The Science of Foams

Proteins such as egg albumin foam in aqueous solutions when aerated. During fermentation processes such as antibiotic fermentations, inhibition of such foams is desirable, particularly with natural food-grade materials. A study was conducted to understand the effects of potato starch, green tea, black tea, grape tannin, and cured tobacco on the percent volume of foam recovery from the aeration of egg albumin. Culinary applications of this process include foam inhibition in drinks and eggbased, foamed pastry dishes.

In a quest to enhance flavor, texture and the art of food, chefs have begun to use foamed eggs, espressos, mushrooms and beetroot in their creation. For other chefs and brew masters, foam can be a hindrance as it decreases production levels. By using potato starch and grape tannin, it is now possible to increase the yield of the edible foam and decrease the amount of undesirable foam in foods and beverages.

In a quest to enhance flavor, texture and the art of food, chefs have begun to use foamed eggs, espressos, mushrooms and beetroot in their creation.

Creating foam

Foam fractionation is an inexpensive separation process in which molecules are separated from a liquid solution via hydrophobic/ hydrophilic interactions. This process is facilitated through the use of a gas, such as air, to carry foaming materials (proteins) out of the solution and into the collected foam.

When foam is collapsed into a liquid, it is called the foamate. Figure 1 shows a schematic diagram of the foam-fractionation apparatus used in this study to create foam.

Figure 1: Diagram of a laboratory batch foam-fractionation apparatus. Arrows denote the direction of air flow.

• Materials

A glass foam fractionation column measuring approximately 25cm in height, 12.4cm in width and 2cm in diameter was used to separate solutions of egg albumin containing the following: grape tannin, potato starch, green tea, black tea, and cured tobacco leaves. Air flow through the column was regulated by a gas rotameter and humidified.

• Experimental procedure

Egg albumin weighing 1g was placed onto tared filter paper and weighed using a mass balance. The measured powdered egg albumin was cut and ground into small particles by slowly pressing another piece of filter paper on the albumin sample.

The pulverized egg albumin was added slowly to a 1000mL glass flask while mixing slowly with a 1000mL of deionized water. The liter flask was rapidly shaken, while the lid was covered, to completely dissolve the egg albumin and produce 1 g/L egg albumin solution.

The solution was also produced by another method where the 1L fl ask was filled with 1L of de-ionized water. A wet glass stir bar was used to collect some of For all solution-based mixtures – green tea, black tea, and cured tobacco – 10g of leaf matter was placed onto a tared filter paper and weighed using a mass balance. The plant matter was then placed in a 250mL Erlenmeyer flask and filled with 150mL of de-ionized water.

The solution was then heated to 100 deg C and mixed thoroughly with a magnetic stir bar for five minutes. After the solution had brewed, it was allowed to return to room temperature. The solution was later filtered through student-grade filter paper and the filtrate was collected for the foaming experiment. This process was conducted for green tea, black tea and cured tobacco.

About 10mL of the solution-based mixtures were repeatedly combined with 150mL of the 1g/L solution of egg albumin. The resulting mixture was then thoroughly stirred to ensure complete dispersion.

For the solid additive experiments, 0.1g of solid, grape tannin or potato starch, was placed onto a tared filter paper and weighed using a mass balance. It was then placed in a 250mL Erlenmeyer flask and filled with 150mL of the 1g/L solution of egg albumin. The solution was thoroughly mixed to ensure complete dissociation. Foaming occurred after each mixture was stirred.

The egg albumin unit additive was placed in a glass foam fractionation column with its right outlet open. The compressed air was turned on and regulated by the rotameter to a flow rate of 85mL/min +/- 5mL/min for 30 minutes.

As the solution foamed, it was collected in a 250mL beaker. After 30 minutes, the air flow was cut off and the collected foam was allowed to settle into a liquid state. The volume of the collected foam was then measured with a graduated cylinder. This procedure was repeated three times for each solution. And a total of 15 trials were run.

Results and discussion

From the data collected, we averaged the volume of foam collected for the three trials of each material and compared the amount foam produced relative to the control. Figure 2 shows the effects of the different additives on the activation or inhibition of foam. The scaling of the graph could be used to determine a cost analysis for the production/ inhibition of foam and possibly predict the amount of foam produced for other materials.

Figure 2: A diagram on the effects of various materials on the proportion of foam produced.

There was a slight amount of error based on the temperature dependence of foam. The lab temperature varied during the experiment by +/-1.9°C. To reduce this error, the solutions were randomly run at various temperatures.

The egg albumin produced a foam volume of 20.7 mL. The cured tobacco mixture produced an average foam volume of 48 mL. The green tea mixture produced an average foam volume of 33 mL. The grape tannin and starch mixture produced an average foam volume of 7.7 mL and 12.8 mL respectively. The black tea mixture produced an average foam volume of 22.7 mL.

However, it should be noted that in the initial set up of this experiment, it was observed that if the mixed solutions were not immediately conducted, precipitates would form. If stirred, the precipitate would dissociate into the solution. The overall yields observed were lesser than those where the solution was conducted immediately.

A study was conducted to understand the effects of potato starch, green tea, black tea, grape tannin, and cured tobacco on the percent volume of foam recovery from the aeration of egg albumin.

Conclusion

For foam reduction, potato starch (38% reduction) and grape tannin (73% reduction) showed the greatest promise in the culinary field because of their efficacy at low concentration. This means that large amounts of foam could be reduced at very low cost, without affecting the integrity of the dish.

Green tea yields, when compared to that of black tea, suggest that less processed leaves might have a greater stimulating effect on the amount of foam produced. Heavily fermented plant matter like cured tobacco (130% increase) was shown to have a large effect on the amount of foam produced. That fermented plant matter could lend its essence to foam, thereby increasing the production of foam.

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