Formation Of Amino Acid Derivatives Research Articles

Effect of different stress conditions on the formation of amino acid derivatives by Brewer’s and Baker’s yeast during fermentation

The effects of environmental stresses on the formation of amino acid derivatives by Saccharomyces cerevisiae NCYC 88 and Saccharomyces cerevisiae NCYC 79 were investigated. Fermentation was performed in model systems under different temperature, pH, alcohol, phenolic, and osmotic stress conditions, as well as in beer and dough. According to stress response molecules, yeasts were more affected by osmotic, temperature, and alcohol stresses. Both yeast strains increased the formation of kynurenic acid, tryptophan ethyl ester, tryptophol, and gamma-aminobutyric acid under osmotic stress conditions in model systems. Indole-3-acetic acid was found to be higher in the ferulic acid stress dough (262 µg/kg dry weight, d.w.) compared to the control dough (132 µg/kg d.w.) at the end of the fermentation. The results may enable the development of new strategies for designing novel foods with a desired composition of bioactive amino acid derivatives.

EGCG-gelatin biofilm improved the protein degradation, flavor and micromolecule metabolites of tilapia fillets during chilled storage

The protein degradation, flavor and micromolecule metabolites changes of (−)-epigallocatechin gallate (EGCG)-gelatin biofilm treatment (EGT) on chilled tilapia fillets in 21 days were investigated. Morphology observations revealed EGT protected good connective myofibrillar protein. It maintained protein secondary structure by significantly increasing the proportion of α-helix (15.20%) and decreasing the ratio of random coils (22.02%) in the EGT group compared to the control (CON) group (P < 0.05). Metabolomics with UHPLC-Q-TOF/MS analysis indicated a distinct separation between the CON and treatment groups at the end of storage. Small peptides analysis demonstrated that the EGT group increased the level of sweet peptides. Additionally, the EGT group significantly reduced the formation of amino acid derivatives and esters and off-flavor development. Overall, EGT effectively improved flavor, inhibited fish protein oxidation/degradation, and verified metabolomics results. This study unveiled the potential of metabolomics to analyze metabolites determined by tilapia and monitor the changes during storage.

Gas-phase laboratory study on PAH/amino-acid cluster cations

ABSTRACT As an important class of carbon reservoirs in the interstellar medium (ISM), polycyclic aromatic hydrocarbon (PAH) molecules play an important role in the evolutionary network of prebiotic molecules. Here, the experimental evidence of astronomically relevant amino-acid derivatives – PAH/amino-acid clusters – is provided, and we study their ion–molecular collision reactions in the gas phase. With the initial molecular precursors dicoronylene (DC, C48H20)/alanine (Ala, C3H7NO2) and DC/isoleucine (Ile, C6H13NO2), the experiments indicate that PAH–amino-acid cluster cations (e.g. (Ala)C48H$_{(0-19)}\, ^+$ and (Ile)C48H$_{(0-19)}\, ^+$) and graphene–amino-acid cluster cations (e.g. (Ala)nC$_{48}\, ^+$ and (Ile)nC$_{48}\, ^+$, n = 1, 2, 3, 4) are efficiently formed in a strong interstellar radiation field. In addition, the structure of clusters and the binding energy of their formation pathways are studied by a quantum chemistry calculation method: gas-phase reactions (ion–molecule reactions) between PAH cations with amino acids readily occur (exothermic energy around 2.0–4.7 eV), and these newly formed clusters have a complex molecular configuration (C–O and C–N bond type). These laboratory studies provide a cluster growth pathway (through an ion–molecule reaction) towards the formation of amino-acid derivatives in a bottom-up process and insight into their chemical-evolution behaviour, opening up aromatic-based chemistry that is available to the species (dehydrogenated PAHs or graphene molecules) that formed from the photofragmentation process of PAHs in interstellar environments. When conditions are suitable (e.g. have similar molecular abundance spatial distributions in the ISM), amino-acid derivatives can form efficiently, and newly built large PAH/amino-acid clusters may be widespread in space.

Formation of amino acid derivatives in white and red wines during fermentation: Effects of non-Saccharomyces yeasts and Oenococcus oeni

This study aimed to investigate the effect of commercial non-Saccharomyces yeasts and Oenococcus oeni on the formation of amino acid derivatives, some of which have neuroactive properties, during fermentation in laboratory-scale processing of white and red wines. Changes in the content of amino acid derivatives during fermentation of large-scale white and red wines were also evaluated. The highest kynurenic, picolinic, and quinolinic acid concentrations were observed in white wine fermented with Torulaspora delbrueckii, Kluyveromyces thermotolerans and Saccharomyces cerevisiae simultaneously. No changes in the content of picolinic and kynurenic acid were observed during large-scale white wine fermentation. Tryptophan ethyl ester concentration in all wines increased significantly during alcoholic fermentation. Natural and O. oeni malolactic fermentation did not alter the content of picolinic acid, a neuroprotective compound, in red wine. The decrease in the content of tyramine, phenylethylamine, and dopamine in laboratory-scale white wines was observed during alcoholic fermentation.

ALTERATIONS OF MUSCLE PROTEIN FUNCTIONALITY BY OXIDATIVE AND ANTIOXIDATIVE PROCESSES1

ABSTRACTOxidation and resulting changes in physical and chemical properties of lipids and proteins occur widely in muscle foods, but oxidatively induced alterations in protein functionality have not been fully assessed. Recent studies have shown that sarcoplasmic, myofibrillar and stromal proteins, whether from red meat, poultry, or fish species, are all susceptible to oxidative damage caused by oxidizing lipids, metal ions, and other prooxidants indigenous to muscle or generated during meat processing. This is demonstrated by changes in protein structure, peptide chain scission, formation of amino acid derivatives and polymers, and decreases in solubility, gelation and hydration properties. However, utilization of antioxidants can minimize functional deteriorations in proteins during processing and storage, thereby assuring the supply of high‐quality muscle food products.

Replacement of the stannyl group in X3SnRe(co)5 complexes by the action of amino acids and their derivatives

In order to establish the possibility of the existence of stannyl derivatives of rhenium carbonyl with ligands of the amino acid type bonded by the NH/sub 2/ group to the Re atom we have carried out the reaction of introducing SnCl/sub 2/ at the Cl-Re bond to the bis-methyl leucinate complex. The reactions of stannyl derivatives of rhenium carbonyl of the type X/sub 3/SnRe(CO)/sub 5/ (X = Ph or Hal) with amino acids and their derivatives (esters, salts) proceed with fission of the metal-metal bond and with the formation of amino acid derivatives of rhenium carbonyl with a facial disposition of CO groups in the Re(CO)/sub 3/ fragment. An organometallic complex with a Sn-Re bond was obtained by an insertion reaction of SnCl/sub 2/ at the Cl-Re bond in the methyl L-leucinate derivative of rhenium carbonyl chloride. The complex contained coordinated amino groups of the leucine ester molecule as ligands.