Abstract
The present study investigated the changes in TL and DHA in TL in DHA-enriched infant milk powder that was stored in a sealed container and an opened container at 25°C and 5°C for 24 weeks, as well as the effects of storage temperature and oxygen control on lipid degradation. TL content did not change under any of the experimental conditions. In addition, oxidation of TL was not apparent when oxygen exposure was controlled. However, when the milk powder was stored in an opened container, the oxidation indexes changed during storage, suggesting that lipid degradation occurred. Furthermore, changes in AV and PV at 25°C in the case of oxygen exposure were greater than that at 5°C, so the effect of storage at a lower temperature for lipid degradation was recognized. Analysis of the ratio of NL and CL in TL demonstrated that, similar to the oxidation indexes, controlling oxygen exposure was an effective means of suppressing lipid degradation. However, the difference of storage temperatures did not appear to influence the ratio of NL and CL in TL. The composition of the major fatty acid (18 : ln9, 16 : 0, 18 : 2n6, 18 : 0, 12 : 0 and 14 : 0 acids) composed in TL changed very little under all experimental conditions. Thus, controlling oxygen exposure appears to be an effective means of suppressing oxidative decomposition of fatty acid. Although DHA in CL changed significantly during storage when exposed to oxygen, CL ratio in TL was small, and the resultant changes in TL were barely affected. Based on the results of the present study, if temperature and oxygen exposure are controlled, the physiological effects of DHA can be maintained for a long time.
