Oxidative decarboxylation of 2‐oxoacids by hydroperoxides can be used to lower peroxide values in citrus oils

2019 ◽  
Vol 35 (1) ◽  
pp. 107-113
Author(s):  
Michael J. Calandra ◽  
Ying Wang
Keyword(s):  
Oxidative Decarboxylation ◽  
Peroxide Values ◽  
Lower Peroxide

Effect of Pre-Cure Freezing and Thawing on the Microflora, Fat Characteristics and Palatability of Dry-Cured Ham1

1982 ◽  
Vol 45 (3) ◽  
pp. 244-248 ◽  
Author(s):  
J. D. KEMP ◽  
B. E. LANGLOIS ◽  
A. E. JOHNSON
Keyword(s):  
Escherichia Coli ◽  
Weight Loss ◽  
Bacillus Cereus ◽  
Clostridium Perfringens ◽  
The Other ◽  
Freezing And Thawing ◽  
Fourth Group ◽  
Microbial Counts ◽  
Peroxide Values ◽  
Lower Peroxide

Hams were placed in cure after thawing by 3 methods: at 2C, at 16C, and in water at 37C. A fourth group was placed in cure while still frozen. Microbiological populations and fat rancidity tests were determined at various intervals during processing. Sensory scores and tenderness values were determined after 3 months of aging. Clostridium perfringens, Bacillus cereus, Escherichia coli, coliforms and enterococci were not detected after salt equalization. Hams cured without thawing had lower initial bacterial, yeast and mold counts but no differences among thaw groups were observed in counts during aging. Hams thawed in water had lower flavor and overall satisfaction scores than the other groups. Fat breakdown as noted by FFA, TBA and peroxide values increased with aging but were erratic although ham cured without thawing had lower peroxide values. Satisfactory dry-cured aged hams were produced regardless of method of thawing. However, since hams cured without thawing had less weight loss, lower peroxide numbers, lower initial microbial counts and similar final microbial counts and sensory scores, it appears that hams do not need to be thawed to produce dry-cured aged hams.

scholarly journals Crystal structures of non-oxidative decarboxylases reveal a new mechanism of action with a catalytic dyad and structural twists

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Matthias Zeug ◽  
Nebojsa Markovic ◽  
Cristina V. Iancu ◽  
Joanna Tripp ◽  
Mislav Oreb ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Active Site ◽  
Enzyme Engineering ◽  
Base Catalysis ◽  
Oxidative Decarboxylation ◽  
Transition State Stabilization ◽  
Major Bottleneck ◽  
Hydroxybenzoic Acids ◽  
Potassium Binding ◽  
Β Sheet

AbstractHydroxybenzoic acids, like gallic acid and protocatechuic acid, are highly abundant natural compounds. In biotechnology, they serve as critical precursors for various molecules in heterologous production pathways, but a major bottleneck is these acids’ non-oxidative decarboxylation to hydroxybenzenes. Optimizing this step by pathway and enzyme engineering is tedious, partly because of the complicating cofactor dependencies of the commonly used prFMN-dependent decarboxylases. Here, we report the crystal structures (1.5–1.9 Å) of two homologous fungal decarboxylases, AGDC1 from Arxula adenivorans, and PPP2 from Madurella mycetomatis. Remarkably, both decarboxylases are cofactor independent and are superior to prFMN-dependent decarboxylases when heterologously expressed in Saccharomyces cerevisiae. The organization of their active site, together with mutational studies, suggests a novel decarboxylation mechanism that combines acid–base catalysis and transition state stabilization. Both enzymes are trimers, with a central potassium binding site. In each monomer, potassium introduces a local twist in a β-sheet close to the active site, which primes the critical H86-D40 dyad for catalysis. A conserved pair of tryptophans, W35 and W61, acts like a clamp that destabilizes the substrate by twisting its carboxyl group relative to the phenol moiety. These findings reveal AGDC1 and PPP2 as founding members of a so far overlooked group of cofactor independent decarboxylases and suggest strategies to engineer their unique chemistry for a wide variety of biotechnological applications.

Chichibabin pyridinium synthesis via oxidative decarboxylation of photoexcited α-enamine acids

2021 ◽  
Author(s):  
Zhiqiang Pan ◽  
Fengchi Hu ◽  
Di Jiang ◽  
Yuchang Liu ◽  
Chengfeng Xia
Keyword(s):  
Amino Acids ◽  
Oxidative Decarboxylation

The photoexcited enamines derived from α-amino acids could undergo an oxidative decarboxylation followed by a Chichibabin cyclization to afford highly substituted pyridiniums.

scholarly journals The Effect of Carnosol, Carnosic Acid and Rosmarinic Acid on the Oxidative Stability of Fat-Filled Milk Powders throughout Accelerated Oxidation Storage

Antioxidants ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 762
Author(s):  
Katerina Tzima ◽  
Nigel P. Brunton ◽  
Noel A. McCarthy ◽  
Kieran N. Kilcawley ◽  
David T. Mannion ◽  
...  
Keyword(s):  
Rosmarinic Acid ◽  
Solid Phase ◽  
Thiobarbituric Acid ◽  
Butylated Hydroxytoluene ◽  
Carnosic Acid ◽  
Gas Chromatography Mass Spectrometry ◽  
Peroxide Values ◽  
Antioxidant Potency ◽  
Antioxidant Effects

The in vitro antioxidant effects of the most potent antioxidants of rosemary, namely carnosol, carnosic acid and rosmarinic acid (c: ca: ra) were assessed in fat-filled milk powders (FFMPs) under accelerated conditions (40 °C and relative humidity (RH) 23%) over 90 days. Lipid oxidation was assessed in FFMPs by measuring peroxide values (PVs), thiobarbituric acid reactive substances (TBARS) and aroma volatiles using headspace (HS) solid-phase microextraction (SPME) coupled to gas-chromatography-mass spectrometry (GC-MS). The antioxidant potency of c: ca: ra exhibited a concentration-related effect (308 ppm > 200 ppm > 77 ppm), with the highest concentration being the most effective at controlling the formation of TBARS and PVs. At a concentration of 308 ppm c: ca: ra were particularly effective (p < 0.05) in inhibiting all the evaluated oxidation indices (primary and secondary) compared to the control samples, but in some cases less effectively (p < 0.05) than butylated hydroxyanisole: butylated hydroxytoluene (BHA: BHT) (200 ppm).

Sustainable Electrochemical Decarboxylative Acetoxylation of Aminoacids in Batch and Continuous Flow

2021 ◽  
Author(s):  
Manuel Köckinger ◽  
Paul Hanselmann ◽  
Dominique Roberge ◽  
Piero Geotti-Bianchini ◽  
C. Oliver Kappe ◽  
...  
Keyword(s):  
Continuous Flow ◽  
Organic Molecules ◽  
Oxidative Decarboxylation ◽  
Active Ingredients ◽  
Synthetic Intermediates

Introduction of acetoxy groups to organic molecules is important for the preparation of many active ingredients and synthetic intermediates. A commonly used and attractive strategy is the oxidative decarboxylation of...

ChemInform Abstract: Oxidative Decarboxylation of Cyclic Amino Acids and Dehydrogenation of Cyclic Secondary Amines with Iodosobenzene.

ChemInform ◽  
1989 ◽  
Vol 20 (26) ◽  
Author(s):  
M. OCHIAI ◽  
M. INENAGA ◽  
Y. NAGAO ◽  
R. M. MORIARTY ◽  
R. K. VAID ◽  
...  
Keyword(s):  
Amino Acids ◽  
Secondary Amines ◽  
Oxidative Decarboxylation ◽  
Cyclic Amino Acids
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