No one knows what was in her esophagus. She could have had a bite of apple crumble on her way out. All that is known for sure is it was a small amount of food that was not analyzed. The defense used it to state an earlier TOD.
I just re-read the Massei report. The four friends remembered that they got home at about 4 pm and started preparing pizza. They each have different memories of the next events: they ate the pizza from 6-7pm. They ate the apple crumble during the movie (or maybe before).
The scientists at court disagreed on times, but combining their testimony, TOD occurred 2 to 4 hours after the last meal. The only undigested food was the fragment in the lower esophagus. If the food was undigested from that meal, you have more accuracy towards a shorter TOD from the last meal. What I don't like in the Massei report is that they take the prosecution scientist testimony and states how that could make TOD as late as midnight. I think you can't push it beyond 11pm, because even with the variability of eyewtiness testimony, I think she had to have eaten the majority of the pizza by 7pm. So, I personally think that the science of stomach contents prove a 100% likelihood between 9 and 11pm, and a 95% likelihood between 9 and 10pm.
As for the cellphone, the fact remains that the cell phone tower did cover the cottage. On some occassions it did pick up phone calls from the cottage. So you just can't use it as proof that the phone wasn't there. I personally think it was on the move at that time, but you can't prove it definitively. The fact that a weak tower picked it up and there was evidence of strange activity at the same time (misdialing) suggests it, but doesn't prove it.
EDITED TO ADD: But thanks for correcting the cell phone info. I should've just said at around 10pm someone pushed the number one key on her phone, so it auto-dialed her bank. And that at the time the cell phone was covered by a cell phone tower that weakly covered the cottage, but strongly covered the area on the way to the garden. Good catch.