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PhD Food Science

Pankaj Sharma

Pulsed electric field pasteurisation and the impact on the functional properties of bovine whole milk

Supervisors: David W. Everett and Professor Indrawati Oey.


Pankaj started his research journey as a Food Technologist at the Central Food Technological Research Institute, India in 2006. Later he moved to the research and development of Unilever Foods, India in 2008. He was also awarded Senior Research Fellowship by Council of Scientific and Industrial Research, India before starting his PhD at the University of Otago in 2011. He loves playing cricket and chess and likes discussion on trends in the food industry.

Project Outline

Thermal pasteurisation of milk is practiced in dairy plants to ensure safety of consumers by killing harmful bacteria that may be present in raw milk. Concerns about heat-induced adverse changes in raw milk and consumers’ demand for untreated or fresh-like product attributes have led to the development of non-thermal and minimal processing techniques. Pulsed electric field (PEF) processing is a promising approach to kill harmful bacteria. The effectiveness of PEF to inactivate bacteria is affected by the composition of the treatment media. Hence, the study on the efficacy of PEF to inactivate bacteria in whole milk, where the presence of fat or proteins can provide protection against bacterial inactivation is essential. Moreover, PEF processing has still not made its debut to the dairy industries perhaps due to the lack of knowledge on the impact of electric fields on the product quality and functional attributes.

In the present study, the effectiveness of PEF treatment against the inactivation of Gram-negative (Pseudomonas aeruginosa and Escherichia coli) and Gram-positive (Staphylococcus aureus and Listeria innocua) bacteria inoculated into raw milk was assessed. Gram-negative bacteria were less resistant to PEF treatments than Gram-positive bacteria. PEF treatments in combination with the pre-heating of milk were found to be effective at reducing bacterial numbers to below the detection limit . The comparable inactivation of bovine alkaline phosphatase after PEF pasteurisation to that of thermal treatments was defined as a pasteurisation indicator.

This study revealed that PEF treatment combined with pre-heating has the potential to pasteurise whole milk. The activities of plasmin and xanthine oxidase, as well as lipolysable fat, were partially reduced suggesting the suitability of PEF pasteurised milk for making dairy products such as cheese where the presence of enzymes is desirable for flavour development. PEF-induced changes led to less damage to the milk fat globule membrane and changes to the protein composition compared to the thermal treatments of whole milk.


Sharma, P., Oey, I., Bremer, P., and Everett, D. W. (2014). Reduction of bacterial counts and inactivation of enzymes in bovine whole milk using pulsed electric fields. International Dairy Journal, 39, 146-156.

Sharma, P., Oey, I., and Everett, D. W. (2014). Effect of pulsed electric field processing on the functional properties of bovine milk. Trends in Food Science & Technology, 35, 87-101.

Sharma, P., Bremer, P., Oey I., and Everett, D. W. (2014). Bacterial inactivation in whole milk using pulsed electric field processing. International Dairy Journal, 35, 49-56.

Subramanian, R., Chandini, S. K., Sharma, P., (2014). Membrane clarification of tea extracts. Critical Reviews in Food Science & Nutrition, 54, 1151-1157.

Sharma, P., Singh, V., and Subramanian, R. (2012). Pasting, swelling, and solubility characteristics of rice batter prepared from different wet grinding systems. Starch/Stärke, 65, 374-381.

Garg, S., Sharma, P., Jayaprakashan S. G., and Subramanian R. (2009). Spray evaporation of liquid foods. LWT Food Science and Technology, 42, 119-124.

Sharma, P., Chakkaravarthi, A., Singh, V., and Subramanian, R. (2008). Grinding characteristics of rice and energy assessment in different wet grinding systems. Journal of Food Engineering, 88, 499-506.