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Lyophilisation - Articles and news items

Lyophilisation: Atmospheric food freeze-drying: challenges and opportunities

Issue 6 2013  •  2 January 2014  •  Davide Fissore, Mauricio M. Coletto and Antonello A. Barresi, Department of Applied Science and Technology, Politecnico di Torino

Freeze-drying is a process that can be used to remove water from foodstuff, thus increasing their shelf-life, avoiding deterioration of aroma and flavour compounds as well as nutrient degradation. In a vacuum freeze-drying process, product temperature is firstly decreased in such a way that all the free water freezes, then the product is exposed to low pressure and the ice sublimates (primary drying). At the end of the sublimation stage, the amount of residual water can be further decreased by removing the bound water (secondary drying); this stage is generally carried out increasing product temperature and decreasing the operating pressure. This way, all the characteristics of the product, e.g. shape, appearance, colour, taste and texture, are retained in the final product. Moreover, the high specific surface area of the final product allows a fast and easy rehydration…

The optimisation of freeze drying processes

Issue 4 2011  •  6 September 2011  •  Javier Silanes Kenny, Associate Principal Scientist, Soluble Coffee Process Optimisation, Kraft Foods

From its infancy to today, lyophilisation has seen a constant but very slow evolution. Indeed, the techniques that we utilise today differ very little to those used industrially, after its development as a viable technique for the preservation of serum during World War II. Its application to pharmaceuticals and from there on to foods at commercial scales followed in very short order, becoming pervasive through the 1960s and 1970s to almost exemplify human progress in peopleā€™s imagination as the food of the space age in the 1980s.

In fact, it would be tempting to say that almost everything that can be invented in freeze drying has been invented, and that any small tweaks that developers today can think of are merely that: tweaks. Where, then, does that leave the technologist or engineer faced with the problem of reducing costs in the very expensive world of freeze drying? In a world where commodity, energy and food prices soar and where our consumers are ever more aware of the environmental impact of what they consume, the competition for the most cost effective and sustainable processes is won or lost in the ability to make those tweaks and to successfully implement them, and the full understanding of the science of the process becomes ever more important.


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