The importance of linoleic acid and linolenic acid as precursors of hexanal and trans-2-hexenal in black tea

During tea fermentation, linoleic acid in the neutral fat fraction,and linolenic acid in both the neutral fat and phospholipidfractions from leaves decreased. The addition of linoleic orlinolenic acid to leaf macerates during fermentation resultedin an increase in hexanal or trans-2-hexenal in the volatilefraction. Tracer experiments showed the direct conversion oflinoleic-U-¹⁴C and linolenic-U-¹⁴C acids to labeled hexanaland trans-2-hexenal, respectively, which were identified as2,4-DNPH derivatives. Further conversion of hexanal and trans-2-hexenal into hexanoicand trans-2-hexenoic acids during tea fermentation was suggestedby the increases in these compounds after the addition of hexanaland trans-2-hexenal to leaf macerates. (Received December 21, 1971; )     

Isolation and Chemical Structures of Two New Catechins from Fresh Tea Leaf

A total of 20 volatile organic compounds from the peel of citrus fruit Ohshima no. 1 were identified by gas chromatography-mass spectrometry (GC-MS). The amount of limonene in Ohshima no. 1 was lower than those in the parent cultivars, Miyauchi iyokan and Yoshiura ponkan, whereas those of γ-terpinene, linalool, sabinene, p-cymene, and terpinolene in Ohshima no. 1 were somewhat higher. However, comparing the results, it was found that volatile components from both parent cultivars were present in the peel of Ohshima no. 1. Principal component analysis (PCA) of data obtained with an electronic nose indicated that the odor of Ohshima no. 1 showed a clear upward displacement as compared with those of parent cultivars in PC1. The oils of Miyauchi iyokan and Yoshiura ponkan showed displacement in a negative direction, and a positive one in PC2. By PCA analysis, it was found that the odor quality of Ohshima no. 1 was very different from those of the parent cultivars.     

The Formation of Aldehydes from Amino Acids by Tea Leaves Extracts

In the reaction system containing amino acid, tea leaves extract and (?)-epicatechin, some amino acids such as glycine, alanine, valine, leucine, isoleucine, methionine and phenylalanine produced formaldehyde, acetaldehyde, isobutyraldehyde, isovaleraldehyde, 2-methylbutanal, methional and phenylacetaldehyde, respectively. The production of these aldehydes was regarded to proceed as Strecker degradation. On the production of phenylacetaldehyde it was revealed in the tea leaves extract-phenol-phenylalanine system that: 1) di-phenol was the most effective co-factor in comparison with mono- and tri-phenols; 2) the optimum concentration of (?)-epicatechin was 5×10-⁴M and the production was depressed at the concentration more than 5×l0-⁴M; 3) the production decreased by diluting tea leaves extract.     

Volatile and Non-volatile Forms of Aroma Compounds in Tea Leaves and Their Changes due to Injury

Fresh tea leaves were homogenized in a chloroform-methanol mixture (1:1, v/v), and separated into chloroform-soluble and methanol-water-soluble fractions after addition of water. From the chloroform-soluble fraction, the volatile forms of the aroma compounds were obtained. The non-volatile forms of the aroma compounds were associated with the methanol-water-soluble fraction, and were converted to volatile forms by hydrolysis with dilute acid.

The amount of the aroma compounds in the free form, such as cis-3-pentenol, hexanol, cis-3-hexenol, trans-2-hexenol, linalool, linalool oxide (cis, 5-membered), linalool oxide (trans, 5-membered), linalool oxide (trans, 6-rnembered), linalool oxide (cis, 6-membered), nerol, geraniol, phenylmethanol, and 2-phenylethanol, markedly increased during black tea manufacture. However, those in the bound form, showed a slight decrease during the manufacture. The increases in the former were also brought about by maceration, or treatment of the tea leaves with monoiodoacetate or malonate.     

Volatile Flavor of Black Tea

The volatile components extracted from fresh tea leaf, fermented leaf and black tea were analysed by gas chromatography.

Quantitative difference in the composition of essential oils was observed between fresh leaf and manufactured black tea; the former was rich in alcohols, whereas the latter in aldehydes and acids.

During fermentation process the following components mainly brought about changes: n-capronaldehyde (4.1 times after fermentation for 3hrs.), trans-2-hexen-l-al (13.2 times) and cis-3-hexenoic acid (1.2 times) increased, but n-hexylalcohol (0.7 time), cis-3-hexen-l-ol (0.7 time) and methylsalicylate (0.8 time) decreased.

These changes during fermentation were scarcely carried out in nitrogen atmosphere.     

Induction of Peroxidase Activity by Ethylene and Indole-3-acetic Acid in Tea Shoots

Chavicol was isolated as a drosophila larva-growth inhibitor from the leaves of Viburnum japonicum Spreng. The inhibitory activities of chavicol and its related compounds against drosophila larvae and adults were examined.     

The Production of Phenylacetaldehyde from l-Phenylalanine in Tea Fermentation

Tea leaves macerated with l-phenylalanine generated rose like aroma. The gas chromatogram of the essential oil obtained from these leaves showed extremely large peak of phenylacetaldehyde. The evidence for degradation of l-phenylalanine to phenylacetaldehyde and carbon dioxide was given by the radioactive tracer experiment using l-phenylalanine-U-¹⁴C. The phenylacetaldehyde was presumed to be an intermediate product in tea fermentation from the data on the changes of the compound in tea fermentation process.     

Effect of shade treatment on biosynthesis of catechins in tea plants

When tea plants were shaded with black lawn cloth for severaldays in the field, the accumulations of (—)-epicatechin,(—)-epicatechin-3-gallate, (—)-epigallocatechinand (—)-epigallocatechin-3-gallate decreased in newlydeveloping tea shoots. Radioactive tracer studies showed thatthe conversions of glucose-U-¹⁴C, shikimic acid-G-¹⁴C and phenylalanine-U-¹⁴Cinto (—)-epicatechin and (—)-epigallocatechin moietieswere depressed by the shade treatment for tea plants but theincorporation of trans-cinnamic acid-3-¹⁴C was not affected.The treatment was found to have no significant effect on theactivities of phospho-2-keto-3-deoxy-heptonate. aldolase (EC.4.1.2.15 [EC] ), 3-dehydroquinate synthase (EC. 4.6.1.3 [EC] ), 3-dehydroquinatedehydratase (EC. 4.2.1.10 [EC] ), shikimate dehydrogenase (EC. 1.1.1.25 [EC] )and trans-cinnamate 4-monooxygenase (EC. 1.14.13.11 [EC] ) in theshoots, whereas the activity of phenylalanine ammonia-lyase(EC. 4.3.1.5 [EC] ) clearly decreased. (Received March 17, 1980; )     

Volatile Flavor of Black Tea

The first effluent of essential oil of black tea in the gas chromatographic analysis is important for characterizing black tea flavor. The isolation and identification of main unknown components were conducted by means of gas chromatography, and also by infrared spectra and ultraviolet spectra. Ethylacetate, ethylalcohol and β-myrcene were identified as the increasing compounds during fermentation. cis-β-Ocimene and trans-β-ocimene were also identified only in completely manufactured black tea. These three terpenoid hydrocarbons are newly found constituents of essential oil of black tea and are supposed to contribute considerably to the black tea flavor.