The role of starch physicochemical properties in determining the Glycemic Index of potatoes

Abstract

Potatoes are a nutrient dense food, despite this, they are often thought of as unhealthy due to their purported high glycemic index (GI). Previously, we found a range of GI values for 8 different potato varieties when freshly cooked (range 52±4 to 81±9, p≤0.05) and that cooling cooked potatoes reduced GI by 20–50%. However, it is unclear if this effect can be seen in potatoes harvested in different years. Thus, the purpose of the present study was to examine the effect of variety and cooling on the GI of potatoes harvested in 2009 and 2010 and to assess the role of starch properties in determining GI. The GI of 4 potato varieties was tested in 10 healthy individuals using standard GI methodology. Each variety was consumed hot or cold (~2 days at 4°C). Cooling reduced GI by 11–54%. ANOVA showed an effect of variety and cooling (p≤0.05). Cooling significantly reduced GI in 1 variety 71±7 (hot) vs. 39±4 (cold) (p≤0.05). A positive relationship between the GI of potatoes harvested in 2009 and those harvested in 2010 was observed (R2=0.620, P=0.02). Studies suggest that these differences in GI between varieties and as a result of cooling may be due to a difference in their starch properties. To assess their role in GI, we measured the amounts of rapidly digestible (RDS), slowly digestible (SDS), and resistant starch (RS) in cooked potato. Contrary to some studies, RDS, SDS and RS did not explain the differences in GI we observed in the present study.

Genotype by Environment Interaction Effects on Starch Content and Digestibility in Potato (Solanum tuberosum L.)

“…The GI values are known for only two genotypes in this study and are closely related to individual starch profiles. CV96044-3 was shown to have a consistent medium GI value (62 to 65 ± 6) compared to V1255-3, which ranged from medium to high GI (59 to 74 ± 6). , In this study, CV96044-3 was found to have low RDS levels, which is consistent with the lower GI values observed by Moreira and Wolever. , Low RDS levels are correlated with low to medium GI values . From a previous report, the GI value of Russet Burbank was 77± 9 .…”

“…CV96044-3 was shown to have a consistent medium GI value (62 to 65 ± 6) compared to V1255-3, which ranged from medium to high GI (59 to 74 ± 6). 47,48 In this study, CV96044-3 was found to have low RDS levels, which is consistent with the lower GI values observed by Moreira and Wolever. 47,48 Low RDS levels are correlated with low to medium GI values.…”

“…47,48 In this study, CV96044-3 was found to have low RDS levels, which is consistent with the lower GI values observed by Moreira and Wolever. 47,48 Low RDS levels are correlated with low to medium GI values. 32 From a previous report, the GI value of Russet Burbank was 77± 9.…”

“…49 This is substantially higher than the GI values for CV96044-3 and V1255-3 reported by Moreira and Wolever. 47,48 On the basis of the current study, the high GI value of Russet Burbank can be explained by the starch profile observed in most test environments (Table 2). With the exception of Elora 2010, Russet Burbank had either the highest or one of the highest RDS values (Table 2: average 8.7%), which would contribute to a rapid release of glucose into the bloodstream, resulting in a high GI.…”

“…The low GI values for CV96044-3, coupled with data reported by Henry et al, 50 highlights the value in exploring the GI values of a wider array of advanced genotypes in Agriculture and Agri-Food Canada and other breeding programs. The combination of results from Henry et al 50 and Moreira and Wolever 47,48 strongly suggests that potatoes with a lower GI already exist as commercial cultivars and/or advanced breeding lines. Unfortunately, the Henry et al 50 study did not include an analysis of the starch profiles for tested cultivars.…”