Is green rhubarb safe to eat? (Rhubarb uses)
In this brief guide, we will answer the question “Is green rhubarb safe to eat?”. We also will discuss the uses of rhubarb and its health benefits.
Is green rhubarb safe to eat?
Yes, green rhubarb is safe to eat. The color of rhubarb stalks varies, ranging from green or pink to pinkish-red, depending on the specific cultivar. This color distinction subtly impacts the flavor profile as well. Cooking rhubarb with sugar is a popular method of preparation, additionally, red and pink stalks tend to be considered sweeter in taste compared to their green counterparts. (1)
How is rhubarb used?
Rhubarb species find applications in both culinary and medicinal domains. The nutrient-rich petioles, also known as leaf stalks, are commonly cooked and prepared as a versatile vegetable in various dishes. Rhubarb is prominently featured in culinary creations like juices, pickles, salads, sauces, jams, and delectable pies due to its nutritional value.
Furthermore, the dried rhubarb rhizome or root possesses notable medicinal properties. In Traditional Chinese Medicine, the dried rhubarb rhizome or root boasts noteworthy medicinal properties.
It is often prescribed to address a range of conditions including fever, constipation, abdominal pain, appendicitis, kidney ailments, liver cancer, and hypertension. Moreover, traditional usage of dried rhubarb root involves its potent cathartic effects as a documented laxative agent. Some even consider it a potential aid for individuals struggling with obesity. (1)
How does color impact rhubarb?
The color of rhubarb doesn’t determine if it’s good for cooking or not. For instance, rhubarb with green stalks tends to be tougher and provides more yield. However, reddish stalks are more favored by consumers.
Rhubarb stalks can take on various colors, from the well-known deep red to dappled pink, or even a solid green. This color variation comes from specific pigments, called anthocyanins. The particular rhubarb type and how it’s grown can influence their presence. (2)
What are the health benefits of rhubarb?
The therapeutic potential of rhubarb is vast, owing to its rich array of bioactive compounds. These include anthraquinones, hydroxyanthraquinone, aloe-emodin, emodin, rhein, stilbene, rhaponticin, dietary fiber, and more. Through their unique properties and functions, these bioactive constituents offer a wide range of health benefits.
They exhibit antioxidant effects, combat cancer cells, fight against microbial infections and diarrhea-related Rhubarb root possesses a mild yet potent laxative effect, effectively promoting thorough bowel cleansing and complete intestinal emptying.
This remarkable attribute stems from its anthraquinone glycoside content, which naturally stimulates the bowels and makes rhubarb an invaluable aid in addressing chronic constipation.
In traditional Indian medicine, rhubarb holds multiple roles. Not only is it used as a purgative, but also recognized for its antimicrobial properties and dependable efficacy in healing skin wounds and cold sores. Rhubarb extracts are also used to mitigate boils and abdominal disorders. (1, 2)
How is rhubarb cultivated?
Rhubarb, a versatile vegetable, thrives in different regions and remains accessible throughout a significant portion of the year due to greenhouse farming. Its prized petioles or stalks can be harvested as early as mid to late spring in temperate climates. Field-grown varieties continue to be available until September.
When freshly harvested, rhubarb stalks boast a firm and shiny appearance, making them perfect for consumption. Moreover, rhubarb plant roots are typically harvested from those that have reached the age of four months or older. This process takes place in autumn, usually during October.
The roots are meticulously cleaned and any external fibers are attentively removed. Subsequently, they undergo a comprehensive drying process. Once completely dried, the rhubarb root is finely ground into powder and securely stored in a sealed container.(2)
How is rhubarb harvested and stored?
After the aboveground parts of the plant are harvested, the leaf blades are separated from the stalks. These stalks then undergo a processing stage. During cutting, there is a potential risk of reduced moisture content in the petiole if the stalk tissues sustain any damage.
To address this concern, it is advisable to employ cold storage methods and closely monitor humidity levels within the storage chamber. For optimal cooking and freezing outcomes, it is recommended to utilize freshly harvested stalks.
To keep rhubarb fresh, it is essential to store it in a cool and humid environment, preferably within the temperature range of 32°-40°F (0°-4°C) with a relative humidity of approximately 95 percent.
However, this poses some challenges since refrigerators tend to provide the necessary temperature but often remove moisture from the air. An effective alternative method for preserving rhubarb involves wrapping the petioles in aluminum foil. (3)
What are the safety concerns with green Rhubarb?
The leaves of the rhubarb plant are widely known to be toxic due to their high oxalic acid content. The main source of toxicity in rhubarb lies in its leaves, while the stems, or petioles, which are the edible part of the plant, are significantly less toxic. It’s important to note that cases of poisoning from rhubarb are more frequently reported in children than in adults. (4)
What are the dangers of oxalic acid?
Oxalic acid poses a threat to the kidneys and has corrosive properties. The lethal dose, which varies based on age, generally ranges from approximately 10 to 25 grams. When oxalate combines with calcium in the bloodstream, it forms insoluble calcium oxalate. This can potentially lead to severe hypocalcemia and involuntary muscle contractions.
On average, rhubarb leaves contain about 0.5% oxalic acid along with higher levels of non-toxic malic acid. Prolonged consumption of rhubarb can present challenges for individuals with kidney disorders, gout, and rheumatoid arthritis as oxalic acid can interfere with essential nutrients.
Oxalic acid can also react with metal ions like Ca2+, Fe2+, and Mg2+ to form deposits of corresponding oxalates, which may irritate the gastrointestinal tract and kidneys. For rats, the lethal dose (LD50) for oxalic acid is 375 mg per kilogram of body weight.
To put this in perspective for a 65 kg person, it would take approximately 25 grams of pure oxalic acid to cause death. Symptoms of rhubarb poisoning include abdominal pain, diarrhea, persistent and severe vomiting, followed by internal bleeding, convulsions, and, ultimately, a coma. (2, 4)
In this brief guide, we answered the question “Is green rhubarb safe to eat?”. We also discussed the uses of rhubarb and its health benefits. In my studies, I was able to find out that the color of rhubarb is dependent on its species, green rhubarb being among those.
From my perspective as a food scientist, green rhubarb can be used as any other variety and the choice to use it goes down to personal preference as red and pink varieties tend to be sweeter.
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BHAT, Rajeev. Bioactive Compounds of Rhubarb (Rheum Species). Bioactive Compounds in Underutilized Vegetables and Legumes, p. 239-254, 2021.
CLEMENTI, Elisabetta M.; MISITI, Francesco. Potential health benefits of rhubarb. In: Bioactive foods in promoting health. Academic Press, 2010. p. 407-423.
ZARDZEWIAŁY, Miłosz et al. Ozone treatment as a process of quality improvement method of rhubarb (Rheum rhaponticum L.) petioles during storage. Applied Sciences, v. 10, n. 22, p. 8282, 2020.
Crews, C., & Clarke, D. Natural Toxicants: Naturally Occurring Toxins of Plant Origin. Encyclopedia of Food Safety, 261–268. 2014.