A study led by Dr. Christoph Hahn and Professor Dr. Dirk Albach from the University of Oldenburg, featured in Horticulturae, examines how kale, a nutrient-rich vegetable, changes its chemical makeup in response to environmental and genetic factors.
The research, conducted by a team from Oldenburg and Bremen, focused on different kale varieties known for their high levels of secondary plant compounds, such as glucosinolates, which give kale its distinct cabbage flavor. These compounds, also called mustard oil glycosides, are influenced by temperature and genetics.
The team discovered that glucosinolate levels in certain kale types rise or fall with colder temperatures. Dr. Hahn emphasizes the importance of both temperature and variety selection in enhancing the nutritional value of kale.
Dr. Hahn’s previous work categorized the 150 global varieties of kale into genetically distinct groups with varying tastes, appearances, colors, and phytochemical compositions. These include the mild-tasting Italian Lacinato kale with elongated, dark leaves and the broad-leaved American varieties that resemble wild or “feral-type” cabbage.
The study investigated the effect of cold on glucosinolate composition in kale leaves. These compounds transform into mustard oils when leaves are crushed, providing chemical defense against predators like caterpillars and snails. The bitter and pungent taste of kale, especially pronounced in feral-type varieties, is attributed to these compounds.
Researchers grew three varieties – “Frostara,” “Palmizio,” and “Helgoländer,” representing curly, Lacinato, and feral-type kales – in a climate chamber. Exposing them to two-degree Celsius temperatures for a week, they analyzed glucosinolate levels at different stages using a mass spectrometer.
Unexpectedly, both curly and Lacinato kale showed increased glucosinolate levels in cold, while feral-type levels decreased. This contradicted previous expectations, as Lacinato kale is adapted to different climates. Dr. Hahn noted that taste is influenced by both glucosinolates and sugar content. His 2020 research revealed that kale’s sugar levels also rise in low temperatures, not just below freezing, but in single-digit above-zero temperatures as well.
This comprehensive study, titled “A Cold Case—Glucosinolate Levels in Kale Cultivars Are Differently Influenced by Cold Temperatures,” was published on 22 August 2023 in Horticulturae and can be referenced with the DOI: 10.3390/horticulturae9090953.
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Frequently Asked Questions (FAQs) about Kale Nutrient Composition
How does cold weather affect kale’s nutrient profile?
Cold weather impacts the nutrient profile of kale by altering the levels of glucosinolates, compounds that contribute to the vegetable’s characteristic flavor. This variation in glucosinolate concentration depends on both environmental (temperature) and genetic factors.
What are glucosinolates and why are they important in kale?
Glucosinolates are secondary plant compounds found in kale, contributing to its distinctive cabbage-like flavor. They play a crucial role in the plant’s defense mechanism against predators and significantly influence the vegetable’s nutritional value.
What did the study by Dr. Christoph Hahn and Professor Dr. Dirk Albach reveal?
The study led by Dr. Hahn and Professor Albach revealed that glucosinolate levels in kale change with cold temperatures. This change varies among different kale varieties and is influenced by both environmental and genetic factors.
What varieties of kale were used in the study and how were they tested?
The study used three kale varieties: “Frostara,” “Palmizio,” and “Helgoländer,” representing different types. These were grown in a climate chamber and exposed to low temperatures, with glucosinolate levels measured at various stages.
What surprising findings emerged from the study about kale’s taste?
The study found unexpected changes in glucosinolate levels among different kale types when exposed to cold temperatures. This suggests that temperature influences kale’s taste, which is also affected by its sugar content.
How does this research contribute to understanding kale’s nutritional value?
This research provides insights into how environmental factors like temperature can affect kale’s nutritional composition. It highlights the importance of considering both genetic and environmental aspects for cultivating kale with optimal nutritional value.
More about Kale Nutrient Composition
- University of Oldenburg Research
- Horticulturae Science Journal
- Glucosinolates in Kale
- Effects of Cold on Plants
- Nutritional Value of Kale
- Dr. Christoph Hahn’s Research
- Professor Dr. Dirk Albach’s Publications
