In present work a batch ohmic heating plant was designed and set up with the aim to obtain a flexible system able to reproduce the three phases (heating, holding and cooling) of a thermal treatment of food matrices, in a wide range of product factor as well as electrical and thermal parameters. The realized system consists of a 15 kW power generator able to deliver electric current in the form of bipolar square wave at 25 kHz to a food matrices (liquid or particulate-liquid product) placed into a batch ohmic heater made of a cylindrical Peek tube (7.6 cm in diameter, 20 cm in length) closed at the ends with two inox electrodes. The electrodes were provided with an internal cavity in which, during the cooling phase, water-ethylene glycol solution was recirculated from an external refrigerated bath. Auxiliary devices were employed for control and measurements of the process parameters. Preliminary tests were carried out to assess the performance of the ohmic system by heating sodium chloride solutions of different concentrations (0.1-0.50% (w/v)) in a wide range of operative variables such as peak voltage (100-1500Vpk), holding temperature (90-121°C), heating time (60-180 s) and electrical conductivity (1-5 mS/cm). Optimal settings of the operative variables were found for different processing conditions.
Set up of a batch Ohmic Heating system for sterilization of solid-liquid mixture
PATARO, GIANPIERO;DONSI', Giorgio;FERRARI, Giovanna
2012-01-01
Abstract
In present work a batch ohmic heating plant was designed and set up with the aim to obtain a flexible system able to reproduce the three phases (heating, holding and cooling) of a thermal treatment of food matrices, in a wide range of product factor as well as electrical and thermal parameters. The realized system consists of a 15 kW power generator able to deliver electric current in the form of bipolar square wave at 25 kHz to a food matrices (liquid or particulate-liquid product) placed into a batch ohmic heater made of a cylindrical Peek tube (7.6 cm in diameter, 20 cm in length) closed at the ends with two inox electrodes. The electrodes were provided with an internal cavity in which, during the cooling phase, water-ethylene glycol solution was recirculated from an external refrigerated bath. Auxiliary devices were employed for control and measurements of the process parameters. Preliminary tests were carried out to assess the performance of the ohmic system by heating sodium chloride solutions of different concentrations (0.1-0.50% (w/v)) in a wide range of operative variables such as peak voltage (100-1500Vpk), holding temperature (90-121°C), heating time (60-180 s) and electrical conductivity (1-5 mS/cm). Optimal settings of the operative variables were found for different processing conditions.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
