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High-Selenium Pinto Beans as a Value-Added Product
April 06, 2006

Investigators:
Phillip Reeves, Ph.D., Principal Investigator (PI)

John Finley, Ph.D., Collaborating Investigator (PI)

                           

Previous work performed with Northarvest Beans:

 

An interim report, submitted in February, 2005, detailed the objectives of, and work conducted under, a grant given by Northarvest Beans to the Grand Forks Human Nutrition Research Center.  The objectives of the grant were to conduct research to:

Objective 1.  Determine the selenium (Se) content of field-grown Pinto beans from the vicinity of Jamestown, North Dakota.

Objective 2.  Quantify the contributors to variation of the Se content in pinto beans.

 

Beans collected from around the state of North Dakota were analyzed for Se and the results are summarized below:

Briefly, beans were collected from 78 different fields and 37 different producers from five different geographical regions across North Dakota.  The selenium content was as follows:

Locations of pinto bean samples collected in North Dakota in 2004.
 

 

 















The mean selenium concentration of all samples was 486 nanograms selenium/g (or 0.49 micrograms per gram) (Table 1), but there was wide variation (136 to 983 nanograms per gram; standard deviation of 253ng/g).  Samples were analyzed as five distinct geographic clusters; selenium concentrations in 4 of the 5 clusters were similar while the Gilby area was lower than the rest (however, there were only 4 samples from this area).  Wide variation was noted in all areas except Gilby.

 

General trends in selenium concentration throughout the 2004 study area.

 













Additional work conducted in 2005:

Additional grant funds were given to the Grand Forks Human Nutrition Research Center, USDA/ARS, by Northarvest Beans for the purpose of extending the scope of the project.  Results of field agricultural projects are highly dependent on the specific environmental conditions (primarily climate) that predominate while the plants are growing.  Consequently, at least two seasons are needed to obtain accurate data, and therefore the primary purpose of the second grant was to extend the study for a second growing season. Additionally, funds were used to extend analyses to minerals other than Se.

 

Results obtained in 2005:

Results obtained in 2005 were by the same graduate student that conducted the project in 2004 (Kristofer Parson).  The project was supervised by Dr. John Finley until his resignation from the USDA/ARS in October, 2005; subsequent to that date the project was directed by Dr. Phil Reeves.  Mr. Parson was a graduate student in the Department of Geography, Univ. North Dakota.  The Department of Geography supervised the geographical modeling aspect of the project.

 

The primary problem encountered in 2004 was the lack of participation by bean growers in North Dakota.  In an attempt to counter this problem, a letter from Northarvest Beans detailing the intent of the study and requesting their participation was included in mailings to bean producers.  Approximately 250 producers were sent packets containing letters explaining the study, tools for collecting bean samples and instructions for doing so.  The producers were asked to return the bean samples in return addressed, stamped envelope included in the packet.  Despite the letter of request from Northarvest Beans, participation was less this year than in 2004 as only 19 producers sent samples from 37 locations (as compared to  37 producers and 78 locations in 2004).  Analyses are ongoing but current results are summarized below:

 

Selenium content of pinto beans grown in North Dakota in 2005 (units in parts per million)

Mean

0.465

Median

0.417

Standard Deviation

0.307

Range

1.880

Minimum

0.92

Maximum

1.972

 

Results from 2005 compare quite favorably with results from 2004 (units in parts per million)

Mean

0.486

Median

0.440

Standard Deviation

0.255

Range

1.090

Minimum

0.119

Maximum

1.209

 













The results of both years are similar in that they demonstrate that pinto beans grown in North Dakota contain modest amounts of Se, and that some beans accumulate very large amounts of Se.  The practical significance of this to the American diet can be calculated by assuming that a standard serving of beans (approximately 130g) contains approximately 33 g of dry beans.  Thus, average
North Dakota pinto beans would contribute 0.450 X 33 = 15 micrograms of Se to the diet, whereas beans highest in Se would contribute 1.5 X 33 = 50 micrograms of Se to the diet.  The dietary requirement for Se is 55 micrograms per day; thus pinto beans could contribute from 30 - almost 100% of this Se requirement.  This information could be used to help market beans grown in North Dakota.

 

Efforts directed toward mapping the Se content of pinto beans grown in North Dakota:

A major objective of the current study was to develop a geographical based map of the Se content of pinto beans.  This effort is on-going.  Preliminary results are summarized in the attached document.

 

Benefits to North Dakota/Minnesota bean growers.  A recent conference hosted by the Grand Forks Human Nutrition Research Center highlighted the potential benefits to human health of enhancing the food supply with the essential trace element selenium (Se).  Selenium is needed in moderate amounts (55 micrograms per day) for nutritionally essential functions such as producing enzymes that guard against oxygen stress in cells.  However, a clinical study conducted in humans found that consumption of an additional 200 micrograms of selenium per day reduces the incidence of cancer, especially prostate and colo-rectal cancer.  A large study (approximately 32,000 subjects) is currently being conducted in an attempt to confirm the previous finding of selenium-mediated reduction of cancer.

The implications of these studies for agriculture are substantial; a demand is developing for selenium-enriched foods, and this demand will certainly increase if the present prostate cancer trial yields positive results.  Plant foods accumulate selenium partially in direct relationship to the selenium concentration of the soil, so soils enriched in selenium may produce selenium-enriched crops. 
North Dakota has areas with very high concentrations of selenium in the soil, and many of these areas are in regions where pinto beans are produced.  Consequently pinto beans from North Dakota are a potentially valuable source of supplemental selenium; this attribute could be used to produce a value-added product and/or help to market pinto beans from North Dakota.

 


 

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Northarvest Bean Growers Association | 50072 East Lake Seven Road | Frazee, MN 56544
Ph: 218-334-6351 | Fax: 218-334-6360 | Email: nhbean@loretel.net