Search results for "Organic acid"
showing 10 items of 27 documents
Recent advancements in lactic acid production - a review.
2017
Abstract Lactic acid, as an organic acid, has essential roles in industrial applications ranging from the food industry to life-sciences. Conventional fermentation methods have been well-studied since late 18th century, but are unable to achieve consumers' expectations regarding both quality and quantity. Therefore, novel technological developments of lactic acid production to increase yield and decrease over-all cost have become the primary goal. Genetic and metabolic engineering are great tools to overcome problems associated with product inhibition, undesired by-product formation, the negative effect of extreme culture conditions and most importantly inefficient use of expensive substrat…
An Arabidopsis Mutant Over-Expressing Subtilase SBT4.13 Uncovers the Role of Oxidative Stress in the Inhibition of Growth by Intracellular Acidificat…
2020
Intracellular acid stress inhibits plant growth by unknown mechanisms and it occurs in acidic soils and as consequence of other stresses. In order to identify mechanisms of acid toxicity, we screened activation-tagging lines of Arabidopsis thaliana for tolerance to intracellular acidification induced by organic acids. A dominant mutant, sbt4.13-1D, was isolated twice and shown to over-express subtilase SBT4.13, a protease secreted into endoplasmic reticulum. Activity measurements and immuno-detection indicate that the mutant contains less plasma membrane H+-ATPase (PMA) than wild type, explaining the small size, electrical depolarization and decreased cytosolic pH of the mutant but not orga…
Application of chemometrics to assess the influence of ultrasound frequency, Lactobacillus sakei culture and drying on beef jerky manufacture: Impact…
2017
The effects of ultrasound (US) frequency, addition of Lactobacillus sakei culture and drying time on key nutritional (protein, amino acids, and organic acids) and physicochemical properties (texture and colour) of cultured and uncultured beef jerky were evaluated. Cultured and uncultured jerky samples were subjected to US frequencies of 25 kHz, 33 kHz and 45 kHz for 30 min prior to marination and drying. Principal component analysis demonstrated a significant effect of beef jerky processing conditions on physicochemical properties. Taurine content of jerky samples was found to increase with an increase in ultrasonic frequencies for cultured samples. No significant changes in colour values w…
Detection of γ‐hydroxybutyric acid‐related acids in blood plasma and urine: Extending the detection window of an exogenous γ‐hydroxybutyric acid inta…
2021
In crimes facilitated by γ-hydroxybutyric acid (GHB) administration, the frequent occurrence of anterograde amnesia of the victims as well as the short detection window and variations of endogenous GHB concentrations complicate obtaining analytical proof of GHB administration. Because elevated endogenous organic acid concentrations have been found in the urine of patients with succinic semialdehyde deficiency (leading to accumulation of GHB in human specimens) and after GHB ingestion, we searched for an alternative way to prove GHB administration via detection of elevated organic acid concentrations in blood plasma and urine. We collected blood and urine samples from narcolepsy patients (n …
Chemical-based methodologies approaches to extend the shelf life of fresh fish — a review
2021
Due to its characteristics, fresh fish is a highly perishable food with a very short shelf-life under refrigeration. Several methods have been introduced to slow down its deterioration, such as by means of oxygen depletion of the food package (vacuum packaging), or by changing the natural atmosphere that is in contact with the fresh fish (modified atmosphere packaging), or by the use of chemicals generally recognized as safe: such compounds can be directly applied (by dipping or spraying) or incorporated into packaging materials and slowly migrate to the product, exerting a hurdle effect against microbial development and lipid oxidation (active packaging). This review aims to cover the most…
Modulation of geraniol metabolism during alcohol fermentation
2004
J. Inst. Brew. 110(3), 213–219, 2004 Geraniol is the main monoterpenol present in Gewurtztraminer white grapes and in some red aromatic grapes from northern Italy. During fermentation, the geraniol concentration showed a dramatic drop and a small amount was transformed into linalool and -terpineol by an acid catalysed chemical reaction. Yeast are responsible for changing most of the geraniol to citronellol through enzymatic reactions. The final aroma of wine is due mainly to both the untransformed geraniol and the formed citronellol. In this study, competition between the geraniol-citronellol transformation and another metabolic process, in which according to our hypothesis sterol biosynthe…
Online atmospheric pressure chemical ionization ion trap mass spectrometry (APCI-IT-MS<sup>n</sup>) for measuring organic…
2012
Abstract. The field application of an aerosol concentrator in conjunction with an atmospheric pressure chemical ionization ion trap mass spectrometer (APCI-IT-MS) at the boreal forest station SMEAR II at Hyytiälä, Finland, is demonstrated in this study. APCI is a soft-ionization technique allowing online measurements of organic acids in the gas and particle phase. The detection limit for the acid species in the particle phase was improved by a factor of 7.5 to 11 (e.g. ∼40 ng m3 for pinonic acid) by using the miniature versatile aerosol concentration enrichment system (mVACES) upstream of the mass spectrometer. The APCI-IT-MS was calibrated in the negative ion mode with two biogenic organic…
Recovery of anthocyanins from eggplant peel
2009
Abstract Tartaric and malic acid solutions were tested to extract anthocyanins from eggplant peel by a discontinuous process to obtain a natural red colorant. Extraction optimization was carried out, using different solvents, acid concentration, temperature, time of extraction and solvent-to-solid ratio as independent variables. Tartaric acid was more efficient than malic acid in both extraction yield and rate. Comparative tests were carried out using acidified ethanol as solvent. Delphinidin-3-rutinoside was extracted and identified as the major anthocyanin in eggplant peel. Concentration of different extracts from eggplant peel was carried out using EXA-31, a methacrylic food grade resin,…
Surface characterization of metal ions loaded TiO2 photocatalysts: structure-activity relationship
2004
Transition metal loaded TiO2 powders were characterised and tested for the photodegradation of some organic acids. Both Lewis and Brønsted surface acid sites were present in the samples containing large amounts of Mo, V and W. The Brønsted sites are associated to the presence of the transition metals as they do not exist in the unloaded support, and in particular to the presence of these metals in high oxidation states. The trend of the pzc values of the various powders matches rather well both with the surface acidity of the samples experimentally determined by NH3 adsorption and with a scale of acidity/basicity for bulk binary oxides. XPS investigation indicates that only the presence of …
Simultaneous enzymatic determination of l(−) malic acid and l(+) lactic acid in wine by flow injection analysis
1991
Abstract A simultaneous determination of two organic acid species in wine by a flow injection analysis method using enzyme-immobilized open tubular reactors is described. The design of the optimal geometry of the FIA system is especially important to avoid the matrix fluorescence. Reproducible results were obtained in the determination of l (−) malic acid and l (+) lactic acid using l -MDH and l -LDH, respectively. The assay reactions utilize the fluorimetric determination of a common product, NADH. The sample was dialyzed on line and injected into the FIA-system. The system responds linearly (log-log calibration graphs) to the injected sample (80 μl) in concentrations ranging from 0·1 m m …