Do High Speed Juicers or Blenders Cause Oxidation of Nutrients?
Here is what my data has consistently shown.
There is a push in the juice machine industry to produce “cold-press” juice or juice made by slow speed crushing. It is said that 43 rpm is better than 80 rpm for the rotation of the auger of some juicers. And 1750 rpm is just way too fast, and centrifugal juicers as high as 12,000 rpm are definitely out by this logic.
Is this true? Where is the data?
First off, the words “cold-press” have historically referred to a hydraulic press process to squeeze juice from the pomace through special press cloths. It wasn’t used to refer to single auger juicers, twin gear juicers, or other masticating juicers that has some kind of pressing action to extract juice. Every juicer has some kind of pressing stage to extract juice, so saying that some of them are ”cold-press” doesn’t make the process like a hydraulic press. The Norwalk juicer and the more recent PURE Juicer are two examples of two-stage juicers that actually could be said to be “cold-press” technology at the household size. Good Nature juicers bring cold-press technology to the larger industrial scale of juice production.
The Good Nature, Norwalk, and PURE juicers do not use slow speed augers to crush the produce. Does the speed of the cutters on these juicing machines cause more oxidation such that they are not the best choice for juicing machines?
I think not, but my thoughts don’t count for that much. And neither do yours. What does the data say?
Previously I have examined enzyme activity in foods and juices to get an objective measure of the effect of food processing. Why measure enzymes? Enzymes are even more sensitive to heat and oxidation than vitamins and other nutrients. When a food is cooked the first indication of damage is the loss of enzyme activity. Before a loss of vitamin C or B vitamins there is a loss of enzymatic activity. So, I have found enzyme activity to be a very sensitive measurement to quantify small losses due to oxidation of a food.
Blender versus Juicer, 2010
Back in 2010 I compared the enzyme activity in produce after using a blender and a juicer. The recipe was about 1 ½ cucumbers (600 grams), 1-2 leaves of kale (90 g), 1 stalk of celery (80 g), and 2 medium carrots (110 g). Each batch was weighed to within 5 grams and the test was performed 3 times. The juicer was a Champion juicer used with the blank in place to function as a homogenizer in combination with a People’s press. This makes a Norwalk-quality juice with relatively high enzyme activity compared to other juicers. The blender was a Blend-tec machine. Care was taken to blend thoroughly without heating the produce. All the produce was added to the blender on cycle “2” and then blended to homogeneity on cycle “3”. Since fiber interferes with the enzymatic assays, the blended produce was filtered through the same press cloth as the juice from the Champion. Five naturally-occurring enzymes were tested: α-mannosidase, β-galactosidase, β-glucosidase, catalase, and acid phosphatase.
As shown in Table 1, the blender did not cause any loss of enzymatic activity. If anything, there was a slight increase in enzymatic activity in the blender. This may be due to the blender releasing more enzymes from inside of the cells. The produce was chopped much finer in the blender than it was triturated in the Champion juicer. These results indicate that there is no nutrient loss when using a blender compared to using a juicer.
Table 1. Enzymatic Activity Compared in Juicer and Blender.
Enzyme Activity of Blender/Press Combination for Juice, 2019.
More recently I published a comparison of six household juicers for yield and enzyme activity. In this comparison I also tested the enzyme activity of a juice produced by blending the produce and then pressing it with the PURE juicer press. As seen in Figure 10 from that publication, there was no loss of enzymatic activity (usually a bit more enzyme activity if anything) using the blender and press compared to using the PURE juicer, nor was there any increased enzyme activity when using a slower speed juicer compared to the PURE juicer (data shown in the publication). The best juice was made by the process that had the most homogenized pulp and pressed the hardest, which was the combination of the blender and hydraulic press.
Vitamin C Blended in Water
Along the way I have also done a simple experiment looking at the concentration of vitamin C in a blender. What would happen to vitamin C if you blended it in water for about 8 minutes on high, so that the water got hot? That is a lot more air and heat exposure than any produce gets while making smoothies or processing vegetables for juice. There was no drop in vitamin C concentration, whether the blender was operating under regular or vacuum conditions even though the temperature of the water went all the way up to 78ºC (172ºF). (The change to a slightly higher concentration was probably not significant.)
Table 2. Vitamin C Concentration Blended in Water.
These results from comparing blenders and juicers for enzyme activity and looking at vitamin C concentration after massive blending time and temperature extremes gives me confidence that blending my food is not having a significant oxidative effect. I can make green smoothies, fruit smoothies, or even blend produce up to make juice in a blender without worrying about losses due to the high-speed processing.
This also means that I can use a juicer with a high-speed impeller without worrying about the oxidation due to its high speed. You don’t have to use an auger that moves at 43 rpm to get good juice. A PURE juicer impeller won’t destroy the nutrients of the produce. In fact, it will help release the nutrients from inside the plant cells so you can assimilate them into your body.
So, when looking to buy your next juicer, or your first juicer, don’t fall for the hype of a “cold-press” juicer. That term really only applies to the PURE juicer, the Norwalk juicer (not produced anymore), and the Good Nature juicers. All the other “cold-press” juicers are some form of masticating juicer and shouldn’t be called “cold-pressed” anything. And don’t worry about your blender oxidizing the nutrients of your produce. It isn’t happening.
Tip to Keep the Original Color of Your Apple Juice / Applesauce
PS: Apple juice will turn brown no matter how you produce it. Want to keep the color? Just add a small amount (like ¼ teaspoon) of sodium ascorbate powder to your glass and it will stay a nice amber color without turning all brown. This is true for fresh applesauce as well.