Prof. Dr. Paul Struik

Through genetic modification, the AmA1 (Amaranth Albumin 1) gene from Amaranthus hypochondriacus (prince’s-feather; qelite in Spanish) has been integrated into potato varieties. This innovation has been developed by Dr. Subhra Chakraborty and her team. Inserting this single gene has been claimed to provide a 35-60% higher protein content with a more balanced amino acid profile, including enhanced concentrations of lysine, tyrosine, and sulfur-containing amino acids, such as methionine and cysteine. But protato can also refer to a trademark of a series of potato-based ingredients used to produce animal feed and pet foods. They are produced by the company ProCeres, which specializes in using side streams from the food industry (including the potato processing industry) thus creating sustainable, high-quality, and circular ingredients to produce pet foods. ProCeres claims to offer a large and diverse range of circular products with low CO₂ emissions. In summary, a “protato” is a protein-enhanced potato tuber or a protein-rich product derived from potatoes.

Potato is traditionally considered a high-yielding, resource-use efficient starch crop, grown as a vegetable or staple crop in more than 100 countries and consumed by more than one billion people worldwide. But potato is also an excellent source of high-quality protein. The fresh weight of a normal potato tuber consists of 75–80% of water, 15–25% of starch, and 1.5–2.3% of protein. The latter figure seems low, but that is misleading because of the low dry matter concentration of potato tubers: based on dry weight, total protein content varies from 4.5 to 13.6%, and even up to 17.8% in special cultivars; it can reach values well above 20% in the genetically modified potatoes of Dr Chakraborty and her team. That is not bad when compared with the total protein content based on dry weight of cereals, albeit significantly lower than the total protein content in soybean.

Moreover, the quality of this protein is excellent. It comprises three main categories: patatins (40%), protease inhibitors (50%), and other enzymes (10%); it is rich in essential amino acids, such as lysine, leucine, and phenylalanine, and that also compares well with cereal proteins. Additionally, potato protein has a protein digestibility corrected amino acid score (the so-called PDCAAS) of 0.93-0.99, on par with protein in dairy products and eggs, slightly below or similar to soy but considerably higher than the PDCAAS of cereals. Furthermore, potatoes are rich in Vitamin C and B6 and in macro-nutrients such as potassium. In addition, they also contain significant amounts of macro- and meso-nutrients phosphorus, magnesium, and manganese, along with bio-available essential micro-nutrients such as iron and zinc.
Potato becomes an even more impressive protein crop if we view it through the lens of nutritional protein yield per hectare. A good potato crop of 50 tons per hectare and 2% protein yields 1000 kg of protein per hectare. But this number can easily be as high as 1500 kg per hectare for high-yielding cultivars with high protein content grown under high input. Using genetically modified varieties, this number can further increase to 2000 kg of protein per hectare. Such protein yields are difficult to realize with the tradi­tional protein crops such as soybean.

But there is a crucial negative side to using potato as a protein crop: we need to transport and process large volumes of tubers containing a lot of water, making it an energy-intense protein crop. Harvesting potato protein by using side- or waste streams of the starch and food processing industries seems most feasible. But then we have to design and optimize starch-first or food-first potato protein production processes. ●