Antifungal efficacy of sunflower oil as a natural preservative for stored grains

Fungal contamination of stored grains by Aspergillus, Penicillium, and Fusarium threatens food security and public health. Grain preservatives are essential to maintain product quality and safety. This study investigated sunflower oil (Helianthus annuus), reported to be rich in fatty acids, tocopherols, phytosterols, and phenolic antioxidants, as an antifungal alternative to conventional preservatives. Non-refined sunflower oil obtained by laboratory extraction (SO) showed broad-spectrum activity against all 21 grain-relevant filamentous fungi tested, with minimum inhibitory concentration (MIC) values of 0.05% to 0.4%. In contrast, commercial sunflower oil (CSO) was inactive (MIC > 50%), indicating that antifungal efficacy depends on extraction and refinement processes. In a 28-day challenge test on barley grains, SO at 1% effectively reduced counts of the two Fusarium species to levels equivalent to the negative control, with only partial efficacy against Aspergillus flavus. Mechanistic assays indicated that SO does not act through cell wall disruption or ergosterol binding. A preliminary ex vivo porcine intestinal assay showed no histological signs of mucosal irritation at ten times the highest MIC. Thus, non-refined sunflower oil shows potential as a natural antifungal agent for stored grains under the conditions evaluated, and further studies are needed to confirm its efficacy and safety.