ISSN 2310-5283 e-ISSN 3041-1432 UDC 67; 68; 33
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https://doi.org/10.52566/msu-econ3.2025.74

Vol. 19, No. 1, 2026

56-72

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    • Effect of pasteurisation on physicochemical and microbiological properties of milk

    Georgi Terziyski*

    terziyski.g@outlook.com

    Received 08.01.2026, Revised 16.04.2026, Accepted 28.05.2026 Published 29.05.2026

    Abstract

    Study was to determine the effect of pasteurisation regimes on the quality and microbiological safety of milk. Five independent production batches of milk from the “Vereya” and “Bozhentsy” brands were examined. The samples were pasteurised at 63°C for 30 minutes, 72°C for 15 seconds and 85°C for 10 seconds, after which their parameters were determined immediately after treatment, and on the third and seventh days of refrigerated storage. Raw milk of the “Vereya” brand was characterised by higher protein and dry matter content and greater viscosity, whilst “Bozhentsy” milk had higher titratable acidity and initial microbial count. All the treatment regimes studied reduced alkaline phosphatase activity to below the established limit, and Salmonella spp., Listeria monocytogenes, Escherichia coli and coagulase-positive staphylococci were not detected in the pasteurised samples. The logarithmic reduction in the total number of microorganisms was 3.40, 3.91 and 4.33 log₁₀, respectively, for the treatment regimes of 63°C for 30 minutes, 72°C for 15 seconds and 85°C for 10 seconds. Treatment at 85°C resulted in the lowest residual microbial count; however, this was accompanied by the retention of only 69.1% of soluble whey proteins, a colour difference of ΔE* 2.50 and an increased aftertaste of boiled milk. The 72°C for 15 seconds treatment ensured the retention of 87.8% of soluble whey proteins, the highest sensory acceptability after seven days of storage, and a slower recovery of the microflora compared with the 63°C for 30 minutes treatment. The results obtained can be used by process engineers at Bulgarian dairy processing plants to select pasteurisation parameters, by quality control laboratories to compile testing programmes, and by producers of drinking milk to adjust production processes without compromising the microbiological safety or consumer properties of the products

    Keywords:

    alkaline phosphatase; soluble serum proteins; sensory acceptability; mesophilic microorganisms; psychrotrophic microflora; colour difference; cold storage

    Suggested citation
    Terziyski, G. (2026). Effect of pasteurisation on physicochemical and microbiological properties of milk. Commodity Bulletin, 19(1), 56-72. https://doi.org/10.52566/msu-econ3.2025.74
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