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I had heard that raw or simply pasteurized milk does curdle if ginger is put in it before it reaches its boiling point.

Alright, so yesterday I boiled the pasteurized milk at 23:00. Room temperature was around 17 degrees Celsius.

In the morning I put in the ginger and then started boiling it, but the milk curdled! (I had put the plain tea leaves and sugar also along with the ginger).

When the milk had been boiled in the previous night, why did it then curdle with ginger in the morning?

I boiled the remaining milk separately and it was fine.

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  • please give answers w.r.t raw AS WELL AS boiled milk. Thanks. And No, no fridge was involved anywhere. Jan 14, 2013 at 5:10
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    I was making Ginger milk tea. Jan 14, 2013 at 5:17

2 Answers 2

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If you want to prevent the milk from curdling when adding ginger, you have to boil the ginger or at least add it to boiling milk.

Ginger protease (the curdling agent in fresh ginger) is rapidly destroyed at temperatures above 70°C. It does not matter if the milk has been boiled in advance if you add ginger to cold or room-tempered milk, it will still curdle.

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    If I understand what you are saying in this answer correctly, it is not that the ginger prevents the milk from curdling in general, but rather that pre-boiling the ginger specifically prevents the milk from curdling as a result of the ginger--it could still curdle from other causes such as microbial action or presence of acids.
    – SAJ14SAJ
    Jan 14, 2013 at 18:25
  • @SAJ14SAJ: Yes, that is exactly what I meant. Jan 14, 2013 at 18:36
  • I think you have your answer, @AnishaKaul -- ginger does not prevent curdling of milk. Heating the ginger above 70 C for some time prevents the ginger itself from curdling the milk, but it could still happen from other causes.
    – SAJ14SAJ
    Jan 14, 2013 at 19:02
  • Tor - helpful answer! So, curdling due to ginger is not related to preboiled or raw milk. It is related to the -temperature- of the milk! Thanks for enlightening. Jan 15, 2013 at 1:04
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    @Anisha: That was not actually what I wrote, but yes, the curdling process itself also depends on the milk temperature. The important issue however is that ginger looses its curdling capacity when heated (once) above 70°C for a few minutes. The ginger juice can then be added to cold or room-tempered milk and the milk will still not curdle. Jan 15, 2013 at 16:33
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Ginger contains an enzyme, zingipain. When milk is added to ginger juice, this enzyme breaks down proteins in the milk, leading to the formation of cheesy-looking milk curds.

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    Welcome! We explicitly exclude health and nutrition except for clearly measurable effects and food safety. Based on that, we can only leave the paragraph with the chemical explanation and will remove the rest - especially as it doesn’t answer the question.
    – Stephie
    Oct 1, 2020 at 20:56

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