Greek yogurt is protein-dense and can be thrown into a smoothie, mixed with almonds and fruit, or used as a substitute for sour cream in cooking. As we investigated how this yogurt is made, we discovered that two-thirds of the milk used doesn’t end up in the final yogurt product and creates an unusable “acid whey.” But, are there ways to repurpose this by-product?
After snoozing the alarm several times, the last thing we like to think about in the morning is cooking breakfast. Because of its creamy taste and texture, dense protein and low sugar content, Greek yogurt is a perfect grab-and-go option. Greek yogurt has almost 2x as much protein as regular yogurt— hence its popularity. Market Research shows that over 50% of consumers that purchase yogurt are buying greek yogurt. And like the statistic, the Dirt-to-Dinner team found we were purchasing more Greek yogurt than traditional yogurt products.
How is Greek yogurt different from traditional yogurt?
It is the straining process that sets Greek yogurt apart from traditional yogurt products. The nutrients from the milk are consolidated into the protein-dense product.
Unfortunate waste in the process of making Greek yogurt
The process of making Greek yogurt, however, creates more waste. For every gallon of milk that is used to make Greek yogurt, two-thirds of that gallon is discarded after straining. The remaining watery substance is too acidic (with a pH of 4.6) and too salty to use productively anywhere else in the food supply chain. This strained residue is called acid whey and is a mixture of lactose, galactose, calcium phosphate, and lactic acid.
While we love Greek yogurt, the Dirt-to-Dinner team was concerned about the sustainability of this food’s production. The under-utilized byproduct that is created by making Greek yogurt is something that doesn’t sit well with us. In fact, on a recent visit to the Agricultural School at Cornell University, we learned about the negative impact this acid whey can have on the environment.
Where is the acid whey going?
Water has a pH of 7. Putting acid whey with a pH of 4.6 into the environment is not beneficial for either the soil or the water. The soil would turn into a perfect environment for weeds and conifers— not crops. The run-off into the waterways can kill fish. Overall it would negatively affect the environment.
Most acid whey is sent to the municipal waste system where huge holding tanks process liquids in an anaerobic environment. Acid whey is able to break down the waste because the protein and sugars help the fermentation process. However, there is little economic value in this AND there is significant water waste to consider.
In addition to the acid whey by-product that is created, there is also the issue of water wasted.
While we support the need to find an application for acid whey, what really caused the Dirt-to-Dinner team to pause and consider whether Greek yogurt was worth the extra protein boost was when we considered the water that is wasted.
According to Tristan Zuber, Dairy Processing Specialist at Cornell, “For every four pounds of Greek yogurt manufactured, about three pounds of acid whey is produced. When you think of the various factors that contribute to creating a gallon of Greek yogurt, you can extrapolate that two-thirds of that are not fully utilized for human or industrial use…
…A dairy cow drinks about 40 gallons of water a day to make about 8 gallons of milk. So for the yogurt that is made from one gallon of milk, the dairy cow must drink five gallons of water. And because not all of this milk is being consumed, inevitably the water the cow drinks to make a gallon of milk is not being fully utilized. So each time you eat a 5.3 oz of Greek yogurt you are wasting 26 ounces of water— about three glasses.”
This is not including all the water, fertilizer, and other inputs used to grow the crops to make the animal feed for the cow.
Time for innovation…
When food is processed into a sellable product, there is usually some type of by-product that can be used in some other type of capacity. For instance, soybean oil residue can be repurposed with asphalt. Or, a by-product of corn processing is used to make ethanol. Unfortunately, in the case of Greek yogurt, an effective application for the acid whey byproduct has not been discovered.
In 2016, 800,000 metric tons of Greek yogurt was produced in the U.S. and the acid whey by-product from that production could fill up approximately 640 Olympic-sized swimming pools! There is an opportunity here…
The cheese industry had a similar problem with the sweet whey that was produced while making cheese. However, sweet whey is less acidic and has a bit more protein so it can be sold as protein supplements. Acid whey is more of an issue, but patents have been filed to try and extract the proteins and lactose into a usable food or animal feed. Right now, when extracted it turns into a lumpy, hard material. Arla Foods has found a solution to mix acid whey with Nutrilac solution to make drinks, cheese, dressings, and other dairy products. One of their drinks was named ‘Best Beverage Ingredient” at the 2013 Beverage Innovation Awards.
Sustainability is a big issue for Greek yogurt. Try adding extra protein to your regular yogurt instead.
- Add Almonds (18) for 6 grams of protein
- Add Chia Seeds (2 tablespoons) for 4 grams of protein
- Add Hemp Seeds (3 tablespoons) for 12 grams of protein
- Add Cashews (14) for 4 grams of protein
The Bottom Line:
Greek yogurt has a lot of protein— but it comes at a cost. Is this protein worth the wasted water or unusable byproduct that can negatively affect the environment? You can get the same benefit from regular yogurt by adding some other nutritional ingredients to increase the protein content.