The present work aimed to evaluate some chemical and antioxidant properties of lemon and orange peels (primary byproducts discarded as waste) to identify their potential use.
Methods of lemon and orange peel sample preparation
Lemon and orange fruits were washed by running tap water, peeled and their edible portions were carefully separated. The obtained fresh citrus peels were cut into small pieces before the drying processes.
Drying Methods
Each of fresh lemon or orange peel pieces was divided separately into two parts and each part was dried using the following two methods:
1.Air Oven-Drying
The fresh citrus peels pieces were dried in an air oven at 40 ± 2°C for ~ 48 h.
2.Microwave -Drying
A programmable domestic microwave oven (type Samsung, 77 QH 400148, MF 2015, with a maximum output of 1500W at 2450 MHz) was used for drying the fresh lemon or orange peel pieces’ samples for 6 min. The two (lemon or orange) dried citrus peels were ground to a fine powder using a mechanical laboratory grinder and passed through a 24-mesh sieve, then packaged in polyethylene bags and stored at 4 ± 1°C until required for use.
Ethanol and methanol extraction
Ethanol and methanol solvents were applied for bioactive compounds extraction to determine and compare antioxidant activity of the tested citrus peel samples. Dried peel powder (10g) and (4g) of each lemon or orange sample was extracted with 100 ml of ethanol (70%) and 80 ml of methanol (80%) at room temperature and several agitations with sonication using the ultrasonic device (200 W, 59 kHz, Shanghai Kudos) for 60 min at room temperature. Both extracts were centrifuged (5000 rpm for 30 min at room temperature). Then the extracts were filtered using Whatman No.4 filter paper.
Ethanolic or methanolic extracts of the dried peels (microwave or air oven drying methods) were conducted. All analyzed samples showed that citrus peels are cheap and good source for natural bioactive compounds with high contents and have good antioxidant activities. As a general conclusion citrus peels have high contents of natural phenolics, flavonoids, carotenoids and ascorbic acid with significant antioxidant activity which could be recommended as useful value added functional ingredients for food industry.
Reference:
Abd El-ghfar, M.A., Ibrahim, H.M., Hassan, I.M., Abdel Fattah, A.A. and Mahmoud, M.H., 2016. Peels of lemon and orange as value-added ingredients: Chemical and antioxidant properties. Int. J. Curr. Microbiol. Appl. Sci., 5: 777-794.
