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Introduction
Welcome to our second newsletter for 2006.
In this issue:
Our joint food engineering committee continues as a combined IMechE and IFST institutional food engineering activity.
Following a recruitment plan we have eighteen IMechE members from the food industry and seven IFST food industry scientists and technologists. We also have six corresponding members from UK universities, Sweden, India and Hong Kong. A great spread of knowledge from industry and academia.
Seven submissions were received for our Food Engineering Award 2006. The winner James Barclay, has been presented with the prize of £1000 and a certificate at our January meeting at the Worshipful Company of Butchers’ in London. The Master of the Worshipful Company of Butchers made the presentation.
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James Barclay, The Master of the Worshipful Company of Butchers,
Douglas Brydges OBE |
Our programme of meetings and activities will be set up at the beginning of 2007, and will be assisted by the advice of DEFRA, with Christina Goodacre.
Christina Goodacre attended our meeting on the 10 January 2007 to advise on the DEFRA view of food engineering in the future.
We would appreciate any comments and advise that you may have which will be discussed at our meetings.
The next issue of the newsletter will include publications from our prize applicants. If you have a paper on food engineering technology and application please email process@imeche.org with a copy for review in a future publication.
Finally I would like to wish you all a Happy New Year.
Don Ives
Chairman, Food Engineering Committee
Collaborative Working
A meeting was held on Wednesday, 15 November 2007 at the IMechE to discuss how the FEC can successfully collaborate with the FMEG, in order to avoid clashes with events organisation. In attendance were Professor John Gray, Don Ives, Jose Spring, Maureen Carter and Dunni Akinola.
The key points for collaboration are detailed below:
- Information sharing is quite key between both parties, to avoid clashes
- FMEG has a meeting in May and one in the autumn (usually November)
- It is a good idea to co-sponsor each other’s events/meetings
- Speakers/representatives can be sent to present at meetings
- FMEG Secretariat will be happy to publicise FEC events on its website; the FEC can upload its events directly on to the FMEG website and the FEC will publicise FMEG events in its newsletters
- Joint mailings can be considered
- Press e-mail group, which includes IET and IMechE will provide information on current issues
- A number of organisations will be contacted by individuals to avoid setting meetings/events in the same period – Jose will contact Daphne Davies at Camden; John will contact Sue at Faraday and also talk to PPMA’s chief executive
Free Research Service
The Information and Library Service provides a free research service to all IMechE members, covering all aspects of mechanical engineering. Whether you need to find a particular fact or statistic, the latest articles/press coverage in an area, or require information on a supplier, market or company the ILS team can help. Salary and course information can also be provided.
Need the latest information published in your area?
ILS staff can search for published information on a specific subject area on the library catalogue and specialist databases. A list of relevant books, papers and articles will then be sent to you so you can get an overview of the subject area. You can then request a loan or photocopy of an item as part of our Document Supply Service. Postal loans are available.
Looking for a particular fact or statistic? A wide range of resources are used to find the specific fact that you are looking for. Some recent enquiries received include:
- What are the mechanical properties of the steel BS 3146?
- What is Poission’s Ratio for pure copper?
- What is the density of dry ice?
- Which British Standard covers vibratory conveyors?
- What is the average salary for a Chartered mechanical engineer in the Midlands?
- Can you provide a list of UK manufacturers of folding machines for plastics?
Information and Library Service
Tel: +44 (0)20 7973 1274
Email: library@imeche.org
The Rheology and Foaming Kinetics of Potato Starch Melts
Nitin C. Nowjee and Malcolm R. Mackley
Department of Chemical Engineering, University of Cambridge
This paper is concerned with the melt processing, foaming and rheological characterisation of low water content potato starch using a Cambridge multipass rheometer. The work is particularly relevant to better understand the foaming behaviour of starch melts, which, in turn, can be directly applied to study and explain the commercial extrusion expansion processes of starch. The extrusion expansion of starch is widely used in the production of cereal foods and snacks. It is a complex process which occurs during high-temperature, low-moisture cooking and is a consequence of several simultaneous events, including nucleation, bubble growth, extrudate swell and bubble collapse associated with pressure and temperature changes at the exit of the extruder die.
Simplified model experiments were developed to follow the rheological and foaming behaviour of starch in a systematic way using a multipass rheometer. This capillary rheometer was used over other conventional rheometers because the test samples could be held in an enclosed volume between two vertical pistons which could then be used either in a pressure variation mode to study foaming or synchronously in a multipass mode for pressure drop measurements across a capillary to eventually determine the rheological properties of the test sample.
Initially, it was found that simple heating of low water content starch powder inside the confined volume of the multipass rheometer degraded the starch into an intractable, opaque material. However, pre-treating the low water content starch by simultaneous heating and pressing between parallel plates of a heat press generated sufficient shear through squeeze flow to thermomechanically break down the starch granules and generate a clear, amorphous melt. The melt, when subsequently quenched into a solid sheet, was used to make starch discs which were stacked inside the rheometer and heated under pressure to produce a homogeneous melt.
A systematic range of capillary rheometry experiments were thus carried out on the starch melt to investigate the effects of water content, temperature and additives like glycerol (as plasticizer) and calcium phosphate (as nucleating agent) on the flow properties of the melt. The apparent viscosity and viscoelastic response of starch melts were studied under different test sample conditions. In-situ nucleation and water vapour bubble growth within potato starch melts were also studied using the rheometer fitted with an optical cell test section. The starch melt, initially held under pressure of 70 barg, was depressurized by moving the pistons apart, thereby introducing thermodynamic instabilities, which led to the nucleation and growth of water vapour bubbles. Different bubble growth kinetics were thus studied using different starch melts, with different water contents and additives at different depressurization steps. An isothermal single-bubble growth model was developed to numerically characterize bubble growth within a melt. The model was based on the overall force balance on the starch melt, mass balance of the water vapour in the melt and the mass balance on the water vapour bubble. A good fit was obtained between the experimental bubble growth kinetics and the model by using realistic equation parameters. Although the model matched the experimental data, it still represents a preliminary step to fully model the commercial extrusion expansion of starch and other foamed polymer
product.
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