The Maillard reaction in gummies containing milk proteins is driven by a non‑enzymatic chemical reaction between reducing sugars and amino groups from the proteins-primarily lysine residues in milk casein and whey. This reaction begins during thermal processing (e.g., cooking, drying) and continues slowly at room temperature. The cascade starts with the condensation of the carbonyl group of a reducing sugar (like glucose or lactose) with a free amine group of an amino acid, forming an unstable Schiff base, which then rearranges into more stable Amadori or Heyns products. Over time, these intermediates undergo further dehydration, fragmentation, and polymerization, producing a range of brown‑colored melanoidins and volatile flavor compounds such as furans, pyrazines, and aldehydes.
Impact on flavor stability over shelf life: The Maillard reaction directly degrades flavor stability. Initially, it can impart desirable caramel‑like or toasted notes, but as it progresses, it leads to progressive browning, off‑flavors (e.g., “stale,” “cardboard,” or “burnt” notes), and a loss of the intended fruity or sweet profile. The rate accelerates with higher temperatures, elevated pH, and longer storage times. The reaction consumes reducing sugars, which can reduce sweetness perception and alter texture as moisture is lost or binding changes. To mitigate these effects, manufacturers control processing temperatures (< 70°C), use low‑reactivity sugars (e.g., sucrose instead of glucose), adjust pH to slightly acidic (pH 4.5-5.5), and package gummies in oxygen‑ and moisture‑barrier materials to slow the reaction during shelf life.