Non-volatile taste active compounds in the meat of Chinese mitten crab (Eriocheir sinensis)

The non-volatile taste active compounds, including soluble sugars, succinic acid, free amino acids and flavour 5′-nucleotides in the meat of Chinese mitten crab (Eriocheir sinensis) were analyzed, and their taste impacts were evaluated by taste active values (TAVs) and equivalent umami concentration (EUC) methods. The total free amino acid content of crab meat was 20.9 mg/g. Arginine, glycine and alanine were the major free amino acids, accounting for more than 70% of the total free amino acids. 5′-Adenosine monophosphate (AMP) was the main flavour 5′-nucleotide (75.3 mg/100 g), followed by 5′-inosine monophosphate (IMP) (34.4 mg/100 g) and 5′-guanosine monophosphate (GMP) (2.3 mg/100 g). Arginine, glycine, alanine, glutamic acid, IMP and AMP were of high TAV (greater than one), and they had strong taste impacts on the crab meat flavour. Glycine and alanine contributed to the major sweet taste, while glutamic acid, IMP and AMP contributed to the strong umami taste. As the TAVs of soluble sugar, succinic acid and bitter free amino acids were lower than one, thus those compounds are likely to have insignificant impact on the taste of the crab meat. The EUC was 4.2 g MSG/100 g crab meat, which meant that the umami taste of the crab meat was very intense.     

Simultaneous determination of flavor enhancers in stock cube samples by using spectrophotometric data and multivariate calibration

Spectrophotometric data followed by a suitable treatment of chemometric analysis were used for the simultaneous determination of monosodium glutamate (MSG), guanosine 5′-monophosphate (GMP) and inosine 5′-monophosphate (IMP) in stock cube samples, without any previous extraction step. By this way, the overlapping of the absorption spectra was resolved using a PLS-1 model. The concentration for experimental calibration matrix were varied between 5.03–34.2 μg mL⁻¹ for IMP and GMP, and 448–1399 μg mL⁻¹ for MSG. The relative errors of prediction (REPCV %) were 1.8, 2.8 and 3.1 for IMP, GMP and MSG, respectively.     

Comparison of umami-taste active components in the pileus and stipe of pine-mushrooms (Tricholoma matsutake Sing.) of different grades

Umami-taste active components in pine-mushrooms (Tricholoma matsutake Sing.) were compared according to different grades (first, second, third, and fourth) and parts (pileus and stipe). The contents of umami-taste active free amino acids, such as aspartic acid and glutamic acid, decreased in the order of second grade > third grade > fourth grade > first grade. Also, the contents of umami-taste active 5′-nucleotides were highest and lowest in pine-mushrooms of second and first grades, respectively. All the contents of umami-taste active amino acids and 5′-nucleotides were higher in the pileus than in the stipe, irrespective of pine-mushroom grades. Equivalent umami concentration values of pine-mushrooms ranged from 13.26 (in the stipe of first grade) to 204.26 g (in the pileus of second grade) per 100 g. All the quantitative data obtained in this study are highly consistent with our previously data on umami sensory intensities of pine-mushrooms.     

Chemical composition and non-volatile components of Croatian wild edible mushrooms

The chemical composition (dry matter, crude protein, crude fat, total carbohydrates, and ash) and non-volatile components content (soluble sugars, free amino acids, and 5′-nucleotides) of 10 popular Croatian wild edible mushroom species (Agaricus campestris, Boletus edulis, Calocybe gambosa, Cantharellus cibarius, Craterellus cornucopioides, Entoloma clypeatum, Flammulina velutipes, Macroleptiota procera, Morchella elata, and Pleurotus ostreatus) were determined. All investigated mushrooms were found to be good sources of proteins and total carbohydrates, with contents varying in the ranges of 27.95–38.89, and 42.62–66.78 g/100 g, respectively. In addition, the fat contents were very low 1.34–6.45 g/100 g. B. edulis (19.87 mg/g) showed the highest concentration of essential amino acids and M. elata (14.25 mg/g) the lowest concentration. Monosodium glutamate-like components and total flavour 5′-nucleotides were the highest in C. cornucopioides (45.85 and 13.88 mg/g, respectively), and lowest in F. velutipes (7.63 and 1.05 mg/g, respectively). Equivalent umami concentration values in 10 Croatian wild edible mushrooms ranged from 73.78 to 1186.45 g MSG/100 g dry weight, and overall, all these mushrooms possessed highly umami taste.     

Enzymatic production of 5′-inosinic acid by a newly synthesised acid phosphatase/phosphotransferase

5′-Nucleotides including 5′-inosinic acid have characteristic taste and important application in various foods as flavour potentiators. The selective nucleoside acid phosphatase/phosphotransferase (AP/PTase) can catalyse the synthesis of 5′-nucleotides by transfer of phosphate groups. In this study, a 747-bp gene encoding AP/PTase from Escherichia blattae was synthesised. After expression, the recombinant AP/PTase was purified using nickel–NTA. The optimal temperature and pH of this enzyme were 30 °C and 5.0, respectively. The activity was partially inhibited by metal ions such as Hg²⁺, Ag⁺ and Cu²⁺, but not by chelating reagents such as EDTA. The values of K_m and V_max for inosine were 40 mM and 3.5 U/mg, respectively. Using this purified enzyme, 16.83 mM of 5′-IMP was synthesised from 37 mM of inosine and the molar yield reached 45.5%. Homology modelling and docking simulation were discussed.     

Non-volatile taste components of Agaricus blazei, Agrocybe cylindracea and Boletus edulis

Three species of dried mushrooms are commercially available in Taiwan, namely Agaricus blazei (Brazilian mushroom), Agrocybe cylindracea (black popular mushroom) and Boletus edulis (king bolete), and their non-volatile taste components were studied. All mushrooms were high in contents of carbohydrate, crude fiber and protein but low in contents of crude ash and fat. Arabitol, myo-inositol, mannitol and trehalose were detected in these three mushrooms, whereas glucose was not found in B. edulis. Contents of total soluble sugars and polyols ranged from 150.33 to 225.08 mg/g. Total free amino acid contents were low in these three mushrooms and ranged from 8.97 to 14.91 mg/g. The contents of MSG-like components ranged from 1.24 to 4.40 mg/g were in the descending order of the A. blazei, A. cylindracea and B. edulis. Total 5′-nucleotides contents of A. blazei and A. cylindracea were higher than that of B. edulis whereas flavor 5′-nucleotides content of A. blazei was higher than those of A. cylindracea and B. edulis. Equivalent umami concentrations values in three mushrooms ranged from 10.46 to 135.90 g per 100 g. Overall, these three mushrooms possessed highly umami taste.     

Non-volatile taste components of various broth cubes

Commercial soup bases, in the form of broth cubes available in the market, include chicken, mushroom, pork and seafood broth cubes. The non-volatile taste components of four broth cubes were studied. Equivalent umami concentration (EUC) values of these broth cubes were evaluated and compared with their sensory results from hedonic tests. Only two soluble sugars, lactose and sucrose, were found. Contents of total free amino acids and monosodium glutamate (MSG)-like components ranged from 0.51 to 1.04 mg g⁻¹ and 0.48 to 0.56 mg g⁻¹, respectively. Contents of 5′-nucleotides and flavour 5′-nucleotides ranged from 2.67 to 3.66 mg g⁻¹ and 2.58 to 3.33 mg g⁻¹, respectively. EUC values were low and the umami intensities of one gramme of four soup bases were equivalent to those given by 0.14–0.32 g MSG. Mushroom and pork soups were more preferred, whereas seafood soup was less preferred. Correlations of EUC values with sensory scores were established for chicken, pork and seafood soups.     

Nonvolatile taste components of fruit bodies and mycelia of Cordyceps militaris

Cordyceps militaris (L.) Link (Clavicipitaceae), northern Cordyceps, is currently available in Taiwan for use in the formulation of nutraceuticals and functional foods. The nonvolatile components in the form of fruit bodies and mycelia were studied. Both fruit bodies and mycelia were high in contents of carbohydrate, crude fiber and crude protein. Content of total sugars and polyols were 260.64 and 189.82 mg/g for fruit bodies and mycelia, respectively. Mannitol content was the highest in both fruit bodies and mycelia (117.66 and 112.55 mg/g, respectively). Contents of total free amino acids in fruit bodies and mycelia were 48.15 and 67.63 mg/g, respectively. The content of monosodium glutamate (MSG)-like components in fruit bodies (10.60 mg/g) was higher than that in mycelia (2.70 mg/g). The contents of total and flavor 5′-nucleotides were high in mycelia (26.27 and 9.34 mg/g, respectively). Equivalent umami concentrations of fruit bodies and mycelia were similar, and equivalent to the umami intensity given by 6.08 and 6.22 g of MSG, respectively. Overall, both fruit bodies and mycelia of northern Cordyceps possessed highly intense umami taste.     

Effects of binary solvent extraction system,extraction time and extraction temperature on phenolic antioxidants and antioxidant capacity from mengkudu (Morinda citrifolia)

An investigation into the effects of ethanol concentration (0–100%, v/v), extraction time (20–120 min) and extraction temperature (25–65 °C) on the extraction of phenolic antioxidants from mengkudu (Morinda citrifolia) was performed using a single-factor experiment. Total phenolic content (TPC) and total flavonoid content (TFC) assays were used for determination of phenolic compounds. Antioxidant capacity was evaluated by measuring the scavenging effect on 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) and 2,2′-diphenyl-1-picrylhydrazyl (DPPH) radicals. Experimental results showed that extraction conditions had significant effect on extraction of phenolic compounds and antioxidant capacities. The optimised conditions were 40% ethanol for 80 min at 65 °C, with values of 919.95 mg GAE/100 g DW for TPC, 472.73 mg CE/100 g DW for TFC, 791.71 μmol TEAC/100 g DW for ABTS and 1928.5 μmol TEAC/100 g DW for DPPH. TPC was significantly correlated with DPPH under the effects of ethanol concentration (r = 0.932) and extraction time (r = −0.938).     

Isolation and properties of 5′-nucleotidase isolated from jumbo squid (Dosidicus gigas) mantle muscle from the Gulf of California,Mexico

The enzyme 5′-nucleotidase of jumbo squid (Dosidicus gigas) mantle was purified and its SDS–PAGE showed a single band of 33 kDa, whereas a protein with a molecular mass of 107 kDa was detected by gel filtration suggesting a homotrimeric nature of this enzyme. Subunits of the named enzyme were not linked by covalent bonds. Isoelectric focusing of this enzyme showed a pI of 3.6–3.8 and presented a hyperbolic kinetics with V_max of 1.16 μM/min/mg of protein, K_m of 1.49 mM, K_cat of 3.48 μM of P_ι s⁻¹ and K_cat/K_m relation of 356.52 ((mol/L)⁻¹ s⁻¹). Purified enzyme preferred AMP as substrate (by 6.7-folds) than IMP, showing a K_m of 6.34 mM, V_max of 0.19 μM/min/mg of protein a K_cat of 0.3388 mol of P_ι s⁻¹ and K_cat/K_m relation of 53.44 ((mol/L)⁻¹ s⁻¹). The low K_m in relation to purified AMP deaminase of the same organism suggested a high contribution of 5′-nucleotidase in AMP degradation in jumbo squid mantle.     

Gut microbial catabolism of grape seed flavan-3-ols by human faecal microbiota. Targetted analysis of precursor compounds, intermediate metabolites and end-products

In vitro batch culture fermentations were conducted with grape seed polyphenols and human faecal microbiota, in order to monitor both changes in precursor flavan-3-ols and the formation of microbial-derived metabolites. By the application of UPLC-DAD-ESI-TQ MS, monomers, and dimeric and trimeric procyanidins were shown to be degraded during the first 10 h of fermentation, with notable inter-individual differences being observed between fermentations. This period (10 h) also coincided with the maximum formation of intermediate metabolites, such as 5-(3′,4′-dihydroxyphenyl)-γ-valerolactone and 4-hydroxy-5-(3′,4′-dihydroxyphenyl)-valeric acid, and of several phenolic acids, including 3-(3,4-dihydroxyphenyl)-propionic acid, 3,4-dihydroxyphenylacetic acid, 4-hydroxymandelic acid, and gallic acid (5-10 h maximum formation). Later phases of the incubations (10-48 h) were characterised by the appearance of mono- and non-hydroxylated forms of previous metabolites by dehydroxylation reactions. Of particular interest was the detection of γ-valerolactone, which was seen for the first time as a metabolite from the microbial catabolism of flavan-3-ols. Changes registered during fermentation were finally summarised by a principal component analysis (PCA). Results revealed that 5-(3′,4′-dihydroxyphenyl)-γ-valerolactone was a key metabolite in explaining inter-individual differences and delineating the rate and extent of the microbial catabolism of flavan-3-ols, which could finally affect absorption and bioactivity of these compounds.     

Isolation and purification of phenylethanoid glycosides from Cistanche deserticola by high-speed counter-current chromatography

Five phenylethanoid glycosides (PhGs), echinacoside, cistanoside A, acteoside, isoacteoside and 2′-acetylacteoside, were isolated and purified from Cistanche deserticola for the first time by high-speed counter-current chromatography (HSCCC) using two biphasic systems, one consisting of ethyl acetate–ethanol–water (5:0.5:4.5, v/v/v) and another of ethyl acetate–n-butanol–ethanol–water (0.5:0.5:0.1:1, v/v/v/v). A total of 28.5 mg of echinacoside, 18.4 mg of cistanoside A, 14.6 mg of acteoside, 30.1 mg of isoacteoside and 25.2 mg of 2′-acetylacteoside were purified from 1412 mg of the n-butanol extract of C. deserticola, each at over 92.5% purity as determined by HPLC. The structures were identified by their retention time, UV, LC–ESI-MS in the negative ion mode, and confirmed by NMR experiments. The characteristic LC–ESI-MSⁿ fragmentation pattern of the five compounds is discussed, and found to be a very specific and useful tool for the structural identification of PhGs from this important medicinal plant.     

Nonvolatile taste components of Grifola frondosa, Morchella esculenta and Termitomyces albuminosus mycelia

Three species of mushroom mycelia are commercially available in Taiwan, namely Grifola frondosa (maitake), Morchella esculenta (morel), and Termitomyces albuminosus (termite mushroom), and their nonvolatile taste components were studied. All mycelia were high in contents of carbohydrate, crude fat and protein but low in contents of crude ash and fiber. Arabitol, glucose, mannitol and trehalose were detected in these three mycelia and total amounts of sugars and polyols were 63.69-83.89 mg/g. Total free amino acid contents in three mycelia ranged from 35.67 to 50.37 mg/g. The monosodium glutamate-like components of G. frondosa mycelia (6.51 mg/g) was approximately twofold higher than M. esculenta and T. albuminosus mycelia (3.58 and 3.11 mg/g, respectively). As compared with other components, sweet and bitter components were much higher in these three mycelia. Contents of total 5′-nucleotides in these three mycelia ranged from 13.32 to 26.19 mg/g and were in the descending order of T. albuminosus>M. esculenta>G. frondosa. Equivalent umami concentration of T. albuminosus mycelia was higher than those of G. frondosa and M. esculenta mycelia. Overall, three mycelia possessed highly intense umami taste.     

Determination of diquat and paraquat in olive oil by ion-pair liquid chromatography–electrospray ionization mass spectrometry (MRM)

For the first time a method for determination of herbicides diquat (DQ) and paraquat (PQ) in olive oil was developed utilising liquid chromatography–electrospray ionization mass spectrometry (MRM). n-Hexane/10 mM HFBA aqueous solution partitioning was used as the extraction method. Separation was carried out in an Xterra C8 column (100 × 21 mm, 3 μm), using the gradient mode. Solvent A was a HFBA aqueous solution (5 mM, pH 2) and solvent B acetonitrile/methanol 75/25 (v/v). Peaks used for quantification were m/z = 157 (diquat) and m/z = 158 (paraquat). Detection limit found for both diquat and paraquat was 4 μg kg⁻¹. The method can also be applied for determination of chlormequat (CQ, quantification peak m/z = 58), the detection limit being 0.3 μg kg⁻¹. Such limits are clearly lower than the MCLs commonly applied to olive oil as reference criteria (5 times MCLs in olives). Good reproducibilities (day to day and run to run) were obtained.     

Comparison of free amino acids and 5′-nucleotides between Tuber fermentation mycelia and natural fruiting bodies

The profiles of free amino acids and 5′-nucleotides were first compared between Tuber fermentation mycelia and natural fruiting bodies. A total of 20 free amino acids and five 5′-nucleotides were identified in the Tuber fermentation mycelia and natural fruiting bodies. Not only the total contents of the free amino acids and 5′-nucleotides, but also the contents of umami amino acids and flavour 5′-nucleotides in the fermentation mycelia were higher than those in the fruiting bodies. By the addition of soybean flour in the fermentation media, the flavour 5′-nucleotides content in the fermentation mycelia was significantly increased, and the equivalent umami concentration of the fermentation mycelia (i.e., 608.07 g/100 g) was approximately 38.1-93.4 times higher than those of the fruiting bodies. From the viewpoint of umami taste, this work confirms the potentiality of Tuber fermentation mycelia as the alternative resource for its fruiting bodies.     

The effect of chilled conditioning at 4 °C on selected water and lipid-soluble flavor precursors in Bison bison longissimus dorsi muscle and their impact on sensory characteristics

Water and lipid-soluble flavor precursors were monitored using chromatography methods in the longissimus dorsi (LD) muscle of six grain-fed Bison bison, stored at 4 °C for 2, 4, 8, 15 and 21 days in order to investigate their potential impact on sensory attributes of cooked bison meat. While pH and lipid-soluble compounds remained mostly unchanged, several changes in water-soluble compounds were observed. The breakdown of inosine-5′-monophosphate (IMP) led to increases in inosine, hypoxanthine and ribose (7-fold). Non-polar amino acids including valine, leucine and phenylalanine showed the most significant increases over 21 days. Trained panelists (n = 8) found a significant increase at day 15 in vinegary/sour aroma, tenderness and juiciness, while chewiness and connective tissue significantly decreased. Although, most flavor attributes were undetectable, partial least squares (PLS) analysis revealed most water-soluble precursors were positively correlated with extended conditioning as well as beef and oily/fatty flavors. Quantitative changes observed in flavor precursors may be responsible for some sensory attributes developed during the heating process.     

Rosmarinic acid,scutellarein 4′-methyl ether 7-O-glucuronide and (16S)-coleon E are the main compounds responsible for the antiacetylcholinesterase and antioxidant activity in herbal tea of Plectranthus barbatus (“falso boldo”)

Plectranthus barbatus, known as “falso boldo” in Brazil, is used in herbal tea or cooked as a vegetable. Infusions and decoctions of leaves from P. barbatus were analysed for their inhibition of acetylcholinesterase and their antioxidant activity. The decoction showed high inhibition activity (31% inhibition with 0.5 mg of extract/ml) and also high antioxidant activity (IC₅₀ = 45.8 ± 0.5 μg of dry extract/ml in the DPPH test; IC₅₀ = 69.8 ± 3.1 μg of dry extract/ml in the β-carotene–linoleic acid test). Rosmarinic acid, scutellarein 4′-methyl ether 7-O-glucuronide and (16S)-coleon E were the main constituents identified. These compounds have antiacetylcholinesterase activity. Rosmarinic acid and the scutellarein derivative have IC₅₀ = 440 μg/ml and 1 mg/ml, respectively. One milligram per millilitre of (16S)-coleon E showed 61% inhibition of the enzyme. Other Plectranthus species, P. ecklonii, P. fructicosus, P. lanuginosus and P. verticillatus, were also analysed and the results obtained correlated with the content in rosmarinic acid.     

Freshness assessment of ray fish stored in ice by biochemical,chemical and physical methods

Ray fish were caught, filleted, and stored in ice. Fillets were analysed for 18 days to determine the chemical, biochemical and physical changes and their relation to the muscle eating quality. Trimethylamine (TMA-N), total volatile bases (TVB-N), ATP content and breakdown products, K value, pH, texture, water-holding capacity (WHC) and colour changes were monitored. At the beginning of the study, the ray fish muscle showed a low concentration of ATP and a high value of inosine 5′-monophosphate (IMP). Regarding to the signs of freshness and deterioration, K value presented an exponential increase (r2 = 0.95) with an initial value of 4.7% and a final value of 47.5%. Furthermore, the TBV-N and TMA-N significantly increased (P < 0.05) during the storage in ice. As for the physical analysis whereas the texture changed (P < 0.05); pH and the WHC were not affected (P < 0.05). The overall results of this study indicated that the edible quality of ray fish muscle was maintained during at least 15 days of ice storage.     

Rhus verniciflua Stokes flavonoid extracts have anti-oxidant,anti-microbial and α-glucosidase inhibitory effect

We isolated four compounds, fustin, gallic acid, 3′,4′,7-trihydroxyflavone, and fisetin from Rhus verniciflua. These compounds showed electron donation ability (87–94%) that was stronger than butylated hydroxyanisole (52%). Gallic acid (OD₇₀₀ = 1.98) showed the highest reducing power, and the other isolated compounds (OD₇₀₀ = 0.66–1.31) showed stronger activity than α-tocopherol (OD₇₀₀ = 0.21). The ethyl-acetate fraction had the highest phenolic content (723 mg GAE/g), followed by the 80% ethanolic extract (597 mg GAE/g). For Gram-negative bacteria, fisetin had the most potent anti-bacterial activity (MIC = 8 μg/ml) against Escherichia coli. 3′,4′,7-Trihydroxyflavone (106%), the 80% ethanolic extract (101%), and ethyl-acetate (98%) had the most powerful α-glucosidase inhibitory effect at 50 μg/ml. R. verniciflua extracts have potential as functional food additives.     

Solubility of disodium 5′-guanylate heptahydrate in aqueous methanol mixtures

The solubility of disodium 5′-guanylate heptahydrate (5′-GMPNa₂) in binary aqueous methanol solvent mixtures with the temperature ranging from 278.15 to 323.15 K was measured by a dynamic method with a laser monitoring observation technique. The solubility data were correlated with the Combined Nearly Ideal Binary Solvent/Redlich–Kister (CNIBS/R–K) model and the modified Jouyban–Acree model, respectively. For the ten groups of data studied, the CNIBS/R–K model was found to provide a more accurate mathematical representation of the experimental data, while the modified Jouyban–Acree model containing provisions for correlating both the solvent composition and temperature.