Does the PH in your mouth affect taste? I’ve eaten plain whole-milk yogurt every day for over 10 yrs.  One 32 oz tub of the brand name I buy can taste sweet &amp; mild one day; sour &amp; acidic the next...or vice versa. 

I’ve complained to yogurt makers so many times; even sending batch info &amp; pics...and they’ve been so nice...thanking me &amp; sending me coupons for free yogurt. 

Now, however, I honestly think the perception of different tastes has to do with the changing chemistry in my mouth or on my tongue. Eating something sweet OR savory OR salty...that does NOT seem to matter. It’s just sour some days; sweet the next. 

What’s going on??
I'm sure you have not expericed the same thing with products other than yoghurt. It is difficult to standardize the taste and consistency of yoghurt despite of climate controlled manufacturing facilities because there are numerous factors other than just temperature. Also, the milk is not always the same despite of homogenization process.

In other words, it's not your mouth, it's the product which comes out different every time. It is also the case with artisan wines.