Trace/small amounts in grain (the article is mostly about wheat, but also mentions barley).
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3931795/
I read through this article. I think it's pretty clear that even the trace amount of pectin compounds they detected are inaccessible during wort production and are therefore not extracted.
"To increase accessibility to pectic epitopes the sections were treated with lichenase (endo-1,3(4)-β-Glucanase) 40 U/ml (Megazyme International Ireland Ltd) overnight at 40°C and then with endo-1,4-β-Xylanase M6 (Megazyme International Ireland Ltd ) 50 U/ml overnight at 40°C in water."
"When the grain sections were incubated with both enzymes, LM20 epitopes were detected in the grain outer layers as well as in the starchy endosperm cell walls (
Fig. 1F) whereas when only one enzyme treatment was applied (lichenase only or xylanase only), no labeling was observed in the endosperm (
Fig. 1D and
Fig. 1E)."
Without the use of their highly specific combined enzymatic degradation, there hasn't been any pectin detectable in grain.
"Until now, no pectin has been reported in wheat grain. In early biochemical studies, the polysaccharide composition of wheat flour, which corresponds approximately to the starchy endosperm, was characterized and did not reveal pectin
[3],
[5]."
Man I don't like reading old articles.
The authors go through a whole litany of factors that make it difficult to extract and purify pectin from hops. In order to extract any tannins they needed to use a solution of acetone (not used in brewing, obviously). They further explain that pectin forms insoluble complexes with calcium (which serves to remove it from wort).
Then at the end of the article they conclude that their samples are impure and they did not successfully validate their method as reliable for quantitatively measuring pectin content in hops.
So, definitely neither one of these articles conclude that pectin makes its way into wort. It seems to me that they support the idea that it doesn't, although obviously not conclusively.
Thanks for the articles, interesting stuff!