*2.3. Colour Measurements*

Juice colour was measured using a Digieye colour measurement system (Verivide, UK). For each juice sample, L\*, a\* and b\* parameters from CIELAB scale were measured. Total colour difference ΔE between untreated and treated juice samples and browning index (BI, for apple juice only) were calculated by equations (1) and (2), respectively. It has to be stated that the untreated juice showed a high degree of colour change due to oxidation and enzymatic browning. Hence, larger ΔE values, i.e., larger deviations from the untreated juice represent the preferred colour for high-quality juices.

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

$$BI = \frac{\left[ (100 \text{(x} - 0.31) \right]}{0.172} \tag{2}$$

where:

$$\mathbf{x} = (a + \mathbf{1}.\mathbf{75L}) / (5.645L + a - \mathbf{3}.\mathbf{012b}) \tag{3}$$

The colour analyses were carried out in fifteen repetitions from each carrot and apple juice sample.

#### *2.4. Antioxidant Activity (DPPH and ABTS Method)*

The carrot and apple juices were centrifuged for 15 min at 10000 × g in a centrifuge (Eppendorf, Germany). The supernatants were for the antioxidant activity analysis by two methods, DPPH and ABTS.

The DPPH scavenging activity was evaluated according to [22]. A spectrophotometer (Photometer model U-1100, Hitachi, Ltd. Tokyo, Japan) set at wavelength of 517 nm was used to measure the absorbance. Quantification of the antioxidant activity was made by plotting a Trolox calibration curve (r2 = 0.9880), and the results were expressed as mmol Trolox/L of juice.

The ABTS+▪ scavenging activity was carried out as described by [23]. The absorbance was measured with a spectrophotometer (Photometer model U-1100, Hitachi, Ltd. Tokyo, Japan) at 734 nm for a total time of 6 min. The results were expressed as mmol Trolox/L of juice by the quantification with Trolox standard curve (r<sup>2</sup> = 0.9946).

The values obtained are the average of three replicates from each juice sample.
