Evaluation of milk powder quality by protein oxidative modifications

Abstract

The objective of the present research was to evaluate commercially available milk powders according to their protein oxidative modifications and antioxidant capacity, and to evaluate if these characteristics are related to physical quality parameters such as dispersibility or stability during storage. Fifteen commercially processed spray-dried milk powders were evaluated: 6 whole milk powders (WMP), 4 skim milk powders (SMP), and 5 infant formula powders (IFP). Protein oxidative status was measured as protein carbonyl (PC) content, dityrosine content, and extent of protein polymerization. The level of PC was slightly lower in SMP than in WMP, whereas IFP had more than twice as much PC as WMP (2.8 ± 0.4, 2.1 ± 0.2, and 6.5 ± 1.3 nmol/mg of protein for WMP, SMP, and IFP, respectively). No differences were detected in dityrosine accumulation. Although all the possible pairs of parameters were tested for correlations, we found that 4 parameters were linked: PC, whey content, protein aggregate level, and dispersibility. After 9 mo of storage at -20°C or room temperature, all milk samples were analyzed to evaluate changes in protein oxidative status (PC, dityrosine, and protein integrity) and related parameters. Compared with the initial condition, PC increased in all tested samples after 9 mo of storage at -20°C or at room temperature. Stored milk powders had increased PC and decreased dispersibility compared with prestorage levels. Our results highlight the importance of protein oxidative status in milk powder and its relationship to other related quality parameters, such as protein integrity and dispersibility. Our findings suggest that the understanding of such relationships could help in developing quality differentiation for different types of milk powders in the product market.

Whey protein hydrolysates reduce autoxidation in microencapsulated long chain polyunsaturated fatty acids

“…Surface coverage was not high enough to provide an ‘internal coating’ as it was observed in other studies on the encapsulation of proteins using hydroxypropyl methylcellulose for surface modification . In contrast, it is described in the literature that protein at the particle surface, especially during ageing of the particle, can adversely affect the solubility . These effects are not likely to be pronounced at the present level of surface accumulation.…”

The Chemistry of Protein Oxidation in Food

“…Fluorescence spectroscopy is sometimes used as as um method for analysis of dityrosine and NFK without prior chromatographic separation. [173,179] This approach suffers from limited selectivity because the contribution to fluorescence signals from concomitantly occurring Maillard reaction products such as imidazolones or pentosidine is not taken into account (Table 4). Ther espective methods need to be validated against chromatography-based assays using wellcharacterized standard substances.…”

Study of Polyphenol Content and Antioxidant Properties of Various Mix of Chocolate Milk Masses with Different Protein Content

“…According to Christian Vásquez, et al [41] milk proteins can act as surfactants and stabilizers that are able to induce the formation of spherical micellar aggregates in the chocolate structure. Moreover, spray drying technology can induce changes in proteins that affect hydrophobicity, solubility, and denaturation [42][43][44]. Milk selected for preparation of milk chocolate masses contained from 11.61 to 31.1 mg of protein in 100 g of powder ( Table 1).…”