Date of Award:

5-2013

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Nutrition, Dietetics, and Food Sciences

Department name when degree awarded

Nutrition, Dietetics, and Food Science

Committee Chair(s)

Marie K. Walsh

Committee

Marie K. Walsh

Committee

Robert Ward

Committee

Silvana Martini

Committee

Bradley Kropp

Committee

Daren Conforth

Abstract

A major class of synthetic emulsifiers used in food is sucrose esters. However, the use of lactose esters in foods is not very well known. Lactose monolaurate was characterized in our laboratory with respect to its antimicrobial, emulsification and fat crystallization modifier properties. The benefits of this study were multifold. A single compound was explored for multiple functionalities. Enzymatic synthesis and characterization of lactose monolaurate was carried out in the laboratory using food grade solvents. This process utilized lactose, a major byproduct of the dairy industry which is cheaper than sucrose.

In the first study, lactose monolaurate was explored for its antimicrobial properties against Gram-positive and Gram-negative food pathogens. Although, it was not an effective bacteriostatic or bactericidal agent against Gram-negative bacteria, it showed both properties against Gram-positive bacteria. In our studies conducted, LML showed antimicrobial activity especially against Listeria monocytogenes, a notorious food pathogen which is the third largest source of food borne illness in the United States. It also showed antimicrobial properties against Mycobacterium tuberculosis. The antimicrobial property was exhibited by LML in media, and its mechanism of action on the bacteria and its effect, if actually used in foods, remains yet to be explored.

The synthesis of lactose monolaurate was also explored in greater detail with respect to lactose solubility and enzyme activity in various solvents. It was concluded that the yield of this compound was dependent more on the enzyme activity than the solubility of lactose in the used solvents. The synthesized lactose monolaurate was evaluated for its emulsification activity in 20% oil-in-water emulsions. The results indicated that it was comparable to commercially used food grade emulsifier, sorbitan monolaurate (polysorbate-20).

It is well known that the use of emulsifiers in bulk fats affects the crystallization properties of bulk fat. It was seen that the use of lactose monolaurate in anhydrous milk fat led to a significant delay (p < 0.001) in induction time at 31°C, and created less viscous fat. On use of high intensity ultrasound during the process of crystallization, the viscosity of the bulk fat could be restored.

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