Aroma Partition and Release from Soft Drinks, Jam, and Jellied Sweets
The research described in the present thesis was focused on the influence of food ingredients and structures on the partition and release of aroma compounds from model systems such as soft drinks, jam, and jellied sweets. The effects on aroma release were studied during both static and dynamic conditions, the latter by both model mouth and in-nose measurements.
Different kinds of the main ingredients sugar, acid, and pectin were added in various concentrations to a soft drink model system. The effects on aroma concentrations in the gas phase above the system were investigated during static conditions. It was shown that the specific properties of the acids were more important than the effect of pH. Unlike hydrochloric acid, citric acid and phosphoric acid reduced the concentrations of most of the aroma compounds in the gas phase. This may have been a result of the complex binding properties of these acids.
Increasing concentrations of sucrose, invert sugar, and starch syrup increased the concentrations of most of the aroma compounds in the gas phase. The increase was probably related to structuring of the water contributing to a so-called "salting out" of the aroma compounds. The sugar with more binding sites for water gave the highest aroma concentration in the gas phase.
With the exception of limonene, pectin did not influence the aroma concentrations in the gas phase above a soft drink. However, pectin was shown to lower the headspace concentrations when used together with citric acid and white syrup in concentrations and proportions needed for gel formation. The reduction was not due to the pectin concentration only, but rather to the formation of a gel network. Differences in air/gel partition coefficients for different aroma compounds could be related to differences in the gel matrices and to the specific properties of the compounds, such as functional group, polarity, carbon chain length, and volatility.
The effect of short-term storage on aroma partition between four pectin gel systems and the gas phase at equilibrium were likewise investigated during static conditions. The air/gel partition coefficients of the aroma compounds for a weak gel were reduced after 4 days, while they were unaffected in the strong gel and the viscous solution.
From the results of model mouth measurements, effects of gel strength on aroma release were also found, although factors such as mastication and saliva were of great importance in this system. Mastication increased the release of aroma compounds whereas addition of saliva decreased the release. In-nose measurements showed that mastication and swallowing increased the release of aroma compounds to the nose.
proton-transfer reaction mass spectrometry