Impact of low refrigeration temperature on colour of milk

The purpose of this study was to investigate the effect of low refrigeration temperatures on bacterial numbers that affect the colour in fluid pasteurised skim milk. Standard plate count increased at 2 and 5 °C with increasing storage days. Bacterial numbers were within the acceptable level at 2 °C until 17 days, beyond the shelf-life of 14 days compared to 5 °C. The decrease of pH in milk was observed with increasing bacterial numbers at both temperatures. The change of colour in the milk was determined using a colorimeter. Values of L* gradually started to change with increased storage days. The negative values of Hunter a* provided the evidence of green and the positive values of Hunter b* indicated the yellow colour in milk samples at the end of the storage day. Results showed increased bacterial numbers were correlated with the values of L*, a*, and b* obtained from the colour measurement. This study showed that even low refrigeration temperatures do not prevent microbiological, chemical, and sensorial changes in milk during storage, however, such changes are slowed down