Concentrate development from Litchi Juice and quality evaluation during storage

Abstract

An attempt has been made to concentrate Litchi juice using fresh juice, using class-II preservatives via laboratory scale single stage single effect glass evaporator with vacuum in a batch. Two litchi varieties viz. Dehradun and Seedless late were procured from the Regional Fruit Research Station, Gangian (Distt. Hoshiarpur) and processing was done at Food Science and Technology department (Punjab Agricultural University, Ludhiana, Punjab) pilot-plant. The extraction of juice was attempted via screw-based juice extractor with subsequent muslin cloth filtration. The filtered juice was divided into two lots of which one was concentrated via evaporation while another was preserved using 2000 ppm potassium metabisulphite in glass bottles for later on concentration. The juice was concentrated at 50-55oC temperature with a vacuum of 27-30 inches of Hg. The final concentration of juice was maintained at 80 oBrix in all the cases. Product was packed in pearl pet jars and was stored at ambient room temperature (12-38 oC) (RT) and low temperature (LT) i.e., refrigerated (0-4oC) for 6 months periodic quality evaluation like physico-chemical because of storage. Stored product was analyzed at 0, 2, 4 and 6 months interval for various storage physico-chemical changes like TSS, pH, acidity, ascorbic acid, sugars, browning, pectin, viscosity, tannins and sensory quality. The result outcome proposed that seedless variety yield more juice, pulp and less seed in comparison to Dehradun variety while the sensory characteristics were found more acceptable in Dehradun variety rather than Seedless variety. Physico-chemical properties observed in concentrates from both litchi varieties doesn’t show much difference but a clear difference can be seen room temperature stored concentrate to low temperature stored concentrate. The flow behavior for the concentrates was found to be decreasing slightly with storage period as compared to controls. However, considerable decrease in flow behavior index was observed for the concentrates prepared from Dehradun variety stored at low temperature for 6 months to the seedless variety. The consistency index values has shown positive drift with extending storage time especially for those low temperature concentrates. So, it can be said concentrates from both varieties could be commercially produced with acceptable sensory characteristics.