Abstract

Milk testing and quality control should be carried out at all stages of the dairy chain. Milk can be tested for quantity, organoleptic characteristic, compositional characteristic, physical and chemical characteristics, hygienic characteristics, adulteration or drug residues. The content of the major constituents of raw milk is important for milk payment system. Enzymes naturally present in the milk can change the chemical composition of raw milk. Also, enzymes secreted by bacteria or enzymes from somatic cells can degrade the raw milk composition. Products of these degradation reactions can have undesirable effects on milk structure, smell and taste. It is very important that farm-fresh raw milk be cooled immediately to not more than 8 °C in the case of daily collection, or not more than 6 °C if collection is not daily. During transport the cold chain must be maintained. An authorized person, properly trained in the appropriate technique, shall perform sampling of bulk milk in farm. Laboratory samples should be dispatched immediately after sampling to the dairy company and consequently to the testing laboratory. The time for dispatch of the samples to the testing laboratory should be as short as possible, preferably within 24 h. Laboratory samples shall be transported and stored at temperature 1 to 5 °C. Higher temperatures may adversely affect the composition of the laboratory sample and may cause disputes between the farmer, the dairy company and the laboratory. The effect of refrigerated storage at temperature 4 °C during 24 h on the composition of raw milk were investigated in this work, because we wanted to know how the milk composition will be changed and how the laboratory results will be affected. In many cases, the samples are not preserved with chemical preservants like azidiol, bronopol, potassium dichromate or Microtabs. We found, that the composition of raw cows' milk after 24 was changed significantly (p >0.005). We found an average decrease in the fat content of -0.04 g/100g, increase in the protein content of +0.02 g/100g, increase in the lactose content of +0.02 g/100g, increase in the solid-not-fat content of +0.02 g/100g and decrease in the total solid content of -0.02 g/100g. It is necessary to cool the raw cows' milk after the milking to decrease the changes in milk composition caused mainly due to the lipolytic activity of lipase.

Highlights

  • The aim of this work was to investigate how composition of raw milk changes after 24 hours of storage at temperature 4 °C

  • According to the international standard ISO 707 (2008) the raw milk should be immediately transported to the laboratory at temperature 1 – 5 °C and analysed within 24 hours after collection

  • There are several studies, which were focused on the relationship between quality of dairy products and quality of raw milk

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Summary

Introduction

The aim of this work was to investigate how composition of raw milk changes after 24 hours of storage at temperature 4 °C. According to the international standard ISO 707 (2008) the raw milk should be immediately transported to the laboratory at temperature 1 – 5 °C and analysed within 24 hours after collection. When sample refrigeration is not possible, sample must be preserved by appropriate means (Kroger, 1985). There are several studies, which were focused on the relationship between quality of dairy products and quality of raw milk. Very important factor is temperature during the storage (Bachman and Wilcox, 1990; Valík et al, 2011). Contamination of raw milk before processing is an important factor (Forsbäck et al, 2010)

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