The differences in cutting operations with kitchen knives were quantified, and damage to food materials caused by cutting was evaluated. The following two types of cutting operations were investigated : “straight-down cutting” (i.e., holding the knife perpendicular to the cutting board and forcing the handle straight down) and “push cutting” (i.e., forcing the knife forward and downward, tracing a parallelogram). An onion was cut into ∼0.3-cm-thick slices by two knives of different sharpness using the two types of cutting operations, and the cutting load values were recorded. The cutting load values during push cutting were smaller than those during straight-down cutting with both knives. The lowest cutting energy was recorded in the case of push cutting with the sharp knife (1.5×10² J/m²). On the other hand, the highest cutting energy was recorded in the case of straight-down cutting with the dull knife (8×10² J/m²). To evaluate damage to food materials, the amounts of onion juice and pyruvic acid, which can be used as an index of pungency, flowing from the cut surfaces as well as the roughness in 3D images of the cut surfaces observed under a digital microscope were quantified. When the cutting energy was low, these three measures were small. These results indicate damage to the cut surface caused by cutting operations is low when the cutting energy is also low.

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Stable isotope analysis of carbon, nitrogen, and oxygen (¹³C/¹²C, ¹⁵N/¹⁴N and ¹⁸O/¹⁶O) was evaluated as a potential tool for discriminating the geographical origin of eel products. We investigated a total of 244 samples collected from two countries ; 139 samples from Japan and 105 samples from China. We also developed method to minimize N₂ contamination of ¹⁸O/¹⁶O measurements, and confirmed the absence of oxygen-exchange during ultrasonic cleaning of the samples. The isotope ratios of carbon, nitrogen, and oxygen were significantly different between the Japanese and Chinese samples. The difference in the isotope ratio between collection years (i.e., 2010 and 2011) was significant for carbon and nitrogen, but negligible for oxygen. Based on these results, we established a linear discriminant model and tested its predictive accuracy by leave-one-out cross validation. Consequently, 97.8 % of the Japanese samples and 83.8 % of the Chinese samples were correctly identified. We concluded that stable isotope analysis is useful for discriminating the geographic origin of eel products.

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The mechanism for maltose generation by heating in the storage roots (SR) of sweet potato cultivar “Quick Sweet” containing starch with a low pasting temperature was investigated in comparison to “Beniazuma”, a cultivar with a normal starch pasting temperature. Starch pasting and maltose generation occurred in the SR of “Quick Sweet” heated at higher than about 60°C, which was about 20°C lower than that observed in “Beniazuma” SR. The β-amylase activity of “Quick Sweet” SR heated at 50-80°C was higher than that of raw SR and maintained about 50 % of the raw SR activity at 90 and 100°C. Meanwhile, the activity of “Beniazuma” SR heated at up to 70°C was not increased from the raw SR activity, and was greatly inhibited at 80°C and above. Because the enzyme activity relative to raw SR of “Quick Sweet” showed greater inhibition than “Beniazuma” at temperatures higher than 80°C, the β-amylase heat stability of heated “Quick Sweet” may be related to earlier starch pasting during the heating process. Therefore, maltose generation occurs earlier and is maintained longer in “Quick Sweet” SR than in “Beniazuma” during the cooking process.

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We investigated the effect of nisin and sucrose fatty acid esters on the growth of spoilage bacteria in fish-paste products. Nisin showed antibacterial activity against Bacillus subtilis and B. licheniformis vegetative cells and spores in liquid medium. Also, nisin exhibited a synergistic effect in combination with sucrose fatty acid esters (sucrose monolaurate and sucrose monopalmitate). The addition of nisin (12.5 μg/g) to fish-paste products suppressed the growth of B. subtilis and B. licheniformis during storage at 20°C and resulted in longer shelf-life of fish-paste products compared to control and fish-paste products with added potassium sorbate. In addition, the growth of spoilage bacteria was strongly inhibited by the combination of nisin (12.5 μg/g) and sucrose fatty acid esters (10 mg/g) in fish-paste products without starch. From these findings, we conclude that the addition of nisin is a potential alternative method for preventing spoilage caused by spore-forming bacteria in fish-paste products.

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For utilization of and high value addition to surplus egg white liquid, we developed a fermented egg white sauce. Aspergillus oryzae HO-117 was cultured using sponge cake made from egg white and bread flour with baking powder. A. oryzae exhibited favorable growth in sponge cake due to the medium’s porous structure. Neutral and acidic protease and glutaminase activities of the high-density koji culture were 2 to3 times higher than in typical koji cultivated using delipidated soybean and wheat. The sponge cake koji was mixed with liquid egg white and salt to prepare egg white moromi. After fermentation of the moromi for 24 weeks at room temperature, the resultant egg white sauce showed a unique egg flavor, abundant umami taste, and lighter color compared with typical soy sauce. No egg white protein was detected in the fermented egg white sauce using the official egg allergen detection kit. Moreover, ovomucoid with protease-inhibitor activity was also undetected.

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We have developed a simple method for removing mucopolysaccharide (MS) impurities from low molecular weight heparin (LMWH) preparations. Crude dalteparin sodium (DN-C) containing high molecular weight impurities such as sodium salts of over-sulfated chondroitin sulfate (OSH) and dermatan sulfate (DSH) was used as a model of LMWH preparations. In preliminary experiments, the sensitivities of OSH and DSH to ethanol were quite different, even though their molecular weights are similar. A two-step ethanol precipitation was used to remove these contaminants. Upon the first treatment, OSH was removed as a precipitate, and upon the second treatment, DSH was recovered in the supernatant. LMWH was concentrated in the precipitate following the second treatment. The contaminants were detected easily by nitrous acid de-polymerization followed by gel permeation HPLC. In contrast, it was difficult to detect small amounts of impurities by ¹H-NMR. We also tried purifying commercial DN products (DNG 1-3) to confirm the efficacy of this methodology and concluded that the two-step ethanol precipitation of LMWH, followed by purity analysis by gel permeation HPLC after nitrous acid de-polymerization of MSs, holds promise for the manufacture of high-quality LMWH preparations.

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Miso paste mixed with stock is popular because of its convenience. However, phosphatase, an enzyme present in miso paste, promotes the decomposition of this type of stock. To inactivate this enzyme, it is therefore necessary to heat miso before stock is added. Unfortunately, heating degrades the color and flavors of fresh miso. Radio-Frequency (RF) heating was thus used to inactivate enzymes in packed miso paste, and enzyme inactivation (phosphatase and protease) by RF heating was subsequently compared to that by conventional heating. Our results showed that the phosphatase and protease in packed miso were completely inactivated by RF heating at 72°C, which is 12°C lower than that observed with conventional heating. Furthermore, the RF heating time was reduced to one-third that of conventional heating.

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