Design and development of sub‐baric thermal processer for frying of Gulab jamun: A deep‐fat fried dairy product

A sub‐baric thermal processor (SBTP) was conceptualized, designed by 3D modeling and simulation for von mises stress analysis, deformation, and factor of safety. The auxiliary system components like electrical heater, surface condenser, vacuum pump, and frying cage with tiered trays were selected based on the design for a flexible capacity to prepare fried snack products and were integrated into the system for smooth functioning. Essential mechanical movements of the frying cage were controlled by frequency‐controlled planetary gear motor along with pneumatic system for rotary and vertical movements. The design concept was transformed into process, instrumentation, and manufacturing drawings. The fully automatic, microcontroller based, skid mounted, mobile SBTP was fabricated asper c‐GMP and 3‐A hygiene fabrication standards. Based on von mises stress analysis (135.79 MPa), the SBTP was fabricated from 4‐mm thick, food grade, acid‐resistant AISI‐316 stainless steel to withstand high vacuum environment. The factor of safety obtained was 1.50, which implies that vacuum vessel can practically withstand a stress up to 205 MPa. The operating process parameters of SBTP, temperature, process time, and pressure were controlled by custom‐made microcontrollers, programmed to work in auto mode. The rotation of frying basket was varied by inverter‐controlled variable frequency gear motor. The basket hoist mechanism was automated and controlled by microcontroller. Results showed that the sub‐baric product had lower oil content (22.74%) and the use of leavening agent could be eliminated due to the development of adequate porosity during sub‐baric frying. Sub‐baric fried Gulab jamun balls at 118°C, 5 min and 48 kPa had a color comparable to the conventional fried balls (140°C, 5 min, 101 kPa) with a browning index of 164/94 and 169/103, respectively, for crust/crumb. From the above results, it concluded that sub‐baric thermal process is a potential alternative technique, which could be adopted by the dairy and food industry for the production of low‐fat dairy and food products. PRACTICAL APPLICATIONS: The developed sub‐baric thermal processer would lead to innovation, which can conveniently replace the conventional frying and soaking process with savings in use of frying oil and could also be applicable to similar other frying applications in the food processing industry especially in the preparation of snack products.