Using Liquid-Only Cans (Equipped with a Single Particle) to Quantify Heat Transfer Phenomenon During Thermal Processing

This study utilizes liquid-only cans (fitted with a single particle) to gain insight into the heat transfer phenomenon during the novel process of reciprocating agitation thermal processing (RA-TP) for sterilization of food. Overall heat transfer coefficient (U) across the can-wall was evaluated for cylindrical cans, filled with different concentration of glycerin and treated with reciprocating agitation thermal processing (RA-TP). Thermocouple-equipped single spherical particle (diameter = 0.019 m) of various densities were also kept inside the cans to obtain preliminary insights into the heat transfer phenomenon at the liquid–particle interface (h_fp). Seven process variables, viz. operating temperature (110–130 °C), reciprocation frequency (1–4 Hz), reciprocation amplitude (0.05–0.25 m), can headspace (0.006–0.012 m), liquid viscosity (0.001–0.942 Pa.s) and particle density (830–2,210 kg/m³), were varied according to three full-factorial designs and corresponding U & h_fp were reported. Depending on the processing condition and product composition, U and h_fp varied in the range 197–1,240 W/m²K and 210–1,230 W/m²K respectively. Higher heat transfer was observed at both can wall and liquid–particle interface with increasing temperature, headspace, frequency and amplitude and decreasing liquid viscosity. The order of heat transfer coefficients for processing conditions was: Frequency > amplitude > headspace > temperature; while for product composition was: Frequency > liquid viscosity > product density. This study is relevant for providing data for process modeling of reciprocating agitation thermal processing.