Micronutrients in vegetable oils: The impact of crushing and refining processes on vitamins and antioxidants in sunflower, rapeseed, and soybean oils

Tocopherols, phytosterols, polyphenols, and coenzymes Q are naturally present in oilseeds such as sunflower, rape, and soybean. Besides contributing to taste and color, micronutrients help protect against health disorders such as cardiovascular diseases and cancer. However, during the conventional oil manufacturing process, many minor components are lost. Given that diet is a major cause of cardiovascular diseases and cancer, it makes sense to optimize the content of micronutrients in food, and specifically in vegetable oils. These micronutrients have antioxidant properties that inhibit the oxidation of low‐density lipoprotein cholesterol. This review summarizes important recent research emphasizing the impact of crushing and refining processes on the micronutrient content of different vegetable oils. After the crushing step, the total sterol content was high in crude rape, sunflower, and soybean oils, at 4358–10 569, 2212–4146, and 1735–4328 mg/kg, respectively. The tocopherol content was lower, at 464–1458, 725–1892, and 1094–2484 mg/kg, respectively, and the level of phenolics was 113–629, 10–120, and 23–148 mg/kg, respectively. The refining process destroyed micronutrients: 10–36% loss of total tocopherols, 6–52% loss of total sterols, and 93–98% loss of polyphenols. Studies have focused on improving the extraction of tocopherols by alternative heating (microwave treatment, roasting, or steaming processes). These treatments improved tocopherol content, and extraction was faster and consumed less energy. Practical applications: Some researchers later tested the ability of different alternative solvents (supercritical CO₂ and pressurized solvents) to raise the concentration of micronutrients. Enzymatic extraction also offered an innovative technique to conserve micronutrients in oils. Researchers and the oil extraction industry have also tested some alternative refining processes, such as alternative neutralization, based on the use of different alkaline agents, and soft refining, which offered the possibility of micronutrient preservation and recovery. Upstream, genetic factors, cultivation conditions, and seed storage strongly influence micronutrient concentration in vegetable oils. Upstream steps in the industrial oil process were important for the nutritional quality of edible oils. This review of micronutrient evolution during oil processing highlights the impact of industrial processes, and points to methods for improved extraction of oil constituents. The micronutrient content in vegetable oils is strongly influenced by crushing and refining processes. A focus on sunflower, rapeseed and soybean oils is performed in this review.