What coffee bean and roast are appropriate with soy milk?

Question

Soy milk tastes quite different from cow milk. Yet coffee chains seem to make their milk-based drinks from the same coffee pot. The pot is most often made of dark-roast blends "from the house", and it seems a good match for cow milk, as the fatty flavour balances the strength of the black drink. Dark-roast blends coffee seems overly strong for soy milk, though, and I am guessing that some cafes do serve "soy lattes" based on lighter roasts (from taste, not from observation at this point).

Blends are usually secrets in contents and proportions. The chains use the same pot anyway, but some cafes may be picking a different blend as well, more suitable to the flavour profile of soy milk.

Are there any criteria on the bean and/or roast when one intends to mix with soy milk?

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Note: This question may seem subjective. The goal is to understand what concrete parameters are "available" to make a drink that preserves the coffee qualities and merges nicely with the soy milk flavour profile.

Answer 1

Though it's not primarily your question, my chief problem with soy(a) milk in coffee is with curdling as described in this question. I have noticed curdling especially in higher-acidity coffee -- e.g., especially in American-origin coffees and lighter-roasted coffees. No matter the preparation, I avoid soy milk in anything lighter than full-city roast. The resulting grainy texture is simply unacceptable! Though admittedly certain brands are less likely to split, especially if steamed, frothed, emulsified etc. as in for certain drinks like latte.

Darker-roast coffees are more common ("popular") in general at mass-market chains, so I think that can also explain some of the prevalence of dark roasts for soy milk.

As for taste, fat content and sugar content vary greatly for soy milk, even when discounting other additives like vanilla or other flavourings... so go for an unsweetened, un-flavoured brand. For my preference, the nuttier taste of soy milk is a good complement for Indonesian or other southeast-Asian coffees, which can be earthy, nutty, toasty, and take to darker-roasting well. Flavour guides such as this one from Serious Eats can help identify general characteristics. If you like a pairing of soy milk with some other food, look for a coffee that expresses that same characteristic!