2.4.2. Determination of Colour and pH

The change in the colour of the AL was determined by means of the colour index (CI), which is defined according to Equation (1) [30].

$$\text{CI} = \frac{\text{SAC}\_{436}^2 + \text{SAC}\_{525}^2 + \text{SAC}\_{620}^2}{\text{SAC}\_{436} + \text{SAC}\_{525} + \text{SAC}\_{620}} \tag{1}$$

Spectral absorbance coefficients (SAC) are defined as the ratio of the values of the respective absorbance over the cell thickness. The absorbances were measured at 436, 525 and 620 nm using a UV/vis spectrophotometer (Thermo Scientific, Heλios γ). The value of pH was measured by means of a pH-meter (Basic-20 Dilabo).
