Preparation and antimicrobial effect of a cinnamaldehyde-based sustained release fumigant tablet for grain storage

Currently, aluminum phosphide tablets have been extensively used as fumigant for grain storage because they could release phosphine that shows highly efficient anti-microorganism. However, phosphine is highly toxic and flammable which usually causes production accidents. Therefore, this study aimed to develop a novel fumigant based on cinnamaldehyde and study its antimicrobial efficacy for grain storage. The novel fumigant tablet was composed of cinnamaldehyde, silica, citric acid and sodium bicarbonate. Results showed that mesoporous silica with ultra-high specific surface area (1036.5 m²/g) served as carrier for cinnamaldehyde. The mixture of citric acid and sodium bicarbonate reacted with moisture to generate carbon dioxide which was helpful to release cinnamaldehyde. As expected, the fumigant tablet displayed a sustained release effect. The in vitro culture experiments showed that cinnamaldehyde had high antimicrobial effect against five fungi including Aspergillus flavus, Aspergillus candidus, Aspergillus niger, Fusarium and Penicillium. In the accelerated mildew simulation experiment (temperature: 35 °C, humidity: 98%), the blank group without mildew preventive began to go mouldy after five days, the control group with only cinnamaldehyde became mildew one week later, whereas there was no visible mildew growth in the experimental group with the fumigant tablet after one week. The number of fungal colonies in the blank group and the control group after one week was 8.3 × 10⁴ and 6.5 × 10³ CFU/g, respectively, while there were no fungi detected in the experimental group. This cinnamaldehyde-based fumigant tablet is a green and safe mildew preventive, which provides an alternative solution to aluminum phosphide tablet for grain storage.