Effect of Sunlight Exposure and Packaging Materials on the Quality and Oxidative Stability of Commercial Vegetable Oils in Cameroon

Background: In Cameroon, edible oils are commonly packaged in translucent 1L polyethylene bottles and opaque 5L, 10 L, and 20L polyethylene containers. The translucent packaging is often favored by customers due to product visibility, potentially influencing purchasing decisions. However, in local markets, these oils are frequently exposed to direct sunlight throughout the day for display purposes until sail. Such exposure can compromise oil quality and pose potential health risks to consumers. Aims: The study aimed to evaluate the impact of ambient and direct sunlight storage conditions, as well as different packaging materials, on the quality and oxidative stability of palm olein, palm oil, and soybean oil. Methods: Palm oil, palm olein and soybean oil were selected for this study. Approximately 2.5 L of each oil was aliquoted into three portions: two 1.2 L portions for experimental storage and one 0.1 L portion to serve as an initial control. Each of the two 1.2 L experimental portions was further subdivided into nine 130 mL aliquots and transferred into three types of packaging: translucent polyethylene bottles (TPEB), non-translucent polyethylene bottles (NTPB), and brown dark glass bottles (BDGB). One set of nine packaged aliquots was stored in dark ambient conditions, while the other set was exposed to direct solar radiation for 8 hours daily over a 30-day period. Samples from both storage conditions were collected every 10 days for analysis of quality and stability parameters, including color, peroxide value, p-Anisidine value, TOTOX value, thiobarbituric acid reactive substances (TBARS), acid values, and Fourier Transformed Infrared (FTIR) Spectroscopy. Results: Our findings indicate that sunlight significantly reduced the L* and b* color values of palm oil. Furthermore, exposure to sunlight markedly increased the peroxide, p-anisidine, TOTOX, and thiobarbituric acid values in all analyzed oil samples compared to those stored in dark ambient conditions. This increase was most pronounced in soybean oil, likely attributable to its higher content of polyunsaturated fatty acids. Notably, the palm oil extraction process significantly elevated its initial acidity. FTIR spectra revealed minor differences, with soybean oil exhibiting the most significant alterations. Both BDGB and NTPB demonstrated superior protection of the tested oils' quality under sunlight exposure compared to TPEB. Conclusions: Based on these findings, we recommend that edible oils sold in the market be packaged in NTPB or BDGB so as to effectively reduce the adverse effects of direct sunlight and limit photo-oxidative reactions. Furthermore, storing oils should under dark ambient conditions is crucial to prevent degradation caused by photo-oxidation. Keywords: Palm oil, Soybean oil, Palm olein, Packaging material, Sunlight, Oxidation.