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Importance of Barley Plumpness and Protein for Malt Quality

Protein content and kernel plumpness affect the speed at which barley goes through the malting process.

The reports on yield and quality of the 2008 barley crop that are coming into the North Dakota State University Institute of Barley and Malt Sciences (IBMS) are good.

However, lower than optimal grain plumpness and higher than desired protein levels have been reported in areas of Idaho, Montana and North Dakota. Deoxynivalenol (DON), mold and preharvest sprouting have been observed in some later crops in North Dakota.

Low plumpness and high protein mostly are attributable to high temperatures and moisture stress during grain filling.

These factors are of concern to maltsters and brewers for a number of reasons, according to Paul Schwarz, IBMS director.

“The main concern with these factors is that they predict potentially lower extract in the finished malt,” Schwarz says. “Extract determines the amount of malt that must be used by the brewer to produce a given volume of beer, so it is an economic concern. Typically, 79 percent to 81 percent of the grain is extractable in laboratory tests.”

Most of the extract and all fermentable sugars are derived from starch. Starch synthesis occurs during grain fill, but when environmental stresses reduce this process, less starch and proportionally more protein are formed in the kernel. The grain then tends to be thinner and has a higher proportion of husk to endosperm.

“Aside from the extract, there are a number of other problems associated with the malting and brewing of high-protein barley,” Schwarz says. “High protein can lead to haze problems in the beer and it is more difficult for maltsters to control the color of the malt during processing. Beer color is derived from the malt. Most popular American beers are very light in color. Higher protein barley tends to yield dark malts.”

Protein content and kernel plumpness affect the speed at which barley goes through the malting process. In malting, the grain first is soaked in water (“steeping”) to approximately 45 percent moisture. It then is allowed to germinate for four to five days until the proper modification or changes in the grain structure and composition are achieved. The germinated barley then is dried, (“kilning”) to approximately 5 percent moisture. The entire process takes six to eight days, depending upon the sample.

Thin grain will absorb water and modify at a faster rate than plump grain. In samples with a wide distribution in kernel plumpness, maltsters first may grade the barley into a number of size fractions and malt them separately. Grading is required more frequently with six-rowed barley than with two-rowed, but can be used to achieve better uniformity in the final malt. Protein also affects the rate of water uptake and speed of modification. For this reason, maltsters will segregate shipments by protein content and malt them separately.

One other issue that tends to arise when discussing protein in malting barley is whether to blend high- and low-protein barley lots to meet protein specifications. The result of this would be a nonuniform rate of modification during malting. This leads to serious problems for brewers.

Essentially, some of the grain in such a sample may be modified properly, while another portion is over or undermodified. Dealing with nonuniform malt actually is a larger problem than dealing with a uniform high-protein sample.

The result concerning protein in malting barley is that maltsters and brewers generally are reluctant to use six-rowed barley with more than 13.5 percent protein and two-rowed with more than 13 percent.

“However, these limits vary between specific companies and depend upon their brewing processes and the products produced,” Schwarz says. “Some protein is needed in brewing for things such as for good beer foam and proper yeast growth during fermentation. Therefore, there also are minimal limits on protein, but low protein is rarely a problem, especially under dryland barley production.”

NDSU Agriculture Communication

Source:Karen Hertsgaard, (701) 793-1146, karen.hertsgaard@ndsu.edu
Source:Paul Schwarz, (701) 231-7732, paul.schwarz@ndsu.edu
Editor:Rich Mattern, (701) 231-6136, richard.mattern@ndsu.edu
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