The Effects of Repeated Heating on Thermal Degradation of Cooking Oil and its Implication on Human Health - A Review

Abstract

Frying is one of the most common food processing methods at household level and in different catering settings. Repeated frying or reuse of vegetable cooking oils is commonly exercised as a cost serving and profit maximization strategy though the practice exposes cooking oils to thermal degradation.  The cooking oils in a non-degraded form have nutritional and health supremacy, which are attributed to their fatty acid composition and other minor components. However, the products of thermal degradation due to repetitive use of cooking oil are implicated to destroy their nutritional and health benefits. Besides, the consumption of food products fried with reused oil on the other hand is indicated to pose health risks to the consumers. This has attracted the attention of several researchers to investigate the health risks associated with thermal degradation products of cooking oil. The present review provides an enriched overview and insight into deteriorative effect on cooking oils due to repetitive deep frying and the associated health risks they inflict. The information on repeatedly used cooking oil, degradation compounds, deteriorative effects and other related literatures were gathered through electronic search (Science Direct, Pub Med, and Google Scholar) and desk reviewed. A narrative literature review approach was used in which the different literatures were critically evaluated and summarized with conclusions drawn and inconsistence / gaps in a body of knowledge revealed. The retrieved data demonstrated and confirmed a variety of deleterious health effects ranging from histo-pathological alterations, damage to the alimentary canal (duodenum and colon) and vital organs (change in size of the liver including swelling heart, kidney and testes cells) and rise in blood pressure BP. Though some mitigation approaches are available including the use of antioxidant and adsorbent extracts, their applicability at household and in other catering service settings can hardly be practiced. It’s thus important for stakeholders to limit the repetitive use of cooking oil to protect the consumers’ health.  Key words: Vegetable cooking oil, repeated frying, thermal degradation, deteriorative effects, health risks