There are different types of yam which cannot be identified by mere look. The tubers I've bought in recent times changes from white colour to red immediately they are peeled and turn blackish afer cooking.

How can I prevent the change of color when I peel them next time? Ive tried putting them in water to no avail, Ive added salt to the water, still there was no difference . Does anybody have a clue to the solution?

if you are based oversea, let me tell you what i do. when i buy my yam, i peel it right away, wash, cut  them in cookable size (like  you want to cook them), and put them in clean storage bag. Then put them in the freezer.

to cook frozen yam, just put them in a pot and add little water.

that's how i keep my yam from spoiling. My mom don't froze hers (that is because we wack it all straight away)

Also try it this way. wrap your half yam with lynon/storage bag and put it in the fridge. i have done something like this. But don't keep your yam for like two weeks.

Thanks, Omoge. Am Naija based and I buy llike a dozen tubers at a time. I actually don't have a problem keeping them from spoiling, I handle that successfully. To prevent them from changing colour from white to red after slicing is the issue, its such a hassle, I always want that whitish/light yellow natural colour. Where are the great 'cookers' in the house nah?

When u peel the yam , just soak it in water (like d water u'll use to wash it - put each slice in water as u peel), it won't change colour, it has never failed me.

chychy:

When u peel the yam , just soak it in water (like d water u'll use to wash it - put each slice in water as u peel), it won't change colour, it has never failed me.

Eeeh. . .sis, some change colour even under water o.I think it all depend on d type of Yam itself ^abi?

The best then is to buy the amount you want to cook and cook them right away. also, Tiv yam is good.

Yes, some do change colour and all the tubers I have at the moment are the 'colour-changing' type. No qualms, I just thought there would be an 'oooold woman' in the house who would have the solution on her finger tips. Thanks Omoge, chychy and Nija_diva.

I belive the redish discoloration that results when yam is cut and exposed to air will have something to do with oxidation. I know it doesn't happen with every tuber so it may depend on the concentration of minerals (like iron) in the tuber. I doubt if there is any way of stoping the oxidation process. I hope some on will come up with something though.

When u peel the yam, soak it in water immediately. Put your pot with some water on the fire, by the time the water starts boiling add the soaked yams immediately and cover with a clean cellophane. I strongly know this should reduce the blackish colour after cooking.

Cheers! But I am not an 'oooold woman'