Production Practices and Quality Assessment of Food Crops. Vol. 1

40 Volker Böhm
5. EFFECTS OF TEMPERATURE
It has long been known that tomatoes ripened at high temperatures failed to develop
the red pigment lycopene. For example Rutger tomatoes ripened at 23.5 °C
contained 4.4 ± 0.9 mg/100 g lycopene. In contrast, using a maturation temperature
of 32.0 °C resulted in a strong reduction of lycopene contents to 0.7 ± 0.4
mg/100 g (Tomes, 1963).
Sub-optimal temperatures were investigated more recently. The authors used
the temperatures (each min./max.) 17.8/25.6; 7.2/18.3; 4.4/15.6; 2.8/13.9 °C and harvested
the tomatoes after 7/14/21 days. Figure 2 shows the concentrations of
lycopene for the different temperatures and harvesting regimens using Early Red
Chief tomatoes (Koskitalo and Ormrod, 1972).
Lycopene concentration increased with higher temperature and later harvest. In
contrast, β-carotene was not affected by the decline in ripening temperature (data
not shown).
In another study (Hamauzu et al., 1998), the effect of post-harvest storage temperature
on the conversion of 14 C-mevalonic acid to carotenes was investigated.
Pericarp sections of tomato fruits were stored at 20/30/35 °C for 5 or 10 days.
They were also incubated with 14 C-mevalonic acid for 10 hours at these temperatures.
Lycopene content was highest at 20 °C and lowest at 35 °C, while β-carotene
showed the highest concentration at 30 °C. Regarding the radioactivity, in samples
after 10 days of storage that of lycopene was the highest in sections exposed to
20 °C and lowest at 35 °C. In contrast, the incorporation of 14 C-mevalonic acid
into β-carotene was lowest in sections stored at 20 °C and highest at 35 °C. The
conversion rate of 14 C-mevalonic acid to β-carotene tended to increase with rising
storage temperature while the conversion rate to lycopene tended to decrease with
rising storage temperature. At high temperature the conversion of lycopene to
β-carotene seemed to be stimulated (Hamauzu et al., 1998).
Figure 2. Concentrations of lycopene in tomatoes ripened at different temperatures for different times
(modified from Koskitalo and Ormrod, 1972).