Valorization of Citrus Peel Waste

Abstract

Citrus sinensis commercially known as an orange tree has a high pectin ratio and valuable essential oils. The huge amount of orange peel is generated in industries and they can be used as a raw material for essential oils and pectin. To obtain essential oils from orange peels distillation method is used and collected oil is analyzed to determine its d- limonene amount, also the yield of the essential oil production is calculated. The essential oil yield was found as 0.19%. GC results revealed that the sample had 94% d-limonene, and the data from the literature indicated that d-limonene amount of orange essential oil may vary between 32% and 98% depending on the variety of orange. In addition to essential oil, pectin was also extracted from the orange peels using two types of acids. First one was hydrochloric acid (HCl) as an inorganic acid, and the other was tartaric acid (TA) as an organic acid. The purpose of selecting the several types of acid was to observe the effects of acid type on pectin yield. The pectin amount obtained with HCl usage (4.72 % g pectin/orange fresh peel) was higher than that with TA usage (4.037 % g pectin/orange fresh peel). The experimental results for pectin contents of samples were also confirmed with the colorimetric test results. According to these results, concentrations of galacturonic acid in the samples obtained with HCl (0.509 mg galacturonic acid/mg) was found to be higher than the concentrations of galacturonic acid in the samples obtained with TA (0.103 mg galacturonic acid/mg).