The study – published in Trends in Food Science & Technology – noted that while spray drying methods could be applied to heat sensitive ingredients, such as enzymes and probiotic bacteria, in industrial practice freeze drying or other freezing processes are often preferred.
“The reason is that optimum drying conditions and tailored matrix formulations are required to avoid severe heat damage leading to loss in enzyme activity or reduced survival of bacteria,” said the researchers.
However the team, led by Maarten Schutyser of Wageningen University in The Netherlands, noted that optimisation of the spray drying process, including use of a single droplet drying process and utilisation of stabilisation mechanisms such as carbohydrate-rich formulations could help to provide a better spray drying process for enzyme and probiotic bacteria.
Commercial value
Schutyser and his colleagues noted that many foods and food ingredients are dried in powdered form to provide shelf-life or retain activity of specific bioactive components.
“Amongst the convective air drying methods, spray drying is a mild technique due to its very short drying times and the relatively low temperatures to which the product is exposed … However, compared to freeze or vacuum drying, the spray drying process is more prone to damaging heat sensitive components such as enzymes and probiotic bacteria,” they noted.
However, because it could process much larger volumes and operated at a higher energy efficiency, spray drying was a much more cost effective and attractive method for industry, they claimed.
They added that while many studies have reported optimisations of the spray drying process or product formulations in order to minimise activity losses, “in practice optimisation results, especially from pilot-scale experiments, have been difficult to translate into general optimisation rules.”
“In this paper we make an appraisal for dedicated single droplet drying procedures and predictive models that can map drying behaviour and inactivation kinetics of enzyme and probiotic bacteria at the droplet level.”
Spray drying challenge
The authors of the review said fundamental insights into the structural changes that occurred during drying could help to provide better understanding of the drying behaviour and possible stabilisation mechanisms for enzymes and probiotics during drying and storage.
“As long as the stabilisation mechanisms are not fully understood, the formulation development for spray–dried powders remains mostly empirical and use of experimental screening methodologies is a must,” they added.
“The spray drying of heat-sensitive products can be accelerated if a more systematic analysis is made of varying product formulations in relation to their effect on the active component and well-defined drying and storage conditions.”
However, Schutyser noted that specific scientific challenges included “amongst others the development of single droplet drying approaches that allow the screening of various drying and storage conditions and formulations in a high throughput manner.”
Source: Trends in Food Science & Technology
Published online ahead of print, doi: 10.1016/j.tifs.2012.05.006
“Single droplet drying for optimal spray drying of enzymes and probiotics”
Authors: M.A.I. Schutyser, J. Perdana, R.M. Boom