Monitoring the physicochemical features of sunflower oil and French fries during repeated microwave frying and deep-fat frying

E Aydınkaptan,I Barutçu Mazı

doi:10.3989/gya.1162162

Abstract

This study investigates the effects of repeated microwave frying at different power levels (360W, 600W, 900W) and deep-fat frying on sunflower oil and French fries. The intermittent batch frying cycle was repeated 15 times a day during five consecutive days. The fatty acid profile and physicochemical properties including free fatty acid (FFA), extinction coefficient (K270), total polar compound (TPC), color, viscosity, refractive index of the sunflower oil were determined each day. At the end of the frying period, the highest values of viscosity (76.29cp) and refractive index (1.4738) were detected in microwave frying at 900W power level. TPC level exceeded 25% after the third day of microwave frying at all power levels. The FFA values during microwave frying increased progressively from 0.157% to 0.320- 0.379% on the fifth day. The loss of polyunsaturated fatty acids was 37-53% more in the case of microwave frying. The oil quality during microwave frying did not have a significant impact on the oil absorption and total color change of the French fries. Microwave frying, even at higher levels, provided lower oil (8.60-12.32%wb) and moisture contents (35.47-41.24%) compared to deep frying. Microwave frying caused longer processing time and significantly higher levels of degradation of the sunflower oil at all power levels compared to deep frying. However, microwave frying has the advantage of reducing oil absorption. The oil content of French fries was lowered by 20-33% (wb) at the highest power level.

Highlights

The popularity of processed potato products, frozen French fries is increasing worldwide
There was a gradual rise in the free fatty acid (FFA) of sunflower oil during microwave frying
Microwave frying increased the rate of sunflower oil degradation compared to deep-fat frying

Summary

Introduction

The popularity of processed potato products, frozen French fries is increasing worldwide. Consumer demand for healthier products has caused a significant increase in research in the area of fried foods Many of these studies have focused on the reduction of oil uptake (Ziaiifar et al, 2008) and oil degradation (Aladedunye, 2015) while keeping the desired characteristics of fried foods during deep fat frying. The oil is in contact with the air and food at a high temperature and this give rise to the emergence of oxidative, hydrolytic and thermal alterations in the oil These simultaneous complex reactions cause the formation of many compounds which change the quality of the oil (Velasco et al, 2009). Crosa et al, (2014) and Nazarbakhsh et al, (2014) observed that the use of vacuum or some gases during the frying process reduced the rate of oil degradation compared to the traditional frying method

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Conclusion