3.2. Effects of cooking techniques on carotenoids
The results related to carotenoids are shown in Table 3. R* values b 1
indicate a reduction, and R* values N 1 indicate an increase of the carotenoid
levels after using a particular cooking technique. A lower R* value
corresponds to a greater reduction of the pigment and vice versa.
According to the selected studies, boiling (R* = 1.01; p = 0.71),
steaming (R* = 0.96; p = 0.42) and stir-frying (R* = 0.77; p =
0.13) techniques resulted in an increase or reduction of carotenoid
levels, mainly due to heterogeneous results with high response
ratios to both increases and reductions of this pigment. Bernhardt
and Schlich (2006) found an increase of 440% (R = 5.4) on levels of
all-trans-β-carotene in broccoli after boiling for 16 min, and after
steaming for 10 min, an increase of 320% (R = 4.2) was noted. In
contrast, de Sá and Rodriguez-Amaya (2004) found a decrease of
17.5% (R = 0.825) in β-carotene levels in broccoli boiled for 5 min.
Pellegrini et al. (2010) also reported a reduction of 18% (R = 0.82)
in concentrations of β-carotene in broccoli submitted to boiling for
8 min.