Results showed that the yield of extracted pectin ranged from
3.2% to 29.4%.The maximum yield was found under the experimental conditions of X1 =75 ◦C, X2 = 40 min and X3 = 2.0.The average
MW of those extracted pectins ranged from 111 to 205 kDa. Pectins with the highest MW were extracted under the conditions of
X1 =55 ◦C, X2 = 20 min and X3 = 2.0. Further,a wide range of degree
esterification (DE) values was also found,ranging from 20.1 to
61.2%. The maximum DE value was found at conditions of X1 =75 ◦C,
X2 = 40 min and X3 = 1.0. Therefore,optimal process conditions
were investigated in order to obtain the maximum extraction yield,
MW and DE of UAE of pectins from grape pomace with citric acid.
Moreover, the sugar analysis revealed a great uniformity for the
type of pectins obtained in all the extraction procedures. Galacturonic acid was the predominant sugar,accounting for 95–97% of
total sugars. Other sugars such as rhamnose,arabinose and galactose were present in small quantities (