Posted on March, 7, 2023 at 08:56 am
Should the days of farmers targeting 13% grain protein for milling wheat quality be over?
After all, typically at least 50% of the greenhouse-gas footprint of growing wheat is associated with nitrogen fertiliser, with higher total emissions for milling wheat than feed.
They also count as Scope 3 emissions within any baked good using milling wheat flour, meaning it is also a problem for millers and bakers.
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The result is meeting net-zero targets without some combination of a reduction in grain protein, use of alternative sources of nitrogen, or much improved nitrogen-use efficiency, which is likely to be a challenge for the milling and baking industries.
Add the pressure from the direct environmental impact of N use, and higher fertiliser prices, albeit ones that have been supported by milling wheat premiums allowing the continued justification of the use of rates by growers to target 13% protein, and some would argue it should be a recipe for change.
But how easy will the milling and baking industry find it to change, while continuing to mass produce the bread the consumer likes and buys?
It is not straightforward, according to Joe Brennan, technical manager for the millers’ trade association, UK Flour Millers.
A trend away from Group 1 varieties started before the fertiliser price hike, partly due to the high input nature of milling wheat production, with last year acting as a further catalyst for growers to rethink how they are using nitrogen, he says.
“But unfortunately, it is not easy for millers to just use grain below 13% protein.”
Protein is the key driver of flour functionality, he explains, with two in wheat – gliadin and glutenin – forming gluten when in contact with water. “Gluten is what gives the end product its structure and shape.”
Both protein quality and quantity are important to millers and bakers, as either too little or weak gluten leads to a dense, coarse, crumbly, poor-quality loaf.
Bread made with lower protein content will also likely have a reduced shelf life, while the interaction between salt and protein means salt reduction targets in bread requires stronger protein.
But wheat quality at intake is measured in protein percent and is effectively a surrogate test for functional quality, Mr Brennan says.
That is partly due to time. Grain-protein levels can be quickly analysed at intake, while doing functional quality tests require the grain to be milled, make a dough, tested, and then baked – a much longer process that is not practically feasible.
Nevertheless, millers often show a degree of flexibility by offering fallbacks on contracts in the event protein targets are missed, and some contracts will even specify a lower level of protein where the miller has a specific use that doesn’t require the standard range.
Consistency of supply is crucial to millers, stresses George Marriage, director of miller’s W&H Marriage & Sons, based in Essex, with the 13% level proving a much more consistent proxy for quality than a lower level.
“Millers are trying to supply a product that is reasonably good for the whole market, and it’s clear that 13% protein is pretty much universal for what’s needed.
“You only need to look at the current £60/t premium for 13% protein over feed wheat to see what the market wants.”
He adds that if there was an ability for millers to use much lower protein wheat, you would see them doing that, especially this year when proteins have been generally low.
Milling industry customers are wedded to using protein level as a proxy for quality, Mr Brennan points out.
“That’s quite difficult to manage. We’ve seen this year some flours even at lower protein provide the functionality to give the quality the baker wants, but they still want the higher protein percentage.
“I think there’s an educational piece for the milling industry to talk to its customers and explain to them about stopping thinking in terms of pure protein and think more in terms of functionality.”
But until there’s a quick test for functionality, it’s unlikely there will be much change to how quality is measured from farm to mill.
There is also seemingly not much impetus to reshape the breadmaking process within the industry currently.
“I suspect there needs to be more market or regulatory pressure to get the ball rolling,” suggests Mr Brennan.
“Perhaps a consistently lower protein wheat crop might provide the impetus on the raw ingredient side. But what equally could happen without any other changes is we’d increase the proportion of high-protein imports.
“I don’t think anyone wants that – it doesn’t benefit farmers or millers as they have to pay more for their wheat, and it won’t benefit the environment as Canadian or German growers are still applying nitrogen, and then there’s the carbon cost of transport.”
That probably leaves wheat breeders, rightly or wrongly, as being seen as the main source of solutions.
There are two potential angles researchers and breeders are looking at: finding traits that improve nitrogen-use efficiency to help use lower amounts of nitrogen to reach 13% protein, and finding ways to improve the functional quality of the protein produced, which might allow lower grain protein to be used.
An example of how researchers are looking to improve nitrogen-use efficiency is through a trait known as grain-protein deviation.
Typically, there is a negative trade-off between yield and protein – increasing one, usually decreases the other.
Grain-protein deviation is a way to break that trade-off, by getting more protein into the grain for the amount of N added, explains Rothamsted Research’s Peter Shewry.
“Some varieties consistently have higher protein than you would expect from their yield at the same fertiliser level, so we know it’s a genetic trait.”
Through quantitative trait locus (QTL) mapping, researchers are trying to identify molecular markers for genes that could be used in breeding, which lead to a change in grain-protein deviation, he explains.
It is a slow process despite all the genetic resources that have been generated by John Innes Centre and through the Niab Diverse Magic project.
Ultimately, the current aim is to have varieties where nitrogen could be optimised for yield while not needing extra nitrogen to make breadmaking quality.
Nitrogen-use efficiency could also potentially be improved by understanding what controls senescence, Prof Shewry says.
“The reason that crops staying green gives higher yields is you delay senescence, but it also delays protein transport into the grain, so you end up with lower protein.
“So what you want is a late senescence, but a complete breakdown in the leaves to get as much protein transported as possible.”
When it comes to grain-protein quality, a higher proportion of glutenin, which determines dough strength, is key, says Nick Fradgley, who has recently completed a PhD on the genetic control of milling and baking quality, while at Niab.
Elasticity or dough strength has traditionally been a weakness of older wheat breadmaking varieties, so over time breeders have aimed to breed varieties with a higher proportion of glutenin to make the gluten stronger so bakers can get away with less protein overall, he explains.
That has resulted in protein levels dropping from 14-15%, sometimes achieved in much lower yielding heritage wheats to the 13% target currently used.
“But the aim now is to increase the strength of glutenin even more, which might allow protein to drop a bit further,” Dr Fradgley suggests.
German quality wheats show there is potential for greater elasticity or strength at lower protein contents, Prof Shewry notes.
“I think there is enough variation to make it a viable target, if you can develop a way of economically breeding for it,” he concludes.
Source: Farmers Weekly