Comparing the organic acids used in this work, it is noteworthy that the curve for the pectin extracted with tartaric acid was shifted to lower molar mass values. This is due to the fact that tartaric acid has two terminal carboxyl groups, thus, its higher hydrolytical power was greater than that of acetic acid which has only one terminal carboxylic. Therefore, despite the use of tartaric acid provide higher yields, your higher hydrolytical power degrades the pectin extracted.
4. Conclusions
The greatest extraction yields in pectin were obtained when highest field strength and exposure time was employed. The type of acid used also affected the yield of extraction and the composition and molar mass of pectin obtained. The hydrolytic power of tartaric acid makes it more active for extraction and also more active for degrading pectin than the other acids investigated. By using the response surface analysis, we can conclude that extraction time significantly affects the yield of pectin obtained using all acids. The microwave power significantly affects the yield only in the case of extractions carried out with nitric and tartaric acids. The pectin extracted from the peels of passion fruit exhibited medium to high degree of esterification (50.00%–64.56%). Pectins obtained by the use of acetic acid and nitric had a yield of approximately 13.0% and showed the highest DE, molar mass and uronic acid contents. Highest yields were obtained the use of tartaric acid (30%), however, the extracted pectin had some undesirable qualities, such as: low molar mass and lower uronic acid content (58.5%) and DE (50%).
Acknowledgment
The authors gratefully acknowledge the Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico (CNPq) of Brazil for the financial support.