Aseptic processing of rice pudding

Risifrutti is a rice pudding that can be eaten directly from the cup either as a dessert or as a snack. While it is simple and convenient to eat, it is not an easy product to make.

Procordia Food in Orebro, Sweden, found the solution to making a rice pudding that didn’t burn and stick was three Alfa Laval Contherm scraped-surface heat exchangers.

In the process, the rice pudding is heated in three Contherm scraped-surface heat exchangers before it is cooled and packaged in cups. The reason Procordia chose Alfa Laval’s scraped-surface heat exchangers for this process is their ability to treat products with particles, high viscosity and a tendency to create a film when heated.

The Contherm’s blades continuously scrape the internal surfaces to keep them clean and free from burn-on. They also agitate the product in order to ensure high heat exchange. This has made it possible to switch from batch operation to continuous operation.

The Contherm scraped-surface heat exchanger is vertically mounted and designed for the heating and cooling of particulate, sticky, viscous and crystallising/phase-change processes. It is available in three sizes and can serve in a wide range of process stages including heating, cooling, slush-freezing, pasteurisation, sterilisation and crystallisation. The Contherm can operate with any of the following media: steam, water, brine, ammonia, glycol, freon, thermal oil or liquid gases.

During operation the product is pumped into the lower end of the heat exchanger cylinder and is removed from the cylinder walls by scraping blades as it flows through the cylinder. This scraping action results in product heating or cooling with a high heat transfer rate without fouling. The scraping action continuously removes the product from the cylinder wall, thereby allowing the fresh product to be exposed to the heat transfer surface and providing high heat transfer. The heating or cooling media flows in the annular space between the cylinder and the insulated jacket. When liquid media or steam is used, a spiral coil is installed in the annulus to provide high heat transfer efficiency.

The Contherm Scraped-Surface Heat Exchanger can handle aseptic products of varying consistencies including chunky home-style soups, cream and cheese sauces, salsa, puddings, dips and hummus. The Contherm had been specifically designed to provide efficient and gentle treatment so that none of the flavour, nutrients or consistency is lost during processing.

During aseptic processing, the Contherm can heat and cool almost any product that can be pumped, especially those that traditional heat exchangers cannot handle. The Contherm is equipped with a two-stage aseptic seal designed to provide constant flushing on the non-product side of the seal in order to minimise the risk of microbiological contamination.

The product is heated in the Contherm to cooking or sterilisation temperature using steam or hot water as the heating medium. The product can then be held in an insulated tubular holding cell for the time required to achieve sterilisation or the right product texture before cooling in the Contherm to the correct temperature for packaging.

During operation the product is pumped through the lower end of the heat exchanger through specially designed tangential heads that provide a gentler introduction of the product into the cylinder than the centre-port high-shear head design. The heating or cooling media flows in the annular space between the cylinder and the insulated jacket. When liquid media or steam is used, a spiral coil is installed in the annulus to provide high heat transfer efficiency.

As it flows through the cylinder, scraping blades remove the product from the cylinder walls, which allows fresh product to continuously be exposed to the heat transfer surface, thereby providing efficient heating or cooling without fouling.