scholarly journals A Comprehensive Evaluation of Flavor Instability of Beer (Part 2): The Influence of De Novo Formation of Aging Aldehydes

Foods ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 2668
Author(s):  
Arndt Nobis ◽  
Melanie Kwasnicki ◽  
Florian Lehnhardt ◽  
Michael Hellwig ◽  
Thomas Henle ◽  
...  
Keyword(s):  
Amino Acid ◽  
Free Amino ◽  
De Novo ◽  
Comprehensive Evaluation ◽  
Degradation Products ◽  
Amino Acid Content ◽  
Natural Aging ◽  
Bound State ◽  
Soluble Nitrogen ◽  
Oxidation Reactions

Flavor instability of beer is affected by the rise of aroma-active aldehydes during aging. Aldehydes can be either released from bound-state forms or formed de novo. This second part of our study focused on the de novo formation of aldehydes during the Maillard reaction, Strecker degradation, and oxidation reactions. Key precursor compounds for de novo pathways are free amino acids. This study varied the potential for reactions by varying free amino acid content in fresh beer using different proteolytic malt modification levels (569–731 mg/100 g d. m. of soluble nitrogen) of the used malt in brewing trials. Overall, six pale lager beers were produced from three malts (different malt modification levels), each was made from two different barley varieties and was naturally and forcibly aged. It was found that higher malt modification levels in fresh beer and during beer aging increased amino acid and dicarbonyl concentrations as aging precursors and Strecker aldehyde contents as aging indicators. Dicarbonyls were degraded during aging. Advanced glycation end products as possible degradation products showed no consistent formation during aging. Therefore, Strecker reactions were favored during beer aging. No alternative oxidative formation of Strecker aldehydes from their corresponding alcohols could be confirmed. Along with the preceding part one of our investigation, the results of this study showed that de novo formation and release occur simultaneously. After 4 months of natural aging, aldehyde rise is mainly accounted for by de novo formation.

Reactions of Cloned Poplars to Air Pollution: Premature Leaf Loss and Investigations of the Nitrogen Metabolism

1992 ◽  
Vol 47 (1-2) ◽  
pp. 109-119 ◽  
Author(s):  
Hans-Joachim Ballach ◽  
Simone Oppenheimer ◽  
Jan Mooi
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Nitrogen Metabolism ◽  
Free Amino Acids ◽  
Free Amino ◽  
De Novo ◽  
Total Concentration ◽  
Krebs Cycle ◽  
Amino Acid Content ◽  
Starch Degradation

Abstract Young poplar cuttings (Populus nigra L. cv. Loenen and P. maximowiczii Henry x P. nigra L. cv. Rochester) were exposed for six weeks in open-top chambers to realistic concentrations of pollutant mixtures: 1) control; 2) SO2/NOx; 3)O3/ NOx and 4)SO2/O3/NOx. In this sequence of fumigation variants, the degree of influence of the various parameters of the nitrogen metabolism and of premature leaf drop increased very frequently compared to the control plants, P. nigra L. proving to be the more sensitive species. The elevated Kjeldahl nitrogen content of the fumigated leaves was accompanied by either an increase in free amino acids or in total protein or, in the case of particularly large rises (SO2/O3/NOx variants), by increases in both substance groups. Proteolytic processes as a cause of the elevated content of free amino acids could be excluded to a large extent. A diminished de novo synthesis of proteins obviously led to a shift in the amino acid/protein relationship. In the younger fumigated leaves, the total concentration of free amino acids exceeded the values of the older leaves. The elevated amino acid content of the fumigated leaves was produced to a high degree by the glycolate pathway and the Krebs cycle. The increased turnover of the carbon skeletons was connected with a drastic starch degradation, especially in the older leaves. The interaction of the amino acid and carbohydrate metabolisms is probably an important regulator in the promotion of rapid growth of young leaves in order to compensate premature leaf loss.

scholarly journals A Comprehensive Evaluation of Flavor Instability of Beer (Part 1): Influence of Release of Bound State Aldehydes

Foods ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 2432
Author(s):  
Florian Lehnhardt ◽  
Arndt Nobis ◽  
Andreas Skornia ◽  
Thomas Becker ◽  
Martina Gastl
Keyword(s):  
Bound States ◽  
De Novo ◽  
Comprehensive Evaluation ◽  
Early Stage ◽  
Active Form ◽  
Bound State ◽  
Free Form ◽  
Soluble Nitrogen ◽  
Strecker Aldehydes ◽  
Lager Beer

Flavor instability of pale lager beer depends decisively on aroma-active aldehydes from the Maillard reaction, Strecker degradation, and lipid oxidation, which are formed in various oxidative and non-oxidative reactions. Therein, aldehydes can be formed de novo and be released from bound states to a free, aroma-active form during aging. During malting and brewing, proteolysis affects the amount of soluble nitrogen and thus flavor instability in different ways (e.g., precursors for de novo formation and binding agents for bound states). To isolate nitrogen-related aging processes, beers from malts (two barley varieties, three proteolytic malt modifications) were produced on a 50 L scale in part 1 of this study. Sensory analysis revealed increased flavor instability for beers with higher amounts of soluble nitrogen. Especially Strecker aldehydes significantly increased with malt modification. The release of bound state aldehydes revealed most free aldehydes in fresh beers and with higher malt modification. During aging, the equilibrium between free and bound state aldehydes shifted toward the free form. These results reveal a nitrogen-dependent bound pool of aldehydes that is depleted during aging and is responsible for aged aroma, especially in the early and medium stages of aging. Therefore, bound state aldehydes are indicators of the early-stage prediction of flavor instability already in a fresh condition.

Evaluation of seed amino acid content and its correlation network analysis in wild soybean (Glycine soja) germplasm in Japan

2021 ◽  
Vol 19 (1) ◽  
pp. 35-43
Author(s):  
Awatsaya Chotekajorn ◽  
Takuyu Hashiguchi ◽  
Masatsugu Hashiguchi ◽  
Hidenori Tanaka ◽  
Ryo Akashi
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Free Amino Acid ◽  
Acid Content ◽  
Free Amino ◽  
Glycine Soja ◽  
Wild Soybean ◽  
Amino Acid Content ◽  
Soybean Seeds ◽  
Free Amino Acid Content

AbstractWild soybean (Glycine soja) is a valuable genetic resource for soybean improvement. Seed composition profiles provide beneficial information for the effective conservation and utilization of wild soybeans. Therefore, this study aimed to assess the variation in free amino acid abundance in the seeds of wild soybean germplasm collected in Japan. The free amino acid content in the seeds from 316 accessions of wild soybean ranged from 0.965 to 5.987 mg/g seed dry weight (DW), representing a 6.2-fold difference. Three amino acids had the highest coefficient of variation (CV): asparagine (1.15), histidine (0.95) and glutamine (0.94). Arginine (0.775 mg/g DW) was the predominant amino acid in wild soybean seeds, whereas the least abundant seed amino acid was glutamine (0.008 mg/g DW). A correlation network revealed significant positive relationships among most amino acids. Wild soybean seeds from different regions of origin had significantly different levels of several amino acids. In addition, a significant correlation between latitude and longitude of the collection sites and the total free amino acid content of seeds was observed. Our study reports diverse phenotypic data on the free amino acid content in seeds of wild soybean resources collected from throughout Japan. This information will be useful in conservation programmes for Japanese wild soybean and for the selection of accessions with favourable characteristics in future legume crop improvement efforts.

scholarly journals Free amino acid content in muscle tissue of bighead carp and wels catfish

2016 ◽  
Vol 72 (10) ◽  
pp. 632-636 ◽  
Author(s):  
Renata Pyz-Łukasik ◽  
Maria Szpetnar ◽  
Waldemar Paszkiewicz ◽  
Marcin R. Tatara ◽  
Adam Brodzki
Keyword(s):  
Amino Acid ◽  
Free Amino Acid ◽  
Muscle Tissue ◽  
Acid Content ◽  
Free Amino ◽  
Amino Acid Content ◽  
Bighead Carp ◽  
Predatory Fish ◽  
Free Amino Acid Content ◽  
Natural Diet

The present research was aimed at a comparative analysis of free amino acid (FAA) levels in the muscle tissue of herbivorous and predatory fish. The FAA concentration in the muscle tissue samples from bighead carp and wels catfish was determined by ion-exchange chromatography. The bighead carp muscle tissue, as compared to that of wels catfish, showed significantly higher concentrations of arginine, histidine, methionine, phenyloalanine, alanine, asparagine, serine, glycine, and taurine, but significantly lower levels of isoleucine, leucine, threonine, valine, glutamine, cystationine, β-alanine, ethanoloamine, as well as aspartic, glutamic, cysteic, α- and γ-aminobutyric acids. The muscle tissues of bighead carp and wels catfish did not differ significantly in the levels of cystine, lysine, tryptophan, tyrosine, α-aminoadipic acid, cytrulline, ornithine and 1-methyl-histidine. Proline was detected only in the wels catfish muscle. The results obtained have shown differences in free amino acid concentration in muscle tissue of examined fish. A differentiated natural diet induces changes in free amino acid content in fish tissues. Knowledge of levels of free amino acids which are precursors for biogenic amines facilitates setting the safety criteria for fish and fishery products from species other than those mentioned in the Commission Regulation No 2073/2005

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