Abstract
Shortwave ultraviolet (UVC) radiation is commonly used for sterilization of drinking water. However, its low transmittance within opaque liquids limits its use for milk and other liquid food products. The objective of this study was to assess the efficacy of UV pretreatment on thermal inactivation of B. subtilis spores in skim cow milk, whole cow milk and whole sheep milk. In this work, UV treatment was applied by using a coiled tube UV unit with a perfluoroalkoxy tube around a quartz sleeve containing a 254-nm UV lamp. It was observed that UV pretreatment (DAct 2.37 ± 0.126 J/ml) combined with thermal treatment at 110 °C for 30 s resulted in a reduction of approximately 6 log CFU/mL in bovine skim milk, 2.90 log CFU/ml in whole bovine milk and 1.1 log CFU/ml in ovine milk. The results showed that UV in combination with heat can possibly be an alternative to sterilization of skim milk at lower temperatures compared to ultra high temperature (UHT) treatment (135 °C, 3 s).
•Skimmed cow milk, whole cow milk and sheep milk were irradiated using coiled tube UV reactor to inactivate spores.•UV-C in combination with heat results in higher inactivation of spores.•UV-C can reduce sterilization temperature of skim milk significantly.