The possibility of using microwaves to obtain extracts from berry press residues and jelly products with bioactive characteristics
Peter the Great St. Petersburg Polytechnic University, Institute of Industrial Management, Economics and Trade, Graduate School of Service and Trade, Novorossiyskaya street 50, RU194021 Saint-Petersburg, Russia
*Correspondence: nilova_l_p@mai.ru
Abstract:
The paper explores the possibility of development a microwave technology for obtaining water extracts from berry press residues (wild bilberries and cranberries as the objects) and jelly products based on them, which will allow using the waste of freshly squeezed juices in business, such as restaurants and catering services. The antioxidant activity (DPPH and FRAP methods), content of phenolic compounds, flavonoids, anthocyanins, ascorbic acid were determined in berries and in berry press residues. The antioxidant activity of bilberry press residues was due to anthocyanins, and the activity of cranberry press residues was due to flavonoids. Using the microwave oven (magnetron power 800 W, frequency 2,450 MHz), water extracts were obtained in the ratio: for cranberries 1.5:10, for bilberries 1:10. The antioxidant activity of extracts depended on the type of berries and was greater in extracts from bilberry press residues. Extracts of bilberries and cranberries and their compositions (sugar-free and sugar-added) with gelatin as a gelling agent were used to produce the jelly products. Combining bilberry and cranberry extracts (70:30) with gelatin makes it possible to obtain jelly products without sugar. Heating of the ready recipe mixture after preliminary swelling of gelatin and without swelling of gelatin was carried out in the microwave oven. The antioxidant activity of jelly products was higher when using bilberry extracts than cranberries. An increase in the antioxidant activity of the extracts led to a slowdown in structure formation, but increased the plasticity of the products.
Key words:
antioxidant activity, berry press residues, bilberries, cranberries, Deformation, extracts, jelly products, microwaves