See also: starch - rice starch - corn starch - wheat starch - potato starch
What is the Fecola
In common parlance, the term starch identifies the starch contained in potato tubers ( Solanum tuberosum, Fam. Solanaceae). In reality the starch name also belongs to the starch obtained from bananas, chestnuts, sago, maranta and cassava.
Production
Features
From a chemical point of view, there are no significant differences between the various types of starch and starch, except for the percentage of amylose / amylopectin and the morphology of the granules, which have different structures and sizes depending on the plants from which they are derived. If observed under a microscope, the starch is characterized by the presence of isolated, rather large (up to 150 μm), oval-shaped granules, similar to a pear or a shell, with eccentric hilum and marked streaks.
Amylose and Amylopectin
Like all starches, starch consists of two different glucose polymers:
- Amylopectin (80%): branched molecule, more easily digestible, with high glycemic index, responsible for gelatinization and thickening and stabilizing properties of gels and emulsions;
- Amylose (20%): linear molecule with less viscosity, responsible for the reorganization of starch after cooking (resistant starch, stale bread, etc.).
| Starch | % Amylose | % Amilop. |
| corn waxy | <1 | > 99 |
| tapioca | 17 | 83 |
| rice | 19 | 81 |
| potato | 20 | 80 |
| wheat | 25 | 75 |
| corn | 30 | 70 |
Compared to wheat starch, and even more to corn starch, the starch is richer in amylopectin (70% in corn, 75% in wheat), while the gelatinization temperature is around 60 - 65 ° C.
Properties Thickeners
In 2005 the cultivation of a new waxy variety of potatoes (Eliane) was started, containing a starch consisting practically of amylopectin alone. Like waxy maize, this characteristic is rather sought after by the food industry, as it increases the thickening properties of the product. The addition of starches rich in amylopectin therefore saves on the basic ingredient (yogurt, sauces, cheeses, creams, sausages, pastries, puddings, preserves, etc.) both in terms of quality and quantity. Unfortunately a more palatable product comes out, with some better organoleptic characteristics but deprived of a part of its precious nutrients.
Influence of Tempeature and Humidity
At room temperature, potato starch is insoluble in water and ethanol, but due to the combined effect of water and heat, its solubility increases significantly. In fact, with heating, the starch particles undergo transformations that make them capable of absorbing water; this leads to a perturbation of the original crystalline structure, with a consequent increase in the viscosity of the system (gelatinization).
If the heating continues, the granules swell excessively, breaking, with leakage and partial solubilization of the starch material (amylose and amylopectin), and loss of viscosity. This phenomenon, after gelatinization, is called "pasting" and leads to the formation of what is commonly called starch salt.
If the system is subsequently subjected to cooling, the starch molecules reorganize themselves into new crystalline structures (retrogradation), restoring structure and viscosity to the system (when this characteristic is negative for the product, it is necessary to choose starches that are less amylose).
Nutritional aspects
Unlike potato flour, starch contains only a high carbohydrate fraction (91%), while fats are present only in trace amounts, with a fairly modest proportion of proteins (about 1.4%). Consequently, starch brings empty calories to the organism, conspicuous from the quantitative point of view but deprived of all those substances necessary in nutrition (proteins, fats, minerals and vitamins).
Given the absence of gluten, potato starch can also be used for celiacs.
In the kitchen, potato starch finds its main use in the preparation of pastry products.
