Identification of the Olfactory Profile of Rapeseed Oil as a Function of Heating Time and Ratio of Volume and Surface Area of Contact with Oxygen Using an Electronic Nose.

Robert Rusinek,Marek Gancarz,Sylwester Tabor,Aleksander Siger,Marzena Gawrysiak-Witulska,Pavol Findura,Urszula Malaga-Toboła,Dominik Kmiecik

doi:10.3390/s21010303

Abstract

The process of deep fat frying is the most common technological procedure applied to rapeseed oil. During heat treatment, oil loses its nutritional properties and its original consumer quality is lowered, which is often impossible to determine by organoleptic assessment. Therefore, the aim of the study was to correlate markers of the loss of the nutritional properties by rapeseed oil related to the frying time and the surface area of contact with oxygen with changes in the profile of volatile compounds. The investigations involved the process of 6-, 12-, and 18-h heating of oil with a surface-to-volume ratio (s/v ratio) of 0.378 cm−1, 0.189 cm−1, and 0.126 cm−1. Samples were analysed to determine changes in the content of polar compounds, colour, fatty acid composition, iodine value, and total chromanol content. The results were correlated with the emission of volatile compounds determined using gas chromatography and an electronic nose. The results clearly show a positive correlation between the qualitative degradation of the oil induced by prolonged heating and the response of the electronic nose to these changes. The three volumes, the maximum reaction of the metal oxide semiconductor chemoresistors, and the content of polar compounds increased along the extended frying time.

Highlights

Plant oils are the main source of unsaturated fatty acid and other substances, e.g., tocopherols and phytosterols, in the human diet
The present investigations demonstrate that oil quality loss as a function of frying time is almost impossible to assess based on changes in the colour of oil
Other chemical methods for determination of total chromanols and total polar compounds efficiently describe changes occurring in oil, but they require higher workload in comparison with the analysis of volatile substances based on the use of the electronic nose

Summary

Introduction

Plant oils are the main source of unsaturated fatty acid and other substances, e.g., tocopherols and phytosterols, in the human diet. Unsaturated fatty acids are very important for human health They play a key role in the structure of membranes, the synthesis of eicosanoids, and the transport and metabolism of cholesterol, reducing its concentration in the blood plasma. They are essential for prevention of the progression of cardiovascular disease (CVD) and for development of the brain, especially during pregnancy and early life. Unsaturated fatty acids may increase tissue sensitivity to insulin, which is important for patients with carbohydrate metabolism disorders, e.g., diabetes. They exert anti-cancer, anti-inflammatory, and immunomodulatory effects [1,2,3]. Tocopherols contained in oil play an important role as vitamins and antioxidants in the human body [4]

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