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Falling numbers gum up wheat quality

Wheat kernels that look
perfectly fine can ambush end users with bread that won’t slice, pancake mix
that is gummy, or cookies that just don’t taste right.

“End users like grain that
comes out like BBs, the same shape and size every time,” says Art Bettge, a
USDA-ARS food technologist. Unfortunately for end users, wheat is a living
organism and exact uniformity isn’t possible. But wheat breeders and growers
can work together to reduce problems for end users.


Look out for falling numbers

Bakeries need consistency.
If the pancake mix package label says to add 1½ cups of water, then consumers
want the same light, fluffy pancakes every time they add that amount to the
mix. Flour milled from wheat that has either sprouted or has late-maturity
amylase (LMA) can be slimy and runny instead, says Katherine O’Brien,
University of Idaho (U of I) cereal chemist.

End users measure problems with
wheat end products by a falling number rating. Falling number is the number of
seconds it takes a weighted plunger to pass through a wheat paste. A falling
number of 300 means the plunger takes 300 seconds to go through the paste.
Ratings below 300 cause trouble for end users.

Sprouted wheat due to
excessive moisture leads to low falling numbers. Farmers can easily spot wet
wheat following rainfall or a late irrigation. About once every 10 or 12 years,
though, conditions are right in the Pacific Northwest for wheat kernels to
essentially sprout internally with no visual signs.

LMA degrades starch and
turns it to glucose that fuels sprouting. If you think of starch as a rope, LMA
turns a neatly coiled rope into an unusable bunch of short pieces, Bettge says.

Genetics control LMA. “The
plant doesn’t think it’s time to make cookies or cake or noodles; it thinks
it’s time to sprout,” Bettge explains.

Problems with falling
numbers in the Midwest usually occur when rain falls at harvest, says Jeff
Edwards, Oklahoma State University small grains Extension specialist. The 2007
crop had low falling numbers but not the 2008 crop.

Unlike preharvest sprouting
where the test weight falls, LMA doesn’t alert flour mills and bakeries of
potential problems. LMA leaves test weight unaffected. The effects of LMA are
seen throughout the entire kernel immediately. Preharvest sprouting starts at
the germ end of the kernel and spreads upward.
 

0428QualitySide.jpg

Grain inspectors can’t
detect LMA wheat. Neither can end users who bought U.S. No. 2, 11% protein
wheat wanting a certain quality. The first hint of trouble is often a low
falling number, which shows amylase is affecting starch composition. Starch is
needed to set baked goods.

“End users are not getting
what they think they paid for and that makes them mad,” Edwards says.
 


Extreme weather triggers LMA

“Last year it didn’t matter
which market class it was or the area grown, there were issues resulting in low
falling numbers, and it seems to be environmentally related,” says Juliet Windes,
U of I Extension agronomist. “We had extremely cold temperatures at grain
fill.”

Quality suffers whenever
temperatures – hot or cold – are extreme during grain fill, she says.

One night of freezing
temperatures at soft dough or prolonged cooler conditions can trigger LMA.  Thus, low falling numbers tend to be a
greater problem in cooler growing seasons, such as 2008, or when growers
stretch a variety’s growing zone.

For example, Blanca Grande
is a hard white spring wheat developed in California. Blanca Grande performs
well during hot summers in southern Idaho but not as well in cooler years,
Windes says. But even WestBred 936, a popular hard red spring variety in Idaho,
had falling number problems in the 2008 crop.

Varieties that have European
or Australian parent lines tend to have LMA. Blanca Grande, Klasik, and Express
fit into that category.
 

O’Brien and Windes are
looking for a correlation between where a variety is grown and low falling
numbers, along with other quality parameters.

Low falling numbers have
caught the industry’s attention, but Bettge cautions against blaming weather
solely for the problem. If LMA genes aren’t present, low falling numbers won’t
be a problem, even under the right environment, Bettge says. Conversely, if the
genes are present but it doesn’t freeze at soft dough, growers also won’t have
a problem.

A low falling number doesn’t
always mean nixing the variety. Waxy and partial waxy ones such as waxy
Penewawa, Alturas, or Cataldo have consistently low falling numbers but make
great Japanese noodles.

Removing amylase from a
wheat kernel may sound like the simplest solution to the problem, but breeders
can’t remove it all. Without amylase, they’d never get the next crop out of the
ground. Some amylase is needed to trigger the seed to germinate and to start
growing.

Learn more


www.wheatflourbook.org/Main.aspx?p=67


www.northern-crops.com/technical/fallingnumber.htm

By Cindy Snyder

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