Performance of zein film modified by glycosylation and in vitro release analysis of hard capsule

Abstract: This article aims to clarify the effect of modification on the film performance and in vitro release pattern of hard capsules coated with the zein-glu film. The zein was modified using wet-heating glycosylation with glucose. The film performance after the modification was determined, including the mechanical properties, moisture resistance, oxygen resistance, oil resistance, and intestinallysis. The results showed that the film tensile strength of modified products significantly increased by 4.67 to 34.06 MPa (P<0.05), compared with the unmodified zein film, indicating that the wet modification effectively improved the brittleness of raw materials. The water absorption rate of zein film reached the maximum of 45.71% at 60 h, whereas, that of the zein-glu film reached a maximum of 84.98% at 24 h. The water absorption of the film might have been improved by wet-heating glycosylation with glucose. The reason was also that the zein introduced hydrophilic carbonyl glucose through glycosylation modification, thereby enhancing the absorption capacity of the modified product in the surrounding environment. The peroxide value of cling, zein, and zein-glu films were 0.55 g/100 g, 0.49 g/100 g, and 0.43 g/100 g, respectively, lower than that of commercially available plastic wrap. There was a great increase in the hydrogen, disulfide, and hydrophobic bonds closely connected between molecules after modification. The formed film with dense space structure presented relatively oxidation resistance. In water resistance of the film, the water vapor transmission rate of zein and zein-glu film enhanced slowly after 7 min, and then gradually stabilized after 32 min, finally decreased with time. The zein film after glycosylation modification behaved always a lower transmission rate of water vapor, compared with the unmodified. The water vapor transmission rate of the zein-glu membrane dropped to 7.89×10-8g·m/(m2·d·Pa), when it reached a plateau, indicating a higher transmission rate of water vapor in the modified film through wet heat with glucose. The oil permeability coefficient of the zein-glu film was 0. The oil resistance of the zein-glu film was similar to that of commercially available cling film. Consequently, the zein-glu film presented excellent barrier properties after modification. In addition, the oil resistance of the zein-glu film was better than that of zein film, indicating that the oil resistance of the zein-glu film was improved significantly. After that, the release pattern was determined, when the zein-glu film was filled with low molecule rhodamine B. Statistical analysis was performed on SPSS software. It was found that the zein-glu-made capsule was broken in the intestinal juice, but kept the film intact in the gastric juice, indicating the classic Enteric-coated capsules. Fitting the coefficient of determination of the simulated in vitro release mathematical model R2 was 0.800.The model was further verified using the chi-square, correlation, and significant test of t statistics.