Submitted to: Journal of Food Science and Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/27/2008
Publication Date: 2/5/2009
Citation: Mikkonen, K.S., Tenkanen, M., Cooke, P.H., Xu, C., Hannu, R., Willfor, S., Holmbom, B., Hicks, K.B., Yadav, M.P. 2009. Mannans as stabilizers of oil-in-water beverage emulsions. LWT - Food Science and Technology. 42:849-855. Interpretive Summary: The need to add value to the by-products obtained from agricultural processing and mechanical pulping of wood has prompted us to develop new uses for these materials. In this study we evaluated the ability of extracts of these byproducts to serve as flavor stabilizers for soft drinks. Natural flavors in soft drinks are usually derived from essential oils that are not soluble in the water based drinks unless stabilizers are added. These stabilizers are polymers with the ability to bind oil-based flavors and keep the tiny flavor droplets dispersed in the drink. The natural polymers arabinoxylan and galactoglucomannan are prepared from the low value by-products of the corn wet milling process and spruce mechanical pulping, respectively. In the present work we show that these plant polymers can associate with oil droplets, stabilize the oil in water emulsion, and prevent the oil from floating to the top. To see the effect of temperature, the experiments were done at different temperatures and it was found that higher temperature decreases the flavor stabilizing capacity of these polymers. The flavor stabilizing capacity may depend on the polymers chain length. To study this effect, the polymers were made in different chain lengths and their stabilizing capacity was studied. It was found that by decreasing the chain length of the stabilizer, its flavor stabilizing capacity decreased. These findings will be useful for commercial manufacturers who are trying to develop a new commercial product based on corn fiber and byproducts obtained from spruce pulp milling industries. Commercialization of these materials will provide new uses for agricultural by-products and more revenue for farmers, processors and manufacturer's of agricultural and forestry products.
Technical Abstract: The stabilizing effect of spruce galactoglucomannan (GGM) on a model beverage emulsion system was studied and compared to that of guar gum and locust bean gum galactomannans, konjac glucomannan, and corn arabinoxylan. In addition, enzymatic modification was applied on guar gum to examine the effect of the degree of polymerization and the degree of substitution of galactomannans on emulsion stability. Use of GGM increased the turbidity of emulsions both immediately after preparation and after storage of up to 14 days at room temperature. GGM emulsions had higher turbidity than the emulsions containing other mannans. The initial turbidity increased with increasing GGM content, but after 14 days´ storage at room temperature, the turbidity was the highest for GGM/oil ratio of 0.10:1 when ethanol-precipitated GGM was used. Increasing the storage temperature to +45 degree C led to a rapid emulsion breakage, but a decrease in storage temperature increased emulsion stability after 14 days. Confocal microscopic study showed that the average particle size in the bottom part of GGM emulsions stored for 14 days was smaller than 1 micrometer. Low degree of polymerization and high degree of substitution of the modified galactomannans were associated with a decrease in emulsion turbidity.