Citrus peels biomass as a source of many bioactive materials and its applied importance

Abstract

Citrus are of big importance; due to their variable chemical and nutritional content. Furthermore, organic residues increase their economic value by obtaining the maximum benefit from these wastes. In this research, several extraction stages were conducted on peels of six Citrus species (Sweet Orange: C. sinensis, Bitter orange: C. aurantium, Limon: C. limonia, Grapefruit: C. paradise, Pomelo: C. maxima, Tangerine: C. tangerina) for extraction of the following compounds: volatile oil, phenols, carbohydrates, proteins, fixed oil, polar and nonpolar pigments which were extracted from the same biomass. Peels resulting after the extraction of the above mentioned compounds were also used in three applications: pectin extraction and use in adsorption process, as well as the possibility to benefit from as an exclusive carbon source for fungi growth. The results and statistical analysis (significance level 0.01) proved the efficiency of applying sequential extraction method with differences in yields accordance to Citrus species. Higher significant yield of water extract represented 52.9% in bitter orange, higher significant yield of volatile oil was about 1.41% in tangerine, higher significant percentage of phenols were obtained from grapefruit (89.6 mg/g extract), higher significant yield of carbohydrates and pigments were obtained from oragne (620.8 mg/g extract), (65.5 µg carotenoids/g extract) successively. However, higher significant yield of proteins (2.77 mg/g extract) in bitter orange, tangerine was higher fixed oil yield significantly 1.97%, finally pectin 5.6% higher significant yield in orange. On the other hand, peels powder showed a good effectiveness in removing methylene blue. Besides, three fungi species were able to grow in a medium containing peels as an exclusive source of carbon. These results revealed the different possible uses of the same citrus peels biomass through sequential extraction stages, which helped to obtain many active compounds with valuable medical, nutritional and industrial importance.