Effect of clove and lemongrass essential oils as natural antioxidants on cake shelf life

The objective of this study was to evaluate the effect of clove and lemongrass essential oils as natural antioxidants on cake shelf life at room temperature. Clove oil (CEO) was obtained by ethanol extraction and lemon grass oil (LEO) was purchased and then they were added to the cake dough in different levels. The samples contain these natural antioxidants were compared with cakes contain synthetic antioxidant (BHT 200 ppm) and control samples which were not contain any antioxidant at all. In this study, corn oil and shortening were used in the production of cakes and the oxidation degree of cakes was presented as peroxide value PV (gives the amount of peroxides that occur due to lipid oxidation during early stages of storage), Thiobarbutiric acid value (TBA) (estimates the amount of secondary oxidation products "malonaldehyde") and gas chromatography results ( reflects the changes in fatty acids composition % within storage). The antioxidant activity of CEO and LEO in additional to cake organoleptic properties were investigated at 1st, 8th 15th, 22th and 29th day of storage. The results showed that lipid oxidation of cake delayed when the concentration of essential oils in cake dough was increased. The highest increment in PV during the 29 days of storage was observed in control sample (from 1.4 to 15.2 mEq O2 / kg oil), while the lowest one (from 1.25 to 6.8 mEq O2 / kg oil) was observed in the sample contain 600 ppm of lemongrass oil (LEO 600). At the end of storage, the PV of (LEO 600) sample was significantly lower (P<0.05) than the PV of BHT samples and not significantly different (P>0.05) from the PV of the samples contain 600 ppm of clove and lemongrass oils mixture (CEO+LEO). On the other hand, there was no significant difference (P>0.05) between the PV of the samples contain 300 ppm clove oil (CEO 300) and the BHT samples. The thiobarbituric acid (TBA) values of the cakes produced by adding antioxidants were found to be significantly lower (P>0.01) from the 15th day of storage compared to the control sample. At the end of storage, the highest TBA value were observed in the control samples (2.4 mg malonaldehyde / kg sample) and the lowest in BHT and CEO 300 samples with no significant difference (P>0.05) between them (0.79, 0.88 mg malonaldehyde / kg sample). The use of clove and lemongrass oils as a mix (CEO+LEO) had no effect on examined parameters. The sensory characteristics of cakes were evaluated and there was no significant difference in terms of general acceptance of LEO 300, LEO 600, control and BHT samples (P>0.05). However, it was found that the samples contain clove oil (CEO 300 and CEO+LEO) has lower general acceptance scores (P<0.05). According to the findings, The use of clove essential oils in cake industry was not recommended due to it's undesirable effect on sensory quality of the cake. While the addition of lemongrass essential oils was acceptable in terms of sensory properties and can be successfully used to increase the shelf life of industrial cakes by delaying the deterioration of oils.