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Shining a light on food

Claire Pizzey of Diamond Light Source describes the potential benefits of using the UK national synchrotron facility to undertake characterisation of foods and food ingredients to enhance understanding of their properties and behaviour.

With rising raw material costs around the world and increasing pressure for local food supplies, sustainability and waste reduction are key drivers for the food industry, particularly for global supply chains. Following food scares, consumers are demanding higher levels of quality control and traceability for food security; this is of vital importance in a very competitive market with new products frequently introduced. Consumer trends, particularly the focus on health and nutrition, also represent research and development challenges for the food industry and meeting these diverse requirements is key to long term business success. Innovation in these areas requires a fresh approach, a good understanding of the science behind the product or process and access to the widest possible variety of research and development tools. Diamond Light Source’s advanced characterisation facilities are actively supporting this innovation.

What is Diamond Light Source?

Diamond Light Source is the UK national synchrotron facility, producing X-ray, infra-red and ultraviolet beams of exceptional brightness for research purposes. This brilliant light, combined with state of the art technological platforms, is extensively used by the scientific community to undertake structural, chemical and imaging investigations of a broad range of materials on very fast timescales and under industrially relevant conditions. Diamond’s capabilities are very well suited to a wide variety of materials research applications ranging from aircraft fan blades to catalysts, hydrogen storage materials and batteries to high performance coatings and fuel additives and complex formulations for the pharmaceutical, food and consumer products industries respectively. 

Located near Didcot in south Oxfordshire, the research facility is used by approximately 8,000 scientists from the UK and overseas every year. These scientists (called ‘users’) are predominantly from academia (90%) and publish over 1,000 high impact journal articles each year as a result of their experiments, which are free at the point of access and awarded via a peer review competition. Commercial activity plays a very important role at the Diamond Light Source and 10% of the facility operational time is dedicated to proprietary use by industrial clients. Clients range from the large multi-national household names through to SMEs and start-ups with 150+ companies worldwide making use of Diamond’s facilities in their R&D programmes by 2018.

Diamond is a not-for-profit limited company funded as a joint venture by the UK Government through the Science & Technology Facilities Council (part of UK Research and Innovation, UKRI) in partnership with the Wellcome Trust. Diamond’s Industrial Science Committee provides guidance on opportunities for a wide range of industries to be engaged in research at the Diamond facility and identifies industrial research priorities that help to shape Diamond’s operational strategy. Companies currently and previously represented on the committee include Unilever, GlaxoSmithKline, AstraZeneca, Johnson Matthey, Infineum, Rolls-Royce, Evotec, Shell and National Nuclear Laboratory.

In order to facilitate the use of the Diamond facility by researchers working in industry, an Industrial Liaison team has been established, comprising highly qualified scientists experienced in a range of techniques, enabling the translation of diverse research problems into meaningful analytical solutions. Diamond offers a range of services including full experimental design, data collection and analysis service, ideal for those with limited time or no prior knowledge of the techniques. Working with initiatives, such as the STFC Food Network+, enables Diamond to gain a greater understanding of the pressures facing the agri-food sector and to tailor its offering to suit the needs of the food industry.

Aerial view of Diamond Light Source
©Diamond Light Source

How is Diamond’s facility used by the agri-food industry?

Diamond provides specialist ‘Formula 1’ analytical techniques for the atomic to microscale characterisation of materials ranging from food ingredients and formulations, packaging and food processing components through to agriculture. They are typically used by scientists who have exhausted the capabilities of lab-based techniques and are searching for characterisation tools that are higher resolution, faster, more chemically specific and more sensitive than are achievable in the laboratory. 

Broadly speaking, the materials characterisation facilities at Diamond fall into three main technique classes:

  • diffraction for structural analysis of materials from the atomic to macro scale,
  • spectroscopy for chemical analysis of local atomic structure in materials,
  • imaging with a wide variety of imaging techniques including high resolution and high speed tomography and phase contrast imaging.

A key benefit of synchrotron facilities is the ability to perform in situ and in operando experiments, closely mimicking the conditions experienced by the sample during processing and monitoring changes in real time (for example baking or freezing).

Measuring the mineral content of grains using X-ray spectroscopy

Understanding the local structure of materials with chemical specificity is of importance in answering central questions in many scientific disciplines. A key advantage of the use of synchrotron facilities is the ability to perform element-specific investigations of materials with high sensitivity. The unique capability of X-ray absorption spectroscopy (XAS) is its ability to investigate the local electronic and geometric information around a particular element irrespective of its state or environment. This powerful technique is suitable for studying solids, liquids and even gases and can cover the vast majority of the periodic table.

Case study: Measuring the mineral content of wheat

This element-specific sensitivity has played a key role in a project by Dr Andrew Neal and his colleagues from Rothamsted Research, in collaboration with scientists from Diamond and Aarhus University[1]. Diets with little or no meat, fruit and vegetables can lead to deficiencies in micronutrients, such as iron and zinc, due to low intake or bioavailability of minerals. The problem is affecting an increasing number of people worldwide and is particularly acute in Africa, the eastern Mediterranean and south-east Asia, where it can lead to serious health problems, such as anaemia.

The Health Grain Programme is focused on improving nutritional value of diets by breeding mineral enriched wheat to increase the mineral content of flour. Understanding the mineral type and content in the wheat is essential for subsequent studies of the digestibility of the wheat. In order to facilitate this, the scientists performed measurements using cross sections of individual wheat grains. They used Diamond’s beamline I18, to perform high resolution X-ray fluorescence (XRF) mapping and X-ray absorption spectroscopy (XAS) experiments. The combined techniques allowed the team to generate high resolution chemical maps of the wheat grain cross-sections (using XRF) and then select regions of interest within the maps, focusing on areas of high metal distribution to perform XAS measurements to obtain information about the local structure, oxidation state and complexation of the elements. The elements investigated were iron (Fe), zinc (Zn), manganese (Mn), copper (Cu) and nickel (Ni) (Figure 1).

Mineral contents of grains has important applications for other reasons. A team of scientists, led by Dr Manoj Menon at the University of Sheffield, has used Diamond to investigate rice plants to further the understanding of dietary sources of arsenic contamination[2]. Rice is one of the most widely-consumed cereals in the world – but if it is grown in regions where soil and water are naturally rich in arsenic, the poison can enter into the food chain with significant adverse effects on human and animal health when rice is eaten in large enough quantities. It is estimated that arsenic contamination in food and water affects nearly 140 million people across 70 countries with South Asia most acutely affected as rice is consumed as a staple food. Rice husk and straw are used for animal feed which could provide an alternative dietary pathway for arsenic consumption through contaminated meat and dairy products.

Different types of rice vary in the uptake and accumulation of arsenic, although this is not well understood and less still is known about where the arsenic accumulates within the rice plant which may have a significant effect on the bioavailability of the arsenic.

The project focused on mapping arsenic in different parts of rice grains using X-ray fluorescence. The high intensity X-rays can be tuned and focused to a very small spot to enable arsenic to be detected at very low concentration in particular regions of the grain. Elemental mapping with this level of specificity for arsenic at low concentration with high resolution is only possible using a synchrotron facility. The next steps in the project seek to focus on rice cultivars that accumulate less arsenic and to inform the development of cultivation practices that reduce arsenic accumulation in rice.

Structural studies on food materials

A wide variety of techniques are available, mainly based around diffraction, that can provide information about the structure of materials on the atomic and nanometre length scales. This level of detail can be extremely important in understanding variations in product or process performance. These experiments can be used to investigate the behaviour of food additives in product formulations by:

  • examining phase behaviour in emulsions, suspensions and gels to assess performance of new ingredients,
  • investigating the behaviour of emulsifiers and complex structures for reducing fat content in products,
  • examining the crystalline and solution structure of food proteins.

Case study: Investigating the purity of lactose crystals

One example is a recent study of the crystallisation of lactose by Dr Elena Simone and colleagues at the University of Leeds[3]. Lactose, the main carbohydrate constituent of milk, is extracted from whey, a by-product of cheese and yoghurt production, mainly for environmental reasons, but it holds significant value in its own right. Purified lactose exists in two main crystalline forms (called anomers), α-lactose and β-lactose, and is commonly used as a food supplement or a pharmaceutical excipient. Both anomers are present during the nucleation and growth of a specific crystal structure which can affect the purity of the precipitated crystals and in particular the α-lactose monohydrate is formed very slowly. It is therefore difficult and time consuming for the dairy industry to achieve a high yield of recovery and to obtain crystals of sufficient size, shape and purity. The team made use of two different, highly controlled crystallisation techniques and focused on determining the effect of crystallisation process parameters on the characteristic properties of lactose crystals including morphology, size distribution, level of agglomeration, crystal structure, purity and overall recovery yield. The study provided a greater understanding of the process parameters that are most effective in obtaining a high purity product in a significant yield.

X-ray imaging of food products

X-ray imaging is a non-destructive technique that has a very large range of applications in fields as broad as bio-medicine, materials science, engineering, environmental science and food technology. X-ray imaging techniques allow high speed visualisation of a sample or retrieval of three dimensional (3D) information to view and measure the internal structure of a sample (tomography).

Figure 2 X-ray imaging studies on some example snack food products showing porosity and microstructure in high resolution. ©Diamond Light Source

Advantages of synchrotron X-ray imaging include:

  • much faster measurement times compared with laboratory based instruments,
  • small beam sizes and special optics to produce images with a resolution of less than 1μm,
  • enhanced contrast available by tuning the X-rays themselves.

The techniques can be used to monitor structural changes with thermal, mechanical and ageing treatments and investigate microstructural changes with varying processing conditions to optimise product behaviour (Figure 2). It is particularly helpful for detecting cracks, voids and bubbles and so can be used for a wide range of food products, such as foams, porous solids and complex structures e.g. confectionery or meat.

Case study: Investigating the 3D structure of ice-cream using X-ray imaging

X-ray imaging at Diamond has been used extensively by Unilever to explore the microstructure of ice cream[4]. The quality of ice cream is considered to depend on the size of constituent air cells and ice crystals - the smaller and rounder the better. Product quality and shelf life can be strongly affected by the temperature variations that can commonly occur during storage and distribution, including by the end consumer, where a significant number of the overall freeze-thaw ‘abuse’ cycles take place. Ice cream is a complex multi-phase soft solid material that consists of ice, air, fat and sugar, containing three states of matter: gas, liquid and solid. An understanding of how the freeze-thaw cycle can influence ice formation is important in controlling ice cream microstructure. The crystal size is small, the material is opaque and the structure is easily disturbed by the modification required by most analytical methods, all creating challenges for detailed microstructural analysis.

A team from The University of Manchester and Unilever performed X-ray tomography of ice cream microstructure over temperature cycles from -20°C to -7°C using instrument Diamond’s I13-2. This instrument provides high flux X-rays tuned to provide both high temporal and spatial resolution to allow 4D in-line phase contrast imaging to be performed. These non-invasive experiments allowed Unilever scientists to investigate the 3D microstructure while largely maintaining the natural product environment and provided a greater understanding of the mechanism of ice formation. The results aided the determination of the influence of processing conditions during manufacture and informed the development of formulations.   

Using the Diamond synchrotron facility

There are two main routes to working with Diamond through our proprietary and peer-reviewed access modes.

Up to 10% of the available experimental time at Diamond is set aside for proprietary access, the most popular choice for our industrial clients. The Industrial Liaison team acts as the main point of contact for our industrial partners and can offer a range of services including a mail-in data collection and full experimental design, data collection and analysis service. Some of our partners prefer to perform their own experiments and simply obtain access to the instruments with some technical support. Some prefer to send their samples for a full analysis service while others participate in the experiments to varying degrees. Our flexible approach means that we can prepare a tailored package depending on the project needs and we charge only for the time and services used. We are able to offer support with as much or as little of the project as necessary. Government funding streams may also prove helpful; previous industrial partners have attracted Innovate UK funding for their projects with Diamond and we are currently partners in the Bridging for Innovators (B4I) scheme, which provides funding for UK based companies to access Diamond and other facilities to overcome product, process or manufacturing challenges.

Dr Claire Pizzey Deputy Head of Industrial Liaison, Diamond Light Source

Claire works closely with the Industrial Liaison team and industrial partners providing a multi-disciplinary approach to solving real-world problems. To find out more about Agri- Food research & development activities at Diamond please get in touch.

Web diamond.ac.uk/industry

Email industry@diamond.ac.uk

Telephone 01235 778797

Twitter @DiamondILO also on LinkedIn

References

1. Neal et al, “Iron and zinc complexation in wild-type and ferritin–expressing wheat grain: implications for mineral transport into developing grain”, J. Biol. Inorg. Chem. (2013) 18, 557-570.

2.  https://stfc.ukri.org/news/uk-scientists-on-a-mission-to-prevent-arsenic-poisoning-from-rice/

3. Simone et al, “Optimal Design of Crystallization Processes for the Recovery of a Slow-Nucleating Sugar with a Complex Chemical Equilibrium in Aqueous Solution: The Case of Lactose”, Org. Process Res. Dev. (2019) 23, 2, 220-233.

4. Guo et al, “Revealing the microstructural stability of a three-phase soft solid (ice cream) by 4D synchrotron X-ray tomography”, J. Food. Eng. (2018) 237, 204-214.

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