*3.5. Color Measurements*

Fifteen biscuits were randomly selected from each batch and color measurements were performed in triplicate. The color of the biscuits was measured using an EnviSense colorimeter NH310 (EnviSense, Lublin, Poland). Color differences were recorded in the CIE L\*a\*b\* scale in terms of lightness (L\*) and color (a\*—redness; b\*—yellowness). Additionally, the total color difference (∆E) was calculated using the following formula:

$$
\Delta E = \sqrt{\Delta \mathbf{L}^{\*2} + \Delta \mathbf{a}^{\*2} + \Delta \mathbf{b}^{\*2}} \tag{1}
$$

where ∆L\*, ∆a\*, and ∆b\* are differences in the L\*, a\*, and b\* values, respectively, between the reference sample and the test sample.

The browning index (BI, Equations (2) and (3)) was calculated using the measured L\*, a\*, and b\* values as follows [51]:

$$\text{BI} = \frac{100(\text{x} - 0.31)}{0.17} \tag{2}$$

where x:

$$\chi = \frac{(\mathbf{a}^\* + 1.75\mathbf{L}^\*)}{(\mathbf{5.645L^\* + a^\* - 0.012b^\*})} \tag{3}$$
