On the efficacy of dielectric spectroscopy in the identification of onset of the various stages in lactic acid coagulation of milk

Abstract

There are five stages in acid coagulation of milk and most studies miss out on a stage or two depending on the experiments performed. Dielectric studies of milk and various physico-chemical studies on the formation of yogurt are well studied and established. However, most of the papers deal with either a limited range of frequencies in the dielectric studies and hence are unable to reflect all the mechanisms of coagulation that occur, or are done as stand-alone experiments, with no correlations to other physico-chemical processes. In this paper, we discuss the broadband dielectric spectroscopy of lactic-acid coagulation of milk, identify the various stages, and compare it with pH, zeta potential, particle size and microscopy. We establish the superiority of dielectric spectroscopy in the identification of all stages of coagulation, the indifference of the process to fat content. Further a strong correlation between tan δ and pH is seen, that is an indicator of the five different stages of lactic-acid induced coagulation. Penetration depth is calculated as milk coagulates and it is seen to be decreasing with coagulation. Broadband dielectric spectroscopy is seen to reveal the onset of coagulation much earlier than other experimental techniques discussed here.

Keywords:

• Milk coagulation
• pH
• particle size
• zeta potential
• dielectric spectroscopy
• penetration depth

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

Aswini Harindran

Aswini Harindran obtained her BSc and MSc in Physics from Kannur University, Kerala, India in 2012 and 2014 respectively. She is currently pursuing PhD in Physics from Central University of Tamil Nadu (CUTN), India.

V. Madhurima

V. Madhurima graduated from Indian Institute of Technology, Madras, India with MSc (Physics) and PhD (Physics) in 1993 and 1999 respectively. She is currently a Professor of Physics at Central University of Tamil Nadu (CUTN). She studied weak hydrogen bonds for her PhD, with emphasis on microwave dielectric spectroscopy. Her current research interest includes the study of wetting and self-assembly of liquid molecules, pattern formation by drying droplets and first principles computational studies of hydrogen bonded systems.