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NMRs & Mid-Oleic Oil Measurement

Tuesday, September 1, 1998
filed under: Utilization/Trade: NuSun

The term NuSun™ - referring to the mid-range oleic (monounsaturated) sunflower oil found in a number of newly developed hybrids - did not exist two years ago. Even as recently as last year, many producers and industry personnel were unaware of this important development within U.S. sunflower - a development in which the majority of the nation's oil sunflower acreage is expected to eventually shift from traditional high-linoleic hybrids over to mid-oleic varieties.

Approximately 100,000 acres of NuSun hybrids were planted in 1998, with that figure expected to climb toward 500,000 next year. Virtually every major sunflower seed company already is - or soon will be - marketing mid-oleic hybrids.

The reason behind the shift is the U.S. sunflower industry's determination to capture a significantly larger share of the domestic vegetable oil market. That goal is particularly focused on the snack food processing and commercial deep-frying sectors - uses for which NuSun oil (which is typically in the range of 55- to 65-percent oleic) is more suitable than the standard high-linoleic oil (with its oleic content of around 16 to 18 percent).

While the expansion of NuSun is expected to result in a larger and more-stable oil sunflower industry, there are - as with any new venture - some bumps along the way. One "bump" receiving increased attention in recent months is the accurate calculation of the oil content of NuSun seeds delivered by the farmer to elevators or processing plants.

The crux of this issue lies within the electronic belly of the Nuclear Magnetic Resonance (NMR) machine, which is the instrument used by grain inspection laboratories to measure a seed sample's oil content. NMRs are calibrated on the basis of sealed seed samples - supplied by USDA's GIPSA* (formerly FGIS) - representative of oil sunflower produced in this country. Since most oil-type sunflower up to this point has been relatively high in linoleic acid and low in oleic, so too are the calibration samples.

The NMR works by "reading" the number of hydrogen atoms in an oil, explains Roger Friedrich, program specialist with GIPSA's Technical Services Division in Kansas City. When the instrument is calibrated, it is, in effect, being told how to convert the amount of hydrogen it senses into an actual oil content. It is this NMR-generated oil figure upon which the farmer is paid a premium if over 40 percent or discounted if under 40.

A critical complication arises, however, when a lab uses an NMR calibrated on high-linoleic seeds to calculate the oil content of mid-oleic seeds. Explaining the problem requires a quick chemistry lesson.

Linoleic oil's chemical structure contains 32 hydrogen atoms, while that of oleic oil contains two additional ones, for a total of 34. "An instrument calibrated for seed containing predominantly linoleic-type oil incorrectly translates the surplus hydrogen it sees in oleic oil as extra linoleic oil, resulting in an error," Friedrich points out. He says that a high-linoleic NMR calibration sample used when testing seeds containing 65-percent oleic fatty acid (a common percentage for NuSun hybrids) "will probably over-predict the oil content by about four percent." So if NMR shows a mid-oleic sample to have 41.7 percent oil, it's actually 40.0 (41.7 x 0.96 = 40.0).

That error favors the farmer delivering mid-oleic sunflower to his local elevator, since he'll be paid on a higher oil content than what those seeds actually contain.

An elevator or processor paying on that basis will naturally have a different perspective, since they're paying for oil that does not exist and hence cannot be extracted from the seed.

GIPSA's response to this oil content accuracy issue has both short-term and long-term facets.

For the long term, the USDA agency will be developing mid-oleic calibration samples for use with certified laboratories' NMR units. Currently, NMR instruments are calibrated with standard samples composed of conventional linoleic seed sealed in glass tubes. When mid-oelic seeds become more predominant in the market, GIPSA will replace the linoleic-based calibration samples with mid-oleic standards for use with the labs' NMR units.

In the shorter term, GIPSA has prepared new calibration samples with known fatty acid composition, thereby establishing a fixed "starting point" upon which to base a correction factor for mid-oleics. GIPSA will develop a correction factor based upon the fatty acid profile of at least 100 mid-oleic seed samples gathered from various sunflower regions this fall and forwarded to GIPSA for analysis. (Since 1997 NuSun acreage was relatively small, GIPSA did not have enough samples from that crop to develop a credible correction factor.)

Once GIPSA has analyzed the '98 crop samples, it will determine and release its correction factor, thus allowing testing labs to take the NMR reading and then subtract the appropriate percentage to come up with the actual oil content of the mid-oleic seeds. This will not, Friedrich emphasizes, constitute a discount. Rather, it is simply a more-accurate method of determining the oil content of mid-oleics.

Since GIPSA will not be able to receive and analyze the 1998 crop samples until later this fall, it also must have an even more immediate process in place for those mid-oleic crops being hauled to market during this year's harvest season.

For that interim period, based on the relatively few samples he looked at last year and what he expects the mean values to be this year, Friedrich has come up with an "interim correction factor" of five (5) percent, i.e., the "true" mid-oleic oil content will be considered to be 95 percent of the NMR reading. Elevators and processors will be able to use this interim figure "so they can pay the farmer - up front - most of what the oil is worth," he says. "Then, when they get the official correction factor [later this fall], they'll look back for any over-corrections and send the farmer another check for the balance."

Friedrich adds that the five-percent interim correction - which was just announced at the end of August - was deliberately set on the conservative side "so that if anything, the company ends up paying the farmer more money" rather than the other way around.

(GIPSA likewise is working to refine the custom calibration factors already being used to calculate the true oil percentage of high-oleic sunflower oil. As with the mid-oleics, NMR readings on high-oleic seed samples also need to be corrected.)

Lori Grieger, service point manager and inspector for North Dakota Grain Inspection Service, says growers and local elevators need to remember two very important points in this transitional period:

(1) The NMR mid-oleic correction factor is not a discount; it is simply a way to rectify an erroneous reading by the instrument and come up with an accurate oil content measurement.

(2) During the initial years when many growers and elevators are handling both mid-oleic seed and conventional high-linoleic seed, it is critical to segregate loads and clearly label every seed sample being sent in for analysis. - Don Lilleboe

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