Occasionally, I see a product in the supermarket that is either sold off the shelf at room temperature (then expected to be refrigerated after opening), or right out of the fridge. I use soy milk as an example, but there are other products that fit the bill as well (though the only other one that comes to mind is almond milk). What's (most likely to be) the difference between a product sold refrigerated and its equivalent sold room-temperature?
I'll use (cow) milk as an example, but the idea is the same for other products like juices and fake milks.
In the case of milk, the milk you get in tetrapak cartons (shelf stable milk) is ultra-high temperature pasteurized (UHT). It is heated briefly (1 to 2 seconds) to over 135 C then cooled down very quickly to kill bacteria and spores and then filled into a sterile container (the entire system is designed to keep bad organisms out, so the result remains sterile). This gives a much longer shelf-life than fresh milk (but once opened, it should be refrigerated), on the order of months. In contrast, the usual method of pasteurizing milk (at least in the US (*); Europe does a lot more UHT) is pasteurized by heated to about 70-75C for 15-30 seconds, then chilled and packaged (and lasts on the order of days).
The flavor can be affected due to things like the Maillard reaction occurring. Also, the temperature can affect the uses of the milk for applications like cheese making affecting the proteins.
(*) This is dependent on the type of milk you get; organic cartons in the US you find in the refrigerated section are often UHT pasteurized.
For milk-alternatives, they're typically the same product (there may be exceptions), but they're often sold chilled for the following reasons:
Marketing: Chilled products are typically perishable foods and therefore perceived to be fresher and of higher quality. Consumers will usually make the same assumption for any product sold chilled.
Familiarity vs. regular milk: As soya-milk is usually consumed as a replacement for dairy, by selling it chilled it's perceived to be more similar to milk - thus making the choice as an alternative less of a "risk".
Convenience: Most people prefer using chilled soya-milk, so when sold chilled it's more ready for use.
Familiarity when shopping: Customers are used to going to the chilled section to buy milk.
This can be verified by looking at the storage instructions on the carton, which will be the same as most foods sold at room temperature: "Store in a cool dark place, refrigerate once opened".