The bitter and astringent taste of tea and tea extract is still not favored by many consumers, which limits its applications to bakery foods and functional foods. Many bitter and astringent compounds ...in tea leaves are susceptible, which transform during tea processing or can be modified by food production technologies. Besides, the accumulations of the major bitter and astringent compounds in fresh tea leaves, such as alkaloids and flavonoids, can be regulated by agronomic practices. Many attempts have been made to reduce the bitter and astringent compounds, in order to improve the sensory quality of tea and tea products.
The aim of this review is to describe the characteristics of major bitter and astringent compounds in different types of teas as well as the bitterness and astringency reducing strategies from the aspects of preharvest, processing and post-processing.
Alkaloids, catechins, anthocyanins, phenolic acids, flavonol glycosides, and theaflavins importantly contribute to the bitter and astringent taste of tea infusion, the contents of which can be modulated during preharvest, processing, and post-processing. Shade treatment is a conventional agronomic practice to reduce the bitterness and astringency of tea. Processing methods like oxidation, roasting/baking and microbial fermentation effectively reduce the bitter and astringent intensities of teas, but have restricted applications to special types of tea. There is a need of new compounds or strategies to decrease the bitterness and astringency of tea and tea products. Employment of these bitterness and astringency reducing strategies should consider the appearance or application requirements of final products.
•Tea taste can be modulated from preharvest, processing, and post-processing.•Shade treatment is an agronomic practice to reduce bitterness and astringency.•PPO-induced enzymatic reaction reduces the bitterness and astringency of tea.•Bitter and astringent flavonoids are susceptible to high temperature.•Microbes transform alkaloids and flavonoids to reduce bitterness and astringency.
Various organisms produce several products to defend themselves from the environment and enemies. These natural products have pharmacological and biological activities and are used for therapeutic ...purposes, retaining bitter taste because of chemical defense mechanisms. Cnicin is a plant-derived bitter sesquiterpene lactone with pharmacological characteristics such as anti-bacterial, anti-myeloma, anti-cancer, anti-tumor, anti-oxidant, anti-inflammatory, allelopathic, and cytotoxic properties. Although many studies have focused on cnicin detection, they have limitations and novel cnicin-detecting strategies are required. In this study, we developed the bioelectronics for screening cnicin using its distinct taste. hTAS2R46 was produced using an Escherichia coli expression system and reconstituted into nanodiscs (NDs). The binding sites and energy between hTAS2R46 and cnicin were investigated using biosimulations. hTAS2R46–NDs were combined with a side-gated graphene micropatterned field-effect transistor (SGMFET) to construct hTAS2R46–NDs bioelectronics. The construction was examined by chemical and electrical characterization. The developed system exhibited unprecedented performance, 10 fM limit of detection, rapid response time (within 10 s), 0.1354 pM−1 equilibrium constant, and high selectivity. Furthermore, the system was stable as the sensing performance was maintained for 15 days. Therefore, the hTAS2R46-NDs bioelectronics can be utilized to screen cnicin from natural products and applied in the food and drug industries.
An aminopeptidase was purified from Proteax, a food-grade commercial enzyme reagent derived from Aspergillus oryzae that showed the highest debittering effect on casein hydrolysates among nine such ...reagents, and its enzymatic characteristics and debittering activities were investigated. Treatment with the enzyme, identified as leucine aminopeptidase A (LapA), on pepsin-degraded casein and cod protein solutions reduced their bitterness and increased the amount of free hydrophobic amino acids such as leucine, valine, isoleucine, and phenylalanine, as well as arginine, tyrosine, and threonine. These results indicated that LapA preferentially released hydrophobic amino acid residues at the amino terminus of peptides including bitter-tasting peptides and reduced the bitterness of protein hydrolysates.
•A refined sensory lexicon enabled characterisation of beer bitterness quality.•Perceived beer bitterness character is linked to hop variety.•Hop aroma significantly impacted perceived bitterness ...intensity and character.•Congruency between hop variety and its aroma constituent may impact bitterness.
The impact of hop variety and hop aroma on perceived beer bitterness intensity and character was investigated using analytical and sensory methods. Beers made from malt extract were hopped with 3 distinctive hop varieties (Hersbrucker, East Kent Goldings, Zeus) to achieve equi-bitter levels. A trained sensory panel determined the bitterness character profile of each singly-hopped beer using a novel lexicon. Results showed different bitterness character profiles for each beer, with hop aroma also found to change the hop variety-derived bitterness character profiles of the beer. Rank-rating evaluations further showed the significant effect of hop aroma on selected key bitterness character attributes, by increasing perceived harsh and lingering bitterness, astringency, and bitterness intensity via cross-modal flavour interactions. This study advances understanding of the complexity of beer bitterness perception by demonstrating that hop variety selection and hop aroma both impact significantly on the perceived intensity and character of this key sensory attribute.
‘Einat’ (‘Redson™’) is a new triploid, red-fleshed pomelo × grapefruit hybrid. We examined the quality, flavor, bitterness and flavanone composition of ‘Redson’ fruit, as compared to 'Oroblanco', ...another pomelo x grapefruit hybrid, 'Star Ruby' grapefruit, 'Goliath' pomelo and 'Newhall' navel orange. ‘Redson’ fruit are seedless with a yellow peel and red flesh and have unique quality characteristics. Descriptive sensory tests revealed that ‘Redson’ fruit are bitterer than other citrus fruit, but earned a high consumer acceptance score and ranked first for preference among all bitter citrus fruits, including pomelo, grapefruit and their hybrids. ‘Redson’ fruit contained the highest amount of the bitter flavanone naringin, but had low levels of other bitter flavanones (neohesperidin and poncirin) and non-bitter flavanones (hesperidin and narirutin). Furthermore, we detected a high correlation (R2 = 0.957) between naringin levels and the sensation of bitterness among citrus fruit, featuring the importance of naringin in determining citrus bitterness.
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•Redson is a new pomelo × grapefruit hybrid with unique fruit quality characteristics.•Redson fruit have a unique and highly appreciated flavor with high bitterness.•Naringin is the main bitter flavanone in Redson fruit.•Bitterness significantly correlated to the levels of naringin in citrus fruit.
•Salivary flow & turbidity of saliva/tannic acid mixtures related to taste intensity.•Greater turbidity sometimes corresponded to less bitterness, sweetness, or sourness.•Greater salivary flow ...sometimes corresponded to less bitterness or sweetness.•Inconsistent patterns indicate specific ingredients may drive these relationships.
The same phytochemicals that stimulate aversive sensations are often also responsible for purported health benefits in fruits and vegetables. Prior work indicates that some salivary proteins may reduce aversiveness of phytochemicals. In rodents, these salivary binding proteins have been shown to reduce bitter taste of polyphenols and alkaloids, but work in humans has focused primarily on polyphenol astringency (dry, rough, or puckery sensations). In this study, we tested if tastes of vegetable products might correlate to either salivary flow rate or the polyphenol binding capability of saliva, as measured by turbidity development when saliva is mixed with tannic acid. Participants (N = 26) provided chewing-stimulated saliva samples and rated five juices and two chopped vegetables for bitterness, sourness, and sweetness intensity. Saliva was mixed with tannic acid and light absorbance was measured for quantification of haze development. Greater absorbance corresponded to less bitterness for one green vegetable juice blend, less sweetness for two green vegetable juice blends and chopped kale, and less sourness from cranberry juice. Greater salivary flow corresponded to less bitterness from chopped brussels sprouts, and less sweetness from one green vegetable juice blend and chopped kale. These findings indicate that greater salivary flow rate and presence of certain salivary binding proteins is not universally associated with lower aversive tastes from phytochemical-containing foods. Whether associations between these salivary properties are ingredient specific or simply not robustly related to taste in commercial products should be further investigated.
In the recent years, extensive research is under way about the use of natural bioactive compounds and production of functional foods to increase community health and reduce the risk of various ...food-related diseases. Among different bioactive compounds, the health benefits of peptides and protein hydrolysates make these compounds as nutraceutical food-additives in the formulation of functional foods. But due to physicochemical instability, hygroscopicity and bitterness, direct use of the bioactive peptides in food formulations is difficult. Encapsulation of these compounds in different carriers is one of the most common techniques to overcome the mentioned disadvantages. Among different techniques of encapsulation, spray-drying is the most economical and flexible process for reduction of hygroscopicity, masking of unpleasant-flavors and increasing the stability of bioactive peptides. In this study, the health benefits of peptides and hydrolysates, their disadvantages and applications of microencapsulation by spray-drying technique have been discussed. Also, the most recent results concerning the effect of encapsulation process with different carriers on physicochemical properties, physical and antioxidant stability, masking of bitterness and morphological characteristics of spray-dried powders loaded with bioactive peptides have been investigated.
Limonin 17-β-D-glucopyranoside (LG) is a terpenoid compound with a high medicinal value produced in different Citrus species. This substance has high anti-cancer and antioxidant properties and ...protects the liver from damage. Although LG is tasteless, many compounds related to it are very bitter, although these bitter substances also have significant medicinal properties. Usually, in most Citrus genotypes, bitter-tasting limonoids are produced more than tasteless types, which are unpleasant despite their therapeutic value. The aim of our study was the in vitro production of LG at high concentrations. For this purpose, hairy roots were induced in ‘Duncan’ grapefruit (Citrus × paradisi) leaf explants. Also, the limonoid UDP-glucosyltransferase (LGTase) gene was transferred from Citrus aurantium to hairy roots by Agrobacterium rhizogenes and forced to overexpression. Two different sets of hairy roots were obtained. The wildtype group only received the Ri plasmid, while cotransformation with the LGTase overexpression constructs in the transgenic group. The gene expression analysis showed that the transcription of the LGTase gene in transgenic hairy roots dramatically increases compared with wildtypes. The overexpression of LGTase significantly increased the total concentration of limonoids in transgenic hairy roots compared with leaves and non-transgenic roots. Evaluation of HPLC chromatograms showed that transgenic hairy roots produced more LG than other samples. In some cases, the concentration of LG increases up to 11 times compared with leaves in some lines. In addition, the concentration ratio of LG to limonin increased in transgenic lines, and transgenic types produced the most LG. Enhancing LGTase gene expression can be a suitable approach to producing high amounts of LG in hairy roots.
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•Hairy roots of grapefruit were produced.•The limonoid UDP-glucosyltransferase gene was transferred to hairy roots.•Overexpression of limonoid UDP-glucosyltransferase gene occurred in transgenic roots.•The production of limonin 17-β-D-glucopyranoside had a significant increase compared to other limonoids.•The ratio of bitter to non-bitter limonoids was reduced in the transgenic line.
To comprehensively explore the contribution and mechanisms of identified low-threshold bitter substances in Idesia polycarpa var. vestita Diels (I. vestita) fruit, we performed quantification and ...elucidated their interactions with main bitter taste receptors through molecular docking. The established method for quantifying bitter compounds in I. vestita fruit was validated, yielding satisfactory parameters for linearity, stability, and accuracy. Idescarpin (17.71–101.05 mg/g) and idesin (7.88–77.14 mg/g) were the predominant bitter compounds in terms of content. Taste activity values (TAVs) exceeded 10 for the bitter substances, affirming their pivotal role as major contributors to overall bitterness of I. vestita fruit. Notably, idescarpin with the highest TAV, played a crucial role in generating the bitterness of I. vestita fruit. Hydrogen bonds and hydrophobic interactions were the main driving forces. This study holds potential implications for industrial development of I. vestita fruit by providing novel insights into the mechanism underlying its bitterness formation.
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•Contribution and mechanism of bitter compounds in I. vestita were first decoded.•An HPLC method for detecting key bitter compounds was established and validated.•Idescarpin was the most abundant bitter compounds in I. vestita fruit.•Idesin and idescarpin were the most important contributor to fruit bitterness.•Hydrogen bonds and hydrophobic interactions serving as the main driving forces.
•Untargeted LC–MS profiling PLS models predict bitterness perception of coffee brew.•Identified ten compounds highly predictive and negatively correlated to bitter intensity.•Recombination testing ...verified three compounds that suppressed bitterness perception.•Bitter modulators reported to impact coffee brew flavor perception.
Untargeted LC–MS flavoromic profiling was utilized to identify compounds that suppress bitterness perception of coffee brew. The chemical profiles of fourteen brew samples and corresponding perceived bitterness intensities determined by descriptive sensory analysis were modeled by orthogonal partial least squares (OPLS) with good fit (R2Y > 0.9) and predictive ability (Q2 > 0.9). Ten chemical markers that were highly predictive and negatively correlated to bitter intensity were subsequently purified by multi-dimensional preparative LC–MS to conduct sensory recombination testing and/or confirm compound identifications by NMR. Three of the ten compounds evaluated, namely 4-caffeoylquinic acid, 5-caffeoylquinic acid, and 2-O-β-d-glucopyranosyl-atractyligenin were identified as bitter modulators in coffee, and significantly decreased the perceived bitterness intensity of the brew.
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