Researchers and industrialists took stock of the technological advances of drying

September 19, 2012 by Hanne-Lys Meyer

Translated by Lisa Infant Milk, from RLF, 09/2012




Created after the initiative of INRA, the 5th edition of the International Symposium for milk powders was held in June at Saint Malo. During three days, it has brought together 420 professionals from 25 countries. This year, the FIL,  has also associated itself to the initiative. The symposium was also punctuated by a commercial session. The equipment manufacturers could present their advanced technologies. Echoes of the conference.


Five thematic sessions devoted to the new processes of testing, to the means of reduction of the expenditure of energy, to the improvement of knowledge on the crystallisation of  lactose, to the characterization of the properties of the powders and to the nutritional aspects, composed the program of the international symposium of dairy powders.


Energy Sobriety

The simulation evaluates the potential savings

At INRA, an expert in spray drying has developed software that predicts the parameters of the process. Thanks to this tool, the manufacturer may decide the best investment to reduce the energy consumption of his site.

At a time when the powders industry seeks to reduce power consumption, simulation becomes a tool for arbitrating among the solutions. INRA Rennes has thus elaborated software which is already sold to 20 dairy processors in the world. One of its functions is to evaluate the savings offered to the manufacturer through the means of improvement of the energy efficiency. The tool’s the name is SD2P: Spray Drying Parameters Simulation and Determination.

The production engineers can, thanks to this software, characterize the existing installation and then simulate the impact of possible changes on the energy consumption of the site. The manufacturer must be prepared to devote time. It takes on average 6 months for the stage of characterization, with a full-time engineer mobilized. But for Pierre Schuck, INRA researcher at the initiative of the software, the challenge is worth it. "Our software allows evaluating the gain which can be pulled by means of the energy consumption reductions. Thanks to the provided estimates, the manufacturer can know whether the transformation envisaged presents an interest and if the investment deserves to be engaged".

Experience shows that installing a dehumidification wheel at the entrance of the drying tower is often profitable. Dehumidifying the atmosphere makes it possible to supply the tower with drier air which will be better able to eliminate water from the product. Installing a recovery system for calories, so as to reuse the energy of the outgoing air to preheat incoming air, and another layout costs even if it is not conceivable on all installations. "There is also the solution of reheating the concentrate before the atomization step", says Pierre Schuck. But again, this practice is not generalizable because if it reduces the overall energy cost, it changes the viscosity of the concentrate and therefore the size of the droplets and the density of the powder which can lead to the refusal of this solution by the manufacturer. To integrate all aspects of drying, INRA continues to evaluate the tool. The next version will take into account the thermo plasticity of product in a way to anticipate the risk of sticking in the tower during drying. The other function of the software is to help optimize the parameters of the process following the product composition, or vice versa. "We have shown for example by exchanging sugar against another less hygroscopic product, the manufacturer can facilitate the product drying, and in return, increasing the evaporation capacity of the installation"  says Pierre Schuck. According to the feedback from the first users, the software SD2P, saves 5% to 25% in productivity. The tool has been elaborated on the initiative of INRA but also of Laiterie de Montaigu and Lisa Infant Milk which contributed to its development.


Proceeding to test

Extrusion promises easy to rehydrate

In Australia, a dairy manufacturer, Murray Goulburn, is experimenting on a process for producing powders where the step of drying by atomization is preceded by a phase of extrusion. The combination of the two operations, imagined by a French equipment manufacturer, Clextral, resulted in powders with better rehydration ability.

One is a French supplier and the other is an Australian dairy manufacturer. Clextral and Murray Goulburn are experimenting, since four years, a new process for the production of powders. Their results give them reasons to continue. At pilot scale, the partners showed that their technology can develop, at lower energy costs, more porous powders that rehydrate better when implemented. Can their method benefit the forms of powders which, such as casein powders, err by their difficulty to rehydrate? The equipment manufacturer and the dairy processor say yes.

Their patented technology, called path EFA (Extrusion Technology Porosification), introduces a step of extrusion and injection of gas before the operation of classical spray drying. This initial phase is the principal interest of the method. With a texturing effect, it increases the granule surface, which results in a better ability to rehydration. Less restrictive in terms of viscosity (the extruder can accept mixtures presenting up to 62% of dry matter and 20 000 cP), it also allows richer mixes from the blow and opens the possibilities of formulation. "Our process can dry mixes which, because of their excessive viscosity, could not be dehydrated by classical methods" says Gilles Maller, head of Clextral.

The equipment manufacturer evokes a series of applications. In the dairy sector, the list goes from powders rich in proteins to the powders rich in fat passing by instant drinks. Without counting the possibility of applications in the industries of aromas and ferments. Because one of the benefits of the technology is to work at temperatures 20 degrees Celsius to 50 degrees Celsius lower than those achieved during the conventional method. "In other words, we are able to better preserve the products which are sensitive to heat" said Gilles Maller.

If Clextral and Murray Goulburn are enthusiastic, it is also because the EPT reduces the energy consumption compared to the traditional way. The equipment manufacturer and the industrialist announce a saving of 40% in the case of powders rich in protein, 50% in the case of powders rich in fat. A logical economy, given the fact that the process helps bring in a more concentrated mixture to the drying chamber than when it is dried by the usual way.

The European industrialists are showing more and more interest for EPT. Considering this fact, Clextral, is envisaging the construction of a second driver to respond to the requests for pilot testing. The first pilot, with an evaporative capacity of 10 to 50 kg / h, will remain in Australia. At the same time, the equipment manufacturer is already anticipating the transition to industrialization. According to his projections, extrusion-porosification-drying may, at the industrial scale, provide an evaporative capacity of 400 to 1000kg / h. Nothing to replace the conventional method for mass production, but can offer an alternative for manufacturing, small volumes, of powders with high added value.


Drying of whey

Crystallization of lactose, better understood

A PhD student has studied the effect of the composition of whey on the kinetics of crystallization of the lactose. 

Crystallization of lactose, at present, has only a few secrets for researchers. At INRA Rennes, a PhD student, Gwenole Gernigon, has sought to understand how small mineral and organic components, whey and permeate acids or intermediaries (which are more difficult to transform) influence the crystallization kinetics and distribution of the size of the crystals. The results reveal that the minor components can be classified into three categories, with one among them being a category of components having accelerating effect, and among these are: lactates and citrates.

If researchers are interested in the mechanisms of crystallization, it is because this operation is a key step in the process of manufacture of whey and permeate powders. Because both compounds are mainly composed of lactose, a sugar very hygroscopic which needs to be brought to crystal state in order to make it 'dryable'. This operation is currently poorly understood, partly because whey and permeates do not crystallize at the same speed. The recent study of INRA helps explain why.

Gwenole Gernigon draws his conclusions from the observation of the isothermal batch crystallization of super saturated lactose solutions (70g.100-1g - 1eau), with or without other added components. The kinetics and the distribution of crystal sizes were checked by refractometry and laser scattering, respectively. According to the student, the proposed method can now be used to study the crystallization of lactose on the field, in industrial practice.


The control line

GEA Niro presents a new online control system designed to analyze the quality of the powders at the exit of the dryer

The new system can measure in one action all the characteristics of the powder, from the rate of moisture (by microwave technology) up to the eventual presence of burnt parts (by analysis of digital images). The equipment is called PowderEye. According to the equipment manufacturer, this is the first time a monitoring tool allows to control all the parameters of quality in a single operation. Samples are levied at the frequency defined by the industry, and the results of analysis are presented in the form of trend curves, with the emission of alarms when the characteristics deviate.



Powder handling

Guerin systems, specialist in handling powders, opened the doors of its testing facility at May sur Evre (near Angers, France) for the SDDP symposium participants. 100 French and international professionals have joined the visit.

In its institute, the equipment manufacturer can simulate all handling methods and also characterize the properties of powders. Because the platform offers both the pilot and the laboratory. Thanks to the pilot, of industrial size, in which R & D can graft different transfer functions but also features air mixing, screening, dosing and draining, the manufacturer can reproduce the actual conditions of production.

At the request of interested manufacturers, it can validate the technical feasibility of the projects involving new handling configurations. The laboratory at May sur Evre, can evaluate the characteristics of the powders with, for example, the possibility to determine their particle size or their behavior in response to shear. Often the results are used to support the design of future workshops.



Three other technologies in the test phase

Overconcentration, zeodration and absorption are other examples of testing methods. According to drying experts, their limit is that they pose difficulties when industrialized at large-scale. But all the three seems to be interesting. Provided their ability to produce is valid, at low energy cost, powders which exhibit the functional properties are expected, especially in terms of rehydration capacity.