WASTES TO PRODUCTS: TOWARDS NEW HIGH-VALUE PRODUCTS FROM EXTRACTION OF CITRUS PEEL AND SPRAY DRYING OF THE EXTRACTS

Abstract

This work has investigated the production of natural antioxidants from citrus peels, which is intended to lower the environmental impacts from the disposal of the waste and also to make additional profit for the citrus fruit industry. Regarding the extraction method, it has been found in this study that MAE could reduce the extraction time and increase the maximum extractable phenolic compounds. Furthermore, the spray-drying experiments to produce Navel orange peel extract powder resulted in yields of between 75% and 92% and the total phenolics content (TPC) recoveries of between 89% and 92%.This result suggested that spray drying is a suitable process for the drying of heat-sensitive materials, such as phenolic compounds. A technico-economic evaluation for the combined processes of MAE and spray drying to produce antioxidant powder has also been discussed. Using the current economic parameters in Australia dan China, this process appears to be economically feasible. In comparison with the production of liquid extracts, the result shows that the spray-drying process could increase the COM of the whole process by around 30-40%. However, the powder form is expected to have better storage stability and also lower storage and transportation costs. Apart from the benefits of antioxidants, bioactive materials have also been reported to show pro-oxidant activities. The study of how processing the extracts, specifically spray drying them, affects the balance between pro-oxidant and antioxidant behavior is novel and significant in terms of modern trends in medicine. Higher main air flow rates resulted in lower pro-/antioxidant recovery ratios, and increases in the feed pump rate improved the pro-/antioxidant recovery ratios, due to their effects on the moisture content and oxidation time. These results are significant due to the developing modern medical understanding that too many antioxidants can be detrimental to health, so it is the balance between antioxidant and pro-oxidant effects in materials that is most important in foods and other compounds for human consumption.