Objective This study aims to optimize the optimal process for preparing Chimonanthus nitens Oliv. leaf flavonoid microcapsules via the piercing method to enhance their stability. Method Single-factor experiments were conducted to investigate the effects of sodium alginate mass fraction，calcium chloride mass fraction，wall-to-core ratio，and coagulation bath temperature on the encapsulation efficiency and drug loading capacity.Subsequently，the response surface methodology （RSM） was employed to obtain the optimal process conditions，and the Chimonanthus nitens Oliv. leaf flavonoid microcapsules prepared under these conditions were subjected to characterization analysis，stability tests，and antioxidant activity determination. Result The optimal process parameters obtained by single-factor and response surface methodology （RSM） optimization were as follows：sodium alginate mass fraction of 2.0%，calcium chloride mass fraction of 3.0%，wall-to-core ratio of 10∶1，and coagulation bath temperature of 54 ℃.Under these conditions，the encapsulation efficiency of Chimonanthus nitens Oliv. leaf flavonoid microcapsules reached 75.0%.After drying，the Chimonanthus nitens Oliv. leaf flavonoid microcapsules exhibited a spherical shape with a smooth and dense surface，and an average particle size of 248.9 μm.The result of fourier transform infrared spectroscopy （FT-IR） confirmed that the flavonoids were effectively physically encapsulated within the wall material.Microencapsulation significantly enhanced the retention rate of Chimonanthus nitens Oliv. leaf flavonoids under high-temperature，light exposure，and storage conditions.After 4 hours of high-temperature incubation，the flavonoid retention rate of the microcapsules was 72.4%，which was 16.2% higher than that of the unencapsulated flavonoids.Following 8 hours of light exposure，the flavonoid retention rate of the microcapsules reached 81.6%，while that of the unencapsulated flavonoids decreased to 68.6%.After 28 days of storage，the flavonoid retention rate of the microcapsules was 94.5%，more than 5 times higher than that of the unencapsulated flavonoids.Furthermore，during the storage period，the microcapsules exhibited a mild downward trend in their scavenging capacity against 1，1-diphenyl-2-picrylhydrazyl （DPPH） radicals and 2，2’-azino-bis （3-ethylbenzothiazoline-6-sulfonic acid） （ABTS⁺） radicals，as well as in their ferric reducing antioxidant power （FRAP） value and ferrous ion chelating rate with the prolongation of storage time.In contrast，after 7 days of storage，all antioxidant indices of the unencapsulated flavonoids showed a sharp decline with the increase of storage time.After 28，the DPPH radical scavenging rate，ABTS⁺ radical scavenging rate，FRAP value，and ferrous ion chelating rate of the microcapsules were 89.8%，42.6%，4.0，and 5.1%，respectively，while those of the unencapsulated flavonoids were 17.0%，26.8%，1.3，and 2.2%.The Chimonanthus nitens Oliv. leaf flavonoid microcapsules not only possess a stable flavonoid content foundation but also exhibit consistent antioxidant activity.The correlation analysis showed that the flavonoid content was significantly positively correlated with its antioxidant activity. Conclusion This study established an optimal process for preparing Chimonanthus nitens Oliv. leaf flavonoid microcapsules via the piercing method，these microcapsules had complete structure and significantly improved stability of Chimonanthus nitens Oliv. leaf flavonoids.It provides technical support and a theoretical basis for the stabilized application of flavonoids from Chimonanthus nitens Oliv. leaf in functional foods or pharmaceuticals.
Fan et al. (Wed,) studied this question.