What causes hardened pulp in tangerines?

[orangedays]

Does anyone know what causes citrus pulp to harden like in this picture?   Here is an example of three fruit from Changsha tangerine.  The one in the middle is intermediate between juicy and hard.  The fruit appear normal in all the other ways and  make seeds that look normal. I cannot tell which ones will have hard pulp by looking at the fruit. Only when opened up is it possible to tell.

[SoCal2warm]

Typically I see that when citrus fruits are not at their freshest.
Have you been having cold dry winds? That might be drying out the inside of the fruits.

Also it is known that Changsha doesn't really have the highest fruit quality, but I don't know if that translates into what you are seeing here.
This variety might be more vulnerable to this phenomena of inner drying out, that is a possibility.

Maybe if you've already been having freezes and the fruits have been hanging on the tree too long.

[orangedays]

The problem does seem to get worse over time. But it starts before we get night time lows in the 30. It may be age and cold weather as you say.  This is late to harvest the Changsha. They turn orange by October and then hang on the trees for a long time before they drop. The trees have been doing this for years and still look good and bear heavily every year. 
Interestingly the flavor  has gotten much  better over time.  When they first started bearing the taste was very watery and not worth eating given all the seed. They have much better flavor this year as good as the Owari but they lack enough acid to make a great tasting juice. That is how I mainly use them.  I can mix the juice with a calamondin or lemon to improve the acid balance. 

[Galatians522]

I have seen this on a lot of different citrus. I think it is part of being over ripe. Some citrus holds well on the tree and some does not. I think variety, rootstock, and water play into it. Navels and some tangerines are really prone to it. Fruits that are naturally less juicy will be the most susceptible I think. Juice oranges rarely have that issue unless they hang on the tree for a looooong time. In July (4-5 months after they ripened) the top half of a Valencia might start to dry out (if it has not dropped). In contrast, a Navel might start drying out in December (just a month after they ripened). I can't say about Changsha (since I have no experience picking them), but with Navels the larger fruit have a higher chance of being "pithy." I learned this the hard way while picking a couple bushels of Navels. I was picking all the biggest fruits I could find, and the old guy I was with was picking all these smaller fruits. I didn't know why until we got home and half of mine were dried out. Every one of his was still good. Lesson learned! 

[Citradia]

Freeze damage. They freeze on inside then dry out.

[orangedays]

I found some information on this phenomenon.  Its called granulation and apparently many things cause it to happen. age, cold, heat, too much water, too little water, fertilizers, fruit size, cultivar, etc etc etc.  But it seems not to be caused by disease.

https://www.biotecharticles.com/Agriculture-Article/Granulation-A-Major-Threat-in-Citrus-Production-3794.html