Researchers at the John Innes Centre, UK, have discovered that the ubiquitous enzyme (PHS1) is crucial for forming B-type granules in wheat. 

“This is a scientific breakthrough because decades of research on this enzyme have failed to find a clear role for PHS1 in plants and it shows that the A- and B-type granules of wheat form via different biochemical mechanisms. We can now use this knowledge to create variations in starch for different food and industrial applications,” Dr. Nitin Uttam Kamble, first author of the study, tells us.

“By combining traditional breeding methods with cutting-edge molecular techniques, we are exploring the biological mechanisms governing variation in granule shape,” he adds.

Dr. David Seung, senior author of the study, details: “We anticipate that the starch could find additional use in achieving desirable gelatinization and textural properties. Numerous studies suggest that starch granule size affects these properties and having very few B-type granules is a very significant change in the overall size distribution of wheat starch.”

The approach is expected to provide “a deeper understanding of starch synthesis” while also allowing researchers to “engineer” modifications in starch tailored to specific requirements.

Small granules, big impact
Wheat starch granules observed under the Scanning Electron Microscope. (Image credit: Brendan Fahy and Nitin Uttam Kamble).The researchers flag the importance of starch in the food and beverage industry.

“Starch serves as a pivotal source of calories in our diets and is critical to food applications such as brewing and baking. It also has diverse industrial applications (paper, glue, textiles, and construction materials),” says Dr. Kamble.

The study, published in the journal nclick="updateothersitehits('Articlepage','External','OtherSitelink','Starch science: Researchers discover crucial enzyme for better baking, brewing and milling','Starch science: Researchers discover crucial enzyme for better baking, brewing and milling','336280','https://pubmed.ncbi.nlm.nih.gov/37595145/#:~:text=The%20plastidial%20%CE%B1%2Dglucan%20phosphorylase%20(PHS1)%20can%20elongate%20and,endosperm.', 'article','Starch science: Researchers discover crucial enzyme for better baking, brewing and milling');return no_reload();">Plant Cell, states that wheat starch has two distinct types of granules: large A-type granules and smaller B-type granules.

Dr. Seung tells us: “We have created a panel of diverse, novel wheat starches. Not only can we reduce B-type granule content, we can also increase it, as well as change the size and shape of the starch granules.”

The ratio of A- and B-type granules can affect the quality of wheat-based foods, such as bread and pasta, the study informs.

Furthermore, the two granules pose a problem for the starch manufacturing industry because many smaller B-type granules are lost and wasted during the milling process.

A large number of B-type starch granules in barley can also cause a “hazy or cloudy appearance in beer” because they do not get digested and filtered out during the brewing process.

Over the years, the food industry has gone to the expense of salvaging methods to solve the problem of mixtures of large A-type and small B-type granules, including using multiple filtrations to catch granules lost during processing, the study notes.

From ideation to implementation
The ratio of A- and B-type granules can affect the quality of wheat-based foods, such as bread and pasta.The lead authors take us through the road leading to the discovery.

“To develop our technique to reduce B-type granules in wheat, we first needed to develop fundamental knowledge of how they are synthesized,” notes Dr. Kamble. 

“We first started working on PHS1 because we discovered that it interacts with BGC1, which is another important protein involved in forming B-type starch granules,” he explains.

By leveraging techniques such as in silico TILLING (Targeting Induced Local Lesions IN Genomes), the team obtained varieties wher PHS1 is not functional and discovered that PHS1 is required for making the B-type granules. 

“This technique uses chemical mutagenesis, like in traditional breeding, but is combined with advanced sequencing technologies to quickly identify lines carrying variation in our genes of interest, like PHS1.” 

The “breeding platform” used in the study uses molecular methodologies to discover genes and proteins involved in starch synthesis. 

Interestingly, the scientists point out that bread wheat was not the original focus of the study. “The exploration was initially confined to a tetraploid pasta wheat variety, Kronos, as the genetics are simpler than in bread wheat,” remarks Dr. Kamble.

“We are now using a similar TILLING-based method, as well as genome editing, to translate the trait into bread wheat varieties and barley,” he adds.

“The journey from inception to having lines with low B-type granules in wheat spanned approximately three to five years,” he underscores.

The baking industry is currently on the radar of scientists worldwide and FoodIngredientsFirst recently reported a study in Germany that identified the key flavor compounds in sourdough bread.

Navigating evenness and nutrition
"The industry does not generally like heterogeneity; it wants something nice and even to process smoothly."The study flags the demand for an even texture in wheat for easy processing.

Starch used in industry is often modified using physical and chemical methods to achieve the specific properties required for each end use, states the study.

Dr. Seung says: “The industry does not generally like heterogeneity; it wants something nice and even to process smoothly and having these different types of starch granules in wheat has always represented a challenge.”

“So, for us to discover the enzyme responsible for making the smaller granule population and to be able to use our breeding platform to reduce the number of B-type granules will hopefully be of great interest to many industry users,” he continues.

According to the study, removing the requirement for these processing steps will reduce costs and improve product performance.

“Like the effects on food texture, there may be some exciting changes in nutritional value,” he says.

“This needs to be tested after our wheat flour is processed into a final product, like bread or pasta. We currently don’t know the impact of granule size on digestibility after the starch is cooked and processed, but our material is ideal for investigating that.”

Sea & Flour’s recent seaweed-infused bread is an example of how food scientists are enhancing the nutritional value of bread worldwide.

Looking ahead
Future lines of inquiry will be how the size of granules affects starch digestibility, cooking quality, nutritional value and the impact of dietary starches on human health.The team of researchers hopes to open a market for starch tailored to specific requirements.

“Since we now have the means to reduce B-type granules, we can work together with the food industry to test the applicability of this starch to enhance food quality, as well as explore how it can streamline processing and manufacturing,” Dr. Kamble states.

“We now invite businesses to work with us to investigate the potential benefits of these starches, such as in milling, pasta and breadmaking.” 

Future lines of inquiry will be how the size of granules affects starch digestibility, cooking quality, nutritional value and the impact of dietary starches on human health, the study notes.