3.8. Browning index
Generally browning index is considered as an indirect measurement
of the contents of pigment compounds produced from browning reactions
(Trugo & Macrae, 1986) and it is well known that the browning
of roasted foods is mainly caused by Maillard reactions (Ozdemir &
Devres, 2000). The content of browning index of peanut kernels before
roasting was 0.156 nm and roasting process led to increase browning
index on peanut kernels (Fig. 5). The results of our research showed
that with increasing IR power and time of roasting, the BI of samples increased.
The effect of temperature on BI value was not significant.
The correlation coefficients showing the relationship between BI
(abs at 420 nm) and BI (color parameter is also presented in Fig. 6. It
shows a good correlation coefficient (r2 = 0.82) between BI (abs at
420 nm) and BI (color parameter). BI (color parameter) development
is generally used as a method for measuring degree of roasting because
it is a quick, easy and nondestructive testing method, as well as being an
indicator of final peanut flavor but BI (abs at 420 nm) is a destructive
testing method and is expensive. This positive correlation demonstrates
that BI (color parameter) can be used to control roasting with low cost
and without any destruction in roasted peanut kernels.