ARS | Publication request: DETECTING CORN SYRUP IN BARLEY MALT EXTRACTS

Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 1, 2001
Publication Date: June 30, 2001
Citation: PETERSON, D.M., BUDDE, A.D., HENSON, C.A., JONES, B.L. DETECTING CORN SYRUP IN BARLEY MALT EXTRACTS. CEREAL CHEMISTRY. 2001. 78(3):349-353.

Interpretive Summary: Extracts of malted barley are produced as food ingredients, as a source of flavor, enzymes, sweetener, and color. Because pure malt extract, which is relatively expensive, can be adulterated with corn syrup, which is relatively cheap, methods to detect the presence of corn syrup in malt extract are needed to ensure quality standards of the product. This research evaluated three methods of detecting corn syrup in malt extract. In the first method, specific carbon isotope ratio analysis (SCIRA), the ratio of two carbon isotopes, 13C/12C, is determined by mass spectrometry. This ratio is higher in organic material derived from plants that use the C4 photosynthesis pathway (corn) than in that from C3 plants (barley). Mixtures of corn syrup and malt extract had higher 13C/12C ratios than pure malt extract. A second method was to measure the protein concentration. Mixtures had lower protein concentrations than pure malt extract, because the corn syrup has no protein. The third method was to measure concentrations of various sugars. Malt extract contains sucrose, not present in corn syrup, and a higher concentration of maltose. The concentrations of these sugars in mixtures are lower than in pure malt extract. It was concluded that all of these methods will detect adulteration of malt extract with corn syrup, with SCIRA having the greatest discrimination power, and sugar analysis the least. The impact of this research is to provide a method that food manufacturers can use to determine the purity of their malt extract ingredient.

Technical Abstract: Methods for detecting corn syrup in barley (Hordeum vulgare L.) malt extract were evaluated. Twelve samples representative of commercially available 2-rowed and 6-rowed malting barleys were malted. Extracts prepared from the finely ground malts were analyzed for their 13C/12C ratios, expressed as delta-13C, and their concentrations of protein and sugars. The 13C/12C ratios were sufficiently different to differentiate corn syrup from malt extract. By calculating the mean values for the barleys, it was determined that a delta-13C > 24.3 parts per thousand indicated that the malt extract had been adulterated with corn syrup (99 percent confidence). Protein concentrations < 4.5 percent (2-rowed malt) or < 5.0 percent (6-rowed malt) of the extracts also indicated probable adulteration with corn syrup, which is devoid of protein. Because of differences in sugar concentrations between the malt extracts and corn syrup, carbohydrate analysis also indicated probable mixtures. These findings were confirmed by analysis of extracts from composite 2-rowed and 6-rowed barley malts that had been mixed with known quantities of corn syrup. The regressions for delta-13C, protein concentration, and most sugar concentrations against percent dilution with corn syrup in the mixtures were significant.