Date of Award:


Document Type:


Degree Name:

Doctor of Philosophy (PhD)


Nutrition, Dietetics, and Food Sciences


Marie K Walsh


There is a constant need of new synthetic emulsifiers in the food industry. Sugar esters are widely used as food grade synthetic emulsifiers, amongst which sucrose esters are the most common. Although sucrose esters are used very frequently, little is known about the use of lactose esters in food. There is a need for characterization of lactose esters before they can be used in foods. The objective of this study was to characterize a lactose ester, lactose monolaurate (LML) as an antimicrobial agent on food pathogens, evaluate its effect on 20 % oil-in-water emulsions as an emulsifier, and to explore its effect on crystallization behavior of anhydrous milk fat. In the first study (Chapter 3), the effect of LML was evaluated on survival of some Gram-positive and Gram-negative bacteria. For Listeria monocytogenes, a concentration of 1 mg/ml showed some inhibition in growth media whereas the cells were completely killed at 5 mg/ml. For Mycobacteria, an LML concentration between 0.1-1mg/ml was lethal. Scanning electron microscopy was also conducted to examine any changes in the morphology of cells. Listeria exhibited a change in morphology and a wrinkling effect was shown in Mycobacteria. In the second study (Chapter 4), the effect of LML as an emulsifier was evaluated in 20 % oil-in-water emulsions. The use level of LML was comparable to commercially available emulsifier polysorbate 20, and produced comparable stabilization in the emulsions upon use. In this study, an attempt was also made to optimize the synthesis of LML with respect to the immobilized enzyme and solvent combination. It was concluded that for 20 % oil-in-water emulsions, LML is a promising emulsifier at 0.5%. In the third study (Chapter 5), the effect of LML was evaluated at two concentrations on the crystallization behavior of anhydrous milk fat at two temperatures with high and low supercooling. On application of high intensity ultrasound (HIU) to anhydrous milk fat (AMF) at 31°C and 0.05 % LML the effect on viscosity of sample and crystallization behavior was evaluated. It was concluded that the viscosity of AMF decreased with the addition of 0.05% LML. The lower viscosity of anhydrous milk fat on addition of LML could be restored with the application of HIU.