Effect of storage conditions and inclusion of milk on available lysine in infant cereals

Infant cereals have a prolonged shelf-life. Available lysine was determined in order to ascertain the stability of lysine during storage for different periods under varied temperature and water activity conditions. Studies were undertaken on wheat-based (“7 cereals” brand) and rice-based (gluten-free) infant cereals (with and without the inclusion of milk powder). Samples of all cereals were monitored during 1, 3, 6 or 12 months of storage at 32 or 55 °C. Samples of “7 cereals” and “7 cereals+milk” were also stored at 25 or 55 °C for 1, 2, 3 or 4 weeks under modified aw. A gradual decrease in available lysine during storage was observed at all temperatures and times studied. Lysine losses at 32 °C reached values of 4.26% (wheat-based) and 5.47% (rice-based) in infant cereals without milk after 12 months of storage and at 55 °C, 11.2 and, 19.4%, respectively. For the same storage time, infant cereals with milk exhibited higher losses: 8.09 and 10.5% at 32 °C and 21.4 and 23.2% at 55 °C. Increased aw during the storage of “7-cereals” (with and without milk) samples caused a considerably greater loss of lysine.