Mulberry Silkworm (Bombyx Mori) Pupae Extract as A Substitute for Synthetic Antioxidants in Vegetable Cooking Oils

Shelf stability of vegetable cooking oils is affected by their oxidation process (rancidity). Rancidity is a chemical process that involves oxidation or hydrolysis of oils/fats on exposure to moisture, air, light or bacteria giving rise to products such as ketones, aldehydes or free fatty acids. Rancid oils have a bad smell which affects vegetable oil quality. Synthetic antioxidants such as butylated hydroxytoluene (BHT) have the ability to slow down the oxidation process. However, their usage is discouraged due to toxicity after prolonged intake. Natural antioxidants may hold the solution to the rancidity problem. Silkworm pupae extract has been tested and found to be a potent natural antioxidant. This work evaluates the efficiency of the silkworm pupae oil extract as an antioxidant in vegetable cooking oils. Silkworm pupae extract was obtained by chloroform/methanol/water extraction. The extract was then added to sunflower and corn oils and their fatty acid profiles determined by GC-MS analysis. Thermal stability of the treated vegetable cooking oils and efficiency of the extract against autoxidation was also evaluated. The data obtained was analyzed using Stata version 12 package. Variations in studied parameters were compared using analysis of variance at a confidence level of 95% (p < 0.05). The oxidative stability of mulberry pupae extracts enriched - vegetable oils under typical cooking and shelf storage conditions was also statistically determined. The addition of silkworm extract into corn and sunflower oil as well as storage period had a significant effect on the physical and chemical characteristics of the oils. The silkworm extract contributed to more than half of the SFA in all the corn oil samples, specifically the corn oil treated with 200ppm of silkworm extract had significantly high levels of myristic acid (9.23%) while lauric acid was notably high in corn oil samples (7.8% & 2.13%) with both 100 ppm and 200 ppm silkworm extract respectively. Oil samples preserved using 100 ppm BHT had significantly high viscosity (25.41 & 32.03 Pa. s for corn and sunflower respectively) and density (0.91 & 0.92 Kg/m3 corn and sunflower respectively) as compared to samples preserved using 100ppm silkworm extract (21.83 & 28.25 Pa. s for corn and sunflower respectively) and (0.89 & 0.88Kg/m3 for corn and sunflower respectively); 200ppm silkworm extract (24.43 & 26.85 Pa. s for corn and sunflower respectively) and (0.88Kg/m3 for both corn and sunflower oils respectively. This therefore means that the silkworm extract had better influence on the flowability of the oils compared to BHT. The oils also had improved fatty acid profiles, corn and sunflower oils preserved using 200ppm silkworm extract had the highest MUFA content (36% & 35.5% for corn and sunflower oils respectively) with the predominant MUFA being oleic acid. Oil samples preserved using 100ppm and 200 ppm silkworm extract PUFAs accounted for 49% and 36% of the total fatty acid content; the major PUFA was linoleic acid. Oleic and linoleic acid are unsaturated fatty acids important for cardiovascular health, immunity and brain function. This study concludes that the incorporation of silkworm pupae oil extract improves vegetable cooking oils quality and supports the use of edible insects as a sustainable source of nutrition.