Experimental Feasibility Study of a Three-Stage Scraped Surface Heat Exchanger for Manufacturing of Dhap Khoa—A Heat Desiccated Milk Product

The aim of the present investigation was to evaluate the feasibility of a three-stage scraped surface heat exchanger for the manufacture of dhap khoa, a traditional Indian heat desiccated milk product. A variety of milk products were made using a three-stage scraped surface heat exchanger (TS-SSHE). In experimental trials, steam pressure and scrapper speed of the first stage (3.5 kg/cm² and 200 rpm) and that of the second stage (1.5 kg/cm² and 150 rpm) of the TS-SSHE were kept constant. The independent process parameters, that is, milk flow rate (200–225 kg/h), the third stage of TS-SSHE scrapper speed (15–35 rpm) and steam pressure (1.0–1.5 kg/cm²) were optimized for the manufacturing of dhap khoa using response surface methodology (RSM). The major significant dependent variables (responses) were moisture and fat contents, flavor score, color attributes, and gumminess. Optimized process parameters were found to be a 205 kg/h milk flow rate, a 15 rpm scrapper speed, and 1 kg/cm² steam pressure for the third stage of TS-SSHE. Energy requirement analyses in terms of electrical energy, steam economy, and overall heat transfer coefficient were also presented. The experimental validation of predicted values at optimized conditions was carried out. It was observed that the manufacture of dhap khoa using a three-stage scraped surface heat exchanger was feasible at the optimized conditions.