Detection of shiikuwasha (Citrus depressa Hayata) juice adulterated with calamondin (Citrus madurensis Lour.) juice was investigated by the analyses of (1) phloretin dihydrochalcone glucoside, 3',5'-di-C-β-glucopyranosylphloretin (PD) detected by thin-layer chromatography and high-performance liquid chromatography (HPLC), (2) polymethoxylated flavones (PMFs), included nobiletin, tangeretin, and sinensetin, detected by HPLC, and (3) γ-terpinene peak percentage obtained by headspace solid-phase microextraction gas chromatography with cryofocusing. PD was detected in calamondin juice (25.5 mg/100 mL) but not in shiikuwasha juice. Shiikuwasha juice contained higher levels of nobiletin (48.8 mg/100 mL) than calamondin juice (2.4 mg/100 mL). Shiikuwasha juice was characterized by containing a higher percentage of γ-terpinene (12.3%) than calamondin juice (0.7%). A discrimination function obtained by a linear discriminant analysis with PMFs and a peak ratio of [nobiletin/tangeretin] and γ-terpinene detected the adulteration with accuracies of 91.7%. These three chemical markers were useful to detect shiikuwasha juice that is suspected of being adulterated with calamondin juice.
The composition of volatile components in 18 Citrus Archicitrus species, 17 Citrus Metacitrus species and two Fortunella species, according to the classification system established by Tanaka, was investigated using headspace gas chromatography-mass spectrometry. The composition of 48 volatile compounds in the juice of these species was determined, and principal component analysis was performed. Scores for the 1st and 2nd principal components are plotted as a scatter diagram. In Citrus Archicitrus, samples of Citrophorum, Cephacitrus and Aurantium formed individual groups, but others did not. In Citrus Metacitrus, samples of Acrumen were divided into two different groups. The composition of volatile components in citrus juice was consistent with each grouping of Tanaka's system, in particular, in the case of dividing the Citrus genus into the two subgenera Archicitrus and Metacitrus.
Cowpea (Vigna unguiculata) is one of the traditional ingredients of Japan. The objective of this study was to investigate the nutritional and chemical composition, and the biological activities of cowpea grown in Okinawa region, a subtropical area located in south west Japan. This study demonstrated that the protein and dietary fiber content of cowpea grown in the Okinawa region was similar to that of cowpeas grown in other countries. In addition, it was found that the sodium content and anthocyanin composition of cowpeas grown in the Okinawa region was different from that grown in other regions of Japan; however, no significant differences were observed in proanthocyanidin composition and content among the cowpeas grown in different cultivation areas in Japan.
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