Release Kinetics Studies of Early-Stage Volatile Secondary Oxidation Products of Rapeseed Oil Emitted during the Deep-Frying Process.

Tomasz Majchrzak,Andrzej Wasik

doi:10.3390/molecules26041006

Abstract

The research concerns the use of proton transfer reaction mass spectrometer to track real-time emissions of volatile secondary oxidation products released from rapeseed oil as a result of deep-frying of potato cubes. Therefore, it was possible to observe a sudden increase of volatile organic compound (VOC) emissions caused by immersion of the food, accompanied by a sudden release of steam from a potato cube and a decrease of the oil temperature by more than 20 °C. It was possible to identify and monitor the emission of major secondary oxidation products such as saturated and unsaturated aldehydes, namely acrolein, pentanal, 2-hexenal, hexanal, 2-nonenal and 2-decenal. Each of them has an individual release characteristic. Moreover, the impact of different initial frying temperatures on release kinetics was investigated. Subsequently, it was possible to approximate the cumulative emission by a second-degree polynomial (R2 ≥ 0.994). Using the proposed solution made it possible for the first time to observe the impact of the immersion of food in vegetable oil on the early emission of thermal degradation products oil.

Highlights

As a result of thermal treatment, food becomes more digestible, microbiologically safe and gains desirable taste and aroma
When the food is placed in the oil, the temperature drops drastically to reach a local minimum after one minute of frying - even beyond 20 ◦C of temperature decrease
After a minute of frying, it is possible to measure the burst of volatiles, manifested as the high value of TVOC

Summary

Introduction

As a result of thermal treatment, food becomes more digestible, microbiologically safe and gains desirable taste and aroma. One of the most commonly used methods of food thermal processing, is characterized by high process temperature and versatile application. Studies are conducted on the texture of fried food [3] or identification of compounds responsible for food taste and flavour [4]. This is a consequence of multiple reactions taking place in food, oil, or between food and oil, including oxidation and hydrolysis of oil [2,5] or Maillard reaction [6,7]. The oxidation of fatty acids leading to secondary oxidation products (SOPs) can directly describe the frying behaviour, together with the loss of oil quality [8]

Methods

Results

Conclusion