Retrograde means moving back toward an earlier, worse, or less developed state, and in food science the word belongs above all to starch retrogradation. After cooking gelatinises starch, the amylose and amylopectin molecules slowly reassociate on cooling, squeezing out water and firming the texture: this is why bread stales, cooked rice hardens in the fridge, and leftover pasta turns gritty. Retrogradation is a form of recrystallisation, fastest at refrigerator temperatures, and it can be slowed by freezing, by certain emulsifiers and enzymes, or by reformulation. Nutritionally it has a silver lining: retrograded starch resists digestion, becoming resistant starch that feeds beneficial gut bacteria. The same process that ruins texture can thus improve the fibre profile.