3.5. Colour
Initial L⁄ of fresh sliced mushrooms was 88.5 and it decreased
slightly after 3 days, initial a⁄ was 1.2 and did not vary significantly,
and initial b⁄ obtained was 11.6 and it increased, after
3 days of storage. Browning index increased after 3 days, from
14.7 to a range of 16.1–26.3, as a consequence of a decrease in
L⁄ parameter and of an increase in b⁄ parameter. Mushrooms lost
luminosity and turn dark with decrease of L⁄, and became yellow
with increase of b⁄, with time. This discoloration was induced by
bruising, slicing, storage and physiological disorders and the very
high polyphenol oxidase (PPO) content and phenolic compounds
make them very susceptible to enzymatic browning. Browning is
attributed mainly due to the oxidation of phenolic compounds catalysed
by tyrosinase (Heard, 2002).
All factors did not show significant effect (p > 0.05) on L⁄ and
a⁄, as shown in Fig. 5. Whereas, b⁄ was significantly affected
(p < 0.05) by number of perforations and CO2 scavenger; it increased
with number of perforations and CO2 scavenger, leading
to yellowness in sliced mushrooms. Similar to firmness, it would
be recommended to use high number of replications (more than
7), for decreasing mean square residual. Browning index was significantly
affected (p < 0.05) by the number of perforations, and it
increased with number of perforations, since this allowed higher
entry of O2 and browning enzymatic reactions could occur effectively
(Lamikanra, 2002).
Table 2
Parameters values of polynomial equation for O2 and CO2
concentrations, and respective coefficient of determination.
Parameters O2 ± SE CO2 ± SE
b0 7.13 ± 0.28 10.98 ± 0.12
b1 1.24 ± 0.15 0.58 ± 0.07
b2 5.44 ± 0.15 1.39 ± 0.07
b12 0.81 ± 0.19 1.04 ± 0.08
b11 0.08 ± 0.26 0.32 ±