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Proposed Study – Analysis of degermed corn meal and corn flour

July 30, 2012

Background

Retail degermed cornmeal was sampled nationwide and analyzed in 2002 and 2005 by Nutrient Data lab (NDL). Acid hydrolysis methods, AOAC 933.05 and 954.02 respectively were used to determine fat content. The total fat contents of the samples ranged from 1.51-2.5 g/100g.

Lab analyses sponsored by the members of the North American Millers’ Association, using six different methods have yielded a range of 0.6 – 2.5 g/100g for total fat for equivalent samples.  The results were higher when the acid hydrolysis method was used.

Farm Service Agency (FSA), USDA routinely conducts spot analysis of degermed cornmeal bought as part of its Commodity Programs. According to Patrick Dardis of FSA, the method currently used is the AOCS (American Oil Chemists Society) Am 5-04 (rapid Determination of oil/fat utilizing high temperature solvent extraction) method (Patrick Dardis, personal communication, June 25, 2012) that is equivalent to AOAC 920.39.

Proposed study

Rationale: Concerns have been raised by members of the North American Millers’ Association that the fat content of degermed cornmeal is high in the USDA National Nutrient Database for Standard Reference (SR) (USDA, 2011). This may be related to the analytical methods used for SR. Acid hydrolysis methods are the methods of choice for fat analysis for SR. Fat analysis by ether extraction can under estimate total fat content (Palmquist and Jenkins, 2003).  In addition of the fat analysis, fatty acid content will be determined.

Additionally there are no recent data available in SR for degermed corn flour, and no data available for cornmeal and corn flour used for commercial purposes. According to members of the North American Millers’ Association, 90% of the cornmeal produced in US is used for commercial purposes. Corn flour is a common ingredient in commercial formulated foods.

Approach: This study will be conducted jointly by Nutrient Data lab and the North American Millers’ Association. Table 1 lists the proposed analyses. North American Millers’ Association will provide sales information for the white/yellow and enriched/unenriched forms for both retail and commercial use and samples for analyses. NDL will provide the technical expertise and monies for the analyses. All analyses will be conducted using methods similar to those used for the National Food and Nutrient Analyses Program (NFNAP), which are documented and published (Pehrsson et al, 2000). The samples will be processed at the Food Analysis Laboratory (FALCC) at Virginia Tech (Blacksburg, VA) and then sent to labs approved by NDL. The samples will be analysed using validated analytical methods and quality control procedures.

Analysis of samples
Table 1 is a summary of the proposed sampling and analysis plans.  It is anticipated that the cost of the analyses for 4 composites per type of material would be approximately $13,000.  This cost would be covered by NDL through the NFNAP study.

Table 1: Proposed analyses

Food* Sample Composites Fat/FA Analysis** Other analyses
Degermed corn meal – retail 3-4 mills (major suppliers); 3-4 different lots from each supplier One composite per mill made up of 3-4 lots for a total of 3-4 composites for analysis Fat content by ether extraction and acid hydrolysis methods; fatty acid analysis Proximates
B-vitamins
Minerals, tocopherols
(Carotenoids if yellow)
Archived samples from 2005 NFNAP collection N/A Fat content by ether extraction and acid hydrolysis methods; fatty acid analysis N/A
Degermed corn meal – commercial 3-4 mills (major suppliers); 3-4 different lots from each supplier One composite per mill made up of 3-4 lots for a total of 3-4 composites for analysis Fat content by ether extraction and acid hydrolysis methods; fatty acid analysis Proximates
B-vitamins
Minerals, tocopherols
(Carotenoids if yellow)
Degermed corn flour – retail 3-4 mills (major suppliers); 3-4 different lots from each supplier One composite per mill made up of 3-4 lots for a total of 3-4 composites for analysis Fat content by ether extraction and acid hydrolysis methods; fatty acid analysis Proximates
B-vitamins
Minerals, tocopherols
(Carotenoids if yellow)
Degermed corn flour – commercial 3-4 mills (major suppliers); 3-4 different lots from each supplier One composite per mill made up of 3-4 lots for a total of 3-4 composites for analysis Fat content by ether extraction and acid hydrolysis methods; fatty acid analysis Proximates
B-vitamins
Minerals, tocopherols
(Carotenoids if yellow)

* Cornmeal and Corn flour are available in both white/yellow and enriched/unenriched forms. Samples will be selected based on sales information.

**Ether extraction (920.39 Fat (Crude) or Ether Extract in Animal Feed), acid hydrolysis (922.06 (32.1.14) Fat in Flour, Acid Hydrolysis Method), and fatty acid analysis (996.06 (41.1.28A) Fat (Total, Saturated and Monounsaturated) in foods)

Anticipated Results:

This study will provide a comparison of the different analytical procedures for fat for degermed cornmeal, conducted under standardized conditions. In addition, this study will generate current nutrient data for corn flour and new data for corn meal and corn flour ingredients used for commercial use.  These data will be useful in NDL’s formulation program, used for generating nutrient values from ingredient information.

Citations:

Palmquist, D.L. and Jenkins, T.C. Challenges with fats and fatty acid methods. Journal of Animal Science (2003). 81: 3250-3254.

Pehrsson, PR, Haytowitz, DB, Holden, JM, Perry, CR, and Beckler, DG. USDA’s National Food and Nutrient Analysis Program: Food sampling. J Food Comp Anal, 2000; 13(4):379–389.

U.S. Department of Agriculture, Agricultural Research Service. Nutrient Data Laboratory Home Page, http://www.ars.usda.gov/ba/bhnrc/ndl. Accessed July 16, 2012.

AOAC Official Method. Official Methods of Analysis of AOAC International (16) Gaithersburg, MD: AOAC International.

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