When it comes to pairing specific ingredients, the general thinking seems to be that ingredients that share "flavour notes" in significant quantity will go well together.
In practice it goes much deeper than that, because in addition to taste, foods have very specific and recognizable aromas which affect the perception of flavour; wine is mostly sweet and sour, but you wouldn't substitute ordinary grape juice for it; the aroma of the alcohol is unmistakable, and even between different wines you will have varying levels of "fruitiness" or "woodiness".
But let's start with tastes:
Chocolate and coffee go well together because they share characteristic bitter notes. The roasting of the beans also makes a difference; the pairing works best when the roasting is enough to thermally degrade the bitterness without losing too much sweetness due to caramelization. This emphasizes the sweetness and de-emphasizes the bitterness and acidity of the coffee, making it closer to the flavour profile of chocolate.
A traditional stock combines a mirepoix (onions, carrots, celery) with meat (well, bones), both very high in umami. The end product may have varying notes of bitterness or saltiness from the vegetables but is basically one huge kick of umami. A lot of people also enjoy peanut butter and bacon together, which combines the significant umami and saltiness in both foods.
Beets and sour cream are a traditional (or so I'm told) Polish dish, both obviously sharing strong sour notes. Often chives are added, which are mildly pungent in nature and pungency tends to go with sour or bitter (since it is created by sulfur which is perceived as sour, bitter, and also "metallic").
This tends to work reasonably well for basic pairings, but another very strong element of this is balancing all of the different flavours in a dish.
Peanut butter and jam don't seem to have much in common, flavour-wise. But when you combine them together in a sandwich you have the high umami and saltiness of the peanut butter, the sweet and slightly sour notes of the jam, and the hints of bitterness and/or sourness in the bread. Together you have strong notes of all five tastes and the result is appealing to most people.
Five Spice is usually a mixture of cinnamon (sweet), star anise (mildly sweet and bitter), fennel (mildly sweet and fairly savoury), ground cloves (pungent and somewhat bitter), and Szechuan peppercorns (salty and pungent with a sour aftertaste). The quantities are generally adjusted to balance out the tastes; for example, fennel is the only really savoury ingredient so Five Spice tends to have more of that than other ingredients. Anyway, this is used all over Chinese cuisine as a sort of "wonder spice".
A really good roast chicken starts off high in umami and is then brined (salty), buttered (sweet), and roasted which involves the Maillard reaction (bitter). This is missing sour, which is why a lot of cooks will throw a few lemon slices in there.
But truthfully, even though this all sounds plausible, it's really so much more complicated than that. Even though there's some science at work here, the five tastes are a little like the four elements or humours; it's an almost archaic way of thinking about food chemistry, because our mouths and noses can detect so much more than that.
If you want to see just how little we actually really know about flavour today, check out They Go Really Well Together on Khymos, linked to from one of the related questions. There you'll see totally nonsensical combinations like chocolate and garlic or mint and mustard that actually - with the right preparation of course - produce pretty pleasant flavours/aromas.
The truth is people are still gathering data on this and we don't really know, exactly, what makes some flavours work together. At least we're starting to approach this scientifically and actually experiment and document this stuff, but there's not enough data to form a coherent theory yet. Check the answers to my question about flavour pairings and the other question on pairing resources if you want detailed data on which flavour pairings can "work", although you might not get much of an explanation for why.
Thinking about this from first principles, a banana is about:
- 75% water
- 20% carbohydrates (mostly sugar and a small amount of starch)
- Less than 5% combined fiber and protein
- Trace amount of fat (generally considered to be zero).
The anti-crystallization effect of guar gum works on the water component, so adding a small amount of guar gum actually should be of some benefit. The hard part is getting it all dispersed; you don't want to over-process the banana (you'd lose the creaminess) but you also need to hydrate the guar gum in order for it to work its magic. You also need to avoid over-thickening, which might be difficult even with the very small starch content in a typical banana.
Bananas convert more starch to sugar as they ripen, so I suspect you'd have more success trying this on very ripe bananas that are, essentially, little more than sugar and water to begin with.
Incorporating and maintaining air is something that I just don't think you're going to be able to do. Proteins and fats can both participate in foaming (egg whites being an example of the former, and heavy cream being the canonical example of the latter), but bananas have neither of those. There's simply nothing to whip, and thus nothing to stabilize, so neither xanthan gum nor any other emulsifier/stabilizer is going to do you much good here.
If you really want to incorporate air then you're going to need more than one ingredient. My instinct would be to say coconut milk, which has relatively high fat and pairs well with banana (and obviously is also vegan / non-dairy), but I can say from experience now that coconut milk just doesn't have enough fat. You could try cooking it down first to get the fat ratio up, or using coconut oil, but I'm not sure how it would taste.
Traditional ice cream is about 60% water, which means the amount of guar gum that most people seem to get the best results with (about 1 tsp/qt) is about 0.87% of the total water. For a small (100 g) banana, that's about 75 mL of water corresponding to very close to 1/8 tsp of guar gum.
So, I'd give this a try with 1/8 tsp of guar gum, forget the xanthan gum. Try adding it after you've frozen the banana for the first time, when you first pop it into the blender.
No guarantees, but, you can probably afford to waste one banana in the attempt.
Update:
I thought I'd give this a try myself since (a) it seemed pretty easy and (b) I can always use more non-dairy dessert recipes. Here's how it came out with 1/4 tsp of guar gum for 2 bananas, after being frozen for two days:
You can see that ice crystal formation is pretty minimal, and although some parts did harden a bit (much like ordinary homemade ice cream with low overrun), they returned to normal consistency within just a few minutes.
Of course it still tastes like frozen bananas, so if I were to do this again I think I'd probably try adding a few other flavours. Also note that even though the texture is decent, the colour is getting dark, and I have no doubt that this would eventually turn black after enough time in the freezer - and the lemon juice trick doesn't really work so well when the whole thing has been blended up.
Best Answer
Modified on the label literally means... well... modified, that is changed or altered.
I am unable to find a Standard Of Identity formally for "modified starch."
Modified starches are typically modified in a number of ways (see the linked Wikipedia article for the full detail), but the most common one in instant mixes is to pre-gelatinize the starch. This permits it to more instantly dissolve and thicken items, even without being heated.
Your description of the filling thickener makes it sound like the starch is in fact modified for low temperature thickening.
In the case of your pie glaze, reverse engineering an industrial product which consists largely entirely of chemicals that are not easily obtained for home use may be... erm... fruitless.
You would be better off describing the outcome of the glaze, and trying to create a home recipe to come close. You are likely to get a good result, perhaps even better than the commercial product.
Fruit pie fillings are are typically starch thickened, during the baking process. However, you want an "instant" pie which is not cooked. No-bake fruit pies are fairly unusual. You may get better results by making a more traditional baked fruit pie.
This remainder of this answer is educated speculation, but I have not tried it.
To recreate this affect at home, you want a stove top filling method. Sugar, tapioca starch (which tends to give a transparent effect, and is not sensitive to acid), lemon juice (for flavor and tartness, replacing the citric acid in your mix), and salt, perhaps with some spices should come very close.
Baking911 suggests running instant tapioca in your food processor to get a finer powder, that dissolves more easily. Note that instant tapioca is in fact modified, as it is has been gelled, and then dried—so it may be close to what you are looking for.
You can bring this mixture to a low simmer, with your fruit, and then pour it into your shell, and it should do fairly well, although you will have to find the right proportions.