Processed and unprocessed by-products coming from the extraction of orange juice have been analyzed by researchers from the Institute of Food Science Research (CIAL) (CSIC-UAM), finding antioxidants and extract pectin of good quality. The results could reduce the environmental impact of industrial waste
In some orange juice extraction industries, fresh orange waste is pressed, concentrated and dried at high temperatures in order to obtain pellets for animal consumption, without paying attention to the possibility of extracting bioactive compounds that can be used as functional ingredients in human foods.
In the present work, after the characterization of four by-products coming from García-Carrión company, different parameters were analysed, as well as their content in polyphenols (the fresh peel showed the highest content of phenolic compounds), antioxidant activity, total, soluble and insoluble fiber, carbohydrates being the main components. Due to the high content of carbohydrates and the conditions used in the manufacturing process, the presence of furosine was detected; an indicator of the initial stages of non-enzymatic browning in foods. This quality indicator is very useful, since it gives us an idea of the loss of nutritive value due to the participation of lysine in that reaction, and it allows us to retrospectively know the conditions of the processing.
The liquid residue (orange liqueur), which was obtained by pressing the fresh peel and subsequent concentration, can be used as a source of fructose, a carbohydrate that provides greater sweetness than sucrose, but with a lower caloric content.
On the other hand, given the content of galacturonic acid observed in the solid residues, pectin was extracted using enzymes (cellulases) responsible for releasing it from cell walls, where it is in contact with cellulose and hemicellulose. The pectin thus obtained, besides galacturonic acid, presented contents of xylose, arabinose, rhamnose and galactose, monosaccharides characteristic of citrus pectins. The three dried by-products (fresh, dried and orange peel) had pectin with galacturonic acid levels above 70%, which could be considered by FAO, as a food additive.
This polysaccharide can be used as a thickener, stabilizer and gelling agent in the preparation of desserts, creams, soups, beverages, etc.. In addition, it resists the intestinal digestion reaching the colon, where it serves as a nutrient for beneficial bacteria whose products of metabolism (short chain fatty acids) help to prevent the proliferation of pathogenic bacteria, among other beneficial effects. The consumption of this soluble fiber can also strengthen the immune system and reduce the amount of sugar and cholesterol in the blood, thus avoiding serious diseases such as diabetes and obesity.
The extracted pectin has a wide application and is very easy to obtain. The extraction process involves an environmentally friendly technique, since the enzymes are biodegradable and can be reused for biomass.
Currently, the research group of Carbohydrates and Derivatives Chemistry and Functionality of CIAL is studying pectin extracted from other by-products of food industry, by simple or combined methods, as well as its chemical modification, in order to increase even more the quality, the performance and its functional properties.
Additionally, based on these results, our group is working in collaboration with the Group of Pharmacology from the Granada University, and we have carried out a study to evaluate the in vivo consumption effect, of these by-products and citrus pectin, on inflammatory bowel disease, opening an important field of research regarding the application of this type of by-products, to avoid or minimize their symptoms.
Reference:
Pacheco, M. T., Moreno, F. J., & Villamiel, M. (2018). Chemical and physicochemical characterization of orange by-products derived from industry. Journal of the Science of Food and Agriculture. DOI: 10.1002/jsfa.9257
