Olive oil is a key ingredient in worldwide cuisine. Microwave cooking is also increasingly used as a timesaving
technology but it induces severe changes in the lipids, such as hydrolysis and oxidative reactions
that lead to quality and nutritional losses. In this sense, the present work intends to verify the potential increased
olive oil stability under microwave cooking induced by white and green tea aqueous extracts, rich
in antioxidants. Quality parameters (free acidity, peroxide value, K232, K270 and ΔK), composition (fatty
acids profile, tocopherols and total phenols content), antioxidant activity and oxidative stability were studied
during different microwave heating exposure times (0, 1, 3, 5 and 10 min). Until the first 3 min of heating the
tea extracts protect olive oil from the oxidative process. However, with higher heating periods the extracts
were pro-oxidants, mainly green tea extracts. Globally, and independently from the addition of tea extracts,
the olive oils suffered drastic changes in their quality and composition. PUFA content decreased with exposure
time as well as antioxidant activity, total phenols and total vitamin E content, and oxidative stability,
with higher losses in the olive oils with green tea extracts. Positive correlations were established between
the quality parameters and the increasing heating time, and negative correlations with the composition
and bioactive and stability indexes.
The authors are grateful to the POCTEP -Programa Cooperação
Transfronteiriça España-Portugal 2007 -2013 for financial support
through the project "Mejora de la competitividad del sector agrario
de Castilla y León y Norte de Portugal a través de la innovación y el
desarrollo de productos diferenciados de alto valor".
