Maillard Reaction Stages and Reactants

• Non-enzymatic browning reactions such as the Maillard reaction occur during cooking and are responsible for the brown color and flavors in foods like cooked meat, fried onions, roasted coffee, and toasted bread.

Maillard Reaction

• Melanoidins, which give cooked food its brown color, are the end products of the Maillard reaction.
• Reactants include saccharides (glucose, fructose, ribose, lactose, maltose, sucrose) and amino groups (proteins, guanidyl group, thiol group, biogenic amines, ammonium hydroxide, ammonium salts, amines).
• The reactive group in proteins is mainly the ɛ-amino group of lysine.
• Less reactive sugars are bound as glycosides, but their aglycones yield free reducing sugars upon heating.
• Other carbonyl sources can include sugar derivatives like ascorbic acids and oxidized lipids.

Three Stages of the Maillard Browning Reaction

• Amine reacts with a reducing sugar to form a glycosyl amine, followed by the Amadori rearrangement
• Dehydration and fragmentation of intermediary products such as the saccharidic moiety, and Strecker degradation of the products
• Reactions of intermediary products result in heterocyclic flavor compounds and high molecular weight brown pigments

Factors Affecting the Maillard Reactions

• Temperature affects the rate and mechanism; activation energy ranges between 10 and 160kJ/mol; rate increases with temperature, up to water activity of 0.3-0.7
• Low water content slows reaction; and high water content lowers reactant concentration
• Rate increases with pH until it reaches its maximum in a slightly alkaline medium.
• Sulphur dioxide and sulfites inhibit browning because sulfites react with aldehyde and keto groups or sugars and decrease their reactivity

Caramelization

• Complex group of reactions occur when heating carbohydrates (sucrose and reducing sugars) without nitrogen-containing compounds
• Reaction is facilitated by small amounts of acids and salts.
• The final product of caramelization is a complex mixture of polymeric compounds made from unsaturated, cyclic (five- and six-membered ring) compounds, as well as flavor and aroma compounds.
• Heating causes dehydration and formation of anhydro rings; 3-deoxyosones and furans are also formed as intermediates.
• Unsaturated rings condense to form conjugated double-bond-containing, brown polymers.
• Catalysts increase the reaction rate and can direct the reaction to specific attributes, such as caramel colors, solubilities, and acidities.

Commercial Production of Caramel

• Dark-brown liquid produced by heat-induced caramelization of carbohydrates, acts as a a coloring and flavoring agent
• Sucrose, d-fructose, d-glucose (dextrose) invert sugar, glucose syrups, HFCS, malt syrups, and molasses are the most often used carbohydrates
• Food-grade acids used acids include sulfuric, sulfurous, phosphoric, acetic, and citric acids
• Bases used include ammonium, sodium, potassium, and calcium hydroxide
• Used Salts may include ammonium, sodium, and potassium carbonates, bicarbonates, phosphates (mono- and dibasic), sulfates and bisulfites

Caramel Classifications

• Plain caramel is stable in alcohol, tannin, and salt-rich environments, with a strong aftertaste/mild aroma and color range from yellow to red.
• Caustic sulfite caramel has a mild flavor/aroma, exceptional red tone, and good stability in alcohol.
• Ammonia caramel has a sweet aroma, red-brown color, and is stable in alcohol and salt-rich environments.
• Sulfite ammonia caramel has a very mild flavor/aroma, rich dark brown color, and is stable in alcohol, tannin, and acid-rich environments.