Plant-based dairy alternatives have made huge strides in taste, nutrition and texture. But many new products still suffer from low rebuy rates. This can often be traced to high astringency causing mouthfeel issues that reduce the sensory pleasure of consuming these products.
Els de Hoog, senior project manager flavour & texture at NIZO, talks to René Floris about why astringency is an issue for plant-based products and how manufacturers can reduce it.
René Floris: What is astringency?
Els de Hoog: Astringency is that drying or puckering feeling that you may be familiar with from black tea or high-tannin red wine. While astringency is appreciated in those foods, it is not welcome in dairy alternatives like yoghurts or cream cheeses where consumers expect a creamier mouthfeel.
RF: Why is it a specific challenge for plant-based dairy alternatives?
EH: We experience astringency when we eat or drink something that disrupts the layer of lubrication that we have in our mouths. That disruption can be caused by small aggregates or by certain chemicals including particular proteins and polyphenols. Plant protein ingredients are typically high in both astringency-causing proteins and polyphenols, which lead to unpleasant mouthfeel issues. Astringency is a particular focus for dairy substitutes partly because it is a stark contrast to the desired creamy consistency and partly because reducing astringency while retaining nutritional parity is challenging. Astringency could become an issue for meat substitutes too, but currently manufacturers in this area are more focused on characteristics such as texture and juiciness.
RF: Why is astringency such a difficult challenge to address?
EH: It is actually possible to combat astringency simply by adding more lubrication into the product. But that means adding more fat and sugar, which is not a good solution nutritionally and could affect the taste of the product. Tackling astringency while delivering a product that is similar to the (dairy) original in taste and nutrition is a much more complex task. And that’s because, as NIZO’s research over the last few years has shown, astringency itself is a very complex issue.
Firstly, the sensory experience of astringency isn’t straightforward. You typically sense some astringency as soon as you consume a product. Depending on the product, the astringency can intensify over the course of a couple of minutes before fading. But in some cases, you can still be experiencing astringency an hour or more after consuming the product. What’s more, astringency is a complex attribute that requires precise definition and alignment in interpretation. This makes it difficult for consumer panels to explain – and therefore for manufacturers to assess – the level of astringency in a new product accurately. As a result, consumer tasters need training to ensure consistency of language when talking about astringency.
Secondly, different astringency-causing elements in food react with the oral lubrication layer via different mechanisms. The product’s food matrix can also influence these interactions. So, even if you know certain astringency-causing elements are present in a product and in what concentrations, there is no straightforward way to predict how that will translate into a perceived intensity of astringency. And you need to know which astringency-causing elements are most dominant in the perceived astringency if you want to formulate a product with better mouthfeel.
RF: So, how do you reduce astringency in a plant-based product?
EH: Over the last few years, we have seen that the best results on reducing astringency and improving mouthfeel come from an iterative approach based on four steps. Step 1 is to assess astringency through taste tests with a trained expert sensory panel. Step 2 is to measure the astringency using a tribometer (it is worth noting that even this isn’t straightforward as commercial tribometers need to be modified to mimic the softness of the mouth and the chemical composition of the lubrication layer). Step 3 is to detect the presence and role of the various astringency-causing elements in the formulation through lab analysis. Then, armed with this information, you can choose the most appropriate strategy or combination of strategies to reduce astringency.
At this point, the product goes back to the measure and detect steps to verify the reduction in astringency and determine if there are opportunities for further improvements. A product may need to go through multiple measure-detect-reduce cycles before it goes back to the expert sensory panel to assess if it is ready to go to market.
RF: What kind of strategies can be employed to reduce astringency?
EH: There are many ways to reduce astringency in a plant-based dairy substitute. Which one – or, more likely, which combination – is the best option will depend very much on the specifics of the individual case. That’s what makes the assess, measure and detect steps so important.
We have already talked about adding fats and sugars to mask the astringency. While this obviously brings nutritional issues, it can be a good option when the astringency is relatively low or for budget price-point products. If the astringency can be traced to high levels of polyphenols or other “co-passengers” in the protein ingredient, then additional processing steps could be used. Techniques such as rinsing and filtration could remove the unwanted polyphenols, while fermentation can offer a way to mask astringency without lowering the nutritional value of the product. In other situations, the product may need to be reformulated. For example, if the chosen plant protein itself plays a dominant role in astringency or the protein ingredient has high levels of polyphenols that can’t easily be removed, it may be necessary to change the plant protein ingredient to a different plant source or an ingredient that uses a different extraction technique.
One innovative new technique that could be promising for astringency is biopurification. This is a form of fermentation where the fermenting microorganism is specifically chosen for its ability to degrade a particular, unwanted molecule rather than to create typical fermentation products. Biopurification has already been used successfully to reduce off flavours in plant-based products. Recently, researchers at NIZO have begun using biopurification to target astringency-causing molecules, and the early results are very encouraging.
RF: Could biopurification be the golden bullet for perfect taste and mouthfeel?
EH: There is no one-size-fits-all solution for astringency. The variety of possible interactions in the mouth, the number of different potential causes and the complexity of perceiving astringency means you need to consider every new project individually. But through the iterative assess-measure-detect-reduce approach, it is possible to plot a knowledge-based route to the optimal astringency-reduction solution to suit both your product and your marketing proposal. And that should lead to the perfect mouthfeel and taste combination that will keep consumers coming back for more.
