INFLUENCE OF TECHNOLOGICAL PARAMETERS OF THE ULTRAFILTRATION PROCESS OF CITRUS JUICES ON THEIR QUALITY

Abstract

Fresh fruit juices contain organic acids and mineral substances (potassium, calcium, iron, copper, magnesium, phosphorus, manganese, molybdenum, boron, iodine), and their salts, large amounts of fiber, pectin and enzymes - complex substances, that contribute to the food processing and absorption of nutritional elements. Natural citrus juices contain essential vitamins and nutrients for the human body. Therefore, they represent a good opportunity for the treatment and prevention of various diseases. With the vitamins, taken through the juice, the human body becomes more resistant to viruses and infections, stressful situations and intense physical stress, and the body’s metabolism becomes normalized. Beverages, prepared from juices improve intestinal motility and thus contribute to improving the allocation of toxic substances and slags from the organism.

The purpose of this work is the development of technological parameters of the ultrafiltration process to obtain natural juices which are sterile, resistant to precipitation and turbidity, and have a long shelf life. This paper examines the performance of the ultrafiltration process of citrus juices (lemon, tangerine, orange) and its dependence on the pressure and duration of the process, type and porosity of the membrane, the nature of the juice, and acidity. The juice composition was studied before and after ultrafiltration. It was established, that the productivity of the ultrafiltration process depends on: the duration of the process and this dependence is determined by the nature of the process: membrane type, in particular, filtration material and pressure: with an increase in membrane porosity and pressure, the productivity of the process, the volume of filtered juice, filtering speed and duration increases; the productivity of the ultrafiltration process, during the filtration both in dynamic and static mode, depends on the type and consistency of the juice: it increases with the increase of juice acidity. It was established: the general acidity (1.17%), density (1.038 g/cm³), the content of dry substances (9.9%), sugars (7.8%), including invert (7.2%), ash ( 0.26%), and vitamin C ( 20mg/ 100gr.), do not change in the course of ultrafiltration of tangerine juice. The viscosity, the content of carotenoids, cellulose and pectin decreases. The amino-acid structure practically does not change; hollow fibers detain only 6 - 8% of proteins and amino acids. For obtaining high-quality citrus juices, ultrafiltration should be carried out at a pressure 0.2MPa, on hollow fiber, in a dynamic, circulating mode.

The juices obtained by ultrafiltration on hollow fibers (AP-2.0) are sterile, resistant to precipitation and turbidity, have significantly increased shelf lives, and they retain their organoleptic properties and nutritional values.