Early morning when you run late for office or you have to prepare a quick breakfast for your husband or family, what do you make?
Probably an upma? Why?
Simply because it’s easy and fast.. But ever wondered why does it become a solid – like mass when it cools? Or have you ever noticed that even though the entire upma is coalesced together, every grain of upma retains its individual existence??
Yes, that happens… And yes, there is science behind this simple dish prepared by Indians all over the world..
Upma is cooked by basic 3 ingredients. Semolina or suji, ghee and water. The recipe shall be available everywhere on the web, and so I’d only focus on the science involved in the recipe.
1. ROASTING : The first crucial step in making upma is roasting the Suji or semolina. Why? Suji is roasted with a little amount of fat so that each grain is separated and coated with fat. This is done to avoid lumping when the water is added. Also, in this way, each starch(suji) grain will Be exposed to uniform hear and water and hence will swell independently. This is why at end of the entire cooking process and with so much of stirring, the suji grain remins as it is.
2. COOKING : When suji is roasted evenly, water is added and cooked by stirring continuously. A process called GELATINIZATION takes place. When the temperature reaches 60-71 degrees Celsius, the starch starts to Gelatinize and at a temperature of 88-92 degrees Celsius, this process is completed.
In this process, the kinetic energy of the hot water breaks the bonds between starch molecules and hence the crystalline structure of the starch is lost. Also, it loses its birefringence property (a property due to which, when a polarised light passes through the non – hydrated starch grain, it gets deflected in two directions).
Water then forms hydrogen bonds with the starch grains and penetrates into it. As a result, the grain swells up. As the grains are completely swollen, the amylose of the starch leaches out and it becomes viscous. This results in a thick paste like consistency of the upma. This is what happens in the process of Gelatinization. So when u see any mixture of starch and water (Sol) become think on heating, be rest assured that the process of Gelatinization is taking place..
3. COOLING : Now comes the actual question of why does the above viscous Sol become a solid mass on cooking? Here’s the answer.
On cooling, the Gelatinization mixture undergoes a process called GELATION. On cooling, the heat energy is released. A hydrogen bond is formed between the amylose moities that were earlier leached out of the grain. This causes the water molecules to get entrapped between these bonds and form a three dimensional structure. So this structure formation is responsible for the solid mass of upma.
RETROGRADATION is another process that takes place when upma is refrigerated. What happens is, due to the hydrogen bonding between the amylose moities, the lost crystallinity and birefringence re-appears and we get a gritty texture of upma when it cools. This process may lead to SYNERSIS or oozing out of the water from the upma undesirably. Specially when the food is subjected to continuous freeze – thaw cycles.
So yes, this was all you need to know about the upma Science… Next time you cook upma, make sure you notice the changes and store your upma accordingly.
And yes, you can always apply these same principles to any starch that you are cooking.