In order to utilize rice flour in food systems with high water content, rice flour was dispersed into water to prepare a rice flour suspension and emulsion. Stability of the suspension was significantly increased by heating processes in combination with homogenization processes. The improved stability was probably due to finely dispersed rice flour particles (-10microm) and gelatinized starch granules. Since oil droplets with a size of several micrometers disperse in an aqueous phase of many real food emulsions, rice flour is expected to be utilized as a fat replacer mimicking oil droplets. Emulsions were prepared dispersing soybean oil into a rice flour suspension. The emulsion was relatively stable to oil droplet coalescence for 7 days. Starch and proteins such as 10-16 kDa prolamin adsorbed to oil droplet surfaces to stabilize the emulsion. These results suggest that rice flour is expected to be utilized as a natural emulsifier in the food industry.

A new kind of solid phase extraction (SPE), which we named in situ surfactant-based solid phase extraction (ISS-SPE), represents a simple, selective and rapid method for preconcentration and determination of manganese from food and water samples. This method has distinct advantages: extraction times are short and recoveries are high; further, we can see formation of fine particles of large specific surface and their good dispersion in the solution. In this work, a small amount of cationic surfactant, n-dodecyltrimethylammonium bromide (DTAB) was injected into the water sample containing Mn ions, which were complexed by 1-(2-pyridylazo)-2-naphthol (PAN). After shaking, a little volume of NaPF6 as an ion-pairing agent was added into the solution by a microsyringe. After preconcentration, the settled phase was dissolved in a specific volume of ethanol and then aspirated into the flame atomic absorption spectrometer by using a homemade microsample introduction system. The effective parameters such as pH, concentration of surfactant, concentration of chelating agent, concentration of ion-pairing agent and effect of salt concentration were optimized by a fractional factorial design to identify the most important parameters and their interactions, and central composite methodology was used to achieve the optimum point of effective parameters to the response. Under the optimum conditions, preconcentration of 10 ml of the sample solution permitted detection of 0.88 μg l−1 with enhancement factor of 45.6, and the relative standard deviation (RSD) for five determinations of Mn ions was 3.5%. The developed method was applied to the determination of trace manganese in various real samples with satisfactory results.