In vitro availability of starch in heat‐treated potatoes as related to genotype, weight and storage time

Abstract

The objective of the study was to determine the influence of potato variety, weight and storage time after lifting on the glycaemic index (GI) and resistant starch (RS) content predicted from measurement of the rate and extent of in vitro starch hydrolysis, respectively. The potatoes were either boiled, or boiled and subjected to different heat-cycling conditions selected to promote retrogradation of amylose or amylopectin, respectively. The hydrolysis indices (HI) and predicted GIs of all 19 potato products were high and fell within narrow ranges of 122-144 and 118-138, respectively. No correlation between average weight of the potato tuber and HI was found. Furthermore, there was no difference in HI between potatoes stored for 1-3 or 8-10 months, nor between varieties of new potato and winter potato. However, the HI was significantly lowered by temperature cycling at conditions known to promote retrogradation of amylopectin (6 • C, 48 h) compared with 6 • C for 24 h followed by 70 • C for 24 h. RS content was already substantial in boiled potatoes, 4.5 g 100 g −1 (starch basis), and could be increased further by temperature cycling, the highest yield obtained, 9.8 g 100 g −1 (starch basis), following heat treatment at 6 • C for 24 h followed by 70 • C for 24 h; that is at conditions known to favour amylose retrogradation.

Glycaemic and satiating properties of potato products

“…Data on french fries are based on manufacturer's data, whereas the remaining values are from food tables (Livsmedelsverket, 2001). The starch content in the potatoes was calculated by use of a formula stated by Leeman et al (2005), where a strong correlation between dry matter content and available starch content was found in boiled potatoes. In Table 1, there are also data on serving weight, meal volume, energy density and dry matter content.…”

“…Remaining values from food tables (Livsmedelsverket, 2001). The starch content in the boiled potatoes was calculated by use of a formula stated by Leeman et al (2005). (Livsmedelsverket, 2001).…”

Influence of different processing methods on the glycemic index of potato (Nicola)

“…Leeman et al (2005), using analytical methods developed by Å kerberg et al (1998) also found a significant increase of resistant starch in potatoes after extended time periods of temperature cycling at conditions known to favor amylose retrogradation.…”

“…In vitro tests have also shown lower digestibility for cooled potato products (Garcia-Alonso and Gon˜i, 2000;Kingman and Englyst, 1994) and for temperature-cycled potatoes (Leeman et al, 2005). These all suggest to formation of type-3 resistant starch, when potatoes are stored at refrigerator temperatures after boiling or baking.…”

Effect of native crystalline structure of isolated potato starch on gelatinization behavior and consequently on glycemic response

“…to linear for pure starch. There should be noted that retrogradation (reassociation of amylose/amylopectin chains that occurs during storage of gelatinized starch by means of hydrogen bonds) can lower the digestibility of starch due that its structure turns less accessible to digestive enzymes, so glycemic response of retrograded starch is more moderated than of gelatinized starch (Rosin, Lajolo, & Menezes, 2002;Karlsson & Eliasson, 2003;Fernandes et al, 2005;Leeman, Bårström, & Björck, 2005;Morita et al, 2005;Burton and Lightowler, 2008). Due to this, the linearity between DG and glycemic response is probably lost or the curve slope could be modified if retrograded starch is present (Chung, Lim, & Lim, 2006).…”