Elsevier

Food Chemistry

Volume 85, Issue 2, April 2004, Pages 215-220
Food Chemistry

Utilization of potato peels extract as a natural antioxidant in soy bean oil

https://doi.org/10.1016/j.foodchem.2003.06.015Get rights and content

Abstract

Potato peel extract, as natural antioxidant was evaluated during 60 days storage of refined soy bean oil at 25 and 45 °C. Free fatty acids (FFA), peroxide values (POV) and iodine values (IV) were used as a criteria to assess the antioxidant activity of potato peel extract. Different organic solvents, including ethanol, methanol, acetone, hexane, petroleum ether and diethyl ether, were used to prepare extracts of potato peels. Maximum amount of extract (21%) was obtained with petroleum ether, followed by diethyl ether (15.25%) and methanol (14.75%). After 60 days’ storage at 45 °C, soy bean oil, containing 1600 and 2400 ppm of petroleum ether extract of potato peels, showed lower values of FFA (0.120, 0.109%) and POVs (10.0, 9.0 meq/kg) than the control samples (FFA 0.320%, POV 59 meq/kg). Soy bean oil containing 200 ppm of BHA and BHT showed FFA values of 0.102 and 0.078%, whereas POVs were 8.0 and 6.0 meq/kg, respectively, after 60 days, storage at 45 °C. Similarly, after 60 days, storage at 45 °C, iodine values of soy bean oil containing 1600 and 2400 ppm of potato peel extract were 71 and 77, respectively, which were higher than the control samples of oil (58). However, iodine values for soy bean oil treated with 200 ppm of BHA and BHT were 80 and 84, respectively, after 60 days’ storage at 45 °C. These results illustrate that potato peel extract, at various concentrations exhibited very strong antioxidant activity which was almost equal to synthetic antioxidants (BHA & BHT). Therefore, potato peel extract in oils, fats and other food products can safely be used as natural antioxidant to suppress lipid oxidation.

Introduction

Fats and oils undergo pronounced oxidative changes at elevated temperature during storage. The oxidative changes decrease the nutritional quality of fats and oils. However, addition of some suitable antioxidant in fats and oils retard the oxidation process. Synthetic antioxidants, especially butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA) are commonly used to prevent the oxidation process (Sobedio, Kaitaramita, Grandgiral, & Malkki, 1991). These synthetic antioxidants are known to have toxic and carcinogenic effects on humans (Ito et al., 1986). Synthetic antioxidants may cause liver swelling and influence liver enzyme activities (Martin & Gilbert, 1968). There is a strong need for effective antioxidants, from natural sources, as alternatives, to prevent deterioration of foods. The literature is replete with reports of extracts from natural sources that have demonstrated strong antioxidant activity (Alexander et al., 1998). Extracts from spices, herbs and hulls are known to have varying degrees of antioxidant activities (Nakatani et al., 1986, Kohchi, 1995). These extracts have been reported to be more effective than some major synthetic antioxidants (Kikuzaki and Nakatani, 1993, Marinova and Yanishlieve, 1997). Recently, petroleum ether extract of potato peels showed strong antioxidant activity due to the presence of chlorogenic, gallic, cinnamic and ferulic acids as the major antioxidant compounds in the extract (Onyenecho & Hettiarachchy, 1993). However, effects of temperature and time period of storage on the antioxidant activity of potato peel extract have not yet been reported. Therefore, the present work was undertaken to investigate the effects of storage temperature and time period on antioxidant activity of potato peel extract in soy bean oil. Attempts were also made to extract natural antioxidant from potato peels using different organic solvents.

Section snippets

Raw materials

Refined, bleached and deodorized soy bean oil was obtained from a local refinery, whereas the potato chip manufacturing industry supplied potato peels to carry out this study. Synthetic antioxidants, namely butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) were purchased from Sigma Chemical Co., USA.

Potato peel extract preparation (natural antioxidant)

The potato peels were washed and then dried in a hot air oven (Horizontal Forced Air Drier, Proctor and Schwartz Inc., Philadelphia, PA) at 55 °C. The dried peels were ground into a

Extraction

Table 1 shows the percentage yield of potato peel extract obtained after refluxing ground potato peels with different organic solvents, i.e. ethanol, methanol, acetone, hexane, diethylether and petroleum ether. About 5.88–21.00% potato peel extract was obtained with these six different organic solvents. However, the maximum amount of potato peels extract (21.00%) was obtained with petroleum ether. followed by diethyl ether (15.25%) and methanol (14.75%). About 12 different phenolic antioxidant

Conclusion

It is apparent from the study that potato peel extract (with petroleum ether), exhibited strong antioxidant activity in soy bean oil during storage which was almost equal to the antioxidant activity of synthetic antioxidants (BHA and BHT). However, the level of potato peel extract needed was 8–12 times higher than that of the synthetic antioxidants to control the development of rancidity during storage of cooking oils at elevated temperature. Therefore, it is suggested that natural antioxidant

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