Pangium edule Reinw. is a tropical plant from Southeast Asia and southern Pacific islands whose seeds are commonly consumed by the native population after being treated to remove its high content of cyanogens. It can be consumed directly as vegetable or exposed to pit fermentation that changes the appearance and adds specific savory flavor, and consumed as spice. The fermented feed is called kluwak. It has been reported that the seeds contain high level of antioxidant activity and high amount of its components. Here we report the distribution of the antioxidant activity and component and the effects of pit fermentation and thermal cooking process on the antioxidant components of Pangium edule seed, measured using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and oxygen radical absorbance capacity (ORAC), total phenolic, ascorbic acid and vitamin E contents, and fatty acid composition assays. In addition, the changes in physicochemical properties of the seeds during pit fermentation were also quantified. The antioxidant components of the seed is mainly distributed in the non-oil fraction when measured using DPPH radical-scavenging activity and almost equally distributed in non-oil and oil fractions when measured using ORAC. The antioxidant components in the non-oil and oil fractions consist mostly of phenolic compounds and γ-tocotrienol, respectively. Pit fermentation significantly increased the antioxidant activity of both fractions, most likely caused by the formation of Maillard reaction products. Similarly, thermal cooking process increased the antioxidant activity of both fractions.

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The aroma concentrates were prepared from raw soy sauce, heat-treated soy sauce, and the cooked forms of both the raw and heat-treated soy sauces. The gas chromatography-olfactometry analysis of the aroma concentrates showed that more compounds with “roasty” and “sweet” aroma and less compounds with “burnt” aroma were detected in raw soy sauce than in heat-treated soy sauce and that the detectable aroma compounds in raw soy sauce increased by cooking. The results of aroma extract dilution analysis showed that sweet-caramel-like 5 (or 2)-ethyl-4-hydroxy-2 (or 5)-methyl-3(2H)-furanone (HEMF) and flowery 2-phenylethanol had the highest flavour dilution factor (FDf) in raw soy sauce, while HEMF and roasty 4-vinylguaiacol had the highest FDf in heat-treated soy sauce. After cooking, HEMF had the highest FDf in raw soy sauce, while the FDf of HEMF in heat-treated soy sauce reduced. Compared to the cooked heat-treated soy sauce, the cooked raw soy sauce, having a “sweet” and “roasty” aroma characteristic, clearly had more complicated aroma components. In addition, a quantitative descriptive analysis showed that the “roasty” and “sweet” aroma in the cooked raw soy sauce was significantly stronger than that in the cooked heat-treated soy sauce, and this aroma characteristic was found to be suitable for cooking.

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The salt dissolution rate in the boiling process of dried noodles was determined by applying the principles of first-order reaction. The salt dissolution rate (λ, %/min) was computed from the gradient of the straight line, according to the following formula: ln ([NaCl_∞]-[NaCl_t]) = ln [NaCl_∞]-λt. The λ of the dried noodles decreased inversely with the cross-sectional area of the noodles (R² = 0.968, n = 12). However, the λ of Inaniwa-udon samples did not decrease, even with an increase in the cross-sectional area. This may be due to the cavities generated inside the Inaniwa-udon samples that potentially decreased the apparent cross-sectional area.

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