E951: Aspartame (Dipeptide Sweetener / 200x)

Direct Answer

E951 (Aspartame) is a methyl ester of the aspartic acid/phenylalanine dipeptide yielding ~200x the sweetness of sucrose. INS 951, ADI is 40 mg/kg bw/day, the historic sweetener in Diet Coke and tabletop sweetener packets.

Source: EFSA ANS Panel (2013 Comprehensive Re-evaluation) / WHO JECFA (2023) · Last reviewed Aug 28, 2026

Specs

E-Number Code	E951
INS / Codex Number	INS 951
Functional Class	High-Intensity Artificial Sweetener
Acceptable Daily Intake (ADI)	40 mg / kg body weight per day (US FDA: 50 mg/kg)
Relative Sweetness Index	200x Sucrose
Caloric Value	4.0 kcal / g (Negligible at use levels / ~0.1 kcal per serving) kcal/g
Primary Mechanism	Stimulates T1R2/T1R3 sweet taste receptors with clean, sugar-like taste profile
Common Target Foods	Diet sodas, tabletop sweetener packets (Equal), sugar-free gelatin desserts, drink mixes
Dietary Compliance	Vegetarian, Halal, Kosher, Contains Phenylalanine (Warning for PKU patients mandatory)
Safety Approval	EFSA Authorized / FDA Approved (21 CFR 172.804)

Thermal Lability in Baking

Aspartame breaks down into diketopiperazine and constituent amino acids upon prolonged baking above 100°C, losing sweetness. For this reason, heat-stable sucralose or Ace-K is preferred in baked goods.