# Impact of Fat Content and Lactose Presence on Refractive Index in Different Types of Cow Milk
## 4 Conclusions  
In conclusion, milk is primarily composed of water, proteins, fats, and lactose, with variations in different types of milk mainly attributable to differences in fat content and processing methods. Milk with higher fat content tends to exhibit a higher refractive index due to larger fat globules, which effectively bend light. Conversely, skim milk or lactose-free milk, with reduced fat content, tends to have lower refractive indices, resembling water more closely.  
Furthermore, our study successfully discerned variations in particle size and volume fraction among different types of cow's milk. This highlights the efficacy of the optical  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Type of Cow’s Milk** & \begin{tabular}{c} **Refractive Index** \\ **(Real Part)**\(\pm\) **0.0002** \\ \end{tabular} & \begin{tabular}{c} **Refractive Index** \\ **(Imaginary Part)**\(\times\) **10\({}^{-8}\)** \\ \end{tabular} & \begin{tabular}{c} **Particle Radius (a) [um]** \\ \end{tabular} & \
\begin{tabular}{c} **Volume Fraction** \\ \end{tabular} &
\begin{tabular}{c} **Extinction Coefficient** \\ \(\times\) **10\({}^{-7}\)** \\ \end{tabular} \\ \hline Whole & 1.36462 & 5.56853 & 1.5 & 0.018 & 13.3288 \\ Light & 1.35199 & 4.13283 & 1.5 & 0.013 & 9.89232 \\ Lactes-Free & 1.36455 & 11.3113 & 1.0 & 0.038 & 27.0747 \\ Lactes-Free Light & 1.36148 & 1.08914 & 1.5 & 0.0024 & 2.6096 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Change in extinction of different milks based on particle radius and volume fraction.  
Figure 7: Composition of the different types of milk.  
characterization technique in accurately classifying and differentiating between diverse cow's milk types based on their distinct and unique compositions.  
In addition, our research contributes a novel and cutting-edge methodology to the scientific community for characterizing different types of liquid samples. In this instance, we shed light on the refractive index of cow's milk for the first time, as far as the authors know, providing valuable insights that could enhance industrial processes for milk storage. Finally, this technique holds promise for analyzing the optical properties of complex samples beyond milk, offering a versatile tool for various applications across various industries.  
Received and accepted the experiment: [PERSON]; Investigation: [PERSON]; Software: [PERSON] and [PERSON]; Formal analysis: [PERSON] and [PERSON]; Writing--original draft: [PERSON]; Manuscript revision and editing: [PERSON]; Automation of experimental setup: [PERSON]. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
The data presented in this study are available upon request from the corresponding author.  
[PERSON], [PERSON] and [PERSON] would like to acknowledge the Division de Investigacion y Posgrado of Universidad Iberoamericana for the financial support in the 16 th Call proposals in 2021. Also, the authors would like to thank the employees of Starbucks (Mexico City, Arcos Bosques) for providing us with the different types of cow's milk.  
The authors declare no conflicts of interest.