## 3 Results and Discussion
### Colour and Moisture Contents of Spray-Dried Anthraquinone-Loaded Casein Micelles
The chroma values of CMAQP and CMFDP were 12.13 \(\pm\) 0.5 and 12.19 \(\pm\) 0.5 (Table 1) respectively, corresponding to early Maillard reaction products in CMAQP and advanced glycation in the case of CMFDP. In CMAQP, the anthraquinones might limit the early glycation of casein micelles by forming more favorable quinones under these pH conditions (5.5). The anthraquinones-loaded CMAQP and CMFDP appeared less saturated in color, which corresponds to the binding of anthraquinones inside the hydrophobic core of the CMs and early and advanced stage of Maillard reaction as evidenced by encapsulation efficiency and zeta potential. The chroma value for CMWLAG was 22.82, representing the more intense yellowish color due to melanoidins. These results are consistent with previously reported chroma values of spray-dried reconstituted skim milk [46]. In addition, the highest chroma value in CMWLAG corresponds to the more structural changes of casein micelles and accumulation of anthraquinones on the hydrophilic terminal as a result of spray-drying and the final stage of Maillard reactions, as shown in Table 1. These changes in chroma values of the samples are similar to the trend observed previously to measure the extent of the Maillard reaction based on the fluorescence of tryptophan and advanced Maillard reaction products' AMP/Trp ratio [25]. The hue angle value is the measure of the degree of the color circle, which ranges from 0 to 360 degrees, red-purple at angle 0\({}^{\circ}\), yellow at 90\({}^{\circ}\), bluish-green at 180\({}^{\circ}\) and blue at 270\({}^{\circ}\). The hue angle of the controlled CMs was 92.81 \(\pm\) 0.34, which means it should be yellow to green; nevertheless, its low chroma C* value of 3.50 \(\pm\) 0.80 explains a very low color saturation; hence the powder appears white. The CMWLAG presents a hue angle \(H^{\star}\) of 77.88 \(\pm\) 0.27, followed by CMAQP (63.29 \(\pm\) 0.82) and CMFDP (50.79 \(\pm\) 1.22) correspond to yellow and slightly red as these values indicated that the colors of the anthraquinone-loaded casein micelles were between red (0\({}^{\circ}\)) and yellow (90\({}^{\circ}\)) as per color quadrant [47]. Standalone \(L^{\star}\)\(a^{\star}\) and \(b^{\star}\) values are not sufficient to describe the colors of powders. The overall color change is given by color difference (\(\Delta E^{\star}\)ab) in terms of spatial distance between two color points and has been used to describe the color of powdered samples in other studies [45] as all spray-dried anthraquinone-loaded casein micelles have \(\Delta E>\) 1.5. This difference described the degree of browning due to the Maillard reaction during spray-drying while encapsulating anthraquinones [48] into casein micelles as a result of spray-drying. Overall, all spray-dried anthraquinone-loaded-casein micelles exhibited low moisture contents ranging from 4.45-6.50% (<5.50%), which contributed to their high storage stability [19]. The water retained in the spray-dried casein micelles during spray-drying may be due to the water binding capacity of casein micelles and the degree of Maillard reaction. Regarding CMAQP, it exhibited the lowest moisture content with an average of 4.45 \(\pm\) 0.4. This decrease in moisture contents compared to spray-dried controlled casein micelles was due to the incorporation of anthraquinones (aloin, alocemodin, rhein) that interact firmly within casein micelles while displacing water moleculesduring spray-drying. These results aligned with encapsulation efficiencies and the smallest microstructure of CMAQP. The CMWIAG had the highest moisture content with an average amount of 6.50 \(\pm\) 0.8 due to water molecules and the condensation mechanism between the amino group of casein micelles and the carbonyl group of sugars containing aloin. Moreover, the water retained in casein micelles during spray-drying might be due to the water binding capacity of CMs, as evident from the lowest encapsulation efficiencies and larger microstructure of CMWLAG.