spinach
ingredient / ingredient-spinach
ほうれん草 / Spinacia oleracea
Spinach is a leafy vegetable containing a relatively high amount of oxalic acid. Its unpleasant aftertaste has traditionally been attributed to oxalic acid (egumi), but oxalate taste and bitterness have been reported to separate into different fractions by solid-phase extraction.
On this page (6 sections)
Reading the bitterness
The bitterness of raw leaves when eaten differed by sample origin. When a trained panel of 6 evaluated about 10 g of unseasoned raw leaf 3 times each on a 15-point scale, the mean ± standard deviation of bitterness was 3.0±0.56 for the open-field product and 2.4±0.50 for the commercial product, with the open-field product significantly higher. The tunnel-covered product was 2.8±0.63, intermediate between the two. Because the commercial product's cultivar, growing method, and days since harvest were unknown, the difference cannot be determined to be due to growing method alone.
In another test that examined salt-boiling, spinach was boiled for 1 minute in distilled water or 1-3% saline at 10 times its weight, then soaked in changing water for a total of 5 minutes. When 10-21 women aged 19 to their 40s answered on a 5-point scale, there was a tendency for egumi to be felt less as the salt concentration increased, but there was no significant difference among the concentration conditions. What was scored here was egumi, not bitterness itself.
In a test from the same paper that varied the type of salt, samples boiled with 3% refined salt or 3% table salt were significantly less egumi than samples boiled with water alone (p<0.01). 「天塩」 (Amashio) salt, however, showed no difference from water-boiling. It cannot be said that any salt gives the same result, and egumi cannot be read as a measurement of bitterness.
Sources for this overview
Reducing food losses and improving the quality of locally produced spinach
Checked for this overview: Used for the trained panel of 6, about 10 g of unseasoned raw leaf, the 15-point scale, 3 replicates, mean ± standard deviation, the overall test and letter groupings, and the unknown conditions of the commercial product.
食塩添加ゆでホウレンソウのえぐ味の感じ方とシュウ酸および無機成分含量との関連
Checked for this overview: Used for the 10-times boiling water, 1-3% saline, 1-minute boil, total 5-minute soak, 10-21 women, the 5-point egumi evaluation, and the absence of significant difference among concentrations. / Used for the p<0.01 between 3% refined salt/table salt and water-boiling, the 「天塩」 (Amashio) condition, and the limitation of the egumi scale.
Other names: ホウレンソウ (ja)
Structured claims — open a section to read each claim's confidence, evidence and limits
Sensory (7)
Scope: Layer: food. Green-vegetable purees of broccoli, spinach, and kale, evaluated by a trained panel of 9 adults (Experiment 1).
Note: Based on a summary reached via a search engine (the full original text has not been verified). The same trend is reported for all 3 vegetables, and the figures limited to spinach alone cannot be separated out from the summary.
Show data
ingredient-spinach —has_perceived_bitterness_suppressed_by→ "Adding a small amount of sugar (0-1.8%, 4 levels) or salt (0-0.2%) to spinach puree lowered bitterness intensity. Other sensory attributes such as texture and aroma did not change."Scope: Layer: Food. Vegetable purées of spinach, kale, and broccoli; a forced-choice task with 84 adults (Experiment 2).
Note: Based on a summary obtained through a search engine (the full original was not confirmed).
Show data
ingredient-spinach —has_perceived_bitterness_suppressed_by→ "Spinach purée with 2% added sugar was chosen as less bitter in a forced-choice task against purée without additives."Scope: Layer: Food. Experiment 3 (9-point hedonic evaluation, 99 adults).
Note: Based on a summary obtained through a search engine (the full original was not confirmed). This concerns an increase in liking scores, not an evaluation of bitterness intensity itself.
Show data
ingredient-spinach —has_sensory_acceptability_increased_by→ "Adding 1% or 2% sugar increased liking for spinach purée in a 9-point hedonic evaluation by 99 adult consumers."Scope: Layer: Food. Sensory evaluation of spinach-leaf-blade extract (undiluted and 20-fold diluted).
Show data
ingredient-spinach —has_perceived_bitterness_affected_by→ "When spinach-leaf-blade extract was diluted 20-fold, bitterness became markedly weaker than in fresh-leaf extract, while oxalate taste remained relatively strong; the two showed contrasting dilution responses."Scope: The cultivar Sunlight, boiling water at 10 times the sample weight, a panel aged 19 to their 40s including female students and staff, a 5-point evaluation
Note: The item evaluated was egumi, not a direct evaluation of bitterness. The 1-3% concentration difference is not treated as a significant effect.
Show data
ingredient-spinach —has_sensory_response→ "In a comparison of boiling for 1 minute in distilled water or 1-3% saline followed by a 5-minute water soak, there was a tendency for egumi to be felt less as the salt concentration increased, but there was no significant difference among the concentration conditions"Scope: The cultivar Tonic, boiling water at 10 times the sample weight, boiled for 1 minute and soaked in water for 5 minutes, a 5-point sensory evaluation of 4 salt types and distilled water
Note: The 「天塩」 (Amashio) condition showed no significant difference from the distilled-water condition, and this is not generalized to all salts. The item evaluated is egumi.
Show data
ingredient-spinach —has_sensory_response→ "Samples boiled with 3% refined salt or 3% table salt were significantly less egumi than samples boiled with distilled water alone (p<0.01)"Scope: Chapter 4 of a doctoral dissertation, a trained panel of 6, about 10 g of unseasoned raw leaf, a 15-point intensity scale, 3 replicates per sample
Note: The open-field product and the tunnel-covered product were both the cultivar Corvair, but the commercial product's cultivar, growing method, and the period from harvest to testing were unknown, so this is not treated as an effect of growing method alone.
Show data
ingredient-spinach —has_perceived_bitterness_affected_by→ "In a descriptive evaluation of 3 raw-leaf samples, the bitterness of the open-field product was significantly stronger than the commercial product, and the tunnel-covered product was intermediate, with no significant difference from either"