Drinks play an important role in movies. Why does James Bond drink his Martini shaken, and not stirred? Does it show complexity of the character or does it show status in relation to the other characters in the scene and movie? According to the above video, milk also plays a significant role in the portrayal of the character in the story, and can mean different things in context of the film.
In "Catch Me If You Can" Leonardo di Caprio gets into the cockpit with the other two pilots but his age is given away due to his order of a glass of milk.
In "Rebel Without a Cause" James Dean drinks milk from a bottle to show his conflict between his maturity and his youth.
When discussing this with others, it became clear that there might be more to it than the video shows. It can be used for practical reasons too. Alfred Hitchcock could've used milk because he wanted to light up the drink in-hand to push up the contrast in the shot and milk diffused and hid the bulb the best in "Suspicion."
Why they use milk in certain stories is an interesting argument. Does it show the innocence of the child, does it give contrast between the hitman's killing spree in The Professional, and his maternal side as he looks after Matilda in the film. The video sheds light on the thinking behind how certain props are used to communicate ideas from the storyteller's perspective. It's never confirmed or stated in any way. It's rather done in a subconscious level to enhance the story's objectives.
Being a photographer and videographer it's always good to know what the directors are using as tools. What props or strange uses of drinks and food have you seen used in film lately? And do you think this video is valid or is it taking a stance that with no research? Let us know in the comments.