Fermentation of purple coneflower herb as a method to increase the hydroxycinnamic acids extraction

Abstract

Purporse. To establish the influence of natural, temperature and cold fermentation on the content of hydroxycinnamic acids in purple coneflower herb.
Material and methods. The object of the study is fresh purple coneflower herb of industrial series and harvested from cultivated forms.
The effect of the following types of fermentation on the content of hydroxycinnamic acids and the activity of polyphenol oxidase was studied: temperature, cold, natural, as well as thermal and ultrasonic pre-treatment, natural drying. The content of hydroxycinnamic acids was determined by the spectrophotometric method with Arnov's reagent, the activity of polyphenol oxidase – by the spectrophotometric method according to A.N. Boyarkin.
Results. Fermentation at 40 ºС for 2 hours increased the content of hydroxycinnamic acids by 64.8%, at 60 ºС the content of hydroxycinnamic acids and the activity of polyphenol oxidase were lower. Natural fermentation increased the content by 26.5%, which corresponded to the minimum activity of the enzyme. Temperature pre-treatment of fresh herb increased the content by 2.3 times with a sharp drop in the activity of polyphenol oxidase. Thermal inactivation of the enzyme in all the studied methods of preliminary pre-treatment led to a decrease in the content of hydroxycinnamic acids. Temperature and cold fermentation of dried herb reduced or did not affect the content of substances.
Conclusions. Among all the studied methods of pre-treatment of fresh purple coneflower, the highest increase in the content of hydroxycinnamic herbal acids was determined during heat pre-treatment, which led to a sharp drop in polyphenol oxidase activity.