Formation of Carotenoid Oxygenated Cleavage Products - Carotenoids: Physical, Chemical, and Biological Functions and Properties - page 224

It should be noted that partial or total organic synthesis was used to produce carotenoid oxygen-
ated cleavage products such as, for example, apo-8 -lycopenal (Surmatis et al. 1966).

The ready availability of carotenoid oxidation products through chemical methods will facilitate
their use as standard identii cation tools in complex media such as biological l uids, and it will
enable in vitro investigation of their biological activity. Moreover, these studies can help in under-
standing the mechanisms by which carotenoids can be either chemically or biochemically cleaved
in vivo .

′

11. 5 FORMATION DURING FOOD PROCESSING
OR MODEL FOOD SYSTEMS
Elevated temperature is the main factor affecting the integrity of carotenoids during food processing.
Numerous studies have been made in order to quantify carotenoid degradation, some of which
analyzed the products formed in detail, commonly oxygenated cleavage compounds. A review on
the thermal degradation of carotenoids, which produces volatile and nonvolatile compounds, was
published by Bonnie and Choo (1999). Some articles mentioned in this chapter dealing with carote-
noid oxygenated cleavage compounds are discussed here along with other articles published at that
time.
Thermal treatments generate not only oxygenated cleavage compounds of carotenoids but also
oxidation compounds that do not necessarily undergo a cleavage reaction of the hydrocarbon chain,
such as epoxides or furanoxides of the parent carotenoids, most often in positions 5,6 and 5

,
because the electron density of the double bonds is the highest at the extremities of the conjugated
carbonated chain. Their rearrangement products possessing 5,8- and 5

′ ,6 ′

-furanoxide groups can
also be found. These compounds can be generated from a 5,6-epoxy-carotenoid, itself produced
from a nonepoxy carotenoid during the thermal treatment (Kanasawud and Crouzet 1990a,b), or
from a 5,6 (5

′ ,8 ′

)-epoxy-carotenoid already present in the product before heating (Dhuique-Mayer
et al. 2007). Thermal treatments can also transform carotenoids into compounds formed by cleav-
age of the polyenic chain followed by a rearrangement, by means of a radical mechanism (Edmunds
and Johnstone 1965), without the introduction of an oxygen atom.
The degradation of

′ ,6 ′

-carotene during different heat treatments and extrusion cooking, a widely
used processing technique in the food industry, has been studied by Marty and Berset (1988, 1990).
Several apocarotenals were identii ed by HPLC together with

β

-carotene epoxides in E and Z forms.
The authors of the articles propose that chain breaks progress from the end of the molecule to the
center with increasing strength of the treatments since the longest chain compounds (apo-8

β

′ - and

apo-10 -

carotenals) were obtained for the more severe treatments, except for the shortest compound, i.e.,
apo-15-carotenal, which was detected for each heating treatment. Thus, a direct attack on all double
bonds, and particularly on the central C15

′ -carotenals) were obtained for all treatments, whereas shorter ones (apo-12 ′ - and apo-14 ′

, cannot be excluded.
These results are coni rmed by two studies on the effect of high temperatures (170°C -250°C)
used for the deodorization of palm oil, which led to the oxygenated cleavage of

= C15 ′

β -carotene, form-

ing apo-13-carotenone, apo-14 - and apo-15-carotenals, i.e., relatively short chain length apocaro-

tenoids (Ouyang et al. 1980). A “dioxetane mechanism” was suggested to explain the formation
of these products. The effects of similar treatments applied to palm oil deodorization for deep
frying were tested on

′

-carotene by Onyewu et al. (1986) After 4 h of heating at 210°C, more than
70 nonvolatile compounds were detected: 7 of them were identii ed, including 2 apocarotenoids
(apo-13-carotenone and apo-14-carotenal). Other products included hydrocarbons of shorter chains
formed from cleavage and rearrangement reactions, but without the addition of oxygen atoms. Three
volatile compounds were also identii ed.
Most of the studies on the thermal degradation of carotenoids analyzed the volatile fraction, as
the identii cation of nonvolatile fractions was probably more complex to analyze. A study was pub-
lished recently on the volatile compounds generated by the thermal degradation of carotenoids in

β