eggplant
ingredient / ingredient-eggplant
なす（茄子） / eggplant (nasu) / Solanum melongena L.
On this page (7 sections)
Short definition
A fruit vegetable in the nightshade family. Polyphenols such as chlorogenic acid are considered to be involved in the astringency of the flesh, and Japanese cooking science has examined by sensory testing how perceived astringency changes with steaming, grilling, simmering, sautéing and deep-frying.
A reader-facing overview for this entry is in preparation. What has been checked, and its sources, can be followed from the claim cards below.
Other names: ナス (ja), aubergine (en)
Follow the connections
eggplant →— combined bitter-astringen…→ chlorogenic acid
eggplant →shows the sensory response→ bitterness →can be measured separately …→ astringency
Structured claims — open a section to read each claim's confidence, evidence and limits
Sensory (5)
Scope: 1 type of commercially available eggplant bought in Kyoto city, cooked as skin-on boat-shaped pieces cut lengthwise into 8 (200 g from 2 eggplants). 14 students and staff of Doshisha Women's College evaluated by ranking test. The term evaluated was astringency; bitterness was not evaluated.
Note: The order of astringency of eggplant by cooking method did not match the order of total polyphenol amount or chlorogenic acid amount (the chlorogenic acid amounts in steamed and deep-fried eggplant were almost the same, 179.6 and 178.9 mg%, yet astringency was strongest in steamed and weakest in deep-fried). The authors infer that oil does not reduce the astringent components but weakens how they are perceived (not measured). Read the fact that sautéing and deep-frying, which use oil, were weaker separately from the inference about the reason.
Show data
ingredient-eggplant —has_bitter_astringency_affected_by→ "Cooking method. Commercially available eggplant was cooked in 5 ways (steamed, grilled, simmered, sautéed, deep-fried), and 14 panelists compared the strength of astringency by ranking test. Astringency was strongest in the steamed eggplant and weaker in the order grilled, simmered, sautéed and deep-fried, with deep-fried the weakest (rank sums: steamed 21, grilled 30, simmered 39, sautéed 54, deep-fried 66; Kendall's W test, significant at the 1% level)."Scope: Simmered eggplant made by simmering 200 g of commercially available eggplant in 300 mL of second dashi for 10 minutes, then adding light-colored soy sauce and salad oil and simmering for 5 more minutes (the control had no oil). Paired comparison (2 samples) by 14 students and staff of Doshisha Women's College. Astringency was evaluated; bitterness was not evaluated.
Note: The key point is that astringency was perceived as weaker although the components (total polyphenol amount and chlorogenic acid amount) were the same. The components were measured as the total of the pieces and the cooking liquid. There is no comparison with varying amounts of oil.
Show data
ingredient-eggplant —has_bitter_astringency_affected_by→ "Adding edible oil (salad oil) when simmering. Eggplant simmered with oil was judged less astringent than eggplant simmered without it (in a paired comparison of 2 samples by 14 panelists, 3 answered that the one with oil was more astringent and 11 answered that the one without oil was more astringent; significant at the 5% level). There was no difference in total polyphenol amount or chlorogenic acid amount between the two."Scope: A comparison among 6 to 7 eggplant cultivars and lines (including the Nara Prefecture native line 'Yata'). The sensory evaluation was by 16 to 19 panelists, mainly staff of agricultural research institutions, in comparison with the reference cultivar 'Senryo-nigo' (7-point scale from -3 to 3). The correlations are on the means for each cultivar (n=6 for salt pickling and seasoned pickling, n=7 for the others), and astringency was evaluated (bitterness was not evaluated).
Note: The correlations are rank correlations between the means of 6 to 7 cultivars and do not include individual perception or variation within the same cultivar. The author states that the relation between the chlorogenic acid amount of raw eggplant and astringency after cooking needs further study, because the chemical changes of decomposition and oxidation during heating are not understood. The coefficients in the table, such as 0.875 to 1.000 for the flesh, are also written in the main text (the main text gives "0.875 to 1.000").
Show data
ingredient-eggplant —has_bitter_astringency_affected_by→ compound-chlorogenic-acidScope: Fruit of 7 eggplant cultivars and lines. Cooking used a mild Japanese-style seasoning. The sensory evaluators numbered 16 to 19, in comparison with the reference cultivar 'Senryo-nigo' (-3 to 3). Astringency was evaluated (bitterness was not evaluated). Steamed and grilled samples also had ponzu or soy sauce poured on just before eating, so this is not a comparison divided by the strength of seasoning.
Note: The authors interpret that seasoned pickling and nibitashi have complex seasoning that makes astringency harder to perceive, and that agedashi has oil that weakens astringency (this is an interpretation, not a comparison that varied the seasoning or the presence of oil). For steaming, the differences in astringency among cultivars were significant, and so were flesh texture and wateriness.
Show data
ingredient-eggplant —has_bitter_astringency_affected_by→ "Cooking method. Astringency ratings differed significantly among cultivars and lines for salt pickling, steaming and grilling, but no significant difference in astringency among cultivars was found for seasoned pickling, agedashi and nibitashi (the coefficient of variation of the astringency rating index was 25.0% for salt pickling and 7.9% for agedashi)."Scope: A dynamic sensory evaluation of purple eggplant and zucchini boiled or baked for 15, 30 and 45 minutes (as described in the abstract). The abstract does not show which cooking conditions were bitter.
Note: A claim read from the abstract only. The abstract states that the longer chewing counts and eating times were in the baked samples and the briefly cooked samples, so the correspondence between bitterness and cooking method and time must be checked in the full text. If incorporated, do not generalize it as a relation between cooking time and bitterness.
Show data
ingredient-eggplant —has_sensory_response→ sensation-bitterMechanism and receptors (1)
Scope: A model experiment using an aqueous solution of caffeic acid (a constituent of chlorogenic acid; the authors presume that the astringency of eggplant is caused by its caffeic acid portion). 14 students and staff of Doshisha Women's College. It is not an evaluation of cooked eggplant itself.
Show data
ingredient-eggplant —has_bitter_astringency_affected_by→ "Coexistence of edible oil. When 5% edible oil was added to an aqueous caffeic acid solution (0.6 × 10^-2 mol/L) at a concentration close to the astringency of eggplant and shaken, all 14 panelists answered that the one without oil was more astringent (significant at the 1% level). The astringency with oil was about the same as that of a 0.46 × 10^-2 mol/L solution without oil, and the authors regarded it as weakened by roughly a quarter."How processing and cooking change it (2)
Scope: Commercially available eggplant (Sennari), cut lengthwise into 8 skin-on boat-shaped pieces. Components were measured only; no sensory test was conducted.
Note: The authors write that eggplant cooked in oil after soaking in water would be perceived as less astringent than eggplant cooked in oil without soaking, but this is an inference, and this paper has no sensory result. Read it as material that raises, from the side of the components, a question about the reasons given for soaking in water, namely preventing browning and removing astringency.
Show data
ingredient-eggplant —is_processed_by→ "Soaking in water. Even when eggplant cut into 8 pieces was soaked 3 times for 5 minutes each in water (20°C) at 5 times its weight, only 3.1% (5.1 mg) of the total polyphenols (165.3 mg per 100 g of raw eggplant) and 1.1% (1.0 mg) of the chlorogenic acid (88.8 mg likewise) came out into the water, and most remained in the eggplant."Scope: Commercially available eggplant (Sennari) cut into eighths (8 pieces). A case sautéed for 4 minutes in 30 mL of salad oil and a case deep-fried for 3 minutes in 500 mL of salad oil at 170°C. Components were measured only; no sensory test was conducted.
Note: This measures the distribution of total polyphenols and chlorogenic acid, which the authors call "astringent components"; the sensory astringency was not measured. The components in the adhering oil are the amounts washed out with methanol. The reasons for the different transfer ratios in sautéing and deep-frying (heating time, oil uptake, tissue breakdown by stirring) are the authors' conjecture. Read it together with the 1986 sensory result (astringency was weaker when sautéing or deep-frying with oil).
Show data
ingredient-eggplant —is_processed_by→ "Sautéing and deep-frying. When 100 g of eggplant was sautéed, 51.7% of the total polyphenols and 59.8% of the chlorogenic acid had moved into the oil adhering to the surface; when deep-fried, 37.3% of the total polyphenols and 47.7% of the chlorogenic acid had moved into the adhering oil. Only 0.7 mg of total polyphenols and 0.2 mg of chlorogenic acid had moved into the frying oil left in the pan."