For those of you living the shade-grown, organic, fair-trade, made-with natural-flavor life, it can be tricky to suss out which of those labels are actually regulated terms, and which are just a buzzword salad. When it comes to fruits and vegetables, some of those identifiers really do matter in a big way. Take, for example, cold-pressed: what does it mean? Does it matter? And are cold-pressed juices any better for you than the alternative?
So...what does cold-pressed really mean?
This is going to shock you to learn, but cold-pressing is the process of separating the fiber from the cells of fruits and vegetables – you know, juicing – without the aid of any heat. Machines and tools built to aid in cold-press juicing are also called masticating juicers, because they use hydraulic power to effectively chew and crush the juice out of otherwise fibrous plants. Cold-pressing takes longer and produces less juice. Though in theory, that juice created is richer in nutritional content.
Are there hot-pressing juicers then?
There are! But they go by a different name. Centrifugal juicers are what we’re talking about when it comes to hot-pressed juicers, and the name is a bit of a misnomer. Centrifugal juicers aren’t outright boiling or steaming the juice out of fruits and veggies. What they are actually doing is using a rapidly spinning set of blades – usually powered by electricity – to pulverize produce as it is forced through a machine. The blades generate a bit of heat as they spin, while also forcing the juice into contact with air, beginning the process of oxidation. More of the initial product makes it into the final juice through this process, but it is exposed to potentially degrading heat and air along the way.
What’s the problem with heat then?
Heat can destroy certain enzymes and nutrients, like notoriously delicate Vitamin C. Cooked broccoli, for example, is less nutritionally dense than the same amount of raw broccoli. On the other hand, cooking carrots actually results in increased levels of beta carotene. Heat is even necessary for human consumption of plenty of vegetables, and certainly animal proteins. Uncooked, certain vegetables are downright indigestible within the human body due to their naturally hardy cellulose fiber. And then there’s the matter of chemicals like solanine and chaconine, naturally present in raw vegetables like potatoes. Cooking potatoes is required before human consumption, unless you want to make yourself sick. Some foods require heat; some don’t.
Wait, so is heat good or bad then?
Frankly, it’s complicated. Mushrooms, asparagus, cabbage and peppers all join carrots on the list of vegetables that release higher levels of nutrients like antioxidants, carotenoids and ferulic acid when exposed to heat via steam or boiling water. Sure, those veggies aren’t exactly popular components of green juices, but smoothie staple spinach is also on the list. The science on the benefits of cold-pressing is decidedly mixed, with the effect of heat varying dramatically on crop to crop. But remember, heat isn’t the only thing cold-pressing is meant to protect produce from. There’s the matter of oxidation as well.
OK, so is oxidation bad for juice then?
Unlike the complicated relationship between heat and raw plant-based foods, oxidation is most assuredly not good. As soon as the inner flesh of fruits and vegetables is exposed to the surrounding air, degradation begins to occur. On a miniature scale, nutrients begin breaking down. On a more visible, if drawn-out scale, food begins to spoil. Centrifugal pressers kickstart the oxidation process by exposing newly liquid juice to air as it is forced through spinning blades. Vitamins B and C, as well as antioxidizing phenolic compounds, are particularly sensitive to degradation when forced into contact with air. Oxidation is the reason we store leftovers in plastic containers, and refrigerate foods that would otherwise spoil. It’s the reason that foods carry sell-by dates on them.
Why isn’t it just called non-oxidized juice then?
Cold-press juicers still expose juice to air. They just aren’t pumping air into newly liquid juice. Hydraulic mastication of vegetables is a slower, less efficient process. But it’s one that does preserve more of what we find advantageous within plenty of fruits and vegetables.
So is it worth spending the extra money for cold-pressed juices?
The inefficiencies of cold-pressing are precisely what make it so sought after. As long as you’re otherwise consuming enough fiber in your diet, the more concentrated nature of cold-pressed juices make for more nutritionally dense products. But there is an enormous caveat here – the absolute healthiest way to get your fruits and veggies is just to consume the actual produce whole. Cold-pressed juice is fantastic for you if that’s the only way you’re otherwise getting these food groups into your diet. But if you’ve got the time, you’re better off just eating a salad.