Coating formula containing clove oil suppresses Aspergillus flavus growth on unshelled nutmeg seeds

Abstract

Aflatoxin contamination has become a constraint on nutmeg. The study aimed to determine the effectiveness of clove oil coating formula to suppress Aspergillus flavus growth on unshelled nutmeg. Clove oil, Curcuma oil, and coconut shell liquid smoke were evaluated for their fungicidal action on A. flavus and formulated the best one with powder carriers. The seeds were pre-treated with gelatin solution (1%) to improve coating adhesiveness, sprayed with A. flavus conidia, and incubated in humid conditions. Clove oil showed the strongest fungicidal action on A. flavus and was formulated (10%) with MgO, CaSO4, and CaO (1:1:1) powder. The coating formula could inhibit A. flavus growth, but A. flavus still colonized the seed's inner part. The coating formula did not affect the seed's water content, ranging from 9.8-10.22%. Pre-coating the unshelled source with gelatin solution (1%) improved the formula's coverage on the seed surface. The coating was more resistant after mechanical impact by falling from a 30 cm high. The amount of coating formula for treating 1000 unshelled seeds (11.75 kg) was approximately 2.8 kg. The coating formula of clove oil mix with carrier powder minimized A. flavus contamination of nutmeg shells.