Physicochemical changes of barberry juice concentrated by liquid desiccant-assisted solar system and conventional methods during the evaporation process

The preservation of the quality characteristics of fruit juices during the processing is one of the major challenges in the fruit juice industries. The high costs of fossil fuels and their environmental pollution increased the need to use of the renewable energies. In the present study, some quality characteristics of barberry juice were investigated during concentrating by the methods of liquid desiccant-assisted solar juice concentration system (LD-ASJCS) at the air flow rates of 0.006-0.014 kg/s, rotary vacuum evaporation system (RVES), and evaporation at atmospheric pressure (EAP). Although evaporation rate in LD-ASJCS increased by 25% with increasing of air flow rate from 0.006 to 0.014 kg/s, but it had negative effects on some quality properties of concentrated juices. The anthocyanins retention in the concentrated juices with different air flow rates of LD-ASJCS method were 16-28%. Reduction of the air flow rate resulted in a lower browning index and less variation of color indices (L*, a*, and b*). The a* values, browning index, and sensory attributes of the concentrated juices in the LD-ASJCS at the air flow rate of 0.006 kg/s were comparable to the concentrated juices by the RVES method. Although, RVES method compared to EAP and LD-ASJCS methods better improved the quality of barberry juice, but the LD-ASJCS method can be considered in fruit juice industries because of maintaining quality and sensory attributes, saving energy, and reducing environmental pollution. The mathematical modelling of physicochemical changes of LD-ASJCS concentrated juice showed that these variations are fitted with first-order and zero-order models.