Abstract
Fats and oils deteriorate physically and chemically at frying temperatures due to several reasons. The objective of this study was to assess the effect of carvacrol on the oxidative stability of palm oil during a repeated frying process. Potatoes were serially fried in carvacrol-added palm oil, BHT-added palm oil and a control oil (without any antioxidants). After each tenth frying cycle, several chemical analyses were carried out on collected samples to evaluate deterioration in the oils. The free fatty acid, para-anisidine, iodine, and total polar component values of the fresh oil were 0.080, 2.85, 57.1 and 7.5, respectively. These values changed to 0.165, 11.80, 46.7, 11.0, respectively for the control oil; 0.151, 11.28, 49.2 and 10.5 for BHT-added oil; 0.140, 7.19, 51.7, 10.0 for carvacrol-added oil after 40 frying cycles. The results revealed that the use of carvacrol could significantly improve the oxidative stability of palm oil when compared to the control samples. This effect was also comparable to BHT. Using carvacrol in frying oil slowed down the rate of the formation of conjugated dienes and trienes compared to the oil with BHT and the control. The frying process significantly changed the viscosity of the oil samples.
Highlights
The great demand of food prepared in a cheap and quick way due to the rapid increase in population, excess urbanization and economical drawbacks has resulted in an increase in the production and consumption of the ready-foods, especially fried foods all around the world
Carvacrol slowed down the formation of Free Fatty Acids (FFA) significantly (p
The results in the current study revealed that there were increasing trends in both specific extinction, the E1% values of 232 and 270 nm corresponding to the conjugated dienes (CD) and conjugated trienes (CT) contents for all of the oil samples with increasing frying numbers (Figures 5 and 6)
Summary
The great demand of food prepared in a cheap and quick way due to the rapid increase in population, excess urbanization and economical drawbacks has resulted in an increase in the production and consumption of the ready-foods, especially fried foods all around the world. Despite the trend towards low-fat foods, fried foods have become more and more popular with their unique sensorial properties, since frying increases the palatability of foods due to fat absorption, crust formation and desired flavors and odors (Farhoosh and Moosavi, 2008). Besides desirable changes, frying causes undesirable changes which result in the deterioration of oil leading to a shortening of the oil’s frying life. These negative changes in the oil affect the quality of fried food at the same time. The most important reaction causing oil deterioration which affects both the sensory and nutritional quality of the food product is lipid oxidation. The compounds formed as a result of oxidation cause off-tastes and offflavors in the fried products, reducing the organoleptic characteristics and perhaps causing a health hazard (Moreira et al, 1999, Innawong, 2001)
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