Produce Color and Appearance 195
influenced by genotype and numerous other factors (Heinonen, 1990). In a recent
study by Surles et al. (2004), carotenoid profiles of specialty carrots were determined
and compared with consumer acceptance. The amounts of alpha-carotene, beta-
carotene, lycopene, and lutein were determined in the following six carrot varieties:
high-beta-carotene orange, orange, purple, red, yellow, and white. Beta-carotene
content ranged from 18.5 to 0.006 mg/100 g of fresh carrots. Sensory evaluation
showed that high-beta-carotene orange and white varieties were favored.
While anthocyanins and related compounds contribute to the color of wines,
carotenoids are considered to be important precursors of compounds influencing
aroma. The qualitative and quantitative composition of carotenoids in mature grapes
is influenced by variety, soil, and climate (Razungles et al., 1988; Marais et al.,
1989; Guedes de Pinho et al., 2001). Mendez-Pinto et al. (2004) analyzed carotenoids
in grapes of three port winemaking varieties of Vitis vinifera L., cv. Tinta Barroca,
Touriga Francesa, and Tinta Roriz. Twenty-eight compounds were found in extracts
of all three cultivars utilizing reversed phase and normal phase HPLC-DAD. Seven
previously reported carotenoids (neochrome, neoxanthin, violaxathin, flavoxanthin,
zeaxanthin, lutein, and beta-carotene) were identified. A new type of neochrome and
two geometrical isomers of lutein and beta-carotene were tentatively identified. The
remaining 17 compounds need to be analyzed further for identification.
7.2.3 POSTHARVEST DEGRADATION
Degradation of carotenoids in produce may be a part of natural biological senescence
or may occur as a result of postharvest commercial handling, packaging, processing,
storage, and food preparation. Due to the large number of conjugated double bonds
in carotenoids these compounds are susceptible to various biochemical and chemical
changes.
The enzymatic oxidation of carotenoids is an important aspect of carotenoid
degradation in nature and in commercial postharvest handling, storage, and process-
ing of produce. As early as 1932, Andre and Hou gave the name lipoxidase to the
enzyme from soybeans responsible for bleaching carotenoids in bread dough (Gross,
1991). Subsequently it was demonstrated that oxidation of carotenoids occurs when
lipoxygenase simultaneously oxidizes unsaturated fatty acids. The presence of
lipoxygenase in produce was reported by Pinsky et al. (1971). Eskin et al. (1977)
isolated lioxygenase from various food plants. According to Robinson et al. (1995),
co-oxidation of carotenoids occurs as a result of the action of an activated form of
lipoxygenase. Several volatile compounds, including beta-ionone and beta-ionone
epoxide, were identified as a result of bleaching with soybean lipoxygenase (Grosch
et al., 1977). There is only limited information available on the nonvolatile products
formed by co-oxidation of carotenoids. Wu and Robinson (1999) reported tentative
identification of several nonvolatile compounds generated by lipoygenase-catalyzed
co-oxidation of beta-carotene, including apocarotenal, epoxycarotenal, apocaroten-
one, and epoxycarotenone. GC/MS and HPLC combined with photodiode array
detection allowed determination of a large number of high-molecular-weight com-
pounds. The authors proposed a mechanism that involves random attack along the