Studying physical and chemical properties of extracted pectin from fruit residues (orange, pomegranate, apple) and applying it in jam and jelly processing

The study was carried out in the laboratories of the Department of Food Sciences at the Faculty of Agricultural Engineering, University of Damascus, the laboratories of agricultural scientific research, and the central laboratory for forage analysis in Damascus during the period between 2019- 2012 AD.The study included extracting pectin from orange peels, pomegranate peels and apple pomace, using chemical materials (ammonium oxalate, oxalic acid, citric acid), and studying its effect on some of its chemical and physical properties .The results showed a high yield of pectin extracted from orange peels, where orange peels exceeded their pectin content using all the aforementioned extraction materials on pomegranate peels and apple pomace. The highest value was reached by using the extraction with oxalic acid, which amounted to 40.1% on a dry weight basis. Whereas Citric acid reached 10%. the results also showed that there were no significant differences in the percentage of ash in pectin extracted from orange peels, pomegranate and apple pomace by using all extraction materials for each type of residue. With regard to the equivalent weight of pectin, there was a significant superiority in the equivalent weight of pectin extracted from orange peels by the citric acid, reaching 905.57 mg compared to the other extraction methods. With regard to pectin extracted from pomegranate peels and apple pomace, a significant increase in the equivalent weight of pectin was observed when extracting using the oxalic acid, which reached (444.8-941.77 mg) for the two samples, respectively. The results showed a high metoxyl content of pectin in orange peel and apple pomace by using the oxalic acid (7.1-8.1%), respectively), while the lowest value of metoxyl was in pectin that extracted from pomegranate peel by using the citric acid and It reached (4.3%). The results are also indicated that there is a significant increase in the content of pectin from anhydroglactronic acid extracted from pomegranate peels and apple pomace using the citric acid, which reached (79.7% - 67.7) respectively. It was also noted that there were significant differences in the degree of esterification of pectin extracted from orange peels according to the different extraction materials. while the lowest value of the degree ofesterification was in pomegranate peels by using the citric acid, reaching (30.56%). On the other hand, there was a significant significant superiority of the degree of esterification when using the oxalic over pectin extracted from apple pomace. It reached 70.73% compared to other extraction materials.The moisture of the pectin extracted from the samples was recorded, and the highest moisture content of the pectin extracted from apple pomace by using the ammonium oxalate (9.8%), while the lowest content was of the pectin extracted from orange peels by using the citric acid (7.8%). It was also noted that the pectin extracted from all the mentioned samples and by the different extraction materials had good solubility in water. On the other hand, the extracted pectin was used in the manufacture of carrot and orange jam as well as pomegranate juice jelly and gave good results. The sensory evaluation of the manufactured products was done in terms of colour, taste, smell, texture and overall acceptance. The samples of jam made from pectin extracted from orange peels by citric acid had the highest overall acceptance. As for pomegranate jelly, the gel samples ,which pectin extracted from pomegranate peels by oxalic acid was used in, showed the highest levels of sensory evaluation in terms of texture and overall acceptability.