Getting the moisture right for dried vegetables
Vegetables vary widely in their water content, due to growing and harvesting conditions, not to mention variations due to type of vegetable. Drying vegetables to preserve them for further processing is therefore a complex process. Getting it wrong can be expensive in terms of energy usage in over-drying and there will also be a reduction in nutritional content and quality as well as weight loss, reflected in the unit price of the product. As automatic control is one solution, the EU-funded project DRY Control aimed to develop a prototype incorporating reliable sensors for humidity and protein content for an industrial rotary drier set up. To achieve this, the scientists developed a family of processing models with the necessary algorithms and a control system was designed in real time for resolving problems. Credentials of project partners were necessarily multidisciplinary and included end users, specialists in drying a variety of vegetal products such as herbs, hay, onions and cereals. Also active as partners were real time designers of sensory systems in rotary drier manufacturers for the agrofood and forage industries. A modelling simulation expert in agrofood and a highly skilled team in information technologies (IT) control systems represented research and technology development. The team achieved three main results during the two-year project. First, algorithms for a mathematical model to handle all inputs with a database and a rule base to be able to control protein and humidity. For control of the three controlling variables, drum speed, raw material feed and temperature in turn controlled by input signals such as humidity and protein reading, the scientists developed an adaptive fuzzy logic controller (AFLC). This allows the use of three or more control exit signals. Lastly, a completely innovative real-time control system was developed which reduces energy consumption in the plant by 20 %. Project partners developed business plans outlining staff and funding requirements to develop a prototype. The overall aim is to apply for patents and bring the new technology to the market.
