Levels Of Total Free Amino Acids Research Articles

The comparison and analysis of nutritional qualities of Chinese mitten crabs (Eriocheir sinensis) in rice field and pond culture modes

The nutritional quality of three edible parts (gonads, hepatopancreas and muscles) of Chinese mitten crabs (CMCs) from rice field culture and pond culture was firstly compared in our current study. It was found that the contents of mineral elements and volatile compounds in rice CMCs were superior to those in pond CMCs, and the antioxidant enzyme activities of rice CMCs were markedly higher than those of pond CMCs. Besides, the total free amino acid levels in the edible parts of pond CMCs were higher than those of rice CMCs. Compared with other tissues, the nucleotide and equivalent umami concentrations of the gonads in female rice CMCs were the maximum. Overall, both types of crabs demonstrated good nutritional quality, which met human nutrition and dietary needs. In comparison, the quality of rice CMCs was better than that of pond CMCs.

Ultrasound improves the low-sodium salt curing of sea bass: Insights into the effects of ultrasound on texture, microstructure, and flavor characteristics

The purpose of this study was to evaluate the effects of ultrasonic pretreatment on the quality of cured sea bass. Compared to static marination, ultrasonication significantly increased the rate of NaCl transfer, reduced the hardness and chewiness of fish, and improved water retention. Microstructural observations revealed that the sea bass muscle fibers were severely fragmented, with their borders becoming increasingly blurred with increasing ultrasonic intensity. In addition, ultrasound-assisted marination significantly increased the degradation of proteins, total free amino acid levels, and relative levels of volatile flavor substances such as aldehydes and esters. Therefore, the use of an appropriate ultrasound treatment for the salt curing of fish has a positive effect on the textural and flavor characteristics of sea bass, with the most optimal approach being 300.W ultrasound treatment for 60 min. Overall, the results of this study provide technical evidence for improving the quality of lightly cured low-salt content seafood.

Proteolytic Development and Volatile Compounds Profile of Domiati Cheese under Modified Atmosphere Packaging

This study explored the impacts of modified atmosphere packaging (MAP) treatment on the proteolytic development and volatile compounds of Domiati cheese during storage. Domiati cheese samples were kept for 75 days at refrigerator temperature, under aerobic packaging (C1) or vacuum (C2). In parallel, other Domiati cheese samples were kept under MAP, at different levels of CO2 and N2, as follows: 10% CO2/90% N2 (D1), 15% CO2/85% N2 (D2), 25% CO2/75% N2 (D3), 100% CO2 (D4), and 100% N2 (D5). The normal control (C1) treatment showed the highest reduction in pH from 6.64 at zero time to 6.23 and 6.01 after 40 and 75 days of storage, respectively. On the other hand, the under-vacuum samples (C2) showed the lowest reduction in pH, from 6.64 at zero time to 6.49 and 6.28 after 40 and 75 days of storage, respectively. Proteolysis during cheese storage was lower in MAP of cheeses than in the C1 treatment. Total free amino acids (FAAs) were higher in C1 treatment than other cheeses during the whole storage period. The lowest level of total FAA was detected in D4 treatment after 75 days of storage. Volatile acids, aldehydes, ketones, and esters compounds were detected in all treatments during storage, but particularly higher in aerobic packaging than the other treatments after 75 days. The level of each acid compound increased with storage period, and the increases were particularly clear in pentanoic acid, hexanoic acid, heptanoic acid, benzoic acid, and n-decanoic acid. The normal control (C1) showed high contents of the different volatile ketone compounds. However, the samples packaged under 100% N2 (D5) showed the significantly highest levels of all the volatile ketones after 75 days of storage, particularly 2-pentanone, acetoin, methyl isobutyl ketone, 2-heptanone, 2-nonanone, and 2-undecanone. Some important compounds contributing to the good flavor of the cheese are acetic acid, butanoic acid, pentanal, benzaldehyde, acetoin, and 2,3-butanedione. The CO2 and N2 treatments exerted significant changes in all groups during the storage of cheese. All cheese samples showed gradual increases in CO2 co-occurring with parallel decreases in N2 during refrigerated storage periods, except for D4 treatment (100% CO2), which showed a decrease. A significant decrease in O2 level occurred in C1 treatment during cold storage.

Preparation of mechanically strong and active composite films based on fish myofibrillar proteins: The dual effects of oxidized polyphenol crosslinking and layered double hydroxide reinforcement

To improve the properties of films prepared from silver carp muscle, a cross-linked nanocomposite antioxidant film based on myofibrillar protein (MP) was prepared using oxidized caffeic acid (OC), p-coumaric acid (OP), eriodictyol (OE) and naringenin (ON) as crosslinking agents in combination with layered double hydroxide (LDH). The structural, physical properties and antioxidant activity of the film were investigated. The examination of the changes in the side-chain groups of MP revealed that the addition of oxidized polyphenols decreased total sulfhydryl and free amino acid levels, showing a greater decrease in OC and OE with o-phenolic hydroxyl groups, whereas LDH showed no significant effect. Additionally, FTIR (Fourier transform infrared) and XRD (X-ray diffraction) confirmed the covalent or non-covalent interactions between oxidized polyphenols, LDH and MP, in which resulted in increased surface hydrophobicity of MP and a shift of the α-helical structure to random coils. This suggests that the protein underwent unfolding, which tends to induce intermolecular aggregation. Additionally, the microregional structure in the film became more compact. Moreover, the mechanical properties of MP-based films were significantly enhanced by the combination of oxidized polyphenols and LDH, especially the incorporation of OE and LDH resulted in a tensile strength reaching 17.4 MPa. Furthermore, the water vapor and oxygen permeability, surface hydrophobicity, UV barrier and thermal stability of MP-based films were also improved. Therefore, the dual effect of oxidized polyphenol cross-linking and LDH complex confers excellent free radical scavenging abilities and iron-reducing antioxidant functions to MP films.

Role of Exogenous Application of Alpha-Tocopherol in Reducing Low Temperature Stress in Bell Pepper

Changing climatic conditions have an impact on the commercial harvest and production of Capsicum annuum L. across the world. It is a summer crop that grows best at 21°C (low) to 37 °C (high) temperature. Changes in normal growth, poor shoot and root length, increased antioxidant activity, low sugar content, high proline content, and poor yield were observed in bell pepper at low temperature stress. A research trial was conducted on bell peppers in the Department of Plant Pathology at University of Agriculture, Faisalabad. Bell peppers were cultivated hydroponically and alpha-tocopherol control (0ppm), 25ppm, 50ppm, and 100ppm were applied in foliar application. At the reproductive period, a low temperature stress of 18 °C day and 15 °C night was used given. After seven days of foliar spray, plants were exposed to cold temperatures during the day and night. After seven days of stress, the plants were harvested and morphological, physiological, and biochemical data were examined. Plant growth, leaf area, number of leaves, buds, and flowers, photosynthetic pigments, relative water content, cell membrane permeability, total soluble sugar, total reducing sugar, protein contents, and total free amino acid levels were all reduced when exposed to high temperatures. When the stress of low temperature was applied, there was a rise in proline, phenolic, flavonoid, H2O2, MDA, enzymatic antioxidants SOD, CAT, POD, and in APX. Under temperature stress, foliar application of alpha-tocopherol significantly improved CAT, POD, APX activity, decreased MDA, H2O2, and improved proline content. Exogenously administered alpha-tocopherol was found to be effective in boosting capsicum growth and antioxidant capability under low temperature stress.

Effect of Dietary Fermentable Carbohydrate Supplementation on Amino Acid Homeostasis

Abstract Objectives Homeostasis of amino acids (AA) such as branched chain AAs (BCAAs), and aromatic AAs are associated with glucose regulation. Fermentable carbohydrates (FC), such as xylooligosaccharide (XOS), have been shown to improve glucose and lipid metabolism. Therefore, we aim to study the potential of dietary FC to modulate systemic and tissue specific amino acid (AA) homeostasis in normal physiological condition. Two FCs of different molecular size were included in this study, XOS (0.3–1 kDa) and a new sulfated fucose containing polysaccharide (SPS) isolated from seaweed (82 kDa). Methods Male C57BL6 mice at age 7 week were randomized into three groups and fed AIN93M, AIN93M supplemented with 2% XOS or SPS (w/w) for 8 weeks (n = 6–8/group). SPS was prepared from Laminaria japonica. At the end of the intervention, fasting serum samples were collected and processed for glucose, insulin, AA analysis. Liver and skeletal muscle samples were frozen and processed for AA analysis. Results Blood glucose was significantly lower in XOS-fed mice but not SPS-fed mice compared to mice fed the control AIN93M diet. No significant differences in blood insulin, lipids, AA as well as body weight and fat depots were observed among the three experimental groups (XOS, SPS and control). In skeletal muscle, the concentration of total free AA, as well as 9 AAs (Asp, Glu, Arg, Tyr, Met, Phe and BCAAs) was significantly lower and 1 AA (Thr) was higher in SPS mice compared to control mice, while free AA levels in skeletal muscle were not significantly different between XOS and control mice. In liver, levels of total free AA, Arg, Thr and leucine metabolite ketoleucine were significantly lower in XOS mice compared to control mice. No significant change in free AA levels in liver was observed between SPS and control mice. Conclusions Our data show the differential modulation of systemic and tissue-specific AA and glucose homeostasis by dietary XOS and SPS intake, indicating the key role that AA signaling may play in metabolic homeostasis. Funding Sources This project was supported by the National Institutes of Health and UCLA Center for Human Nutrition.

BINARY ACTION OF CHLORPYRIFOS-METHYL AND METHOPRENE ON THE LARVAL BIOCHEMISTRY OF ALMOND MOTH, EPHESTIA CAUTELLA WALKER (LEPIDOPTERA:PYRALIDAE)

Sub-lethal concentrations i.e. 1, 2 and 4 ppm mixture of chlorpyrifos-methyl and methoprene in the ratio of 9:1 caused a significantly dose-dependent reduction in the levels of total protein, DNA, RNA and RNA/ DNA ratio and a significantly dose-dependent enhancement in the total free amino acid levels in haemolymph and fat body tissues of the larva of almond moth, Ephestia cautella Walker, a serious pest of stored cereals. The highest concentration ( 4ppm ) of this mixture caused abrupt changes in the metabolic framework of the larva that impairs its physiological fitness, which ultimately leads to death, if exposed to 8ppm concentration of this binary mixture. The present study states that methoprene enhances the toxicodynamic property of chlorpyrifos-methyl in a synergistic way.

Proximate composition, Free amino acids and peptides contents in commercial chicken and other meat essences

Ten commercial meat essences of chicken, beef, clam and eel contained the moisture ranged from 91.1 to 97.5%, protein from 0.6 to 7.8%, and ash from 0.3 to 1.7%. Freshwater clam and hard clam essences had a much higher level of glycogen than other products. The total amount of free amino acids (FAA) in six chicken essences varied from 150 to 725 mg/100 g. Taurine was the dominant FAA and accounted for 16∼30% of the total FAA. Though beef essence had the highest level of total FAA among ten products, its taurine was accounted for only about 2%. Taurine in freshwater clam essence was also very low, but a high level of ornithine was found. Anserine in six chicken essences, ranging from 36 to 437 mg/100 g, was higher than carnosine, ranging from 8 to 162 mg/100 g. In beef essence, however, anserine was far less than carnosine. These dipeptides in both clam essences were not detectable, and only a small amount of carnosine was present in eel essence. Another dipeptide, balenine, was found only in a chicken essence. The amount of low-molecular-weight peptides in chicken essences, ranged from 1,187 to 3,296 mg/100 g, was more than the level of FAA in each product. Both clam essences contained a much lower amount of small peptides than other products. Consequently, hard clam essence was the only product with lower level of peptides than its FAA.

Mould starter selection for extended solid-state fermentation of quinoa

Solid-state fermentation of plant materials with food grade moulds is considered a method of obtaining bioactive food products and additives. However, the use of quinoa seeds as a substrate in such a process has not been thoroughly studied to date. In this paper, extended fermentation with Rhizopus oligosporus, Aspergillus oryzae and Neurospora intermedia (tempe, koji and oncom moulds, respectively) was performed in order to enhance the antioxidant potential of coloured quinoa (as measured by the total soluble phenols, ABTS˙+ and ˙OH scavenging activities, and the reducing power).The most efficient of the examined strains was Rhizopus, which caused an average improvement in the aforementioned qualities of 220% (black seeds) and 129% (red seeds), as compared to pre-cooked seeds. Four-day fermentation with Rhizopus resulted in a drastically enhanced amount of vanillin in the free phenolic fraction (130-fold in black quinoa seeds). However, the overall level of free and bound phenolics (as measured by the HPLC-DAD-ESI-TOF-MS method) in the material decreased. Both total peptides and individual free amino acid levels were significantly increased, which corresponded with the high antioxidant potential of the material. The fermented quinoa was also significantly enriched with total dietary fibre with dominant insoluble fraction.

Changes in the amino acid profiles and free radical scavenging activities of Tenebrio molitor larvae following enzymatic hydrolysis.

Tenebrio molitor (T. molitor) larvae provide food at low environmental cost and contribute positively to livelihoods. In this research, we compared the amino acids compositions and antioxidant activities of various extracts of T. molitor to enhance their quality as food. For the comparison, distilled water extracts, enzymatic hydrolysates, and condensed enzymatic hydrolysates of T. molitor larvae were prepared. Their amino acids (AAs) profiles and antioxidant activities, including ferric-reducing antioxidant power, oxygen radical absorption capacity, and DPPH, hydroxyl radical, and hydrogen peroxide radical scavenging properties assay were analyzed. DW extracts had the lowest AAs contents and antioxidant activity compared with enzymatic extracts. Condensed hydrolysates with a combination of alcalase and flavourzyme (C-A+F) exhibited the highest levels of total free AAs (11.1759 g/100 g). C-A+F produced higher total hydrolyzed AAs (32.5292 g/100 g) compared with the other groups. The C-A+F possessed the strongest antioxidant activity. Notably, the antioxidant activities of the hydrolysates and the total hydrolyzed AAs amount were correlated. Taken together, our findings showed that C-A+F was a promising technique for obtaining extracts of T. molitor larvae with antioxidant activity as potential nutritious functional food.

Nitrogen remobilisation facilitates adventitious root formation on reversible dark-induced carbohydrate depletion in Petunia hybrida.

BackgroundAdventitious root (AR) formation in axillary shoot tip cuttings is a crucial physiological process for ornamental propagation that is utilised in global production chains for young plants. In this process, the nitrogen and carbohydrate metabolisms of a cutting are regulated by its total nitrogen content (Nt), dark exposure during transport and irradiance levels at distinct production sites and phases through a specific plasticity to readjust metabolite pools. Here, we examined how elevated Nt contents with a combined dark exposure of cuttings influence their internal N-pools including free amino acids and considered early anatomic events of AR formation as well as further root development in Petunia hybrida cuttings.ResultsEnhanced Nt contents of unrooted cuttings resulted in elevated total free amino acid levels and in particular glutamate (glu) and glutamine (gln) in leaf and basal stem. N-allocation to mobile N-pools increased whereas the allocation to insoluble protein-N declined. A dark exposure of cuttings conserved initial Nt and nitrate-N, while it reduced insoluble protein-N and increased soluble protein, amino- and amide-N. The increase of amino acids mainly comprised asparagine (asn), aspartate (asp) and arginine (arg) in the leaves, with distinct tissue specific responses to an elevated N supply. Dark exposure induced an early transient rise of asp followed by a temporary increase of glu. A strong positive N effect of high Nt contents of cuttings on AR formation after 384 h was observed. Root meristematic cells developed at 72 h with a negligible difference for two Nt levels. After 168 h, an enhanced Nt accelerated AR formation and gave rise to first obvious fully developed roots while only meristems were formed with a low Nt. However, dark exposure for 168 h promoted AR formation particularly in cuttings with a low Nt to such an extent so that the benefit of the enhanced Nt was almost compensated. Combined dark exposure and low Nt of cuttings strongly reduced shoot growth during AR formation.ConclusionsThe results indicate that both enhanced Nt content and dark exposure of cuttings reinforced N signals and mobile N resources in the stem base facilitated by senescence-related proteolysis in leaves. Based on our results, a model of N mobilisation concomitant with carbohydrate depletion and its significance for AR formation is postulated.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0901-6) contains supplementary material, which is available to authorized users.

Dietary alpha-ketoglutarate increases cold tolerance in Drosophila melanogaster and enhances protein pool and antioxidant defense in sex-specific manner

Alpha-ketoglutarate (AKG) is an important intermediate in Krebs cycle which bridges the metabolism of amino acids and carbohydrates. Its effects as a dietary supplement on cold tolerance were studied in Drosophila melanogaster Canton S. Two-day-old adult flies fed at larval and adult stages with AKG at moderate concentrations (5–10mM) recovered faster from chill coma (0°C for 15min or 3h) than control ones. The beneficial effect of AKG on chill coma recovery was not found at its higher concentrations, which suggests hormetic like action of this keto acid. Time of 50% observed mortality after 2h recovery from continuous cold exposure (−1°C for 3–31h) (LTi50) was higher for flies reared on 10mM AKG compared with control ones, showing that the diet with AKG enhanced insect cold tolerance. In parallel with enhancement of cold tolerance, dietary AKG improved fly locomotor activity. Metabolic effects of AKG differed partly in males and females. In males fed on AKG, there were no differences in total protein and free amino acid levels, but the total antioxidant capacity, catalase activity and low molecular mass thiol content were higher than in control animals. In females, dietary AKG promoted higher total antioxidant capacity and higher levels of proteins, total amino acids, proline and low molecular mass thiols. The levels of lipid peroxides were lower in both fly sexes reared on AKG as compared with control ones. We conclude that both enhancement of antioxidant system capacity and synthesis of amino acids can be important for AKG-promoted cold tolerance in D. melanogaster. The involvement of AKG in metabolic pathways of Drosophila males and females is discussed.

Disruption of behavioral circadian rhythms induced by psychophysiological stress affects plasma free amino acid profiles without affecting peripheral clock gene expression in mice

Disordered circadian rhythms are associated with various psychiatric conditions and metabolic diseases. We recently established a mouse model of a psychophysiological stress-induced chronic sleep disorder (CSD) characterized by reduced amplitude of circadian wheel-running activity and sleep–wake cycles, sleep fragmentation and hyperphagia. Here, we evaluate day–night fluctuations in plasma concentrations of free amino acids (FAA), appetite hormones and prolactin as well as the hepatic expression of circadian clock-related genes in mice with CSD (CSD mice). Nocturnal increases in wheel-running activity and circadian rhythms of plasma prolactin concentrations were significantly disrupted in CSD mice. Hyperphagia with a decreased leptin/ghrelin ratio was found in CSD mice. Day–night fluctuations in plasma FAA contents were severely disrupted without affecting total FAA levels in CSD mice. Nocturnal increases in branched-chain amino acids such as Ile, Leu, and Val were further augmented in CSD mice, while daytime increases in Gly, Ala, Ser, Thr, Lys, Arg, His, Tyr, Met, Cys, Glu, and Asn were significantly attenuated. Importantly, the circadian expression of hepatic clock genes was completely unaffected in CSD mice. These findings suggest that circadian clock gene expression does not always reflect disordered behavior and sleep rhythms and that plasma FFA profiles could serve as a potential biomarker of circadian rhythm disorders.

Study of the chemical composition, proteolysis, volatile compounds, and textural properties of industrial and traditional Beaten (Bieno sirenje) ewe milk cheese

The objective of this study was to determine the gross composition, proteolysis, and volatile and texture profiles during ripening of industrial (IND) and traditional (TRD) Beaten (Bieno sirenje) cheeses made by using ewe milk. In the course of the analyses, statistical differences were determined in some physicochemical parameters, nitrogen fractions, and total free amino acid levels between TRD and IND types of cheese. Higher levels of proteolysis were observed in IND cheeses than in TRD cheeses during ripening. Levels of residual β- and αs-caseins were 72.2 and 48.7%, respectively, in 180-d-old TRD cheeses. However, the residual levels were 52.8% for β-casein and 18% for αs-casein in IND cheeses. Similar differences were noted for the reversed-phase HPLC peptide profiles of 2 types of cheeses. Also, higher concentrations of peptides were eluted in IND cheeses than in TRD cheeses during ripening. A total of 73 volatile compounds, including alcohols (16), esters (17), acids (14), terpenes (7), ketones (5), aldehydes (4), and miscellaneous (10) were identified. The IND cheeses contained higher levels of carboxylic acids, esters, alcohols, and terpenes than the TRD cheeses; however, the same levels of methyl ketones were determined in the 2 types of cheeses at the end of ripening. These may be due to some differences (e.g., pasteurization and scalding temperature, among other factors) in the manufacture of the 2 types of Beaten cheeses. The textural profile of Beaten cheeses showed that TRD production method resulted in firmer, less fracturable, and stiffer cheeses than the IND production method. In conclusion, the results suggest that the use of industrial production method (pasteurization of cheese milk and curd scalding at 70°C) in the manufacture of Beaten ewe milk cheese enriched the volatile profile of the cheese.

Use of UPLC-ESI-MS/MS to quantitate free amino acid concentrations in micro-samples of mammalian milk

Although free amino acids (FAA) account for a small fraction of total nitrogen in mammalian milk, they are more abundant in human milk than in most formulas, and may serve as a readily available source of amino acids for protein synthesis, as well as fulfill specific physiologic roles. We used reversed phase Ultra Performance Liquid Chromatography (UPLC) coupled to electrospray ionization tandem mass spectrometry (ESI-MS/MS) technique for FAA profiling in milks from three species (human, rat and cow) with a simple and rapid sample preparation. The derivatization procedure chosen, combined with UPLC-ESI-MS/MS allowed the quantitation of 21 FAA using labeled amino acids (Internal Standards) over a 10 min run time in micro-samples of mammalian milk (50 μL). The low limit of quantitation was 0.05 pmol/μL for most FAA with good repeatability and reproducibility (mean CV of 5.1%). Higher levels of total FAA were found in human (3032 μM) and rat milk (3460 μM) than in bovine milk (240 μM), with wide differences in the abundances of specific FAA between species. This robust analytical method could be applied to monitor FAA profile in human breast milk, and open the way to individualized adjustment of FAA content for the nutritional management of infants.

Toxicity of Triphenyltin Hydroxide to Fish

Triphenyltin (TPhT) is used worldwide in pesticide formulas for agriculture. Toxic effects of this compound to aquatic life have been reported; however, the biochemical response of fish exposed to different concentrations of TPhT hydroxide (TPhTH) was investigated for the first time in this study. The lethal concentration (LC50) of TPhTH to silver catfish, Rhamdia quelen, was calculated from an acute-exposure experiment (96h). In addition, acethylcholinesterase (AChE) activity in brain and muscle-as well as glucose, glycogen, lactate, total protein, ammonia, and free amino acids in liver and muscle-were evaluated in a chronic-exposure experiment (15-day exposure). Speciation analysis of tin (Sn) was performed in fish tissues at the end of both experiments using gas chromatography coupled to a pulsed-flame photometric detector (GC-PFPD). Concentrations of TPhT, diphenyltin, and monophenyltin (reported as Sn) were lower than limits of quantification (10σ criteria). Waterborne TPhTH concentration used through the experiment was also evaluated by GC-PFPD, and no degradation of this species was observed. The LC50 value for silver catfish juveniles was 9.73μgL(-1) (as Sn). Decreased brain and muscle AChE activities were observed in fish exposed to TPhTH in relation to unexposed fish (control). Liver glycogen and lactate levels were significantly higher in fish kept at the highest waterborne TPhTH concentration compared with the control. Liver and muscle glucose levels of fish exposed to all TPhTH concentrations were significantly lower than those of control fish. Silver catfish exposed to all TPhTH concentrations showed lower total protein values and higher total free amino acids levels in liver and muscle compared with controls. Total ammonia levels in liver and muscle were significantly higher for the highest TPhTH concentration compared with controls. In conclusion, TPhTH caused metabolic alterations in silver catfish juveniles, and the analyzed parameters can also be used as bioindicators for TPhTH contamination.

Non-volatile taste components of several cultivated mushrooms

Five species of dried mushrooms are commercially available in China, namely Agrocybe cylindracea, Pleurotus cystidiosus, Agaricus blazei, Pleurotus eryngii, and Coprinus comatus, and their nonvolatile taste components were studied. Trehalose (12.23–301.63mg/g) and mannitol (12.37–152.11mg/g) were considered as the major mushroom sugar/polyol in the five test species. The total free amino acid levels ranged from 4.09 to 22.73mg/g. MSG-like components contents ranged from 0.97 to 4.99mg/g. 5′-Nucleotide levels ranged from 1.68mg/g in P. eryngii to 3.79mg/g in C. comatus. Fumaric acid (96.11mg/g) in P. cystidiosus were significantly higher compared with the other mushrooms, and citric acid (113.13mg/g), as the highest of any organic acid among the five mushrooms, were found in A. blazei. Equivalent umami concentrations values in these five test mushrooms ranged from 11.19 to 88.37g/100g dry weight. A. blazei, C.comatus and A. cylindracea possessed highly strong umami taste.

Tolerance and avoidance responses to salinity and water stresses in Calotropis procera and Suaeda aegyptiaca

This study was designed to evaluate the response of 2 wild shrubs, Calotropis procera and Suaeda aegyptiaca, to salinity (100% seawater), drought, and waterlogging stresses. The 90-day-old plants were subjected to the stress treatments for 3 weeks, and growth and some physiological parameters were evaluated. The total plant dry mass of C. procera plants was reduced by 40%, whereas S. aegyptiaca was not significantly affected by salinity stress. Water deficit and waterlogging stresses significantly reduced the total dry mass of both species. Under all conditions, the root/shoot ratio in C. procera was 3-fold higher than in S. aegyptiaca. All applied stresses markedly increased leaf shedding in C. procera plants only. These plants appeared to have a higher salinity and waterlogging stress intensity index as manifested by chlorophyll levels lower than those in S. aegyptiaca. Under all conditions, Na^+ levels of S. aegyptiaca were twice those of C. procera plants. All stresses reduced the K^+/Na^+ ratio in C. procera leaves. On the other hand, S. aegyptiaca plants were able to maintain this ratio near control levels under salinity and drought stresses. Consequently, S. aegyptiaca leaves had higher partial osmotic pressure than C. procera. The proline and total free amino acids levels in C. procera were between 1.3- and 2-fold higher than in S. aegyptiaca. Among all amino acids, the common change in both species under all stresses was an accumulation of free proline and a decrease in methionine levels. The results revealed that the response of both species to salinity and water stresses included avoidance and tolerance mechanisms with some differences between them.

Application of UHPLC for the simultaneous analysis of free amino acids and biogenic amines in ripened acid-curd cheeses

A new UHPLC method for the simultaneous determination of amino acids and biogenic amines in a single run, and its first application to profile ripened acid-curd cheeses was presented. After pre-column derivatization with 6-aminoquinolyl-N-hydroxy succinimidyl carbamate (AQC), 23 amino acids and 15 amines were separated in 9min only (12min total run time), and eluates monitored using their UV response at 249nm. Limits of detection (0.05-0.29mg/100g) and quantification (0.16-0.97mg/100g), repeatability for sample preparation (1.0-6.1% RSD) and method recoveries (83-120%) were found suitable for cheese analysis. In total, 47 acid-curd cheeses classified into sub-groups like cooked, Quargel-type or grey cheeses were analyzed for their free amino acid and amine (histamine, tyramine, putrescine, cadaverine, and tryptamine) contents, which (as expected) were highlighted by a great variability. Total free amino acid levels ranged between less than 100 and more than 4000mg/100g (median 567mg/100g), implying that for some cheeses less or not ripened/fresh quark was used for production or, in contrast, a higher degree of proteolysis had occurred. For the sum of biogenic amines, median concentration was determined at 7.0mg/100g, while only 5% of all cheeses had levels higher than 161.9mg/100g. Thus, the obtained results suggest quite acceptable biogenic amine levels for (mostly underrated) ripened acid-curd cheeses, although partly exceptional high concentrations (>250mg/100g) were indeed observed in individual samples.

Degradation characteristics of proteins in cheonggukjang (fermented unsalted soybean paste) prepared with various soybean cultivars

In order to select the most ideal soybean cultivars for producing cheonggukjang, the protein degradation characteristics of cheonggukjangs prepared with 30 different soybean cultivars were compared. Cheonggukjang prepared with ‘Nampung’ (18.00±0.28%) and ‘Sohwang’ (17.91±0.63%) soybeans showed the highest contents of viscous substances. Acidic-protease activity was highest (590.24±2.92 μg/mL) in cheonggukjang prepared with small ‘Pungsannalmul’ soybeans. Neutral-protease activity was highest (528.13±3.11 and 527.36±0.44 μg/mL, respectively) in cheonggukjang prepared with ‘Singi’ and ‘Nampung’ soybeans. Cheonggukjang prepared with ‘Wonkwang’ and ‘Sohwang’ soybeans had amino-type nitrogen contents of 780.50±2.92 and 729.95±1.07 mg%, respectively. Glutamic acid, which is a major component of viscous substances, was also detected. Although total free amino acid levels in cheonggukjang prepared with ‘Daewon’ and ‘Wonkwang’ soybeans measured 2,551.21 and 2,340.02 mg%, respectively, cheonggukjang prepared with black soybeans exhibited low levels of total free amino acids. Therefore, based on protein degradation characteristics, large ‘Daewon’ soybeans and small ‘Wonkwang’ soybeans were the most suitable for producing cheonggukjang.