Biology ATP

[abcde]

AOA!
http://www.xtremepapers.net/CIE/Cambrid ... _ms_62.pdf

In the last part of the last question, are there two alternative answers? does it suggest that (a) the pH continues to fall or (b) it remains constant? These are contradictory.

 

[CaptainDanger]

Dont confuse urself... When the process goes on pH continues to fall but when yoghurt formation is complete then the pH remains constant...

I hope this helps....

 

[hElPsEeKeR15]

i didnt get it...

 

[CaptainDanger]

Read the question first...

 

[intelnehalem]

During the production of Yoghurt, the pH of milk begins to fall once the starter culture of Lactobaccillus is added. This is because Lactobacillus uses the lactose in milk for its functions(it carries out extra cellular digestion on lactose, turns it into glucose) This glucose that is obtained is used for ANAEROBIC respiration by lactobaccillus and lactic acid is released which is the main reason for the pH of milk to fall. (the acid denatures the milk proteins-casein and milk is coagulated) Once the required texture/flavour for yoghurt is obtained, the yoghurt is taken and refrigerated. When the temperature falls(due to refrigeration) the activity of Lactobaccillus ceases - enzymes dont work at low temperatures . Due to this, there is NO FURTHER COAGULATION(NO SECRETION OF LACTIC ACID) and so the pH of the yoghurt remains the same. If you take the yoghurt out of the refrigerator and keep it outside for sometime, it will become sour- pH has fallen again since Lactobaccillus is functional now
i hope you understood

 

[CaptainDanger]

Explained better... Thanks...