Gelatinisaation

Gelatinisaation, or gelatinization in English, is the physical and chemical transformation of starch when heated in water. In this process, starch granules absorb water, swell, and lose their crystalline structure, producing a viscous paste that often thickens foods. Upon cooling, the paste may set into a gel.

Mechanism and temperature: The main change occurs as temperature rises to near the starch's gelatinization temperature, typically around 60–65°C for many native starches, with peak viscosity between 70–90°C depending on source (corn, wheat, potato, tapioca). Water availability and heating rate influence the extent of swelling; amylose may leach into the surrounding water, and the granule's crystalline regions melt.

Factors: Water content, pH, sugars, acids, salts, lipids, and proteins affect gelatinization. Sugars tend to raise the temperature; acids can delay swelling; lipids can form complexes with amylose, reducing swelling. Particle size and starch grade (native vs modified) also matter.

Relation to other processes: Gelatinization is distinct from gelation, the network formation on cooling that yields a gel. Retrogradation is the gradual firming of a gelatinized starch paste during storage, which can lead to syneresis.

Applications and analysis: Gelatinization is central to cooking and food processing, affecting sauces, gravies, puddings, and baked goods. It is studied by differential scanning calorimetry, rheology, and microscopy to assess onset temperature, peak viscosity, and gel strength. The type and amount of starch determine texture and stability.