The last time I used slightly sour commercial curd (it usually isn't sour and was well within the expiry date) for marinating chicken. An hour or so after cooking, there were little bubbles bubbling up to the top of the curry, and I had stomach trouble after eating the chicken. But I wasnt sure if it was the curd or whether the shop owner had left the chicken at room temperature for too long or whether it was because the shop was just unhygenic.
This time too, the curd is slightly sour and I just wanted to know if it is considered safe to use slightly sour curd for marination. Or does the sourness indicate that that it has too much acid or that the curd has got spoilt and can be bad for the meat?
Update: Slightly sour curd (it's not supposed to be sour) did create a slightly sour taste in the cooked chicken, but it got masked to a reasonable extent by the spices, salt and onion flavour. The little bubbles are just a normal phenomenon I've observed even if I cook without marinating in curd. After cooking with slightly sour curd a few times, I could conclude that it is ok to use it.
Best Answer
There are types of curd* that are supposed to be sour.
If the kind you are using is not supposed to be sour, then do not use it if it is. Expiry date is not everything. How it was stored in shop plays a big part in food safety, and dairy products that soured uncontrollably are safety risk.
You can make sour dairy products in home if you know what and how you are doing, and they will be safe to eat, but that's it. If it soured not on purpose, throw it out. Maybe you can also change shop you get your food from, or send it to your local food safety agency for examination. If there is one, they can examine your curd, inspect shop, and fine shop owner if souring was due his neglect.
* Note, English is not my primary language and what word means what gets blurry when it comes to Polish-English translation.