Infant Milk Formulas: Effect of Storage Conditions on the Stability of Powdered Products towards Autoxidation

Abstract

Thirty samples of powdered infant milk formulas containing polyunsaturated fatty acids (PUFAs) have been stored at four different temperatures (20, 28, 40 and 55 °C) and periodically monitored for their malondialdehyde (MDA) content up to one year. MDA levels ranged between 250 and 350 ng/kg in sealed samples with a maximum of 566 ng/kg in samples stored at 28 °C for three weeks after opening of their original packages, previously maintained for ten months at 20 °C. Sample stored at 40° and 55 °C were also submitted to CIE (Commission Internationale de l’Eclairage) colorimetric analysis, since color is the first sensorial property that consumers may evaluate. Overall, the results demonstrated a good stability of PUFA-enriched infant milk formulas in terms of MDA content. However, some care has to be paid when these products are not promptly consumed and stored for a long time after first opening.

Correlating Volatile Lipid Oxidation Compounds with Consumer Sensory Data in Dairy Based Powders during Storage

“…In the present study, freshly opened WMP and SMP remained acceptable to the sensory panel for the whole 16 weeks of storage despite levels of primary oxidation products being present above their odour thresholds. Storing samples in ACC versus AM accelerated the formation of LO compounds, which contradicted the results of Cesa et al [12], which stated that 40 • C was too low a temperature to perform accelerated oxidation studies and that the levels of MDA in samples stored at 40 • C were comparable to those stored at 20 • C after 12 weeks of storage. The study by Cesa et al [12] recommended a temperature of 55 • C for performing acceleration studies.…”

“…Storing samples in ACC versus AM accelerated the formation of LO compounds, which contradicted the results of Cesa et al [12], which stated that 40 • C was too low a temperature to perform accelerated oxidation studies and that the levels of MDA in samples stored at 40 • C were comparable to those stored at 20 • C after 12 weeks of storage. The study by Cesa et al [12] recommended a temperature of 55 • C for performing acceleration studies. However, in the present study, differences in the volatile profiles were evident in FFWMP and SMP samples stored in AM and ACC.…”

“…However, it is not unusual to see higher levels of LO products in IMF when compared to conventional milk powders. Cesa et al [12] reported the levels of malondialdehyde (MDA), a common indicator of the LO process, up to five times higher in IMF compared to bovine milk samples. Furthermore, Jia et al [13] conducted an accelerated stability study on milk based IMF stored at 42 and 50 • C for 90 days.…”

“…Some studies have been carried out investigating the effects of exposing whole milk powder (WMP) to accelerated storage temperatures (45 • C) on the products' oxidative stability [7], LO of WMP [8], and flavour and shelf-life of WMP [6]. However, less information is available on the effect of storage conditions on skim milk powder (SMP) [9,10] and infant milk formula (IMF) [11][12][13]. IMF undergoes extensive processing with the aim of simulating human breast milk from bovine milk as closely as possible [14].…”

“…IMF is usually fortified with PUFA such as linoleic acid (C18:2 n6), α-linolenic (C18:3 n3), arachidonic (C20:4 n6), and docosahexaenoic acid (C22:6 n3) [16], prior to thermal processing, i.e., spray drying, for potential health benefits. Due to their unsaturated nature and low oxidative stability, PUFA are readily degraded into primary and secondary oxidation products [17], a process that can be initiated by the high inlet temperatures required for spray drying (120-180 • C) and contact with oxygen [12]. Hydroperoxides are the initial products formed by the LO cascade process and are unstable and reactive, eventually forming compounds that are known to cause off-flavours in dairy powders, such as aldehydes and ketones [17].…”