Learn to modify the GI of food According to your goal
Before starting, it is essential that you look these posts from our colleagues to understand what the glycemic index and its importance:
Although studies indicate what the link 2 is not good consume large quantities of carbohydrates high glycemic beyond during and post-training because it can generate hyperinsulinemia and Type II diabetes.
- 1 Two types of starches
- 2 Parameters that influence the glycemic index GI:
- 3 amylose-amylopectin ratio
- 4 The type of heat treatment and “pasting”.
- 5 The retrogression: the reverse of gelatinization
- 6 The content of protein, fiber and fat
- 7 The degree of maturation and aging
- 8 The particle size
- 9 Some final tips for reducing GI
Two types of starches
For starches from carbohydrates are absorbed and pass into the bloodstream, they must be converted into glucose. Digestive enzymes (a-amylases mainly) are what make this work.
The starch grain is formed by two types of molecular components: amylose (more resistant to digestion) and amylopectin (easier to digest). The proportion of amylose compared to amylopectin is what essentially determines the physicochemical nature of starchy foods and nutritional effects on the human organism.
- Starches cereals usually contain between 15 and 28% amylose but some maize varieties containing less than 1% (as waxy maize whose extracts are used in the food industry as thickeners).
- Starches from tubers (called starches), such as potato, amylose have much less than it is believed (between 17 and 22%). However, starches of legumes (lentils, beans, chickpeas) contain much more amylose (from 33 to 66%).
Parameters that influence the glycemic index GI:
When subjected to heating in excess water (cooking), the starch structure is modified, the starch granules swell progressively and amylopectin fraction of the water emerges. If heating is prolonged, a fraction of amylase is also released in the water.
The result is a higher or lower viscosity food. It is the phenomenon of gelatinization of starch. The lower the proportion of amylose greater the gelatinization and vice versa. That is, more easily absorb the a-amylase enzymes and has propensity to become glucose, glucose thus evidently has more tendency to increase (greater GI).
Conversely, if the proportion of amylose is high, there is less gelatinization and therefore, the starch will not transform both glucose and glycemic index will be lower.
This explains very well why the potato, whose rate is very low amylase, has a high glycemic index. Instead, the pulses have a very low glycemic index and contains much amylose.
Corn “Waxy” (known as waxy maize) essentially free of amylose. It is often used to thicken fruit jellies, texturing food canned or frozen. In the food labels it appears as corn starch. Its glycemic index is very high (close to 100) which helps increase blood glucose in all industrial culinary preparations in which it operates. In sports supplements, it is known as “Waxy maize” (amylopectin corn).
The type of heat treatment and “pasting”.
Hydration and heat have the effect of increasing the glycemic index of food. Carrot, for example, has a glycemic index of 20 when raw. But when boiled in water is 50 index due to the gelation of the starch.
Similarly, when the corn grain exploited to become popcorn or rice grain to puffed rice, the initial glycemic index increases between 15 and 20%.
Furthermore, there is a natural technical process which tends to slow the hydration of the starch. This is the case of “pasting” of durum wheat. This process involves pressing a heating effect which results in the formation of a protective layer that will help slow the gelatinization of starch upon cooking.
But what is true for spaghetti, macaroni, noodles, etc … Is not valid for ravioli or lasagne, even for fresh pasta. Thus, from the same flour products it is normal glycemic index that can vary to such an extent that duplication (fresh pasta 70, spaghetti 40).
In addition, domestic cooking to be held just before consumption will also modify the final glycemic index. A “al dente” (6-7 minutes) cooking will preserve the glycemic index of the spaghetti at the lowest level, while prolonged cooking (over 15 minutes), lead to an increased GI.
The retrogression: the reverse of gelatinization
Once the starch has been cooked and gelatinized, upon cooling becomes modified. Progressively, the gel develops into a new reorganization of the macro molecules of amylase and amylopectin, ie, a return to previous molecular structure. In fact, the phenomenon of retrograde increases with time and with decreasing temperature.
Prolonged storage at low temperature 5 degrees’ of starch (cooked dishes vacuum) food promotes, therefore retrogradation. For this reason, spaghetti (even white) cooked al dente and then cooled to consume salad will have a glycemic index of 35.
The same is achieved by letting dry certain foods. For example, the harder is the bread retrogradation is favored more because they let moisture to escape to the outside. Same thing happens when the bread is toasted.
In relation to this, it seems obvious state that steaming, which involves little hydration regarding immersion cooking causes lower gelatinization (= lower GI).
The content of protein, fiber and fat
In some glucides natural protein may be causing less hydrolyzing (digestion) of starches and therefore a decrease in glycemic index. This is the case of the family of cereals:
- Pastes containing gluten slow the action of digestive amylases, which further limits glucose uptake.
- Also keep in mind that dietary fiber content is in a starch can be a barrier to the action of amylases and therefore further decrease the GI.
- Fats, because of their slow digestion, decrease the glycemic index of foods that accompanies it.
The degree of maturation and aging
Fruits modify its glycemic index according to their degree of maturation. A green banana, for example, has a very low glycemic index (about 40) but when it has reached the maximum degree of maturation, their glycemic index is much higher (65) because the starch has become amylase to amylopectin.
The particle size
When a comminuted starch, the starch particles become finer so its mastication and digestion is facilitated, which results in increased glycemic index.
It is precisely the case of cereals when reduced to flour. Thus, rice flour has a higher source rice GI (also occurs with oats and oatmeal).
|NUTRIENTS||Pumpernickel bread (100g)||Traditional white bread (100g)|
Some final tips for reducing GI
- Cooking al dente if pastas.
- For foods high percentage of amylopectin (boiled potatoes, cooked carrots, heated in microwave, food etc …) it would be appropriate cool them in the fridge before eating.
- Toast the bread.
- Accompany meals with high GI healthy fats.
- Choose organic, whole foods, and some ripe fruit.
- Avoid foods (cold cuts) containing outstanding percentages of corn starch for preserves.
- Assess the overall glycemic load of the food