## 3 Results and Discussion
### Native Casein Micelle Size and Milk Gelation Properties  
Feeding system was demonstrated to have a significant effect (\(P\) = 0.013) on the size of casein micelles and the gelation properties of the mills (Table 10). All z-average size distributions showed normal, mono-modal distributions. The CONC diet milks had the largest micelle size (167 nm), which was significantly greater than that of SOYA milk (153 nm) (\(P\) = 0.011), while the micelle size of PALM milks (163 nm) was also greater than that of SOYA (\(P\) = 0.058). [PERSON] et al. (2018) reported a similar trend of effect of feeding regimen on casein micelle size, whereby cows fed an ecologically rolled barley supplement produced significantly larger casein micelles than cows fed commercial supplementary concentrates. While genetic factors are typically reported to determine the size of casein micelles, micelle size is also affected by heat treatment, which causes pH-dependent interactions between \(\beta\)-lactoglobulin and \(\kappa\)-casein (on or off the casein micelle). Such factors impact on the volume fraction and packing arrangements of interacting casein micelles. The presence of minerals, especially calcium, also affect micellar interactions through neutralization of charge repulsion-induced stability. Neither of these influences were determined in the present study but should be considered in the future.  
Alterations to casein micelle size and other characteristics of milk can be an important consideration as it has been previously demonstrated to play a significant role in the gelation properties of mills ([PERSON] et al., 2018). [PERSON] et al. (2018) showed that milk gelation was affected by pH, protein profile, casein micelle size, and lactose. Gelation of milk forms the basis for the production of stabilized, high-value dairy products such as yoghurt, cheese, and their variants. There was a significant effect between feeding systems on the gelation properties of mills (\(P\)\(\leq\) 0.01). The storage modulus of SOYA-derived mills was significantly higher than each of the other diets, storage modulus of SOYA > PALM > BEET > CONC, respectively. The CONC milk had the lowest storage modulus, significantly lower than that of PALM (\(P\) = 0.016) and SOYA (\(P\)\(\leq\) 0.01). A similar trend was observed for loss modulus measurement whereby SOYA had significantly higher scores than BEET (\(P\) = 0.003) and CONC (\(P\) = 0.001), loss modulus of SOYA > PALM > BEET > CONC.  
Gelation properties of milks can be influenced by a variety of factors including protein profile, milk composition, and stage of lactation. It seems that differences in the gelation properties observed in this study correlated with diet-induced changes to casein micelle size. Indeed, there was a significant negative correlation between casein micelle size and storage and loss modulus values (\(P\) = 0.009, \(r\) = \(-\)0.712 and \(P\) = 0.014, \(r\) = \(-\)0.686, respectively). It has been demonstrated, however, that combined changes in the casein micelle size and MFG size can influence curd firmness ([PERSON] et al., 2018). While the links between cow feeding system and casein micelle size requires further investigation, given these findings on impact of cow diet supplementation on milk gelation properties, dairy manufacturers should be aware of the types of dietary supplements used on farms and the potential implications for downstream product properties.