Posted by kathryn in Carbohydrates

One question that came out of yesterday’s Q & A Thursday was why the difference in rice GI values. While jasmine has a whopping 109, basmati rice has a much more sedate GI of 58. Given I’ve been talking so much about rice this week, I thought I’d answer this question now, rather than holding it over to next Q&A Thursday.

The GI of a food depends on a range of different things. When it comes to rice though, it’s all about the chemical structure of the starch component.

Starch is a carbohydrate which is found in most plants. The plant uses it as a way of storing excess glucose and it makes up one of the primary carbohydrates in our food. There are two types of starch in what we eat – amylose and amylopectin – and each of these has quite a different effect on the glycemic response.

Amylopectin is a large molecule and has a branching, open structure. This makes it easy for the starch-digesting enzymes in your body to get in there and break the molecule down. Amylose, in contrast, forms tight, compact clumps, which makes it much harder and slower to digest.

Therefore the foods that have a high amylose content have a lower GI than those with plenty of amylopectin. Basmati is a high-amylose containing rice, hence it has a much lower GI. Whereas jasmine rice is high in amylopectin and therefore has a super-high GI.

08 June, 2007