Influence of Cultivar, Processing, and Food Form on the Glycemic Index of Barley

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Replacement of refined high glycemic index (GI) carbohydrates by whole grain products such as barley may prevent the progression of cardio‐metabolic disorders due to their favourable effects on glycemia. However, processing, cultivar variation, physiochemical properties and food form may alter their impact on glycemia. To examine these factors on the GI of barley, 3 experiments were performed in separate groups of 10 healthy subjects. GI was determined using standard methodology and in vitro starch digestibility was measured. Cultivars varied in starch and β‐glucan content. In Experiments 1 and 2 cultivars were processed into four fractions ranging from hull removal only to hull, bran, germ, and crease removal. Experiment 3, a wet pasta‐like product was made from 100% barley flour with wet semolina pasta as a control. In experiments 1 and 2 the GI range was (22.8 – 40.9); processing increased the GI significantly (p>0.05). Cultivars differed in their nutrient composition (p = 0.024), but without significant interaction between pearling and cultivars (p>0.05). Regardless of the cultivar, the least processed kernels had significantly lower total starch and higher total low molecular sugars, insoluble and total fiber. Resistant starch (RS) was inversely correlated with the GI (r = −0.58; p< 0.05). The barley pasta had medium‐high GI values similar to semolina pasta. Results suggest that processing affects the GI and the physiochemical properties. These results will improve knowledge in the development of low‐GI functional foods and improve future consumer guidelines. Financial support from the Ontario Ministry of Agriculture.