Compare stability of different hydrocolloid emulsions.

Many hydrocolloids are derived from natural sources. For example, carrageenan is extracted from seaweed, gelatin is produced by the hydrolysis of proteins of bovine and fish origin, and pectin is extracted from citrus peel and apple pomace. Gelatin desserts are made from gelatin powder.

Scientists at the University of Minnesota investigated the performance of several hydrocolloids used to stabilize emulsions and diluted beverages. They used different core materials: orange oil terpenes and medium-chain triglycerides (MCTs). They tried different emulsifier levels and different storage temperatures: 25 C and 35 C.

In general, all gum acacia and modified gum acacia emulsifiers were superior in stability to modified starches at both temperatures for orange terpene-based beverages. In MCT-based beverages, similar results were seen, except one modified starch performed as well as the gum acacia products.

The hydrocolloids that were evaluated by the researchers included three gum acacias, three modified starches and one modified gum acacia from different commercial sources. Concentrated emulsions were prepared using core material weighted on a 1-to-1 basis with ester gum. These were stored at both temperatures and analyzed on days 0, 1 and 3.

On the third day of testing, the researchers made beverages from each emulsion containing a 10% sugar solution and preservatives. The pH of each beverage was 3.6. They were stored at both temperatures and analyzed weekly for four weeks. The scientists defined the emulsion stability for concentrated emulsions to include change in mean particle size and visual observations of ringing. Beverage stability was determined by the same parameters and loss in turbidity from the bottom of the bottle.

Measurements made of particle size showed that the concentrated emulsions using gum acacia and modified gum acacia with both core materials were stable over three days storage at both temperatures. Those made with modified starches were not stable. Destabilization occurred more rapidly at 35 C.

In beverages, those based on terpenes, compared with those based on MCTs, yielded smaller mean particle sizes both upon their manufacture and during storage, regardless of the hydrocolloid used. Visual observations by the scientists supported this finding. They observed ringing in MCT-based beverages after one week at both temperatures. Modified gum acacia was evaluated at both recommended and higher usage levels. Stability increased when higher than recommended levels were used.

Further information. Gary Reineccius, Department Head, Department of Food Science and Nutrition, 225 FScN, 1334 Eckles Ave., St. Paul, MN 55108; phone: [phone]; fax: [phone]; email: [e-mail].