kale
ingredient / ingredient-kale
ケール / Brassica oleracea var. acephala
Kale is a leafy vegetable in the Brassicaceae family. Glucosinolate content varies by cultivar, and raw kale may taste bitter and pungent.
On this page (7 sections)
Reading the bitterness
Kale (Brassica oleracea var. acephala) is a leafy vegetable in the mustard family. A review table lists gluconapin, a glucosinolate shared by several cruciferous vegetables including Cook’s scurvy grass, Brussels sprouts, brown mustard, broccoli, and kale, as a compound with a bitter-taste sensory descriptor from compound-isolation analysis. It gives no values for content or intensity. The same review cites an earlier study reporting that related rape kale (Brassica napus var. pabularia, the 'nabicol' and 'couve nabica' cultivars) is less bitter than conventional kale; this is reported within the bounds of the earlier study as cited by the review.
Another study tested kale purée alongside broccoli and spinach purées, adding small amounts of sugar (0–1.8% in four levels) or salt (0–0.2%). A study reports that a trained panel of nine adults found lower bitterness intensity in all three vegetables, with no changes in other sensory properties such as texture or aroma. In a separate forced-choice task, eighty-four adults chose kale purée with 2% sugar as less bitter than unsweetened purée. A further nine-point hedonic evaluation by ninety-nine adults is reported to have found greater liking for kale purée with 1% or 2% sugar; this is a liking score, not a rating of bitterness intensity itself. The full original paper has not been checked, so this account is limited to the abstract.
A separate laboratory test compared the effects of additions to asparagus, Brussels sprouts, and kale among thirty-seven adults stratified by bitter sensitivity to PROP. The study reports that adding 32 mM sodium chloride lowered bitterness ratings for kale, but the abstract does not mention results for the other tested vegetables. In the same test, aspartame was reported to produce greater bitterness suppression and improved liking in all tested vegetables, including kale, than the sodium-based additives sodium chloride and sodium acetate. The full original paper has not been checked; this account is limited to the abstract.
Sources for this overview
Taste and Flavor Perceptions of Glucosinolates, Isothiocyanates, and Related Compounds
Checked for this overview: The review table lists gluconapin as a compound with a bitter-taste sensory descriptor. / The review cites an earlier study describing rape kale as less bitter than conventional kale.
Mary Poppins was right: Adding small amounts of sugar or salt reduces the bitterness of vegetables
Checked for this overview: Experiment 1 reports that sugar or salt lowered bitterness intensity without changing other properties. / The forced-choice task found that kale with 2% sugar was chosen as less bitter. / The hedonic evaluation found higher consumer liking with added sugar.
Masking Vegetable Bitterness to Improve Palatability Depends on Vegetable Type and Taste Phenotype
Checked for this overview: The experiment found lower kale bitterness ratings with 32 mM sodium chloride. / The comparison found aspartame more effective than sodium-based additives.
Other names: Brassica oleracea var. acephala (la)
Structured claims — open a section to read each claim's confidence, evidence and limits
Composition and content (1)
Scope: Layer: literature. Table 1 of the review (a list of glucosinolates, isothiocyanates, and sensory descriptors for plants of the order Brassicales).
Note: From Table 1 in the same review. The same row also applies to Brussels sprouts, so a separate claim is added there.
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ingredient-kale —is_documented_as_having→ "The review table classifies gluconapin, a glucosinolate shared by several cruciferous vegetables (Cook’s scurvy grass, Brussels sprouts, brown mustard, broccoli, and kale), as a compound with the sensory descriptor “bitter taste.”"Sensory (6)
Scope: Layer: food. Broccoli, spinach, and kale green-vegetable purees, evaluated by a trained panel of 9 adults (Experiment 1).
Note: Based on a summary obtained via a search engine (the full original text has not been confirmed).
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ingredient-kale —has_perceived_bitterness_suppressed_by→ "Adding a small amount of sugar (0-1.8%, in 4 steps) or salt (0-0.2%) to kale puree lowered bitterness intensity. Other sensory attributes such as texture and aroma did not change."Scope: Layer: food. Vegetable purées of kale, spinach, and broccoli; a forced-choice task with 84 adults (experiment 2).
Note: Based on a summary obtained through a search engine; the original full text has not been checked.
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ingredient-kale —has_perceived_bitterness_suppressed_by→ "In a forced-choice task against plain purée, kale purée with 2% sugar was chosen as less bitter."Scope: Layer: food. Experiment 3 (9-point hedonic evaluation with 99 adults).
Note: Based on a summary obtained through a search engine; the original full text has not been checked. This is an increase in liking scores, not a direct rating of bitterness intensity.
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ingredient-kale —has_sensory_acceptability_increased_by→ "Adding 1% or 2% sugar increased adult consumers’ liking for kale purée in a 9-point hedonic evaluation of 99 participants."Scope: Layer: food. Laboratory test of asparagus, Brussels sprouts, and kale with 37 adults stratified by PROP bitter sensitivity.
Note: Based on a summary obtained through a search engine; the original full text has not been checked. The authors present this as an example of an effect that depends on vegetable type.
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ingredient-kale —has_perceived_bitterness_suppressed_by→ "Adding 32 mM sodium chloride reduced bitterness ratings for kale. The same treatment did not have a comparable effect on other tested vegetables, including asparagus and Brussels sprouts."Scope: Layer: food. The same laboratory test of asparagus, Brussels sprouts, and kale.
Note: Based on a summary obtained through a search engine; the original full text has not been checked. Aspartame is an additive, not a pretreatment of the vegetable itself.
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ingredient-kale —has_perceived_bitterness_suppressed_by→ "Aspartame produced a greater effect in suppressing bitterness and improving liking in all tested vegetables, including kale, than the tested sodium-based additives (32 mM sodium chloride and sodium acetate)."Scope: Layer: literature. Summary of earlier studies cited in the review [36, 71].
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ingredient-kale —is_documented_as_having→ "The review cites an earlier study reporting that rape kale (Brassica napus var. pabularia; 'nabicol' and 'couve nabica' cultivars) is less bitter than conventional kale (Brassica oleracea var. acephala)."