EFFECT OF EVAPORATION TEMPERATURE ON BIOACTIVE COMPONENT AND SENSORY QUALITY OF LEMON JUICE CONCENTRATE

Abstract

The objective is to study the effects of processing temperatures on bioactive components of lemon juice concentrates. Lemon was collected from a farm in Budhiganga Rural Municipality, Morang. The juice was extracted and concentration was done to 50°Bx TSS in rotary vacuum evaporator at different temperature (50° C, 60° C, 70° C) and open pan boiling coded as A, B, C, D and market sample was coded as E. Time taken for concentrating was approx. 8.5 hrs. for sample A, 5.5 hrs. for sample B, 2.5 hrs. for sample C and 45 minutes for sample D. Physicochemical parameters (acidity, ascorbic acid, browning index) and bioactive components (total phenolic content, total tannin content, total flavonoid content and antioxidant activity DPPH free radical scavenging activity) was studied. The mean values of TSS, acidity, pH, ascorbic acid, browning index (BI), total phenolic content, total tannin content, total flavonoid content and antioxidant activity of fresh lemon juice was found to be 5.0° Bx, 5.02%, 2.2, 455 mg/L, 0.268, 926.63 mg GAE/L, 510.61 mg TAE/L, 320.22 mg QE/L and 81.01% respectively. All the bioactive components were decreased while increasing evaporation temperature. From concentrated sample, sample concentrated at 60°C was found to be most effective on preserving bioactive components of juice concentrates in terms of higher polyphenol retention, flavonoid retention, tannin retention and higher antioxidant activity. For all bioactive properties there was significant different (p<0.05) along with difference in processing temperatures. Sensory evaluation was conducted and statistical analysis of sensory data showed that sample C i.e. concentrated at 70°C was found to be best sample among all the concentrated sample and market sample. The present findings indicates that it is possible to improve nutritional and sensory quality of concentrates by optimizing temperatures and reducing thermal processing time.