Wednesday, November 17, 2010

Amylose ended up black and blue in Hanoi.

DISCLAIMER: What follows is a somewhat technical article. Prepare tissue, cotton balls, and ice in case of nosebleeds. You have been warned. Hehehe.

Have you ever tried adding iodine to potatoes or to bread in science class? The bread and the potato normally turns dark blue because the starch in these food items react with iodine. To be more specific (take a deep breath), the long and linear molecules of starch, known as amylose, turn blue. For the longest time, quality evaluation programs have been relying on the proportions of amylose in a sample to predict whether the cooked grains become hard or soft after cooling. In seminars I've attended, a breeder always mentions amylose content when asked about consumer preference. 

Enter the International Network for Quality Rice (INQR). The group is composed of rice scientists involved in quality evaluation programs in different national agricultural research and extension systems (such as PhilRice, BRRI, RRRI, etc.). Its first project is to standardise the measurement of amylose across all systems because in the light of the globalisation of rice trade, it is important to make sure that amylose content values of a sample measured in one country will be the same as those measured in another. After a few years of fieldwork, lab work, correspondence, and complex statistics, the INQR has succeeded in developing a standard method that is now being processed by ISO. As a result, rice traders in different countries will now hopefully begin to be on the same page.

So, amylose content is an important trait. However, the merits of amylose content was put under a more criticising light. According to Dr. Harold Corke, amylose content is not enough. We "don't eat amylose content", as he put it. 

To illustrate this point clearer, I presented my work on glutinous rice; varieties of this type do not have amylose because of a mutation in a gene, and yet have different texture profiles (which I still have to verify in a larger set of samples). At the opposite end of the spectrum, Tran pointed out a different mutation in the same gene, which apparently makes varieties with high amylose content have different textures. 

Amylose content, the golden boy of quality evaluation programs of old, ended up black and blue during the rice quality session of the IRC 2010. It may not predict cooked rice texture ALL the time, but it is still an important test nonetheless.