Prediction of critical times for water-extracted avocado oil heated at high temperatures
Vegetable oils are used in various cooking processes. However, when they are heated at high temperature and/or for a long period, chemical reactions can generate damaging substances for the health. The aim of the study was to predict the critical times at high temperatures of avocado oil. A four-level two-variable Central Composite Design was used to model the thermal oxidation of avocado oil extracted using the aqueous method. Temperature (120 – 180 °C) and time (11 – 209 min) were the independent variables. The response variable was the content in total polar compounds (TPC) with an upper limit defined at 25% (w/w). The composition and the oxidative status of fresh avocado oil were also investigated. The results obtained by a multiple regression analysis showed that data can be fitted with a second order polynomial equation (R2 = 0.98, Adj. R2 = 0.97) with all regression coefficients being significant (p < 0.05). The critical heating time ranged from 232 min to 214 min between 120 °C-140 °C and from 188 min to 4 min between 140 °C-180 °C. It was influenced by avocado oil composition. Thus, water-extracted avocado oil is not recommended for frying (140 °C – 180 °C) while it can be used for recipes involving long cooking time at moderate temperature (120 °C-140 °C).
Keywords: Avocado oil, heat treatment, polar compounds, Central Composite Design, upper limit heating time.