Thus, if one compares the extraction process under microwave heating with the conventional extraction process it is observed that in addition higher yields it is possible to get significant energy savings, since the conventional process lasts for about an hour, while microwave process has duration of only a few minutes.
3.2. Characterization of pectin
Pectin extracted under the conditions that generated the highest yield (9 min and 628 W), for the three types of acid, were characterized and compared with commercially available citrus pectin (Vetec) for its degree of esterification, chemical composition and molar mass distribution.
3.2.1. Degree of esterification
Table 3 enlists the values of the degree of esterification (DE) of pectins isolated from passion fruit peels which were in the range of 50.00–64.56%. The DE values were influenced by the kind of acid used in the extraction. The highest DE were observed for pectins obtained with acetic acid (64.56%) and nitric acid (64.15%) while the extraction with tartaric acid afforded pectins with the lowest DE (50.00). The DE values for pectins extracted with acetic acid and nitric acid were close to that found for commercially available citrus pectin (70%).