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.
Description:
A dissertation submitted to the Department of Food Technology, Central Campus of
Technology, Tribhuvan University, in partial fulfillment of the requirements for the
degree of B. Tech. in Food Technology
