250 nm.It is speculated that there were three encapsulation forms of curcumin in the nanocomposites,the first and the most important one was the encapsulation of the hydrophobic cavity structure inside the nanocarriers,the second one was the inclusion of the spiral cavity structure of amylose,and the third one was the selfadsorption of the nanoparticles.By exploring the encapsulation mechanism,this paper found that the encupsulation of curcumin by OSD mainly relied on intermolecular hydrogen bonding and hydrophobic interaction.Finally,this paper examined the stability of the nanocomposites and the release characteristics of curcumin.The results showed that the light stability of curcumin was increased by20.56% after encapsulation with starch-based nanocarriers;the retention rate of curcumin was96.67% after heating at 95°C for 20 min,indicated the thermal stability was significantly improved compared with free curcumin;antioxidant and free radical scavenging ability were improved,which were 1.94 times and 4.18 times of free curcumin,respectively.Realized the effective release of curcumin in the intestinal environment,inhibited the degradation of curcumin in neutral and alkaline environments,and increased the digestion and absorption rate to 28.21%,which was 5.95 times of free curcumin;the cumulative release rate in the simulated intestinal fluid environment and blood environment was 66.20% and 60.25%,respectively.