Drying is an important and long-used method of increasing the shelf life of fruit and vegetables. The end result depends on the method used. Conventional air drying often involves structural changes to the product. The vegetable or fruit is usually shrunken and does not resemble the original.
Current method for industrial freeze drying
Freeze-drying is a process which removes water from a product while keeping its structure almost intact. In addition, the low temperature used makes it possible to preserve most of the valuable raw material components.
Lyophilisation is nowadays applied on an industrial scale using intermittent apparatuses, in which it is easier to maintain the low temperatures of 20°C and a pressure of ~150 Pa, necessary for the process. However, periodicity is cumbersome and operating costs are significant. During the depressurisation that begins freeze-drying, the raw material may over-melt or overheat locally, leading to quality losses.
New technology
The new solution assumes a continuous freeze-drying process for strawberries. The heat to the frozen material will be supplied hybrid (heating shelves, infrared radiators, ultrasound generators), which will shorten the freeze drying time (especially the second drying period, i.e. desorption) and consequently reduce the energy consumption of the process. Drying control will be carried out using intelligent/self-learning algorithms allowing continuous (on-line) optimisation of product quality parameters and minimisation of energy consumption. A significantly improved final product will be created. It is also planned to obtain freeze-dried strawberry particles, e.g. in the form of cubes or slices.
The advantage of the proposed method is also evidenced by a higher content of polyphenols (ed.: natural compounds found in plants that have a protective effect and give them colour and flavour), better texture obtained by limiting the collapse of the structure of freeze-dried products, and more favourable sensory qualities.
From prototype to implementation
The developed technology of freeze-drying strawberries will be applied in the food industry. Recipients will be manufacturers of breakfast cereals, muesli, sweets and various types of healthy snacks. During the project implementation, the 9th level of technological readiness will be achieved - a prototype sublimation dryer will be constructed and tested for continuous operation. After reaching full technological efficiency, the installation will be used commercially. The results of the project will be implemented by the consortium leader - GP KLASA Sp. z o.o.
Besides Lodz University of Technology the scientific partner is Wroclaw University of Environmental and Life Sciences, Division of Heat Technologies and Processing Engineering. The leader is the fruit processing company Grupa Producentów KLASA Sp. z o.o.
The total budget of the project is PLN 28 million and the funding obtained from the EU under the Operational Programme Intelligent Development 2014-2020 is PLN 17 million.