πŸ§ͺ CUBE ChatShaala Summary: 01.07.2025

Topic : Milk Curdling by Lemon Juice vs Red Chili β€” What is Real Curd?

The ChatShaala began by observing and comparing two methods of milk curdling:

1. Addition of Lemon Juice

2. Addition of a Ripped Red Chili into Milk



:microscope: Key Discussions and Observations

:milk_glass: What happens when lemon juice is added to milk?

● 4 drops of lemon juice were added to a bowl of milk.

● This caused acidification, primarily due to citric acid in lemon juice.

● Citric acid acts on:

  1. Proteins – Especially casein, a milk protein

  2. Lipids/Fats – No precipitation observed

  3. Carbohydrates – Dissolved in water

:dna: Casein and Protein Precipitation

Casein proteins in milk carry negative charges and remain dissolved in water under normal conditions.

On acidification ( pH drop ), the negative charge is neutralized, causing proteins to clump and precipitate, forming curd.

:test_tube: Molecular Understanding

:black_small_square:︎ Milk protein chains ( polypeptides ) are formed by amino acids of (Aa) with functional groups like –NHβ‚‚ and –COOH.

:black_small_square:︎ Upon acidification, ionic interactions break, causing structural collapse and aggregation of proteins.


:hot_pepper: What about Red Chili-induced curdling?

A ripped red chili was placed in milk and left for several hours.

Preliminary observation: some thickening/coagulation was noticed.

Suggests possible microbial action or leaching of acidic compounds or enzymes from the chili.

But is it the same as traditional curd? β€” This remains an open question.


:ocean: Control Observations with Oil, Water & Lemon Juice

Coconut oil and lemon juice separated into distinct layers, showing that fats don’t precipitate upon acidification.

Water layer remained separate; sugars dissolved, as expected.

This supports the idea that only proteins like casein are responsible for curd formation.


:thought_balloon: Open-ended Queries for Further Discussion:

  1. Is the milk curdled by red chili truly curd or just a precipitate?

  2. Can microbes ( like Lactobacillus ) grow on red chili skin and initiate fermentation?

  3. Is there a pH difference measurable between lemon-curdled and chili-curdled milk?

  4. What is the role of time and temperature in chili-induced milk thickening?

  5. Can ripped red chili be used to culture milk like traditional curd starters?

  6. What does the white precipitate from lemon-juice milk consist ofβ€”pure casein or a mixture?


:books: Reference


Please reflect on these questions and post your thoughts or experimental plans in the group. Let’s continue the exploration! :petri_dish::cheese:

@Arunan @KiranKalakotiR @sakshiconsultant2002 @2020ugchsncnseethala @Akantidas @akanksha @Chitralekha @SN1261 and others

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