Stabilize emulsions and foams using barley beta-glucan.

Barley beta-glucan (BBG) is receiving increasing attention as a food hydrocolloid. As you know, hydrocolloids are added to foams and emulsions in order to increase the viscosity of the continuous phase, decrease bubble and droplet movement, and slow drainage and creaming. This results in more stable foams and emulsions.

Scientists at the University of Alberta have assessed the stability of foams and emulsions using whey protein concentrate (WPC) as an emulsifier and foaming agent, as well as BBG gum extracted at a pilot plant or on the laboratory scale as a stabilizer. Their goal was to investigate physical properties of BBG, such as surface activity and differential scanning calorimetry (DSC) behavior; to see if BBG gum can stabilize foams and emulsions alone and in the presence of WPC; to determine the influence of sugar on foam stability; and to study the effect of BBG viscosity on the stability of foams and emulsions.

The BBG gums exhibited mild surface activity, probably due to the presence of impurities, such as proteins, which are not expected to have a significant impact on the stability of foams and emulsions at the levels studied by investigators. BBG forms a reversible gel network. When WPC was used as an emulsifier and foaming agent, BBG increased the stability of foams and emulsions. Sugar increased the stability of foams only when applied with certain gums. BBG gum's foam and emulsion stabilization capability is the result of increased viscosity.

WPC had a significant lowering effect on the surface tension of water and water-oil interfacial tension, while the effect of beta-glucan was time-dependent. DSC indicated that BBG formed a gelled network, responsible for stabilizing product, that melts at 58 C to 62 C. Reversible gels of BBG melt at around 63 C. Emulsion droplet size decreased several-fold when emulsions were prepared with BBG gum. Phase separation substantially decreased as well.

Foam volume and drainage significantly improved with the addition of beta-glucan. Sugar significantly enhanced foam stability only when used together with beta-glucan. Researchers believe that BBG shows potential as a stabilizer in foam- and emulsion-type food products.

The presence of other food ingredients can affect the properties of hydrocolloids. For example, sucrose in concentrations of 20% to 50% increased the viscosity of oat beta-glucan. Higher concentrations of 65% or 75% lowered viscosity.

Further information. Feral Temelli, Department of Agricultural, Food and Nutritional Science, University of Alberta, Agriculture/Forestry Center 4-10, Edmonton, Alberta T6G 2P5, Canada; phone: [phone]; fax: [phone]; email: [e-mail].