Carotenoids are one of the most widespread pigments in nature and can be used as health-promoting natural food colorants. Banana peel, which is a by-product of banana processing, contains a range of bioactive compounds including carotenoids. This study evaluated the change in the banana peel carotenoid content over its ripening stages and determined the best possible solvent to extract carotenoid for food applications. Ripeness stage 5 contained the highest content of total carotene at 1.86 l g/g of banana peel. From one gram of banana peel, 0.57 l g of xanthophyll and 0.84 l g of beta-carotene were extracted from ripening stage 5 with a solvent combination of hexane–diethyl ether–acetone and hexane–diethyl ether, respectively.
Banana samples preparation
The bananas were from a single batch harvested from the same location so as to minimise variations due to variety, environmental conditions and cultural practises. The ripening scale was used to determine the ripening stage of the bananas. A single batch of banana (approximately 50 Kg) at stage 1 was obtained at random from a commercial harvest in 2013 and ripened under controlled commercial ripening conditions (11–12 °C) without ethylene treatment. Banana at ripeness stages 4, 5, 6 and 7 were withdrawn from the ripening room for analysis. The banana peel for the pigment extraction was prepared; the samples were washed with deionised water, air-dried and hand peeled. The peels were soaked in 5% (w/w) citric acid solution (22 °C, pH = 2.25) for 10 min as per to inhibit enzymatic browning. As he high water content in fresh banana peels would influence the extraction, the peel was freeze-dried at 0.37 mbar and 30 °C in a CHRIST ALPHA 1-2LD plus (Martin Christ, Osterode, Germany) freeze drier for 22 h. The dried banana peels were ground at 600 g for 40 s in a GRINDOMIX (Model GM200 grinder; Retsch GmbH, Haan Germany) and sieved through a
250l m sieve. Banana peel powder (BPP) from the different ripeness stages was sealed in snap-log bags (Ziploc brand, size 18 9 20 cm) separately and stored at 20 °C for further analysis.
Conclusions:
The study was undertaken to determine the possibility of utilising banana peel instead of dumping it in landfills. Banana peels at ripening stages 4 to 7 are good sources of natural protein, minerals and crude fibre. Carotene content in the banana peel peaks at stage 5. Browning of the banana peel can be prevented by acidifying and then freeze-drying. Food-grade solvents can be used to extract beta-carotenoid and xanthophyll from banana peel. Hexane, diethyl ether and acetone can be used for the extraction of xanthophyll, and hexane and diethyl ether are suitable for the extraction of beta-carotene. Carotenoids can be extracted by the use of food-grade chemicals for use as a natural food colorant. Combinations of food-grade solvents can be employed to extract specific pigments from banana peels.
Reference:
Yan, L., Fernando, W.M., Brennan, M., Brennan, C.S., Jayasena, V. and Coorey, R., 2016. Effect of extraction method and ripening stage on banana peel pigments. International Journal of Food Science & Technology, 51(6), pp.1449-1456.
