| Abstract
| - The aim of the study was to determine and compare reactive and total lysine contents in a range ofbreakfast cereal products. Crude fiber, fat, ash, and crude protein contents of 20 breakfast cerealproducts ranged from 4 to 38, 14 to 144, 7 to 32, and 52 to 253 g/kg, respectively. The concentrationsof glutamic acid (18.7−32.1 g/100 g protein) and proline (4.7−10.8 g/100 g protein) were high whilethose of the amino acids methionine (1.2−2.0 g/100 g protein) and histidine (1.2−3.3 g/100 g protein)were relatively low. There was a strong relationship between reactive lysine determined using theguanidination and fluorodinitrobenzene methods (R = 0.99). The total lysine content, determinedafter conventional acid hydrolysis, ranged from 0.8 to 3.7 g/100 g protein, while the reactive lysinecontent (guanidination) ranged from 0.4 to 2.8 g/100 g protein. Reactive lysine was 20−54% lowerthan total lysine in the cereal products. The large differences between total and reactive lysine suggesta considerable loss of lysine in the breakfast cereals tested. Keywords: Lysine; reactive lysine; food; cereals; processing
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