Determination of quality characteristics for whole milk powder with slight and moderate odour changes

Whole milk powder is susceptible to flavour changes, which is limiting for its shelf-life as well as consumer acceptability. Degradation of natural aroma during production and storage occurs primarily as a result of lipid oxidation, Maillard reactions and the influence of extracellular microbial enzymes. Selected chemical parameters were measured in ten whole milk powder samples to assess their susceptibility to off-odour development. The results of off-odour intensity were correlated with the volatile compounds determined by headspace solid-phase microextraction (HS-SPME) coupled to gas chromatography-mass spectrometry (GC-MS) and with other physicochemical parameters (moisture, protein content, content of organic acids and their salts, peroxide value and content of free fat). The off-odour intensity correlated with contents of volatile compounds, lactic acid, proteins, propanoic acid, moisture and peroxide value. Based on the results, characteristics of a moderate off-odour intensity, which is still acceptable to consumers, were established to predict flavour changes with the following limit values: total content of volatiles with the sum of peak areas of max. 400 V times s, content of hexanal of max. 10 mu g times kg super(-1), content of lactic acid of max. 1 g times kg super(-1), protein content of min. 250 g times kg super(-1), moisture of max. 30 g times kg super(-1), content of propanoic acid of max. 1 g times kg super(-1) and peroxide value of max. 5 milliequivalents O sub(2) per kilogram of fat.