Chapter 16
Aroma Release at the Nano- and Microscale: Molecules to Droplets
Downloaded by UNIV ILLINOIS URBANA on May 6, 2013 | http://pubs.acs.org Publication Date: March 3, 2009 | doi: 10.1021/bk-2009-1007.ch016
A. J. Taylor, K. Pearson, T. A. Hollowood, and R. S. T. Linforth Division of Food Sciences, University of Nottingham, Sutton Bonington Campus, Loughborough LE12 5RD, United Kingdom
Aroma release is governed by physico-chemical factors like partition coefficents which regulate the relative amounts of an aroma in the gas and food phases. While this relationship holds good for many liquid and semi-solid foods, it only applies to systems where aroma is homogenously distributed and where aroma is present in solution. The effect of length scale on aroma release in vivo and in vitro has been studied to better understand release from encapsulated systems. When aroma was incorporated into foods in alternate aromatized and un-aromatized layers, overall release was not affected due to mixing by mastication, which negated the aroma separation. In the presence of co-solutes (propylene glycol, triacetin, ethanol) aroma release from high solids gel systems was affected. The physical state of the aroma (solubilized or microdroplet) also has significant effects and may explain the aroma burst observed from encapsulated flavors.
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© 2009 American Chemical Society
In Micro/Nanoencapsulation of Active Food Ingredients; Huang, Q., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2009.
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Introduction In order for consumers to sense the aroma of a food product, volatile compounds must be released from the food and transported to the olfactory receptors located high in the nose. Flavor scientists recognize two routes for aroma transport. The first route typically occurs before eating when we sniff the food and take in the volatile compounds through the orthonasal route. The second route occurs during eating, when aroma is transported from the mouth to the receptors in the nose (the retronasal route) either by chewing actions, which pump small volumes of air into the throat, or by swallowing, when air is transferred from the mouth to the throat and then exhaled via the nose. Methodologies for measuring the aroma profiles above foods have been developed using in vitro and in vivo techniques. Orthonasal aroma profiles are often mimicked using Dynamic Headspace Dilution Analysis, in which a solution of aroma compound is first equilibrated with a fixed volume of air (the headspace) and then diluted by a known flow rate of air. The concentration in the headspace is monitored with time and a typical exponential decay is seen until the system reaches a steady state where removal of aroma is balanced by release from the solution. This type of analysis has been applied to study the changes in tea headspace aroma (/) or the effects of emulsion composition on aroma release in model systems (2) or in real food (J). To study aroma release during eating, direct monitoring of volatile compounds using mass spectrometry techniques have been used to measure the aroma profile in exhaled air from the nose (4, 5). Other workers have developed model mouths, which reduce the variability found in vivo, but it is difficult to reproduce the complex actions of saliva, tidal air flow and mastication and few systems have been validated by comparison against release in vivo (
