Focus on food structure


Soaring demand for plant-based foods is a major opportunity for manufacturers, but creating an appealing texture in meat analogue products remains a challenge.

Here, Mark Auty and Fred Gates from Reading Scientific Services Ltd (RSSL) explain how understanding the physical and microstructural properties of food can play a vital role in the product development process.


More people than ever before are choosing to reduce meat consumption and adopt a flexitarian diet.  Some 27% of UK consumers are reportedly reducing meat intake[1], and the vegan category is now so popular that product launches make up almost a fifth of all retail food NPD[2].  Ethical, environmental and health concerns are among the key drivers for this shift in eating habits.

But while this move into the mainstream signals exciting opportunities for product development, it also adds a new perspective.  Manufacturers need to ensure that meat analogue products closely match the texture of their animal-based equivalents if they are to win approval from the growing flexitarian audience.  With only 41% of UK shoppers viewing vegan food as tasty[3], it appears there is still work to be done to meet expectations.

Meaty texture


Successfully replicating the eating experience of meat with plant-based proteins is widely acknowledged to be far from straightforward.  

This is because animal meat is a complex structure, comprising proteins, biofilaments, fibres, connective tissue, fats and collagen. It develops over time and delivers a unique set of eating characteristics; from the first bite, the initial chew and the formation of a bolus in the mouth, to the adhesiveness and succulence of the mouthfeel. Not only that, meat is often eaten hot and cold; meaning any substitute product needs to perform in a similar way.

Reconstructing this level of complexity in a plant-based product is the goal for manufacturers seeking to attract - and retain - flexitarians. To so effectively not only requires a detailed understanding of the different parameters associated with meat textures, but also the ability to quantify and translate them into meaningful data. Outcomes which can then be used to create a similar eating experience in meat substitute products.

In this context, food microstructure is proving an increasingly valuable part of the overall development process.  

Measuring mode


An extensive number of tests can be carried out to characterise the physical and structural properties of a food as it moves through different points of the eating process. From bulk properties, such as fracture force and stress, to a detailed analysis of individual fibres, these investigations can establish why a product is behaving in a certain way. 

A meat substitute with an unappealing rubbery or stretchy texture, for example, may be found to be made up of a network of connected fibres when examined using microscopy. Such information is particularly useful for plant-based products which need to successfully mimic the naturally-fibrous texture of meat to win consumer acceptance. So much so, that generating similar fibre structures in vegetable proteins is a key focus for many of the latest extrusion techniques.

Fibres in plants are also known to be weaker than those found in meat, so using a microtensile stage in combination with microscopic scanning to test their strength, pull them apart and closely examine how they break, is a useful exercise. A firmly established technique in other food categories - such as to test the snap or crumble of a biscuit - it now has significant potential as part of increasingly sophisticated meat analogue developments.

For example, a product made up of plant protein and starch or cereal, which is too brittle can be analysed to establish how it behaves when you stretch or press it. In this way, it is possible to identify which part is responsible and whether it is occurring in the continuous phase or the dispersed particle phase within the food. This builds an understanding of the mechanics of the product’s microstructure and, depending on what is seen, provides direction on how to address the issue, such as adding fat, rather than water to the formulation.  

Wider issues can also be explored, such as what happens when the product is heated and how different processes affect the overall structure; information which is only evident when looked at on a micro-level.     

Armed with this data, manufacturers are in a much stronger position to create meat analogue products with the desired textural properties - but only, if the results of the structural research are used correctly. Rather than view these measurements in isolation, these insights have most impact if used to bridge the gap between sensory feedback - how different products are described - and the development of the optimal product.

So how does this work in practice?

Firm foundation


The first step is to understand and quantify consumer perceptions in terms of product texture. Many words can be used to describe the texture of meat, so it is important to start by standardising this vocabulary in a way that enables us to measure each aspect - what exactly do we mean by “tough” or “chewy”, for example?  At RSSL, we recommend carrying out a study with an expert sensory panel to explore this complex area and build a solid foundation from which to work. 

This approach may be used to compare the texture of a meat burger with that of a plant-based equivalent; where the mouthfeel at every stage of the eating process is broken down into specific characteristics and each given a score by the panel. By creating a graphic interpretation of the results for each product and overlaying the two, it is then possible to see the similarities and - just as important - what is lacking. 

The appropriate physical sciences techniques can then be used to measure the structural properties and understand which elements are likely to affect the first bite, the chew, how it develops into the bolus and so on.  These analytical findings can then be linked back to the sensory data and so enable formulators to see what changes need to be made. If a meat analogue is described as too “dry”, for example, the corresponding microstructure can explain the root cause of the problem - potentially the result of it holding less water due to evaporation during processing - and prompt action to address the issue.

That’s why it is so important for manufacturers to decide and define what constitutes “good” in terms of a product’s performance. Rather than trying to address numerous aspects, however, the key is to prioritise two or three parameters, while trying to ensure none of the others fall out of place.  Afterall, if the critical textural factors fall below the acceptable threshold, a product is unlikely to succeed. The ideal strategy is focused on understanding how to change process and composition together in order to achieve the optimum balance.

In action

There are many different reasons for manufacturers to bring in food microstructure expertise and one of the most urgent is a drop in product quality. This can spark consumer complaints and demand an explanation as to the root cause, as well as recommendations for what steps need to be taken to remedy the situation. A change to the process, for example, can affect the chemistry of a product - but without this specialist knowledge, manufacturers may not be aware of the consequences. A microstructure scientist will ask the right questions, carry out appropriate testing and establish why the product is not performing as it should.

Reformulation efforts can also have a knock-on effect in terms of product performance, so being able to understand the impact of different ingredients on product behaviour can be hugely beneficial. Growing consumer concern around the environmental impact of soya, as well as its status as an allergen, is driving a move towards alternative sources of vegetable protein. Pea protein is proving particularly suited to meat analogue applications, but emerging ingredients also include chickpea, lentil and fava bean.   

However, it is not simply a case of swapping these ingredients on a like-for-like basis. Pea protein, for example, doesn’t form such a strong gel as soya, gives a softer bite and has a different flavour profile, which means that manufacturers need to understand how these differences will impact on their product. One effective way to do this is by using analytical testing techniques to establish the textural characteristics of the original soya protein as well as potential alternatives. Generating this data will allow the manufacturer to select the closest match, and so facilitate the transition to a new formulation.  

It should be noted, however, that not all pea protein is created equal. There can be significant differences in the texture - ranging from an extremely soft bite to an almost rubbery mouthfeel - as well as water and fat holding capacity.  Such variations are largely related to the way the ingredient has been pre-processed, scaled up and the type of extraction process used. Yet, this is not always a consequence of using different suppliers; such diversity can also be found in ingredient batches from the same source.

To address this issue and provide a level of quality control, ingredient suppliers may consider the use of microstructure analysis to improve ingredients. They may also invest in research to demonstrate the behaviour of their ingredients under different conditions and so help manufacturers quickly assess how changes to the formulation or processing specifications will impact the end product - a compelling platform which could offer significant commercial advantages.  

New concepts


Supporting new product development is also an important area. As consumers continuing to demand greater variety from the plant-based foods category, manufacturers are under pressure to create exciting new concepts which meet high expectations. Working with a food microstructure team as a research partner from the beginning of this process can be hugely beneficial in the long run.

At the R&D stage, analysing the cause and failure of initial concepts made in the kitchen makes it much quicker to identify precisely what didn’t work and why, and then move confidently to the next step. Ideally, this should be a collaborative process between internal and external resources; where information about the impact of different parameters of product texture is shared in order to shape the next experiment and take the process forward.  

While it is relatively easy to make something in a kitchen, however, scaling up can be fraught with problems. Even moving from pilot plant to commercial scale requires a completely different set of equations as things can change unpredictably - and again, this is where microstructure expertise can help by characterising and predicting the behaviour of the food products in specific conditions.


Category growth


Looking further ahead, the meat analogue category is expected to expand beyond its general focus on burgers, sausages and mince. With flexitarians looking for great tasting, everyday meat alternatives, developing lean options such as a piece of “salmon” or “chicken fillet” is widely recognised as the next challenge - and the latest high moisture extrusion techniques are expected to be part of this evolution.  

Analytical techniques, such as microscopy, will be particularly crucial for these types of products, which have very specific texture associations.  Achieving a flaky fish texture, for example, requires a very different microstructure made up of a lot less fat and connective tissue, but still arranged in a hierarchical structure. 

In the meantime, meat analogue producers would do well to consider the full potential of this rigorous scientific discipline. From benchmarking meat product textures, to reverse engineering competitor products or addressing costly legacy formulations, food microstructure has much to offer forward-thinking manufacturers.








Originally published by Food Science & Technology, September 2019.

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