Changes in Physico-Chemical Properties of Sesame Seed Oil due to Infestation of Aspergillus flavus Link. and Penicillium implicatum Biourge

Abstract

Sesame seeds (Sesamum indicum L.) are nutritionally rich but highly susceptible to seed-borne fungi, which reduce seed viability and degrade oil quality. Fungal infestation, particularly by Aspergillus and Penicillium species, causes significant physicochemical changes in oil, including increased acidity and altered fatty acid composition. The present study was undertaken to investigate the seed-borne mycoflora associated with sesame (Sesamum indicum L.) and to evaluate the impact of fungal infestation on the physico-chemical properties of sesame seed oil. Seed samples were collected from four districts of Rajasthan, namely Jodhpur, Bikaner, Udaipur, and Chittorgarh. Mycoflora were isolated using standard blotter and agar plate methods, both with and without surface sterilization using 0.1% mercuric chloride. A total of 23 fungal species belonging to 18 genera were identified, with Aspergillus, Fusarium, Penicillium, and Alternaria were the most prevalent genera. The incidence of mycoflora was comparatively lower in pretreated seeds than in untreated seeds, indicating the effectiveness of surface sterilization. The seed germination percentage ranged from 32% to 87% using the blotter method and from 30% to 90% using the  agar plate method, higher germination was observed in pretreated seeds. The effect of two storage fungi, Aspergillus flavus and Penicillium implicatum, on oil quality was evaluated. Both fungi reducted in oil content, with P. implicatum causing greater deterioration. A significant increase in free fatty acid content was observed, particularly in seeds infected with A. flavus, indicating lipid hydrolysis. The saponification value increased with fungal infestation, suggesting the formation of lower-molecular-weight fatty acids, whereas iodine value decreased, reflecting a reduction in unsaturated fatty acids. The study highlights the critical role of seed-borne fungi in degrading seed quality and oil composition, emphasizing the need for proper storage and management practices to ensure seed health and oil quality.