Drying kinetics of lemon slice (Citrus limon) fruit as affected by sucrose blanching under indirect forced convection solar dryer

Abstract

Lemon is a commodity that people widely consume because of its benefits for body health. The characteristics of lemons were easy to harm; proper preservation methods were needed. The solar dryer preservation method becomes a solution regarding to the problem concerned. Drying uses the novel indirect solar dryer with double glazing technology, a V-groove absorber, heat storage, heat recovery, and photovoltaic (PV) used in drying lemon slices. This research is limited to the use of a solar dryer with these specifications in influencing lemon slices (95.77 %w.b) with and without sucrose blanching treatment. Drying process was carried out for 32 h in 4 days. The drying behavior of the samples was determined by water content, drying rate, modeling, visible object, and antioxidant activity. The research results showed that the final water content of lemon slices with and without sucrose blanching was 11.98 %w.b and 14.61 %w.b. The most considerable drying rate occurred in lemon slices with sucrose blanching with a range of 0.007–0.085 %w.b/min. Based on model accuracy tests, the best modelling results for lemon slices were obtained using the Two Term Exponential Model (blanching) and the Modified Page Model (without blanching). Physical and chemical properties indicate that visible object and discolouration decrease after drying. Physical properties were diameter (67.8–72.8 %), surface area (66.7–73.2 %), mass (4.9 %), L* (5.1–67.1), a* (−338–11.4), b* (40.6–108.2), and ΔE (53.6–143.8). Chemical properties were DPPH (50.1–57.2 %), FRAP (792.9–811.5 µm/L), total soluble sugar (3.1–4.6 %), citric acid (4.2–4.6 %), and ascorbic acid (39.8–43.0 mg/100 g) after drying. The total cost of dried lemon slices is 10.88 USD/kg, and the payback period is 3.19 years.