Characterization of industrial processed milk by analysis of heat‐induced changes

Abstract

Thermal indicators in milk, which had been subjected to one of the six industrial processes of thermization, pasteurization, direct and indirect UHT-sterilization, pre-sterilization and in-bottle sterilization, were studied. The following three indices of heat damage were analyzed by high performance liquid chromatography (HPLC), hydroxymethylfurfural (HMF), lactulose and acid-soluble ␤-lactoglobulin(␤-LG). Average amounts found were 1710 mg/L of ␤-LG and 2.49 mol/L of HMF in pasteurized milk. In UHT milk, the amounts for direct and indirect processes were 389 and 322 mg/L of ␤-LG, 12.0 and 250 mg/L of lactulose and 5.6 and 8.7 mol/L of HMF. In sterilized milk the amounts were 1120 mg/L of lactulose and 22 mol/L of HMF, without any detectable presence of undenatured whey proteins. On the basis of the time/temperature profiles, a sterilization factor, expressed as seconds, was defined for each thermal treatment. By applying discriminant analysis each industrial process could be classified independently at the 95% confidence level (pasteurization, UHT-treatment and in-bottle sterilization), but direct-UHT treated milk could not be discriminated from indirect-UHT milk, nor thermized milk from raw bulk milk. The simultaneous application of several heat-induced parameters improves the classification of industrial processed milks, and is therefore a useful tool for optimization of the processing conditions.

RP-HPLC analysis of furosine and acid-soluble β-lactoglobulin to assess the heat load of extended shelf life milk samples in Austria

“…The relative standard deviation (RSD) was 1.91% obtained on a UHT milk sample with an average β-Lg content of 339.9 ± 6.5 mg·L −1 milk, and 0.26% on an ESL milk sample (2397.8 ± 6.2 mg·L quality is demonstrated in Figure 2. Compared to the results obtained by other authors [14,21], a faster separation and a much more stable baseline were the most striking advantages of the HPLC column used in the present study.…”

Production of extended-shelf life milk by processing pasteurized milk with pulsed electric fields

“…3), it is possible that other flavor defects such as bitterness may have been detectable at the end of the shelf life, as indicated by the presence of sweet curdling in some of the studied samples. No changes on the sensory characteristics of the product due to the applied thermal or nonthermal treatments were observed, or expected, based on the findings by Morales, Romero, and Jimenez-Perez (2000), and Qin et al (1995a). Microbiological screening of the treated samples for pathogenic bacteria demonstrated that all treated samples were free of Salmonella spp., Listeria monocytogenes and Bacillus cereus, which are thermoduric pathogenic bacteria with the potential to grow at refrigeration temperatures that may cause health concerns if present in milk (Collins-Thompson & Bunning, 1992).…”

Distinction of different heat-treated bovine milks by native-PAGE fingerprinting of their whey proteins

“…Nowadays, various systems and technologies associated with different time-temperature profiles have been developed to obtain pasteurized and ultra-high temperature (UHT) milk, and the effect on the nutritional and sensory quality of commercial milk samples may vary substantially depending on the process (Awad, 2006;Morales, Romero, & Jimenez-Perez, 2000). For regulatory purposes, attention should be paid to evaluate the authentication of heat-treated milks and milk integrity since heat treatments change the biochemical composition of milk.…”