There is a lot of interest in the marketplace regarding the beta-glucan content of medicinal mushrooms. And for good reason, as several studies suggest that many of the health benefits associated with mushrooms may be related to beta-glucans.

So, it’s understandable that customers want medicinal mushrooms with the highest possible beta-glucan content. And what the customers want is what most of medicinal mushroom suppliers are willing to provide. A beta-glucan value that is as high as possible.

Unfortunately, often these very high values are not correct. One of the reasons is that it’s really difficult to accurately measure the beta-glucan content in mushrooms.

There are several reasons why this is the case. Let’s dig deeper.

The complexity of beta-glucans makes them difficult to measure accurately

Beta-glucans can be structured in many ways, so it’s hard to find a one-size-fits-all measurement method. Not only do different beta-glucans affect the human body in different ways, but they also affect the test results.

Beta-glucans are composed of glucose units linked by beta-glycosidic linkages. This basic structure is always the same, but there can be differences in the types and weights of the linkages.

Some linkages may be like a straight chain, while others may be highly branched, like a tree. Their molecular weight can also vary. And while some beta-glucans may have ?-1,3 and ?-1,4 linkages, others may contain ?-1,3 to ?-1,6 linkages.

These differences make it difficult to establish a test method that accurately measures the beta-glucan content of a mushroom. Some test methods may be designed to measure beta-glucans with a ?-1,3 linkage, while other test methods may be more appropriate for other types of linkages.

Therefore, you’d first need to find out exactly what type of beta-glucans a particular mushroom contains and use a test method designed for them. Most likely, you’d have to use more than one test method, as one mushroom is likely to contain several different types of beta-glucans. This need for multiple testing would be really time-consuming and most likely not really. cost-effective

All these structural differences also lead to different biological activities between different beta-glucans. This in turn has an impact on how (strongly) beta-glucans react with immune receptors in the human body.

Therefore, it can’t be said that the beta-glucan content alone is all that matters when it comes to the efficacy of a medicinal mushroom product.

The differences between medicinal mushroom species and processing methods cause further measurement challenges

Different species of mushrooms contain different types and amounts of beta-glucans. This can make it difficult to apply a single measurement method to all medicinal mushrooms that accurately measures the beta-glucan content in each species.

In addition, where a mushroom is grown also influences its ingredients. Two mushrooms of the same species grown in very different climates can have different beta-glucan contents.

The processing method also affects the beta-glucan composition. Drying, grinding, and extraction can all affect the beta-glucan content of a mushroom, potentially altering its structure, solubility, and bioactivity.

Whether the fruiting body is used alone or together with the mycelium or growing materials also affects the beta-glucan concentration. In addition, the maturity of the mushroom also affects its beta-glucan content.

There is no standard testing method for measuring beta-glucans in mushrooms

Not only the beta-glucans and the mushrooms themselves pose challenges, but so do the currently popular beta-glucan testing methods.

There is no universal standard for measuring beta-glucans, so each supplier basically uses whatever testing method they like. Different test methods result in different beta-glucan levels, sometimes even between samples from the same supplier.

Therefore, it’s impossible to properly compare beta-glucan content between suppliers if they use different testing methods.

There is no beta-glucan testing method made especially for mushrooms

The biggest issue with beta-glucan measurement is that there are currently no 100 % accurate testing methods for mushroom beta-glucans.

Most common beta-glucan testing methods have initially been designed for testing beta-glucans in grains, such oats. These grain beta-glucans are however type 1-4, whereas the beta-glucans in mushrooms are type 1-3 or 1-6. Therefore, the tests won’t work for mushrooms.

There are tests to measure polysaccharides, but they aren’t very good either. In addition to mushroom polysaccharides, these tests can also pick up polysaccharides found in other starchy foods such as grains and rice. If these are used in the mushroom substrate and it ends up in the final product, it may be difficult to distinguish the amount of mushroom-based polysaccharides from those from grains or rice.

However, there is still hope. There is currently at least one fairly accurate test on the market for measuring beta-glucans in mushrooms. You just have to find the right one. So let’s take a closer look at some of the more popular testing methods.

Gravimetric methods

One of the most popular methods for measuring beta-glucans are the gravimetric methods, such as the phenolic sulfite assay. However, these methods are not very good at separating the different types of polysaccharides, so they aren’t very good for testing beta-glucans alone.

The resulting value may only be the total amount of polysaccharides in a functional mushroom, i.e. a combination of alpha- and beta-glucans.

Especially if the supplier uses the growing material in their products, there is a good chance that the product contains a lot of non-mushroom specific polysaccharides that they may just label all as beta-glucan. So, next time you see a beta-glucan value between 40 and 50%, you might just be looking the number of all polysaccharides combined.

Enzymatic methods

Enzymatic assays are somewhat more accurate and have been used, for example, to test beta-glucans in cereal products. However, they may have difficulty distinguishing between different beta-glucan structures and linkages. Cereal beta-glucans have very few branches compared to the highly branched fungal beta-D-glucans, so they are structurally very different.

The final results may also be influenced by other fungal components.

For example, a study by McCleary and Draga (2016) evaluating different beta-glucan assay methods found that an enzymatic method tended to underestimate the value of beta-glucan, particularly when measuring 1,3-beta-glucans.

In addition, the choice of enzyme and reaction conditions can affect the results.

Spectrophotometric assays

According to studies, spectrophotometric assays are one of most reliable methods of measuring beta-glucans. It is also relatively fast and cost-effective to be performed in a lab setting.

However, in using this method, everything else mentioned previously also applies: The mushroom species need to be from the same cultivation area and the test need to be performed with care.

For example, it is recommended that the sample is filtrated before the test, to avoid small particles in the sample that might result in overestimation of the beta-glucan content.

A beta-glucan testing kit from a company called Megazyme is regarded as one of the most accurate kits on the market. That’s why we also use it analyze the beta-glucan content of e.g. our special MycoSignature extracts.

End take-aways

There are several reasons why you should take beta-glucan levels, especially very high levels, with a grain of salt.

The complexity of beta-glucans and medicinal mushrooms and different measurement methods make it difficult to get an accurate beta-glucan value.

One supplier may claim a higher beta-glucan content than another, even though the actual bioactive content is the same.

Therefore, we’d like to see suppliers in the marketplace not just slapping a random high number on their packaging before more standardized and accurate testing methods are available and widely used.

Furthermore, we believe that there is more to medicinal mushrooms than just the (often assumed) beta-glucan content. This is not the only thing that makes medicinal mushrooms beneficial to human health.

Reducing the potential of medicinal mushrooms to their beta-glucan content alone overstates the value of a single active ingredient. Yes, it is an important component, but there are other important factors to consider. We’ll go over them in another article behind the previous link, so be sure to check it out.

Sources

• Barry V McCleary, Anna Draga, Measurement of ?-Glucan in Mushrooms and Mycelial Products, Journal of AOAC INTERNATIONAL, Volume 99, Issue 2, 1 March 2016, Pages 364–373, https://doi.org/10.5740/jaoacint.15-0289
• Rômulo César Clemente Toledo, Maiara Andrade Carvalho, Luiz Carlos Oliveira Lima, Eduardo Valério de Barros Vilas-Boas and Eustáquio Souza Dias, “Measurement of ?-glucan and other nutritional characteristics in distinct strains of Agaricus subrufescens mushrooms”, Vol. 12(43), pp. 6203-6209, 23 October, 2013, ISSN 1684-5315