Determination of the distribution of water droplet sizes in butter and margarine using pulsed field gradient-NMR and confocal scanning laser microscopy : this thesis was presented in partial fulfillment of the requirements for [the] degree of Master of Science in Chemistry at Massey University

Abstract

PFG-NMR has been used to determine the distribution of water droplets in emulsions. Especially, it has been used to measure the samples with high optical dense systems and highly viscous systems Butters and Margarines). To refine the method, the optimum measuring condition was investigated. It included delay time (Δ) between the field gradient pulses, τ null (τ0), gradient strength (G), water self-diffusion coefficients (D) and sampling techniques. Under the optimum conditions the water droplet size distributions of commercial butters, experimental butters and margarines were measured. Experimental results showed that PFG-NMR is an accurate, fast method to determine the water droplet size distributions of the butters and margarines. Also, it is can be used to investigate the properties of dispersed phase in emulsions. Especially, the method is suitable not only in the laboratory but also in the factory environment. The method was able to distinguish different distributions in butters of the same water content but with different manufacturing techniques. Differences in the distributions of water droplets were also obtained when comparing butters made by the same manufacturing technique but with different water contents. To confirm the results from PFG-NMR, confocal scanning laser microscopy (CSLM) was chosen to determine the droplet size distributions and the moisture contents of samples. Comparison between PFG-NMR and CSLM shows limitations in the latter techniques and its uses are limited