Flavour Index Research Articles

Antioxidant attributes of tea in North Bengal, India: Relation with its principal constituents and properties of soil

This study was performed in 18 tea gardens in North Bengal, India, from 2012 to 2017. The data were pooled to investigate the relationship with soil physico-chemical properties, phyto-constituents, antioxidant attributes and age of the tea bushes and principal component analysis (PCA). PCA and dendro-hit maps were also performed with each region. The 28 principal components were chosen based on their eigen values, explaining the total data variance for tea in Dooars, Terai and Darjeeling hill. In almost all cases, composite soil physico-chemical attributes were heavily loaded on the second principal component and clustered, as visual evidenced by the dendro-hit map. Different attributes were significantly correlated each other in case of Terai i.e. (value of “r’’ at P<0.01 level) clay fraction (0.778), electrical conductivity (0.618), N (0.777), S (0.748), P (0.514 ppm), flavour index (0.918), total polyphenol (0.687) DPPH (0.794), nitric oxide (0.913), anti-lipid peroxidation (0.717) and metal chelating (0.665). In Dooars region, attributes were significantly correlated with silt (0.718), pH (0.875), P (0.615 ), chloride (0.858), TP (0.776), flavonol (0.923), quinone (0.666), tannins (0.865), DPPH (0.536), superoxide (0.576), ABTS (0.520) and MC (0.777) and in the case of Darjeeling hills, attributes were highly correlated with clay (0.812), sand (0.818), silt fraction (0.974), K (0.932), S (0.999), MC of soil (0.671), TP (0.853), tannins (0.912), DPPH (0.624), ABTS (0.661) and MC (0.633) repectively.

Effects of climatic factors on antioxidant quality of tea (Camellia sinensis) in North Bengal

Tea [Camellia sinensis (L.) O. Kuntze] is one of the important contributors to the growing economy of NorthBengal. The phytochemical and therapeutic qualities of tea prominently altered recently due to continuous change in climatic conditions of North Bengal. The nutraceutical quality of tea is largely dependent on antioxidant attributes. For investigating the relationship between antioxidant attributes and climatic factors, the present field experiment was conducted in 18 tea gardens of Terai, Dooars and Darjeeling Hills of North Bengal during 2012–17. Antioxidant and phytochemical analysis was performed in three different harvest seasons, viz. March, June and December. Phenolic compounds including catechins were low during winter months, and then gradually increased up to warmer spring season. In stress condition, tea plants biosynthesized more flavonoids and high flavour index in Darjeeling hills. However, free-radical scavenging and metal chelating activities were found to increase from spring to winter season. The data were pooled for PCA analysis to determine the relationship between seasonal variations and tea antioxidant quality in each region of North Bengal separately. Different attributes of climatic factors significantly correlated with antioxidant quality and bioactive compounds. Variation in climate is reportedly affecting the antioxidant quality of tea and its shifting pattern grossly influences the key phytochemicals responsible for the flavour of tea.

CHANGES IN VOLATILE COMPOUNDS DURING ORTHODOX BLACK TEA (Camellia sinensis) MANUFACTURING

The content of volatile compounds in tea leaves at different stages of OTD black tea manufacture was measured. Aroma concentrate was prepared by Brewed Extraction Method (BEM) and analyzed by GC/MS. The results showed that volatile compounds were products of lipid breakdown (groupI) and derivatives from terpenoids, carotenoids and amino acids (group II). During processing the changes of group I and group II were significantly different from each others and effect to the flavour index. A gradual increase of percentage relative content from 16.72 to 18.09 in the group I volatile compounds was noticed during withering. While during fermentation, the sum of group II compounds content was higher than than that of group I compounds therefore the value of flavour index, and the value of FI is higher than 1.

Effect of rolling methods and storage on volatile constituents of Turkish black tea

AbstractThe leaves of harvested tea [Camellia sinensis (L.) O. Kuntze] can be processed into different products such as black tea, green tea and oolong tea. Black tea is the mostly consumed worldwide among these products. Black tea production is achieved by a series of processing steps namely withering, rolling, fermentation, drying, sieving and packaging. Rolling is one of the most important steps in the production as it ensures uniform maceration of tea leaves and promotes oxidation reactions catalysed by phenol oxidase enzymes during the fermentation process. The rolling of tea leaves is generally performed by either Crushing‐Tearing‐Curling (CTC), rotorvane or Orthodox methods. However, in Turkey, rolling is also performed using a combination of rotorvane and orthodox which is called the “ÇAYKUR” method. The rolling method provides a unique taste and flavours. Thus, this study was conducted to compare volatile constituents of the black teas produced by the above rolling methods and to determine the volatiles during the 6‐month storage period. Some specific compounds such as 2,6‐nonadienal, 3‐hexen‐2‐one and dodecanal for ÇAYKUR, 2,5‐octanedione for Orthodox and methylpyrazine for CTC were identified to differentiate the rolling system. This study also showed that a few compounds can be used as markers of storage. The number and amounts of volatiles, especially compounds with a high molecular weight, increased by storage. In addition, the flavour quality of the teas was evaluated by the Wickremasinghe–Yamanishi ratio (WYR), Mahanta ratio (MR) and Owuor Flavour Index.

Impact of various foliar diseases on the biochemical, volatile and quality constituents of green and black teas

The effect of various foliar diseases such as blister blight, brown blight, grey blight, bird’s eye spot and sooty mould on physiological functions, important biochemical, volatile and quality parameters of green and black teas were compared and evaluated. The results revealed that there was a considerable reduction in physiological activities such as photosynthetic and transpiration rates. Under natural condition, the diseases caused significant decrease in polyphenols, catechins, and aminoacids contents of green leaf which are known to be important precursors determining the quality of black tea. Consequently, a drastic variation existed between volatile flavor components of diseased leaves when compared to healthy ones. A corresponding decrease in the principal tea quality constituents like theaflavin and thearubigin were substantially reduced in made tea. Due to pathogen invasion in tea leaves, the degree of tea quality is varied in varying levels. Among the various tea pathogens, Exobasidium Vexans affected the overall tea quality extensively when compared to other tea pathogens. In addition, the infestation of diseases declined flavour index value and created difficulty in withering and fermentation during tea processing which ultimately affect the overall quality of tea.

Evaluation of various fungicides and microbial based biocontrol agents against bird’s eye spot disease of tea plants

A field experiment was conducted to study the efficacy of six fungicides comprising contact, systemic and botanical fungicides and three biocontrol agents for the management of bird’s eye spot disease in tea plantations. Among 16 treatments, systemic fungicides were found to be superior to biocontrol agents in controlling the disease whereas the maximum green leaf yield was significantly increased in those applied with biocontrol agents. On the whole, Streptomyces sannanensis offered the maximum yield of 3998 kg ha −1 made tea followed by Trichoderma harzianum (3884 kg ha −1 made tea). Between the two different carrier materials evaluated for the application of biocontrol agents, vermicompost-based bioformulation showed better efficacy than talc-based formulation. Of the three (bacteria, fungi and actinomycetes) groups of biocontrol agents, S. sannanensis was better than Pseudomonas fluorescens and Trichoderma atroviride belonging to bacterial and fungal antagonists; respectively in terms of disease protection and increasing yield potential. Similarly, the biometric, physiological and biochemical parameters were also increased in plants greatly after imposing various treatments. Plucking surface of the bush, number of plucking points per unit area, internodal length, leaf moisture and dry matter contents were found higher in plots applied with biocontrol agents than those treated with fungicides. Almost all of the tea quality parameters such as total liquor colour, thearubigins, theaflavins, highly polymerized substance and caffeine were significantly improved in biocontrol treated plants. Theaflavin and thearubigin contents were increased in the range of 9.00–9.57% and 1.27–1.54% respectively in vermin based treatment. Similarly the amount of caffeine content (3.66–4.08%) and flavour index (4.18–5.31%) were considerably enhanced.

Impact of genotype, seasons and manufacturing process on the activities of peptidase and lipoxygenase in tea

Tea flush shoots comprising three leaves and a bud were harvested from five different cultivars planted in a single area of UPASI Tea Research Farm and analysed for lipoxygenase (LOX) and peptidase activities. Among the cultivars, UPASI-3 recorded high peptidase activity, while UPASI-9 registered significantly higher lipoxygenase activity. This study suggested the influence of genotype on these enzymes. Green leaves sampled during mid-April to May (Premonsoon) exhibited higher peptidase activities, while LOX activity was predominant during monsoon period (June to August). Peptidase activity was higher in actively growing tea tissues (bud) and decreased with shoot maturity, whereas LOX activity significantly increased with the maturity of shoot from bud to third leaf and rapid decline in the internodes. During manufacturing process, the activity of both the enzymes varied widely and maximum peptidase activity was observed in withered leaves and cut dhool had maximum LOX activity. The flavour analysis was carried out in green leaf, withered leaf, cut dhool, fermented dhool and black tea which indicated that the value of flavour index was higher in final black tea and lowest in green leaf. This provides significant information that most of the aroma compounds are formed during processing (after harvesting only).

Influence of region of production on clonal black tea chemical characteristics

Production of black tea from the same vegetatively propagated (VP) cultivars, in Kenya and Malawi, shows variations in both chemical composition and quality. Whereas it is possible to produce black teas with similar total theaflavins and individual theaflavins, brightness and total colour levels, black teas from Kenya generally have higher thearubigins, total volatile flavour compounds and flavour index. The black tea fermentation process is much faster in Malawi compared to that in Kenya, as evidenced by faster production of plain black tea chemical parameters, especially theaflavins. Consequently, in Malawi the maximum amount of theaflavins formation takes a shorter fermentation duration than in Kenya. Given ample fermentation duration, fermentation in Kenya produces a similar amount of theaflavins. This makes it necessary to optimise fermentation time, in different geographical regions even when the same cultivar is being processed. The other plain black tea quality parameters (thearubigins, brightness and total colour) were higher in black tea which was processed in Kenya than those processed in Malawi. However, the pattern in the changes in the individual theaflavins or theaflavins digallate equivalent followed that of total (Flavognost) theaflavins, suggesting that the flavan-3-ols patterns in tea leaf might not have been affected by the geographical area of production. The total volatile flavour compounds (VFC), Group I and II VFC and the flavour index were higher in black teas processed in Kenya, further demonstrating the fact that high grown Kenyan teas are more flavoury. In both Kenya and Malawi black teas, aroma quality declined with a long duration of fermentation. Short fermentation time is therefore a method of producing more aromatic black teas. The variations in black tea quality between Malawi and Kenya were possibly due to difference in environmental conditions, leading to different shoot growth rates and biochemical composition in the shoots.

Physiological response of loquat fruit to different storage conditions and its storability

Loquat ( Eriobotrya japonica Lindl.) fruit were stored in air at 25 °C, modified atmosphere packaging (MAP, polyethylene bag of 0.01 mm thickness) at 1 and 6 °C, controlled atmospheres (CA) of 10% O 2 + 1% CO 2 and, CA with 70% O 2 treatment for 24 h at first, then stored in CA with 10% O 2 + 1% CO 2 at 1 °C, to determine the effects of atmospheres and temperatures on quality attributes, physiological properties and storability during storage periods. The results indicated CA with 10% O 2 + 1% CO 2 was more effective in reducing fruit decay, SSC/TA, pH, activities of endo-PG and exo-PG, inhibiting ethyl acetate accumulation in fruit, inducing ethanol accumulation in fruit at later storage period in comparison with MAP treatment. Loquat fruit could be stored in this CA condition at 1 °C for more than 50 d with normal flavour and low decay index of about 7%. Short term high-O 2 treatment at the beginning of storage had little effect on fruit flavor, but stimulated ethanol accumulation in loquat fruit, and reduced activities of endo-PG and exo-PG. MAP treatment showed more effectiveness in reducing fruit decay, off-flavor and weight loss at 1 °C than at 6 °C. CA conditions were more effective for reducing the activities of PPO and oxidative stress compared to other treatments, which may be the reason why loquat fruit stored in CA conditions had lower decay index than that kept in other conditions.

Quality standards of CTC black teas as influenced by sources of potassium fertiliser

AbstractThe quality aspects of CTC (crush, tear and curl) black teas were examined against different sources of potassium fertiliser. Potassium supplied as muriate of potash (MOP) improved the liquor components such as theaflavin (TF), thearubigin (TR) and TF/TR ratio at higher levels. The same effect was noticed at lower level itself when the source of K was changed to sulfate of potash (SOP). Termination of K application reduced the TF/TR ratio drastically. The entity responsible for strength, body and colour of tea brew, namely highly polymerised substances, attained its optimum proportion at an NK ratio of 1:0.21 using SOP. Generally, there was a good response from SOP‐treated blocks to caffeine. The flavour index was a maximum at a 1:0.42 NK ratio, using SOP. A slight peak and trough were observed in the case of crude fibre content and water extract over control and MOP‐treated blocks. The leaf K content was negatively correlated with CFC content of made tea. An antagonism was observed between leaf K and Mg. Copyright © 2005 Society of Chemical Industry

Investigation of aromatic compounds in roasted cocoa powder

Most of the volatile compounds identified are highly significant in determining cocoa powder flavour, and this paper demonstrates that basic sensory perceptions (undesirable, bitter pungent, repulsive, fruity, nutty, floral, vegetal, and sweet chocolate) can be totally explained by aroma compounds with R2-adjusted values of 0.85 and greater. Samples from five geographical origins of cocoa bean were characterized by chemical compounds and sensory attributes. The aroma extracts were obtained by a two-step procedure involving (1) preliminary steam distillation under reduced pressure to evaluate the methylpyrazines generated in roasted cocoa powder by spectrophotometry (flavour index), and (2) Likens-Nickerson’s simultaneous steam distillation and solvent extraction method with added NaCl. The distilled compounds were separated by adsorption chromatography in six fractions depending on the polarity. A combined total of 114 compounds were detected by gas chromatography/mass spectrometry, 110 of which were identified. About 15 components in the mean milligrams per kilogram range (1.09–4.67 mg kg−1) and 95 components in the mean micrograms per kilogram range (12–980 µg kg−1) were quantified. The major components of cocoa aroma were 2,3,5,6-tetramethylpyrazine, benzaldehyde, 2-phenylacetaldehyde, acetophenone, 3-methylbutyric acid, 5-methyl-2-phenyl-2-hexenal, ethyl phenylacetate, and 3-hydroxy-2-methyl-4-pyrone (mean greater than 1.30 mg kg−1).

Impact of nitrogen and potassium fertiliser application on quality of CTC teas

Tea flush shoots, comprised of three leaves with a bud, were collected from long-term fertiliser trial plots, in four successive plucking rounds after NK manuring, and processed into black tea. The black tea samples were analysed for thearubigins, theaflavins, caffeine, volatile flavour compounds, crude fibre content and water-soluble solids. Results indicated that overall quality of tea was impaired when either nitrogen or potassium was used at high levels. The NK ratio of 1:0.83 appeared to be optimum with respect to quality of made tea as well as for flavour index, particularly when the N dose was 300 (or) 450 kg/ha/year. Amino acid and polyphenol contents of the crop shoots were also higher due to this ratio of NK manuring. A lower polyphenol content was recorded when the plots were supplied with less (or) no nitrogen and potash fertilisers. Positive correlation coefficients were obtained between nitrate reductase (NR) activity of crop shoots and amino acid content.

The impact of pruning and time from pruning on quality and aroma constituents of black tea

The precursors responsible for tea quality, such as polyphenols, were found to increase in the first year and thereafter declined in content with time from pruning. While the green pigment content and ash content increased, the lipoxygenase activity showed substantial and progressive decline with time from pruning. The content of carotenoids were found to increase in the first 3 years after pruning and then showed a decline. A quantitative assessment of the various biochemical and quality parameters, such as theaflavin content (TF), total liquor colour (TLC), and water extract, showed progressive increase with time from pruning. The polyunsaturated fatty acids showed a marked decrease in their contents with decrease in the total fatty acids and various lipid fractions with time from pruning. However, C (18: 0) showed an increasing trend. While the sum of VFC Group II showed an enhancement, that of Group I showed a decline with time from pruning. As a result, the flavour index value was found to increase with time from pruning. The sensory evaluation supported the trends observed in the analytical data.

Flavour index and aroma profiles of fresh and processed honeys

AbstractThis paper discusses the importance of flavour profiling in detecting indicative parameters for quality control of fresh and heated honey. Flavour compounds of six unifloral honeys (Lavandula stoechas, Castanea sativa, Dorycnium pentaphyllum, Rosmarinus officinalis, Eucalyptus sp and Robinia pseudoacacia) were investigated. The aroma extracts were obtained by a two‐step procedure involving (i) preliminary steam distillation under reduced pressure to evaluate the methylpyrazines generated in heated honeys by spectrophotometry (flavour index) and (ii) Likens–Nickerson's simultaneous steam distillation and solvent extraction (SDE) method with added NaCl. A combined total of 64 compounds were detected by gas chromatography/mass spectrometry (GC/MS), 58 of which were identified. Some compounds appeared to be characteristic of the floral source, particularly in Spanish lavender (methylated aliphatic acids and aromatic esters), eucalyptus (2,3‐pentanedione, acetoin, 1‐hexyl alcohol, 2‐acetyl‐5‐methylfuran, furfuryl propionate, 2‐phenylacetaldehyde and nerolidol), chestnut (acetophenone and 2‐aminoacetophenone), rosemary and D pentaphyllum (aromatic acids and esters, 2‐phenylacetaldehyde, farnesol and thymol) honeys. Robinia honey samples were characterised by very low levels of aromatic compounds. Twenty‐six flavour compounds were statistically closely related to the floral origin of the honeys (P ≤ 0.05). The flavour index was evaluated progressively in heated honeys, whereas in fresh honeys it showed a minimal value.© 2003 Society of Chemical Industry

Evaluation of purine alkaloids and diketopiperazines contents in processed cocoa powder

This paper describes the evaluation of purine alkaloids and diketopiperazines (DKPs) contents in 24 samples of processed non-alkalinized cocoa powder. The chemical data obtained were related to sensory evaluation and subjected to analysis of variance. During cocoa roasting, the content of DKPs can be increased, resulting in a negative influence on the sensorial quality of cocoa. A pronounced bitter metallic taste can originate from some of these compounds, and becomes stronger when these DKPs are combined with purine alkaloids. The cocoa roasting process at different temperatures (125, 130, 135, 140 and 145 °C) and durations (3, 10, 16 and 20 min) was evaluated by measuring the flavour indices, formol numbers and DKP contents in 24 samples of cocoa powder. The addition of reducing sugars was also evaluated in the same industrial processes in 27 other samples of cocoa powder. The higher the roasting temperature of the cocoa was, the more elevated the flavour index became, except at temperatures up to 140 °C, where DKPs were generated in large proportions.

Exotic Kondo effects in metals: Magnetic ions in a crystalline electric field and tunnelling centres

The ordinary single-channel Kondo model consists of one or more spin-½ local moments interacting antiferromagnetically with conduction electrons in a metal. This model has provided a paradigm for understanding many phenomena of strongly correlated electronic materials, ranging from the formation of heavyfermion Fermi liquids to the mapping of a one-band model in the cuprate superconductors. The simplest extension of this ordinary Kondo model in metals which yields exotic non-Fermi-liquid physics is the multichannel Kondo impurity model in which the conduction electrons are given an extra quantum label known as the channel or flavour index. In the overcompensated regime of this model, nonFermi-liquid physics is possible, in contrast with the single-channel model. We overview here the multichannel Kondo impurity model candidates most extensively studied for explaining real materials, specifically the two-level system Kondo model relevant for metallic glasses, nanoscale devices and some doped semiconductors, and the quadrupolar and magnetic two-channel Kondo models developed for rare-earth and actinide ions with crystal-field splittings in metals. We provide an extensive justification for the derivation of the theoretical models, noting that, whenever the local impurity degree of freedom is non-magnetic, a two-channel Kondo model must follow by virtue of the magnetic spin degeneracy of the conduction electrons. We carefully delineate all energy and symmetry restrictions on the applicability of these models. We describe the various methods used to study these models along with their results and limitations (multiplicative renormalization group, numerical renormalization group, non-crossing approximation, conformal field theory and Abelian bosonization), all of which provide differing and useful views of the physics. We pay particular attention to the role that scale invariance plays in all these theoretical approaches. We point out in each case how various perturbing fields (magnetic, crystalline electric, electric field gradients and uniaxial stress) may destabilize the non-Fermi-liquid fixed point. We then provide an extensive discussion of the experimental evidence for the relevance of the two-level system Kondo model to metallic glasses and nanoscale devices, and of the quadrupolar and magnetic two-channel models to a number of heavyfermion-based alloys and compounds. We close with a discussion of the extension of the single-impurity models which comprise the main focus of this review to other systems (Coulomb blockade), multiple impurities and lattice models. In the latter case, we provide an overview of the relevance of the two-channel Kondo lattice model to non-Fermi-liquid behaviour and exotic superconductivity in heavy-fermion compounds and to the theoretical possibility of odd-frequency superconductivity, which is realized (for the first time) in the limit of infinite spatial dimensions for this model.

The impact of processing techniques on tea volatiles

The impact of various cultural and manufacturing techniques on volatile flavour composition was studied in order to optimize the conditions for production and retention of aroma in relation to tea quality. The Flavour Index was in the order: clonal variation—Assam > > Cambod > China Shoot maturity—Bud + 1st leaf > > > 2nd leaf > > 3rd leaf; plucking interval 7 day > 14 day; processing—green leaf > withered leaf—fermented dhool < dried tea < < tea brew; withering—soft < normal < hard. VFC Group I was in general dominated by trans-2-hexenal and Group II by linalool, phenylacetaldehyde and geraniol. Fresh green leaf had a high content of hexanol, hexanal, hexenol, hexenal and methyl salicylate. Upon withering, a sharp increase in Group I was noticed, the most remarkable being in hexenol. Group II also increased, but the extent was less except for linalool. During fermentation, Group I alcohols showed a sharp reduction with concomitant increases in aldehydes, especially trans-2-hexenal. In Group II, all compounds increased except methyl salicylate and the ionones. In the firing stage, high losses of Group I and Group II were registered. All the Group I compounds showed a decline with the progress of withering, but the opposite applied to Group II compounds, except for the alcohols. Mechanical injury during handling of leaf before cutting increased the Group I content enormously. The addition of exogenous fatty acids, mainly linoleic acid, produced substantial amounts of Group I compounds, dominated by trans-2-hexenal and hexanal. The inhibition of lipoxygenase totally reduced the formation of Group I volatiles.

The changes in black tea quality due to variations of plucking standard and fermentation time

Catechin levels in green leaf, total theaflavins, brightness, thearubigins, colour, flavour index and sensory evaluation decrease with coarse plucking standard in clone 6/8. The sum of Group I volatile flavour compounds and C 6 aldehydes and alcohols, in particular, increases with coarse plucking standard. The sum of Group II did not follow a particular pattern, but flavour index decreased with coarse plucking standards. The decrease in total theaflavin levels was due to the decrease in all the individual theaflavins. Although all the individual theaflavin levels decreased with coarse plucking standards, the decrease was greater in galloylated theaflavins, especially in theaflavin digallate, compared with simple theaflavin. Short fermentation times produced black teas with higher brightness and flavour index, but lower theaflavins, thearubigins and colour, irrespective of plucking standard. Total theaflavins reached a maximum after 90 min of fermentation, irrespective of the plucking standard, whereas ungalloylated theaflavin levels decreased with extended fermentation duration at all plucking standards, theaflavin-3-gallate and theaflavin-3, 3’-digallate levels increased, resulting in the increase in theaflavin digallate equivalent. Brightness and flavour index decreased while thearubigins, colour, and Groups I and II volatile flavour compound levels increased with long fermentation.

The Impact of Withering Temperature on Black Tea Quality

High leaf temperatures during the withering process of black tea manufacture decrease the theaflavins, brightness, flavour index and sensory evaluation scores of black tea. Black teas manufactured with withering temperature above 30°C have high thearubigins and total colour levels but lack briskness. Results suggest a need to control temperatures below 30°C during withering.

Response of some black tea quality parameters to nitrogen fertiliser rates and plucking frequencies

AbstractThe effects of the rate of application of nitrogenous fertiliser and frequency of plucking (harvesting) on various black tea quality parameters and yields were compared on done 6/8. High rates of nitrogen application and long plucking intervals reduced the theaflavin content and brightness of black tea liquor. The caffeine content of the black tea increased with increasing rates of nitrogen application but decreased with increase in the plucking interval. The Group I volatile flavour compounds increased with nitrogen application rate and long plucking intervals while the Group II volatile flavour compounds and the flavour index decreased. Tasters preferred teas from shorter plucking intervals and low rates of nitrogen application. Yields increased with increasing rates of nitrogen but were lowered by long harvesting intervals. The rate of nitrogen application did not change the distribution of leaf into different standards.