The colour of the bread crust showed a significant decrease (p < 0.05) in L values of supplemented bread while there was significant increase in a (redness) and b(yellowness) values with increasing levels of SF.
The colour became darker as the SF level increased because of the Maillard browning reaction caused by the reaction between wheat proteins and the added sugar and caramelization which are influenced by the distribution of water and the reaction of added sugars and amino acids (Kent and Evers, 1994).
Colour is a very important criterion for the initial acceptability of the baked product by the consumer.
Moreover, as the development of colour occurs classically during the later stages of baking, it can be used to judge completion of the baking process.
Surface colour depends both on the physico-chemical characteristics of the raw dough (i.e. water content, pH, reducing sugars and amino acid content) and on the operating conditions applied during baking (i.e. temperature, air speed, relative humidity, modes of heat transfer) according to Zanoni et al. (1995).
Similarly, it was observed that the crumb colour significantly (p < 0.05) increased in redness (a value) and yellowness (b value) but decreased in L value with higher percentage of SF supplementation.
This might be attributed to the colour imparted by the black sesame flour. In general, L (lightness) was higher in the crumb compared to crust; however, a (redness) and b (yellowness) values in crust were higher than crumb which indicates the browning effect in agreement with values reported by Jusoh et al. (2012).