Adding tiny air bubbles to a gummy makes it lighter without changing its size. If the total amounts of sugar and flavoring fall accordingly, does its flavor become weaker too? In a 2021 study, strawberry-flavored model confectionery with densities reduced by 23% and 38% showed no significant differences in maximum flavor intensity or the time taken to reach that maximum.
To investigate why, the researchers measured not only texture but also aroma compounds reaching the nose during chewing and sugar released into saliva. The study explores how air-bubble structure, alongside ingredient formulation, can change the delivery of flavor.
Comparing equal volumes, not equal weights
The central question was whether adding air to a gummy-like confectionery gel could maintain sugar and aroma release and flavor over time while keeping changes in chewiness small.
Using ingredients including gelatin, starch, sucrose, and glucose syrup, the researchers varied mixing time to prepare three conditions: a standard gel, a slightly aerated gel, and a very aerated gel. The portions compared had the same volume. Their densities were approximately 1.3, 1.0, and 0.8 g/mL. In the aerated portions, the mass of gel and the total amounts of sugar and flavoring per mouthful were approximately 23% and 38% lower.
This was not a design in which 23% or 38% of the sugar was removed from a formulation per 100 g. Instead, part of a confection of the same size was replaced with air, reducing the quantity of material eaten.
Even invisible bubbles change the first bite
X-ray CT measurements showed mean bubble diameters of approximately 0.05–0.06 mm. The standard gel also contained small bubbles introduced during production, but bubbles occupied a larger volume fraction in both aerated conditions. They were widely distributed, and light scattering made the samples, especially the very aerated one, white and opaque.
A trained panel of 10 people separately rated hardness on the first bite and chewiness during continued chewing. Initial hardness decreased in both aerated gels. Chewiness, however, did not differ significantly between the slightly aerated and standard gels, while it decreased in the very aerated gel. Mechanical compression tests showed corresponding patterns.
Thus, adding air did not leave every aspect of texture unchanged. Rather, modest aeration may lower initial hardness while limiting changes in the sensation during continued chewing.
No significant difference in the strawberry-flavor peak
The same 10 people took part in the flavor evaluation, with three replicates of each condition. Numbered samples were presented in randomized order under red lighting. Participants chewed to a prescribed rhythm for 20 seconds, spat out the samples, and continued recording perceived strawberry-flavor intensity until 50 seconds.
Neither the maximum intensity of overall strawberry flavor nor the time to reach it differed significantly among the three conditions. In other words, the flavor ratings did not clearly decrease despite the smaller total amount of material.
However, finding no significant difference in a 10-person study is not the same as demonstrating strict equivalence of flavor. The assessment also concerned flavor intensity, not liking, willingness to buy, or the amount eaten.
Aroma arrives earlier in chewing
The researchers first measured release of six selected aroma compounds while stirring and melting the gels at 37°C. All compounds were released faster from aerated gels than from standard gels. However, the additional acceleration from slight to greater aeration was not significant.
The compounds also differed. The esters studied showed similar patterns, but among aldehydes, aeration accelerated the release of hexanal more than that of the more hydrophobic decanal. Adding bubbles does not necessarily change every compound in an aroma blend in the same proportion.
The researchers next tracked aroma compounds inside the nose while participants actually chewed strawberry-flavored gels. The main measurements covered four esters, including ethyl butyrate. With aeration, a larger share of the aroma released over 20 seconds appeared in the first 10 seconds. For the standard gel, approximately 44% of ethyl butyrate was released during the final chewing cycle.
On the other hand, the lower total amount of material tended to reduce maximum in-nose aroma concentrations. An interesting feature of the study is that peak compound concentrations did not correspond simply to the maximum intensity of perceived strawberry flavor.
Checking sugar delivery and sweetness too
Sucrose in saliva was measured by swabbing the tongue surface during chewing and after the gel was spat out. This measurement used a separate procedure in which the samples were wrapped in a thin cloth to prevent large gel fragments from sticking to the swabs.
Even though each mouthful contained less sucrose overall, the maximum concentration in saliva did not differ significantly. When sweetness alone was assessed using unflavored gels, both aerated conditions produced significantly higher maximum sweetness intensity, with no significant difference in time to peak. Thus, sweetness itself changed in a test separate from the overall-flavor assessment.
The authors explain that bubbles in the gel fragments produced by chewing increase the surface area in contact with saliva, making it easier for aroma compounds and sugar to escape. The release results fit this explanation, but only four aroma compounds were tracked inside the nose. Whether the other compounds in the commercial flavoring behave similarly requires further investigation.
Summary
Adding bubbles to equal-volume gummy-like confections produced no clear differences in maximum strawberry-flavor intensity or time to peak, despite reducing the total sugar and flavoring in each mouthful. Aroma release shifted toward the earlier part of chewing, maximum salivary sucrose concentration did not fall significantly, and maximum sweetness intensity increased in unflavored gels.
For texture, even slight aeration reduced initial hardness, whereas a significant decrease in chewiness appeared with greater aeration. Adjusting the amount of air, while considering when aroma and sugar arrive, offers a clue to designing products that balance flavor and texture.
The research was supported by BBSRC grant BB/P504932/1 and a CASE studentship from Nestlé PTC Confectionery. At the time of the study, coauthor Daniel Festring was affiliated with the company’s confectionery technology division. The authors declared no known competing financial interests or personal relationships.
Reference
Su K, Festring D, Ayed C, et al. Reducing sugar and aroma in a confectionery gel without compromising flavour through addition of air inclusions. Food Chemistry. 2021;354:129579. doi:10.1016/j.foodchem.2021.129579
