Retain white color in sweets

Describe in detail what is that canned sweet product..

Like methai,rasmalai. etc

Most of it are high in protein and reducing sugar so its inevitable it will brown during cooking .To minimize Maillards reaction is to reduce the substrate pH..Try adding little acidulant like citric acid during cooking just to turn the pH from slightly alkaline to very Slightly acid side.

it can also affect taste?

if adding citric acid in milk containing sweets like rasmalai it can change ph of milk as well?

In theory, not as you are forming an emulsion, but that needs to be tested if it has am impact on the taste some recipes even have lemon juice ....

sodium metabisulfite also have an ability to slow down millard reaction,so shoul i try this as well?

Just be careful as it can confer sulfurous off taste ..

try citric acid and sodiummetasulfite in combination?

You will have so much time to play with it...😉

ok ,thanks bro