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Adequate heat treatment of raw milk is required to guarantee microbiological safety, but there is a huge variation in the heat load of different categories of heat-treated milk due to different thermal treatment temperatures when using different processes. However, uncontrolled "over-processing” of milk leads to certain undesirable losses of nutritional and organoleptic quality. To evaluate the actual intensity of heating, numerous analytical tools have been established to determine several associated time‐temperature integrators. Enzymes are appropriate indicators for the assessment of lower heat treatment; higher heat load can be evaluated using indicators such as β-lactoglobulin, α-lactalbumin, lactulose, furosine, and hydroxymethylfurfural. Analytical methods are mainly based on photometric/fluorimetric methods for determination of enzymatic activity, and high-performance liquid chromatography for β-lactoglobulin, α-lactalbumin, lactulose, furosine, and hydroxymethylfurfural. Capillary electrophoresis and other analytical tools (e.g., gas chromatography, infrared methods) are also appropriate to evaluate the intensity of heat treatment of milk and dairy products.

This study provides a direct comparability between milk from cows fed hay or silage produced from the same parent plant material; the influence of feeding either hay or silage on amounts of various milk components was investigated. To give an overview regarding differences in milk composition, protein fractions, free amino acids, polyamines and biogenic amines as well as fatty acid profile and sensory properties were analysed. Moreover, the content of vitamin E and four different B-vitamins (B1, B2, B6 and B12) was determined. Results showed that there are some significant differences between hay milk and silo milk, especially regarding certain key nutrients. Linoleic acid, α-linolenic acid, lysine and putrescine showed higher concentrations in hay milk, while vitamin B12 and spermine were increased in silo milk. Sensory analysis showed that feeding of silage had a significant influence on colour (yellow), consistency and odour intensity, which were more pronounced in silo milk.