Fruit yoghurt and the perfect mixing

The radar sensor VEGAPULS 64 guarantees a reliable level measurement.

The basic principle of the production of this product obtained from the fermentation of milk has always been the same. Nevertheless, today hygienic conditions are over-controlled and processes automated.

 Is it worth automating processing even for small productions? Yes, for the French Savoie Yaourt (since 2009 affiliated to the Alsace Lait cooperative), which produces fruit yoghurt using the 80 GHz Vegapuls 64 radar sensors. Located in the spa resort of Aix-les-Bains, the company produces yoghurt without additives, preservatives and colorants. Few varieties but of quality.

Plaisir des Alpes with fruit, for example, has only four flavours: Red and yellow fruits, summer or winter fruits depending on the season. The basic ingredient is milk, mostly collected every two days on farms within a radius of 50 km. From the arrival of milk at the factory to the storage of yoghurt in the cold store, the natural product passes through three processing steps: Preparation, packaging and storage.

Each product is available in various pack sizes from 120 to 500 ml, made of recycled plastic, cardboard or glass. Pasteurized milk, refrigerated at 8°C, is poured into a tank where it is mixed, tempered at 58°C, treated at high temperature (95°C) for a few minutes and cooled to the fermentation temperature (35°C). Bacterial cultures then convert lactose into lactic acid, lowering the pH and increasing the acidity, resulting in the formation of a dense clot.

Thanks to the particularly small process connections and the small dead zone, Vegapuls 64 is ideal for compact tanks.

Radar level check in the fruit mixing tanks

Under aseptic conditions, the yoghurt mass is pumped into the fruit mixing plant after several hours of fermentation. The critical parameters of the process are hygiene of the plant components, homogeneity of the product and level detection. The latter must not fall below 20% of the total volume of the tank or exceed 90%, so that the subsequent filling process takes place smoothly.

Since different types of fruit are processed in the same mixing tank, the level sensor must be sensitive to the consistency of the different recipes. In the past this caused problems for Savoie Yaourt, as a capacitive measuring probe caused measurement errors or inaccuracies. In yoghurt production, the level of the fruit mixing tank varies constantly. Without a reliable monitoring and a timely topping-up, it is not possible to ensure uninterrupted production operation.

Overfilling may also cause the process to stop. Therefore, constant detection of the filling volume is essential to avoid interruptions or damage to the system. These problems did not occur again after installing the Vegapuls 64 radar sensors in 2017. In the mixing tank (berries, fruit and sometimes nuts) the high frequency level measurement (80 GHz) maintains the asepticity of the process and guarantees reproducibility.

Therefore, fruit yoghurt can be dosed with accuracy and without interruption in 125 g cups. In compact fruit mixing tanks, the measurement must be carried out accurately even at a distance of less than 200 mm. Thanks to the particularly small process connections and the small dead zone, Vegapuls 64 can be easily mounted on these tanks as well. The sensor can be integrated manually, without tools, and subjected to in-line cleaning in the integrated CIP station.