Comparative study on the characteristics and oxidation stability of commercial milk powder during storage

Abstract

The quality of milk powder can decrease during storage. In this study, the characteristics of 12 kinds of commercial milk powder from China were investigated. Changes in various indicators were tracked to comprehensively estimate the oxidation stability of different commercial milk powders. The components of the commercial milk powder were different. The percentages of milk fat, protein, and carbohydrates ranged from 9.8 to 28.5 g/100 g, 15.0 to 24.0 g/100 g, and 32.0 to 67.5 g/100 g, respectively. The water activities ranged from 0.2394 to 0.5286. The diameters of the milk fat globules in different commercial milk powder ranged from 13.99 to 41.09 nm. At the same time, the peroxide value of the control sample was low (≤0.14 mEq/kg). After 3 mo of storage, the peroxide values of some of the commercial milk powder increased significantly. The changes in the thiobarbituric acid values during storage did not follow a common trend. The contents of free fat in the different control samples were 0.21 to 1.67 g/100 g, and these values did not increase during storage. After 3 mo of storage, the hydroxymethyl furfural values and b color values of the different commercial milk powder reached their highest levels. The concentrations of typical oxidized flavor compounds in different commercial milk powder increased greatly with prolonged storage time. The level of hexanal was the highest, and the contents in all the samples ranged from 28.56 to 4,071.28 μg/kg after 6 mo of storage and from 5.91 to 6,281.37 μg/kg after 12 mo of storage. Free radicals were found in some of the stored milk powder, and these were shown as single peaks or multiple peaks. The ratios of the peak areas and masses reached 12.42 × 10 6 to 14.26 × 10 8 . However, the presence of free radicals in the commercial milk powder was not consistent. The water activities and diameters of the fat globules in the commercial milk powder were highly correlated with their oxidation stabilities during storage.

Characteristics on the oxidation stability of infant formula powder with different ingredients during storage

“…Peroxide is the primary oxidation product produced during the lipid oxidation (Zou, 2002; Li et al., 2019). Figure 1 shows the change in peroxide value of infant formula powder with different ingredients during storage.…”

“…A series of free radicals could produce by redox reactions during the storage of milk powder (Li et al., 2019). The free radicals of different milk powder stored for 6 months and 12 months were determined.…”

“…During the storage of milk powder, the index related to oxidative stability changed differently. Free radical was an important indicator for evaluation the lipid oxidation of dairy products (Li et al., 2019; Stapelfeldt et al., 1997). Correlation analysis between oxidation stability index and free radical is calculated using the bivariate analysis (Table 4).…”

“…The sample was sealed immediately, and the free fat dissolved at room temperature over 15 min. The content of free fat was determined after evaporation (Li et al., 2019).…”

“…Peroxide is the primary oxidation product produced during the lipid oxidation (Zou, 2002;Li et al, 2019). ide values of FA4 and M1 were 1.847 mEq/kg and 1.780 mEq/kg, respectively, which were higher than those at 6 months storage.…”