I burnt milk while boiling it. I noticed that the burnt milk on the bottom of the pan, formed a pattern that vaguely resembled the pattern of cork-cells . Why is this pattern being formed?
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$\begingroup$ Can you say how such patterns are cork-like? $\endgroup$– Robbie GoodwinCommented Oct 16, 2023 at 21:57
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$\begingroup$ @RobbieGoodwin I am just using it as a description...It does not need to exactly match the pattern found in cork cells- researchgate.net/figure/Cork-cellular-structure_fig1_26635525 $\endgroup$– Pumpkin_StarCommented Oct 18, 2023 at 7:34
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3 Answers
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Milk comprises sugars and fats, with the sugars being prone to caramelization upon exposure to heat from stovetop. You can see the developing brown color and if you scrape further, you will see burnt organic material (black). The observed markings result from bubbles that were unable to ascend to the surface and consequently became entrapped and collapsed at the base of the pan during the boiling process.
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The pattern has everything to do with the interacting of opposing forces such as in convection, combined with mass transport, precipitation, and agglomeration of particles in the fluid. The same pattern can be formed regardless of the chemistry involved and is certainly not a crystal.
See Turing patterns, which exemplify "how patterns in nature, such as stripes and spots, can arise naturally and autonomously from a homogeneous, uniform state."
https://en.wikipedia.org/wiki/Turing_pattern
Also check out a convection specific instance of pattern formation, Bénard cells, but similar: https://en.wikipedia.org/wiki/Rayleigh%E2%80%93B%C3%A9nard_convection
In this case, the bubbles form hundred/thousands of times, from the same locations called nucleation sites. Each time pushing a little more flocculated milk protein to the edge of the nucleation site. The patterns of the nucleation sites themselves are random at first and then become evenly spread by a process of symmetry breaking, where the nearby sites make it harder to form a site so they become an average distance apart, making the pattern. The physical remnants of the pattern are what you see.
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$\begingroup$ Does this convection pattern apply in this case as there is no convection happening? $\endgroup$ Commented Oct 14, 2023 at 1:08
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1$\begingroup$ What do you mean? Heating the fluid from below 100% caused convection. $\endgroup$– ZakCommented Oct 14, 2023 at 17:10
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$\begingroup$ I mean, those benard cells are formed during convection right? In this case, convection is not happening at the moment right? $\endgroup$ Commented Oct 14, 2023 at 17:16
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1$\begingroup$ @Pumpkin_Star See my update, you are just seeing them remnants of the process that formed the pattern. The bubbles physically push coagulated milk solids away from where the bubble forms. $\endgroup$– ZakCommented Oct 14, 2023 at 17:18
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If you watch carefully boiling of milk or water at lower level of pan , bubble form due to the high heat at bottom rapidly ,the shape you see there is just the result of that the cavity is result of complete evaporation of water and fats get stick to the corner of bubble shape.
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$\begingroup$ The other answer says that the indentations were formed because the bubbles collapsed. So is it because the bubble collapsed or is it because when the bubble escaped to the surface, it left behind the solid in a cavity like shape? Or can it be both? $\endgroup$ Commented Oct 12, 2023 at 15:51
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$\begingroup$ What u mean by bubble escape when their is overheating at last min there's no water to form bubble all left is that circular ring that form as remain of milk fats being pushed away at circumference.imagine like when water boil it spread hit a circular boundary of your pan . There also happen something like that. $\endgroup$– Aman kr.Commented Oct 12, 2023 at 16:39
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1$\begingroup$ Please read the answer too. That answer suggests that the bubbles collapse and form those cavities, while your answer states that the cavities are formed 'while' the bubble is being formed... There is a slight difference between these two statements, I think. $\endgroup$ Commented Oct 12, 2023 at 17:20