The state of analysis
July 01, 1996
by Teresa Acklin
Technology helps flour millers get fast and accurate laboratory results.
Ask a flour miller what he wants from his laboratory tests, and he invariably will respond "fast and accurate results." Given today's competitive pressures and customer demands for guaranteed flour quality, millers can ill afford to spend hours analyzing product to assure it meets specifications — or to absorb the considerable costs associated with quick but faulty measurements.
Luckily for millers, technology in the past decade or so has taken into account the miller's needs in this area. New methods and equipment now can measure, both swiftly and reliably, individual parameters throughout the milling process.
"Until recently, a lot of these tests had been quite slow," one miller said. "But 'fast' is very important anymore. With mills getting bigger and producing more (tonnes) per shift, you can't afford to let any runs get out of spec (specification)."
Near-infrared systems have become widely used as quick and accurate methods to assess protein, moisture and ash content in flour. Compared with previous systems, N.I.R. readings are received "instantaneously." The development of N.I.R. equipment marked a large step forward in the speed with which wheat and flour analysis could be completed accurately. But the technology does have one drawback, according to some millers; N.I.R. equipment must be calibrated precisely to provide the desired accuracy.
This characteristic requires frequent checks and adjustments to be sure the equipment is properly calibrated. In addition, testing different flour streams is complicated by the fact that each N.I.R. unit must be calibrated for the particular stream.
The Kjeldahl process, the long-time standard method of measuring protein content, typically has been used to calibrate N.I.R. equipment. But the Kjeldahl, while highly reliable, is time consuming and involves the use of dangerous chemicals, including concentrated sulfuric acid.
Several years ago, technology involving combustion was developed for protein analysis. This technology uses oxygen to generate combustion, which removes nitrogen from flour or grain for protein measurement.
According to Pat McCluskey, senior scientist/wheat quality at Kansas State University, Manhattan, Kansas, U.S., the combustion analyzer "is the greatest thing since sliced bread." Its primary benefits include speed and precision without the need to calibrate and without hazardous chemicals, he said.
Like other equipment that becomes known in the milling industry by its manufacturer's name, some combustion nitrogen analyzers are called "the LECO" because they were manufactured by the LECO Corp., St. Joseph, Michigan, U.S., and because LECO analyzers now are used for official U.S. protein certification.
Mr. McCluskey said the LECO installed at the K.S.U. mill laboratory analyzed samples of up to 4 grams and returned results in 31/2 to 4 minutes. Little or no sample preparation is required, he said, and samples from any stream can be tested without special set-up or alterations to equipment.
The K.S.U. combustion analyzer has an autoloader, so millers can insert up to 49 samples and "go do other things" while the analysis is under way, he said. Analysis of a full load of samples takes a little more than 3 hours, he said.
"It's extremely precise, with results repeatable to the third decimal place, and there's a 0.998 correlation to Kjeldahl results," Mr. McCluskey said. "But there's no glass, no chemicals to mix, no fumes. Basically, you just put the flour in, and the results come out."
The benefits of this technology led the U.S. Grain Inspection, Packers and Stockyards Administration (formerly called the Federal Grain Inspection Service) to abandon the Kjeldahl process in favor of the combustion analyzer as the official method of measuring protein in wheat and soybeans for U.S. certification, according to Steve Tanner, director of GIPSA's technical services division.
"Safety is one reason, maybe a prime reason, because the Kjeldahl is extremely hazardous," Mr. Tanner said.
Mr. Tanner said another reason for the switch was the efficiency gained from automation.
"We can just load it up and come back in a few hours for the results," he said, although he noted the need for trained personnel to troubleshoot because the equipment was "a little bit sensitive."
The growth in the biotechnology sector also has led to simpler and speedier laboratory analysis for flour millers. Using biological proteins, such as enzymes or antibodies, diagnostic kits now are available to test wheat and flour for an array of contents or characteristics.
Mr. McCluskey of K.S.U. cited an enzyme-based test he used that determines starch damage relatively rapidly. Other kits available allow for measurement of total starch and various specific carbohydrates and proteins in flour.
Testing for mycotoxins also has become important to grain buyers and millers. After aflatoxin was identified in 1993 as a carcinogen, attention and concern have focused more closely on all mycotoxins, heightening the need for simple, fast tests.
While some tests only measure for mycotoxin presence, more sophisticated kits provide quantitative measures. This feature is particularly critical, especially as grain moves toward processing, because grain products can be subject to maximum tolerance levels.