Henk van As - Articles and news items

Microstructure characterisation of processed fruits and vegetables by complementary imaging techniques

Issue 1 2011  •  3 March 2011  •  Adrian Voda, Jaap Nijsse & Gerard van Dalen, Unilever Research & Development and Henk Van As, Wagningen University and John van Duynhoven, Unilever Research & Development & Wagningen University

The assessment of the microstructural impact of processing on fruits and vegetables is a prerequisite for understanding the relation between processing and textural quality. By combining complementary imaging techniques, one can obtain a multi scale and real-time structural view on the impact of processing on fruits and vegetables.

Fruits and vegetables are considered rich sources of several essential dietary micro – nutrients, fibres and phytochemicals, therefore the intake of fruits and vegetables has been associated with a wide range of beneficial health effects. A main hurdle for consumers to raise their daily intake is the lack of convenience in preparing foods. The food industry has addressed this by offering the consumer dried fruits and vegetables that are re-hydrated shortly before consumption.

Magnetic Resonance Imaging for cereal products

Issue 2 2005, Past issues  •  3 May 2005  •  John van Duynhoven and Gerard van Dalen, Foods Research Centre, Unilever R&D, Vlaardingen (NL), Ales Mohoric and Henk van As, Wageningen University and Research Center (NL), Pedro Ramos Cabrer, Utrecht University (NL) and Klaas Nicolay, Utrecht University (NL) and current affiliation Eindhoven University of Technology

How does the microstructure of a food product behave during processing? And what events take place during the shelf life of food products? New developments in Magnetic Resonance Imaging (MRI) enable cereal food technologists to address such questions within the context of product innovation.

In the food industry, pressure to bring new products faster to the market has increased and in the meantime the systems under investigation are becoming ever more complex. An important segment of food innovations comprises cereal products such as snacks and (pre-processed) staple foods. Food technologists well appreciate the importance of understanding structure-property relations in developing these novel food products. Assessment of food micro- and macrostructures by conventional techniques, however, mostly involves invasive and destructive procedures. This precludes the observation of dynamic events in relation to food structures during processing and storage. Hence, Magnetic Resonance Imaging (MRI) has gained considerable interest, since this tomographic technique can map structures in a non-invasive and dynamic manner. The potential of MRI is currently exploited to its full extent within medicine, where it has become one of the most powerful diagnostic tools – an accomplishment for which a Nobel Prize was recently awarded (Sir Peter Mansfield, Paul C. Lauterbur, 2003). In its most widely used form, MRI detects water in soft tissues and image contrast can be obtained by exploiting differences in water density and/or mobility. In the last decade, MRI has also found applications in food science. It has become clear, however, that ‘conventional’ MRI techniques are not always adequate for assessment of cereal products, especially those in the low-moisture regime. Under low moisture conditions, cereal products typically have extended shelf life stability and/or favourable sensory properties such as crispness. In order to address the measurement challenges for such systems, Unilever and the Universities of Wageningen, Utrecht and Delft embarked on a project to develop and implement novel MRI methodology. Here we will present several examples of the application of novel MRI methodology for visualisation of moisture migration in cereal systems. It will be demonstrated that MRI can be used to monitor ingress of water during cooking of processed rice kernels in real time mode. We will also show how MRI can be deployed to assess migration of moisture in multi-component snacks, where differences in water activities exist.


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