Trends in Food Science & Technology 20 (2009) S51eS52

Review

* Corresponding author.

0924-2244/$ - see front matter � 2008 Published by Elsevier Ltd.doi:10.1016/j.tifs.2009.01.010

EHEDG dry materials

handling subgroup e

The past 10 years

Karel Mager*

Givaudan Nederland B.V., Huizerstraatweg 28, 1411

GP Naarden, Netherlands (Tel.: D31 35 699 2186;

e-mail: karel.mager@givaudan.com)

In 2008, the Dry Materials Handling Subgroup cele-brates its 10 year anniversary; this article looks back andreviews the achievements and the plans for the future.

In 1998, the EHEDG had already published a lot of docu-ments on test methods and design principles of equipment.However, these were all focused on the liquid processing area.

There was a lot known about liquid handling and liquidprocessing equipment. Also the design principles wereknown but not written down as practical guidance docu-ments for engineers in the food industry. Besides that, therewere no standard test methods to establish the cleanability,pasteurisability and sterilisability of this equipment. In thearea of dry particulate materials (powders) there was a needfor similar documents: design principles and guidance forhygienic engineering for the safe processing of dry partic-ulate materials.

Karel Mager was asked to start a subgroup on dry mate-rials handling. He succeeded in getting a group of peopletogether from:

- the scientific related area (The Technical University inMunich, The Agricultural University in Vienna andSprayDryConsult)

- the equipment suppliers (Reimelt and Hosokawa), and- a group of end-users (DSM-Gist Brocades, Nestle and

Givaudan (formerly Quest International)

Currently the group has grown to 12 active members.Equipment supplier companies like Glatt, J-Tec, CoperionWaeschle and Hecht Anlagenbau have become active mem-bers and from the end-users, Cargill and Numico alsoparticipate.

The following initial members are still active, KeithMasters (SprayDryConsult), Gabrie Meesters (DSM FoodSpecialties), Wolfhard Rumpf (Reimelt) and Karel Mager(Givaudan) as the chairman.

The participants of the group represent The Netherlands,Belgium, France, Germany and Denmark. So, both from aninternational point of view as well as the technical back-ground, the group is currently well balanced.

As previously mentioned there was a need for practicalguidelines on design principles in the area of powders.However, what is the typical difference in design for pow-ders compared to fluid handling? This has been describedin the first of 6 documents the group has published todate.

Dry food processing and handling require equipmentthat are different from those typically associated with liquidproducts. In the case of dry materials, other considerationsinclude material lump formation, creation of dust explosionconditions, high moisture deposit, formation in the pres-ence of hot air, and material remaining in the equipment af-ter shutdown. Appropriate cleaning procedures aredescribed with dry cleaning being favoured to reduce risksof microbiological proliferation.

See EHEDG document 22, General Hygienic DesignCriteria for the Safe Processing of Dry ParticulateMaterials (2001).

The second document describes the general engineeringguidelines to be applied to ensure that buildings, individualequipment items and accessibility of equipment when inte-grated within the plant layout are designed so that aspectsof the process operation, cleaning and maintenance complywith hygienic design standards. It details requirements re-lated to plant enclosure, including hygienic zoning, build-ing structures and elements (from floor to ceiling) as wellas process line installation.

See EHEDG document 26, Hygienic Engineering ofPlants for the processing of Dry Particulate Materials(2003).

The third document from the subgroup is a descriptionof spray drying and fluid bed systems. Because these plantshandle moist products in an airborne state, they are suscep-tible to hygiene risks. Starting from the basics with regardto design, construction materials, layout, and zone classifi-cation of the drying systems to meet hygienic requirements,this document outlines component design aspects of theprocessing chamber, with particular attention to the

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atomization assembly and the distribution grids for fluidiza-tion. Systems for both supply and exhaust air should oper-ate in a hygienic manner and recommendations for the useand installation of various types of filters are listed.

See document 31, Hygienic Engineering of Fluid Bedand Spray Dryer Plants (2005).

The introduction of the product into the processing sys-tem is a key step in maintaining the sanitation and integrityof the entire process. Discharging systems are designed totransfer, in this case dry solids, from one system to anotherwithout powder spillage, contamination or environmentalpollution. Many dry process protocols do not include anyadditional protective heating steps, as they are merely spe-ciality blending processes. Consequently, any contamina-tion that enters the system will appear in the finishedproduct. Therefore the subgroup described guidance forthe design of product bags, big bags, containers and truckdischarging systems in their fourth document.

See EHEDG document 33, Hygienic Engineering of Dis-charging Systems for Dry Particulate Materials (2005).

Further in the process line, dry particulate materialsmight be transferred (transported or conveyed) between orwithin plant components. The transfer operation must becarried out in a hygienic and safe manner and the physicalpowder properties must not be affected during this opera-tion. As a logic follow-up of the previous documents thesubgroup described the most important transfer systemsfor transport of bulk materials in their fifth document.

This document also covers situations where transfersystems are used as a dosing procedure.

See EHEDH document 36, Hygienic Engineering ofTransfer Systems for Dry Particulate Materials, 2007.

Since it is a point of discussion whether the rotary valveis really a valve or a powder transport system it was decidedto write a separate document about this component, whichis widely used in the powder industry.

It fulfils a number of functions (e.g. ‘‘shut-off’’ of flowpaths, flow control and as a barrier in pressure differencesin the process line). Therefore this sixth document fromthe subgroup gives hygienic design guidelines for this im-portant valve.

See document 38, Hygienic Engineering of Rotary Valvesin Process Lines for Dry Particulate Materials (2008).

The group has published 6 documents to date and the 7thdocument is in progress: ‘‘Hygienic Engineering of Valvesin Process Lines for Dry Particulate Materials’’.

In process lines for dry particulate materials, valvesfulfil numerous functions, for example: shut-off and open-ing of paths, change-over, control of flow, protectionagainst excessive or insufficient pressure and against inter-mixing of incompatible media at intersection points in thesystem. This document will describe hygienic aspects ofseveral diverter valves, metering valves and shut-offvalves.

Since the industry increasingly recognises the value ofthe EHEDG, the subgroup sees a lot of opportunities forpractical guidelines.

Pack-off systems, blenders, dust extraction systems, etc.will be subjected to in depth studies of their hygienicdesign. Discussion will occur where the critical areas arein the design of these systems in relation to the entireprocess.

Equipment suppliers have developed hygienic approachesto individual items of powder processing equipment. How-ever, it is necessary for engineers in the food industry toavail themselves of the guidance on hygienic design consid-erations outlined in the EHEDG documents.

The Materials Handling Subgroup will continue toactively promote the EHEDG and share their experiencethrough seminars and food safety events.

Info about the subgroup and their documents can befound on the EHEDG website: www.ehedg.org.