Simplified Maillard Reaction

Good quality piglet feeds are habitually rich in protein, lactose and occasionally table sugar (sucrose) and dextrose. Lysine from protein or as added in crystalline form and reducing sugars (such as those described above), can combine under the right conditions of heat and humidity and form indigestible compounds. Thus, most piglet feeds contain higher dosages of this lysine to safeguard against projected losses because of pelleting and storage.

In general, when amino acids are heated under humidity a chemical reaction called “the Maillard reaction” takes place. This involves the binding of free amino groups (such as those in crystalline lysine, which in contrast to other amino acids lysine contains two such groups) to reducing sugars (as those from lactose and sucrose/dextrose). This “browning” reaction occurs even at normal room temperatures, but at a very slow rate. However, when browning is excessive (during improper pelleting conditions, for example) or it is out of control (during prolonged storage at high temperatures and humidity), then protein quality is invariably reduced.

A prolonged storage of heat sensitive material that have already been affected by this problem, initiates a second cycle of Maillard reaction. This is of paramount importance in nursery feed management, because the conditions in commercial nursery facilities are extremely favorable for the Maillard reaction. Residual feed moisture also affects the extent of the Maillard reaction during storage. For example, a 10 percent moisture level in milk powder stored for 10 weeks during summer resulted in 20 percent loss of lysine bioavailability. Or, as it was demonstrated in another study, 10 percent of total lysine was destroyed when piglet feed was stored inside a typical nursery room for only 7 days!

In addition, the adverse effects of the Maillard reaction have been demonstrated in many other feed ingredients such as soybean meal, fish meal, dried whey, canola meal and peanut meal. Although crystalline lysine is the most sensitive amino acid, the same problem exists (but to a lesser degree) for the rest of the crystalline amino acids added in piglet feeds. So, this is a serious problem affecting many ingredients when heated under humid conditions.