A couple times since Lyn's diagnosis, her food tastes have changed. She doesn't realize it is happening and doesn't recognize that her tastes are changing. From Lyn's perspective, she's simply offered food that she does not like. From her perspective, she's never liked it because she cannot remember or conceive of having liked it.
Some time ago, she decided she didn't like mashed potatoes. However, she was happy to accept boiled potatoes that you squish onto her plate and top with a pat of butter and sour cream. So, Mom makes Lyn deconstructed mashed potatoes sometimes. Next, Lyn declared that she never liked chicken. This week, she expressed a strong dislike for having tomato paste in her spaghetti sauce. I'm not yet sure if this means she no longer wants any tomato based sauce on her pasta.
For years, we've commented on how limited her diet is becoming. We should anticipate that happening more. Her brain is changing and that impacts not just her ability to remember or her behavior. It also impacts how all of her body functions, including how she perceives and responds to stimuli, including food. It turns out this is pretty common.
There is no way to anticipate how her food preferences will continue to change. She may end up only content to eat from a small handful of selections. That's ok. Getting her to eat will be the more important task than providing her with widely varied diet.
How Dementia Tampers with Taste Buds
Eating Well for People with Dementia - a guide for carers (PDF)
Alzheimer's Society - Food for Thought
Alzheimer's Society - Eating and Drinking