Nutrients and plant compounds in freeze-dried kale and spinach
What it found
Freeze-dried kale and spinach contained different amounts of fatty acids, minerals, vitamins and plant compounds.
Kale had more calcium, phosphorus, vitamin C and glucosinolates, while spinach had more sodium and oxalic acid.
What they found
Fatty acids in kale and spinach
Kale contained 23.61 mg of total fatty acids per 100 g dry weight, and spinach contained 18.67 mg per 100 g. Kale had more omega-3 fatty acids (16.69 mg/100 g) than spinach (10.84 mg/100 g), while omega-6 levels were similar in both.
Plant compounds identified
The analysis identified 103 compounds in kale and 69 in spinach, including flavonoids, glucosinolates, and phenolic and organic acids. Kale contained 11 glucosinolates, which were absent from spinach.
Minerals in kale and spinach
Kale contained more calcium and phosphorus than spinach. Spinach contained more sodium than kale.
Vitamins in kale and spinach
Kale contained more vitamin C (135.0 mg/100 g dry weight) than spinach (51.9 mg/100 g dry weight). Vitamin E levels were not significantly different between the two.
Amino acids in kale and spinach
Kale had the highest amounts of glutamic acid, aspartic acid and leucine compared with spinach. Essential amino acids made up 42% of total amino acids in kale and 41% in spinach.
Organic acids in kale and spinach
Kale contained citric acid and malic acid, while spinach contained citric acid but no malic acid. Spinach contained oxalic acid, which was not detected in kale.
What the authors conclude
“These analyses support the conclusion that diets abundant in these leafy greens have the potential to delay the onset of age-related diseases.”
Also in their conclusions
- They conclude that purslane contained significantly higher amounts of omega-3 and total fatty acids than either spinach or kale.
- They report that kale had the greatest amount of calcium and phosphorus, while purslane had more magnesium and potassium.
- They suggest that diets abundant in these leafy greens have the potential to delay the onset of age-related diseases.
How it was done
The authors wanted to profile the nutrients and natural plant compounds in freeze-dried spinach and kale and compare them with previously published results for freeze-dried purslane. They say these data should promote purslane as a nutrient-dense leafy green for use in food and nutraceutical products.
They freeze-dried kale grown at Van Drunen Farms in Illinois and baby spinach bought from a local grocery store, then analysed both for fatty acids, plant compounds, carotenoids, minerals, amino acids, vitamins and organic acids. Each analysis used at least four replicates, and the kale and spinach results were compared with previously published purslane data.
What it can’t tell you
- This study measured the nutrient and compound content of the freeze-dried vegetables. It did not test what happens when people eat them.
- The results are for specific samples of kale and spinach grown or bought in one place. Different varieties or growing conditions could give different amounts.
Who paid
- Conflicts
- The authors declare no conflict of interest.
- Authors work at
- University of Illinois at Urbana-Champaign, USA
The paper
- Title
- Extraction and Natural Bioactive Molecules Characterization in Spinach, Kale and Purslane: A Comparative Study
- Type
- Study
- Summarised from
- Full text
- Cite
- Nemzer B, Al-Taher F, Abshiru N (2021). Extraction and Natural Bioactive Molecules Characterization in Spinach, Kale and Purslane: A Comparative Study. Molecules (Basel, Switzerland). doi:10.3390/molecules26092515Free full textPubMed 33925848DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error