Date of Award:

2014

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Nutrition, Dietetics, and Food Sciences

Advisor/Chair:

Marie K. Walsh

Abstract

Sucrose esters have an established use in food industry as emulsifiers. Two novel lactose esters (lactose monodecanoate and lactose monomyristate) were synthesized and studied for their antimicrobial and emulsification properties. Lactose is a byproduct in cheese production and is an inexpensive carbohydrate source.

The antimicrobial activity of lactose monodecanoate (LMD) and lactose monomyristate (LMM) was tested against the growth of seven different bacteria. Both esters, when dissolved in dimethoxy sulfoxide (DMSO), proved bactericidal against Bacillus cereus, Mycobacteria KMS and Streptococcus suis. LMM/DMSO was bactericidal against B. cereus at concentrations between 1 and 3 mg/ml. LMM/DMSO was bactericidal against M. KMS and S. suis at concentrations between 3 and 5 mg/ml. LMD/DMSO was bactericidal against B. cereus and S. suis at concentrations between 1 and 3 mg/ml and against M. KMS at concentrations between 0.1 and 1 mg/ml. LMM/DMSO and LMD/DMSO were not effective in inhibiting the growth of Listeria monocyotgenes and Enterococcus faecalis.

The antimicrobial effects of LMD on the growth of Listeria monocytogenes and Enterococcus faecalis were found to be solvent dependent. LMD, when dissolved in 30% ethanol, was able to inhibit the growth of L. monocytogenes at concentration between 1 and 3 mg/ml and E. faecalis at concentration between 3 and 5 mg/ml. The growth of Streptococcus mutans and Escherichia coli O157:H7 remained unaltered in the presence of LMD/ETOH, LMD/DMSO and LMM/DMSO up to 5 mg/ml.

LMM was also analyzed for its emulsification properties. The destabilization rates and droplet size of the emulsion were determined for five consecutive days. At a concentration of 0.5%, LMM produced 20% oil in water emulsion with destabilization rate of 1.1 mm/day, which can be considered a stable emulsion. The droplet size of the emulsion was also within the range of 0-10 μm. Lower droplet size range signifies the effective work of the LMM as an emulsifier. Also the droplet size of the emulsion was found to be consistent over five days, which is indicative of a stable emulsion.

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Nutrition Commons

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