156 Produce Degradation: Reaction Pathways and their Prevention
6.4 Factors Influencing Flavor and Flavor Stability .......................................... 168
6.4.1 Temperature...................................................................................... 169
6.4.2 Ethylene............................................................................................ 169
6.4.3 Controlled and Modified Atmospheric Storage............................... 170
6.4.3.1 MAP of Fresh-Cut Fruits and Vegetables ........................ 171
6.4.4 Aroma Modification by Exogenous Volatiles.................................. 172
6.4.5 Coatings and Wraps ......................................................................... 172
6.4.6 Curing............................................................................................... 172
6.4.7 Irradiation ......................................................................................... 173
6.4.8 Off-Flavor and Taints ....................................................................... 173
6.4.8.1 Anaerobiosis and Off-flavor Development....................... 173
6.4.8.2 Ethylene-Induced Off-Flavors .......................................... 174
6.4.8.3 Sanitizers and Chemical Treatments ................................ 174
6.4.8.4 Microbial Sources ............................................................. 175
6.5 Conclusions .................................................................................................. 175
References.............................................................................................................. 175
6.1 INTRODUCTION
The flavor of a food is an important quality attribute and is often the sole reason
why a product is accepted or rejected by the consumer. Food flavor is linked to
culture and plays a predominant role in the lives of all human beings. The term
flavor is actually the combined or integrated perception of aroma (odor) and taste,
and to a lesser extent pain or nerve response (e.g., heat of capsaicin, astringency of
tea, cooling of menthol, etc.), texture and mouth-feel, and overall appearance. It is
sometimes difficult to differentiate between aroma and taste as being two separate
physiological senses since they are often (i.e., during eating) perceived simulta-
neously. Of these two senses, the perception of aroma is undoubtedly the most
complicated. Most people can distinguish thousands of individual aroma impres-
sions, while there are only four (or five, i.e., umami) basic taste qualities.
Fruit and vegetable flavors are composed a wide range of chemical compounds,
from nonvolatile taste-active (including both inorganic and organic compounds) to
volatile aroma-active organic molecules. Most often it is the aroma components that
are the predominant contributors to the distinctive flavor of fruits and vegetables. It
is this reason that most flavor research has focused on the study of the occurrence
of volatile aroma components, including their origin through biosynthetic or other
chemical reactions.
Before delving into the chemistry and biochemistry of the various types of fruit
and vegetable flavor systems, it is worthwhile to spend a moment on some basic
aroma terminology. First, it must be made clear that not all volatile compounds have
perceivable odors when present in specific food products. While it is possible to
identify hundreds of volatile compounds in a single food product, only a few of
these may actually be “aroma-active” and, therefore, contribute substantially to the
overall flavor. Often a volatile compound has a detectable odor at very high con-
centration but cannot be detected at the low level at which it is found in a food