Changes of Pectin Substances Content During the Pear Fruits Storage With Antioxidant Compositions Treatment

Abstract

Aim. The research is devoted to determination of the regularities of pectic substance changes in pears during refrigeration storage after antioxidant composition treatment. Methods. The content of pectic substances was determined by titerometric method, which was based on alkaline titration of the pre-selected and prepared pectic substances before and after hydrolysis. The titration results are proportional to the number of free esterified carboxylic groups, and when multiplied by the corresponding equivalents, they indicate the content of polygalacturonic acid residues in the pectic substances of the product. Results. The research showed that late ripening pears had greater content of pectic substances when put to storage. During the first 30 days of storage an insignificant (1...4%) increase of pectic substance content was observed in the fruit of control variants, during further storage (130 ... 180 days) a decrease was recorded. The loss of pectic substances by the control fruit amounted to 49 % for the entire storage period. During fruit storage after antioxidant composition treatment the increase of pectic substance content had been lasting for 2-4 months longer than of the control variants fruit, and further transfer of protopectin to the soluble pectin was taking place at a slower rate. It provided for the best preservation of pectic substances during storage. The loss of pectic substances by fruit treated with antioxidants amounted to 15 % for the entire storage period. Conclusions. Minimal losses of pectic substances (7%) were found out at the storage of pears of the varieties Victoria, Conference, Cure, Izyuminka Crimea, which had been treated with the antioxidant composition DL.