The mechanisms of the formation of light-induced off-flavors in sour citrus juices such as lemon and kabosu were examined. Photosensitivity of chlorophylls was observed to promote off-flavor formation, as off-flavors are formed in the presence of chlorophylls. Photosensitivity is concentration dependent, and chlorophylls at sub-ppm levels rapidly promote off-flavor formation in citrus juice. Moreover, chlorophyll photosensitivity strengthens at the strong acid region and reversely weakens at the weak acid region. These results suggest that preventing chlorophyll contamination in citrus juice products packaged in clear bottles can be achieved at low pH. That is, chlorophyll photosensitivity is weaker at the weak acid region, and thus even in the presence of chlorophylls, light can be present and not induce off-flavor formation in citrus juice. Taken together, the concentration of chlorophylls and pH of citrus juice should be strictly controlled during manufacturing to prevent light-induced off-flavors.

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Whey protein concentrate (WPC) is a byproduct of cheese and casein during the dairying process. It is currently used as a food additive or nutritional supplement. To determine a more beneficial use of WPC, we focused on the antibodies against potential pathogenic bacteria and their toxins contained in WPC. The immunoglobulin content of WPC products varied from 0 to 5.2%. Antibody specificity was analyzed for 33 species of heat-killed pathogenic bacteria and 5 types of bacterial toxins. Specific antibodies to the respective antigens were found, suggesting that antibodies to other bacteria and toxins that were not used in this study might also exist in WPC. Moreover, absorption experiments showed that WPC contained cross-reactive antibodies to other bacteria. Based on these findings, whey antibodies may possess a potential therapeutic usage for treatment of patients with autoimmune diseases such as rheumatoid arthritis, in which bacterial toxins and an abnormal balance of intestinal bacterial flora are major fundamental factors.

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Seed shells are discarded as waste products of Japanese horse chestnut seeds used as ingredients in traditional Japanese foods. Hot-water extraction of these seed shells yielded substances that were tested in vitro for their inhibitory effects on pancreatic lipase. The extracts were fractionated by column chromatography on Diaion HP-20 and Chromatorex ODS 1024T columns to obtain the polyphenolic compounds. The polyphenolic compounds were separated by Sephadex LH-20 column chromatography into three fractions (F1, F2, and F3), depending on their degree of polymerization. F1, containing the phenolic substances with the lowest molecular weight, failed to inhibit pancreatic lipase, whereas F2 and F3 both showed potent inhibitory activities to pancreatic lipase. An oral fat tolerance test in mice revealed that these polymeric proanthocyanidins suppressed fat digestion in vivo. Taken together, seed shells of Japanese horse chestnuts may provide a source for highly polymerized polyphenols that could be used as nutraceutical factors with anti-obesity effects.

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A novel dairy cream was developed by combining nanofiltration (NF) of raw milk followed by deoxygenation with the conventional separation and pasteurization process. The deoxygenation was achieved by nitrogen gas dispersion treatment (NT) of NF milk. Nanofiltered and nitrogen gas-treated cream (NFNT cream) was obtained through ultra high temperature (UHT) pasteurization of cream separated from NFNT milk. NFNT cream was characterized with a strong milk flavor and clean aftertaste and its taste was determined to be different from conventional UHT cream based on a sensory test panel. NFNT cream was also found to mask unpleasant odor from other food stuff such as heated egg yolk. The chemical compositions of NFNT cream were proven to fortify the milk flavor. Deoxygenation of cream prior to UHT pasteurization was thought to contribute to the clean aftertaste by suppressing unwanted oxidization-induced flavors. The cause of the masking effect of NFNT cream might have a relationship with the deoxygenated UHT process, but has yet to be elucidated

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We determined the carbon, nitrogen, and oxygen isotope ratios of domestic and imported (China and Taiwan) cultured eel, to devise a tool for verifying the geographical origin of eel commercially distributed in Japan. Carbon and nitrogen isotope ratios of domestic eel (δ¹³C=-17.6±0.6‰ (mean±SD), δ¹⁵N=+16.4±0.7‰) were higher than those of Taiwan (δ¹³C=-20.5±0.7‰, δ¹⁵N=+13.2±1.5‰) and Chinese (δ¹³C=-21.4±0.5‰, δ¹⁵N=+14.3±0.9‰) eel. On the other hand, the oxygen isotope ratio of domestic eel (+7.4±1.4‰) was lower than that of Taiwan (+10.0±1.3‰) and Chinese (+11.1±0.9‰) eel. These results suggest that carbon, nitrogen and oxygen stable isotope-ratio analysis is applicable as a potential tool for discriminating between domestic and imported cultured eels.

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[in Japanese]

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