Evaluation of Methods of Heat Treatment of Black Currant Fruits to Increase Juice Production

Abstract

Black currant is a multivitamin crop with high dietary and medicinal properties and is a source of exceptionally valuable raw materials for juice production. The essence of the problem of this paper is the scientific substantiation of ways and methods of efficient juice extraction while preserving the natural chemical composition and biologically active substances. The purpose of this study is to compare the methods of heat treatment of black currant fruits to increase juice production. Evaluation of the efficiency of juice output from black currant fruits should be carried out differentially according to the level of desirability of Harrington: exceptionally good – more than 55%, good – 48-55%, satisfactory – 40-48%, unsatisfactory – 35-40%, very unsatisfactory – less than 35%. The fruits of black currant, as a rule, yield 18-24% of the juice, which is devoid of its inherent colouring. Heat treatment of raw materials increases the juice yield by 1.5-2.5 times compared to grinding, and at the same time, at 50-55°C, the cells die within 5 minutes. Good juice yield indicators upon pressing the pomace of crushed fruits (49-55%), satisfactory – upon heating whole fruits with the addition of 15% water (38-45%), as well as blanching fruits in water with a temperature of 95-100°C (42-45%). Juice extraction by blanching fruits and pomace in their own juice is inefficient (33-36%). In terms of chemical composition, freshly pressed juices, regardless of the method of processing raw materials, are close to fresh fruits. Heat treatment of raw materials does not adversely affect the taste and aroma of juices. The content of ascorbic acid in juices (142-225 mg/100 g) depends on the variety of fruits and weather conditions of the year. Its preservation in freshly pressed juices during heat treatment is 95-97%, including blanching – 83-90%. In juices with sugar, its content is 1.7 times lower, but the preservation is 98-99%. During the storage of juices with sugar, the preservation of ascorbic acid decreases during the first three months – by 1.5-2%, in 6 months – by 5.5-7%, in 9 months – by 10-13%, in 12 months – by 16-19% or 7-10 times. Factors for stabilising ascorbic acid in juices are sugar, hot bottling, and short-term heating at elevated temperatures