Two Scientists in conversation on Microstructure Analysis

Abstract

Kar-Mun To and Harriet Spatharakis of Premier Analytical Services (PAS) discuss what it is like in their world of food microstructural analysis and why the analysis of a food material's microstructure is crucial to understanding the contribution of both raw ingredients and processing regimes on the physical and sensory attributes of foods.

Meet one of the scientists involved in this conversation: Kar-Mun, who has over 30 years’ experience as a food scientist working across both academic and commercial settings. She has worked with Premier Analytical Services for the last 20 years and currently heads up the Rheology section. As a specialist in ingredient interactions and functionality, she provides technical support to customise textural qualities for product development and troubleshooting services to optimise transport processes and unit operations in manufacture. Kar-Mun is also a Fellow of the Institute of Food Science and Technology.

Kar-Mun starts the conversation by stating: ‘When I hear the word rheology I always think of an old BT advert in the late 80's where a grandmother Beattie Bellman (played by Maureen Lipman) was trying to console her grandson Anthony that he had flunked all his exams except for pottery and sociology. On hearing the news over the phone, she quickly replied to him by saying ‘you got an ology, you’re a scientist!’ In science, the suffix -ology simply refers to the study of something. In the case of rheology, the study of how materials flow. According to the Oxford Reference, rheology—first coined by Eugene C. Bingham in 1928—is the study of the deformation and flow of materials, including their elasticity, viscosity, and plasticity. It has huge industrial significance with applications in a whole host of substances with complex microstructures from non-foods such as suspensions (paints) and polymers (oil recovery) to foods ranging from liquids (drinks) to solids (baked goods).’

Kar-Mun explains that rheology principles are applied in everyday life without us even realising it. Examples lay in the simple actions like softening butter to spread on toast, shaking the ketchup before to squeezing the last bit out of the bottle, squashing the bread in the supermarket to see how fresh it is or pouring the gravy over our roast dinner. Rheologists, Kar-Mun points out, simply apply scientific methods to measure these behaviours in a reliable and objective way. Reflecting on her experience, Kar-Mun admits that she initially found the theory of rheology to be quite dry during university. However, it became much more engaging when she started applying the theory to real food systems. During her postgraduate work, she focused on the hydration of food polysaccharides using a rheometer which was the go-to of equipment to assess their viscosity — the internal friction of a fluid and its resistance to flow.

A rheometer is a laboratory device used to measure how a viscous fluid, such as a liquid, suspension, or slurry, flows in response to applied forces. (Figure 1). At the time, rheometers were relatively new, demand was high and there was a booking system in place and keen students would have to work into the night if they were slow to reserve an early slot during the day! Kar-Mun notes that rheometers have come a long way since her student days. Nowadays, there are many types to suit all budgets. She also emphasises the importance of technical support from manufacturers, which she found invaluable when learning how to use these specialised devices to analyse food properties. In addition to the rheometer, she mentions the texture analyser as another essential piece of equipment. (Figure 2). Texture analysers are used to assess a wide range of both solid food and non-food products for many properties, such as hardness, brittleness, spreadability, adhesiveness, tensile strength, extensibility, just to name a few. As with the rheometer, there are many manufacturers capable of supplying such equipment and companies that have stood the test of time are those that have continually updated and refined their equipment and the great technical support they provide to the end-user. It is needless to say Kar-Mun has an abundance of knowledge and experience in these areas.

Harriet, another expert, comes from a different background. She has over 14 years of experience as a microscopist at Premier Analytical Services. She is a foreign body expert, with strong problem-solving skills and is a specialist in investigative microscopy for the food production industry. She helps customers understand the effects of ingredients and processing on product structure and their relationship with product texture and appearance attributes, aiding product development and helping to troubleshoot issues.

Following the conversation, Harriet adds: ‘Food science was not something I had really heard of and after studying forensic and analytical science, I thought my days would be comprised of inputting chemicals into machines and looking at numbers and graphs. Sometimes those things still cross my path, but now I get to investigate the world of food microstructure. I fell into this novel world by accident, using the industrial placement student programme that was offered by Premier Analytical Services and I have never looked back. Starting with the world of foreign body analysis, which is a fascinating subject on its own, I started specialising in investigative microscopy. Investigative microscopy fascinated me from the get-go. The ability to visualise and unravel the mystery of a food product's microstructure is bewitching and who knew it can tell you so much about why a food product behaves the way it does.’

Harriet explains that while she knew food was analysed for its nutritional value—something most people are familiar with from reading food labels, especially after indulging over a weekend or holiday—she didn’t realise just how carefully the majority of foods are designed and developed to meet consumer demands and follow new trends. Understanding the microstructure of a food product and its ingredients can turn the ambitions of research and development teams into reality. This knowledge allows teams to explore diverse ideas, implement improvements, and address problems that may be costing companies valuable time and money.

The microstructure of a material, such as a food product, is fundamentally the ‘building blocks’ of a material on a very small scale. The microstructure of a product plays an important role in determining its physical properties, which can include texture and firmness. Therefore, product quality is highly dependent on how the food product's microstructure turns out after undergoing processing. Product quality could be significantly compromised if the microstructure is damaged during processing or affect an ingredient's ability to perform. Therefore, understanding the microstructure of a product/ingredient can be used to predict any changes in food quality that may occur during any processing when developing a food product, or when installing/upgrading new processing equipment, or when introducing a new step in a process. A few examples of the types of things Harriet has expertise in include crystal growth, starch cook and the distributions of ingredients (Figure 3), as well as things like aeration, emulsion stability and the kinetics of dissolution. She goes on to say that each one is important for creating the different properties of the food products consumers love.

Harriet explains that, while optical microscopes have been used to see the wonders of detail since the early 1600s, they remain one of the best techniques for the analysis of food microstructure, along with specific component staining techniques. Alongside these traditional tools, more modern equipment has aided in the analysis of microstructures. In Harriet's case, a scanning electron microscope with its array of attachments is another key piece of equipment she frequently uses when examining a wide range of products and ingredients. These key tools let her understand the complex relationships between structure and function in her clients’ food products and ingredients. Harriet goes on to say: ‘The world of microscopy is not for the faint-hearted and I wish it was as easy as slapping sub-samples on slides/stubs and snapping some pretty pictures, but it must be acknowledged that it needs an expert's eyes and experience to get the bottom of what the product's true microstructure really is. Firstly, it is important to know the strengths and weaknesses of each technique used. While being able to interpret if what you are seeing is really the microstructure of the product or if it is something that has been created, either by the preparation stage(s) or from using the equipment itself, is a real skill. To be able to understand the difference, using a correlative approach, to ensure correct interpretation is a big factor in being able to help customers get to the bottom of issues or help them create the product of their dreams. These days there are a whole host of techniques to choose from and sometimes you need to think outside the box, finding the equipment and corresponding experts in order to support conclusions drawn from microscopical examinations. Those experts can be difficult to find when perhaps other careers might be seen to have more allure, but at PAS by providing expert knowledge and guidance, both in-house and with our host of connections, we have helped many a customer.’ Harriet gives massive credit to her mentor Dr Sue Gedney and the relationships she has formed with various people across a wide range of companies and institutions throughout her career.

Premier Analytical Services is part of Premier Foods, one of the UK's largest food businesses, but also work with other clients in production, supply chain and retail within the Food Industry. As such, Harriet and Kar-Mun work across a range of iconic brands and products with widely different microstructures and textures. They believe that understanding the microstructure and rheological properties of a food material goes hand in hand with understanding the sensory properties of taste, texture, and aroma. The instrumental analysis they provide complements the work done by the highly trained sensory panel located at the research and development centre in Worksop. Instrumental analysis can provide fast, accurate, repeatable data in a way that human assessors cannot. Even though it is human consumers that will ultimately judge the quality of the products, relying on humans for objectively measuring foods has its limits.