Gluten-Free Pasta: A Dedicated and Versatile Press

10 October 20134 min reading
Michele Darderi  / Pavan Group The growing number of people affected by coeliac disease (steadily increasingly over the past 20 years), and the ever greater spreading of food intolerances, have led to a strong market demand for “alternative” food products characterized by the total absence of gluten. Among these, pasta has been taking up an increasingly important role, probably because it is sold all over the world (thanks to the universal appreciation of Italian food and the recognized value of the Mediterranean diet) and also because it actually represents one of the main everyday dishes in many countries around the world. In addition, it is worth considering that many geographical areas have a significant local production of corn, rice, sorghum, millet and other cereals of interest from the nutritional and technological point of view; pasta production from such cereals increases their added value and solves the problem of their preservability, not a minor one in most countries. The main problem in producing gluten-free pasta is precisely the lack of gluten, the perfect structuring agent of traditional, durum wheat pasta: in the absence of this protein lattice, which grants pasta its consistency, body and elasticity, it is necessary to “build” something similar, starting from the starch matrix: a certain percentage of starch must be gelatinized up to such a level that the pasta reaches a good consistency without becoming gummy. There are two possible ways to achieve this: by using pre-gelatinized flour (usually subjected to a thermal or hydrothermal treatment, but sometimes also chemically modified) or by suitably processing the original flour. Already since the late ‘80s Pavan chose to go for the second option, well aware of the problems connected with using chemically modified raw materials, the high cost of pre-treated flour and its own ability to develop an adequate technological process; in addition, pre-gelatinized flour does not allow to “guide” the process according to the desired final quality. The process developed initially envisaged a first hydration phase, followed by a thermal treatment phase with steam injection and a final phase where the extrusion screw was fed under vacuum. Each phase took place in a mixing tank connected to the next one by short sealing screws that allowed vacuum to be kept in the last tank. The need to rationalize process and machine led to the first hydration phase being completed with the sole help of a premixer, which directly loads the hydrothermal treatment tank. This part of the process has become a stand-alone unit through which the dough, precooked and hot, is conveyed to the vacuum valve on the press tank. The solution turns out to be especially convenient since it can also be adopted to turn a production line for traditional durum wheat pasta into one for gluten-free pasta from alternative cereals, while also allowing, if required, to keep making durum wheat pasta. This set up is used for production lines with a capacity of over 500 kg/h. Often, however, the hourly production demands for these special pastas are quite low and the focus is on the variety of formats produced, including long and short pasta, on the same machine. This means setting up plants with static or semi-static drying and with a flexible press, not only suitable to handle dough cooking and the forming of short and long pasta, but also capable of producing excellent quality pasta using under vacuum extrusion, while all working parameters are monitored in automatic mode. In order to meet these requirements, Pavan has specifically created a family of compact presses called PST. The main characteristic of these machines is the fact that they have a single tank, preceded by a fast premixer for a first hydration phase, where the dough is cooked with injected steam. From this tank a variable speed extraction screw feeds directly the extrusion screw. The vacuum, very important in order to ensure look and quality in cooking even for these non traditional pastas, is created between the extraction screw of the steaming tank and the extrusion screw. Given the special rheological properties of this type of dough, the extrusion screw is slightly different in design from the standard screw used for durum wheat pasta. Finally, the head is hinged to the machine so it can be easily opened up for cleaning. The hinged head solution also allows to have on the same machine the short and the long past head with a minimum distance between the extrusion screw and the pasta die, a very critical area for these gelatinized mixes.
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