Cyclocondensation of 2,3-butanedione in the presence of amino acids and formation of 4,5-dimethyl-1,2-phenylendiamine

The chemical interaction of 2,3-butanedione with amino acids through Strecker reaction has been studied extensively. However, the formation of previously reported 4,5-dimethyl-1,2-benzoquinone from 2,3-butanedione/amino acid model systems has not been investigated in detail. In this study such model systems containing 2,3-butanedione were investigated under pyrolytic conditions using glycine, sodium glycinate and glycine hydrochloride as amino acids able to modulate acid/base catalytic activity of the reaction medium. The analysis of the data indicated that replacing glycine with its corresponding salts promoted significantly the generation of 2,3,6,7-tetramethylquinoxaline relative to tetramethylpyrazine, the indicator compound for the Strecker reaction. The origin of the 2,3,6,7-tetramethylquinoxaline was traced back to the formation of 4,5-dimethyl-1,2-benzoquinone through isotope labelling studies. Furthermore, these studies have also indicated the ability of glycine not only to catalyse the cyclocondensation of butanedione into 4,5-dimethyl-1,2-benzoquinone but also its conversion into 4,5-dimethyl-1,2-phenylenediamine through Strecker-type transformations. The trapping of 2,3-butanedione by this in situ generated 4,5-dimethyl-1,2-phenylenediamine gave rise to the observed 2,3,6,7-tetramethylquinoxaline.     

Determination of acid number and base number in lubricants by Fourier transform infrared spectroscopy

This paper describes the development of practical Fourier transform infrared (FT-IR) methods for the determination of acid number (AN) and base number (BN) in lubricants through the combined use of signal transduction via stoichiometric reactions and differential spectroscopy to circumvent matrix effects. Trifluoroacetic acid and potassium phthalimide were used as stoichiometric reactants to provide infrared (IR) signals proportional to the basic and acidic constituents present in oils. Samples were initially diluted with 1-propanol, then split, with one half treated with the stoichiometric reactant and the other half with a blank reagent, their spectra collected, and a differential spectrum obtained to ratio out the invariant spectral contributions from the sample. Quantitation for AN and BN was based on measurement of the peak height of the v(C = O) or v(COO) absorptions, respectively, of the products of the corresponding stoichiometric reactions, yielding a standard error of calibration of < 0.1 mg KOH/g oil. The AN/BN FT-IR methods were validated by the analysis of a wide range of new and used oils supplied by third parties, which had been analyzed by ASTM methods. Good correlations were obtained between the chemical and FT-IR methods, indicating that the measures are on the whole comparable. From a practical perspective, these new FT-IR methods have significant advantages over ASTM titrimetric methods in terms of environmental considerations, sample size, and speed of analysis, as well as the variety of oil types that can be handled. FT-IR analysis combining stoichiometric signal transduction with differential spectroscopy may be of wider utility as an alternative to titration in the determination of acid or basic constituents in complex nonaqueous systems.     

Functional and molecular properties of calcium precipitated soy glycinin and the effect of glycation with κ-carrageenan

This study describes an extraction process for the preparation of highly purified calcium precipitated glycinin (11S). Initial extraction of soy proteins using isoelectric precipitation at pH 6.8 followed by cryo-precipitation yielded 4.2% product (11S) recovery with 98% protein purity for the control extracted with NaOH. Addition of calcium chloride (CaCl₂) doubled the extraction yield (9%) compared to the control and when two other salts were used (i.e., sodium (Na₂SO₄) and ammonium (NH₄)₂SO₄ sulfate, average yields of 4.4% and 5.17%, respectively). Thermal and molecular stability under varying conditions (pH, salts, SDS as a protein structure perturbing agent), and effect of glycation on functional and structural properties were investigated. Size exclusion chromatography and electrophoresis confirmed the predominance of a major band with MW of ～342 kDa with 98.4% purity. Differential scanning calorimetry (DSC) yielded one endothermic transition peak at 95.5 °C. Denaturation temperatures were >100 °C for all salt concentrations studied. The pH had a dominant influence on the structural properties of glycinin. In the presence of NaCl and CaCl₂ (0.2–1 M), the protein structure showed very little denaturation and no aggregation bands were observed even on heating to 95 °C. Lower SDS concentrations (0.5–1%) resulted in denaturation and aggregation, while at 2% SDS only denaturation was observed. Glycation did not alter the conformational structure of protein. Improvements in surface properties were observed with moderate degree of glycation (6–24 h).     

Carotenoproteins from lobster waste as a potential feed supplement for cultured salmonids

Lobster waste (including the head and hard carapace, viscera, mandibles and gills) contains approximately 54 μg/g total astaxanthin, 29% protein, 23% chitin, 34% ash and 2.2% crude fat on a dry weight basis. Trypsin from bovine pancreas was applied to facilitate the recovery of carotenoid pigments and protein as carotenoprotein complex, which was subsequently air‐dried to a stable powder form at 45°C and 15% relative humidity. The product obtained was found to contain 60% protein, 15% crude fat, 6% ash, 8% chitin and 295 μg/g total astaxanthin. Thus, the process achieved a substantial reduction in the levels of anti‐nutrients associated with lobster waste (i.e., ash and chitin) while elevating the levels of carotenoid pigments and essential nutrients such as protein and fat in the recovered product These characteristics of the final product suggest that it could be used as an inexpensive source of pigment and protein in diets of cultured salmonid species.     

Chemical Analysis of Defense Secretions of Sipyloidea sipylus and Their Potential Use as Repellents Against Rats

The defensive secretion of Sipyloidea sipylus was analyzed using a GC-MS technique. Five chemicals were identified (diethyl ether, acetic acid, benzaldehyde, limonene, and benzothiazole) and mixed in about the same ratio as detected in the secretion to determine the potential effectiveness of such a mixture as a repellent against lab rats.     

Vinylogous Amadori rearrangement: implications in food and biological systems

The 4-hydroxy-alkenals are important lipid peroxidation products and are known to play a major role both in the development of degenerative diseases in biological systems and off-flavors, or rancidity in food systems. The 4-hydroxy-alkenals can also be formed in nonlipid systems from 2-deoxy-sugar moieties such as 2-deoxy-ribose. FTIR spectroscopic evidence was provided for such a transformation catalyzed by amino acids through monitoring the decrease in intensity of the aldehydic band centered at 1716 cm(-1) of the open form of 2-deoxy-ribose and increase in the intensity of the formed conjugated aldehydic band centered at 1672 cm(-1). Furthermore, 4-hydroxy-alkenals can react with nitrogen nucleophiles such as amino acids and proteins to form Schiff base adducts that are able to undergo vinylogous Amadori rearrangement (vARP) and subsequently cyclize to generate a pyrrole moiety. This cyclization is prevented in the case of secondary amino acids such as proline to form a stable vinylogous Amadori rearrangement product (vARP). Monitoring this reaction of proline with 4-hydroxy-2-nonenal (HNE) has indicated that within 15 min at 28 degrees C the 1685 cm(-1) band of HNE completely disappears and that at 50 degrees C, vARP is formed within 5 min, as indicated by the formation of a characteristic band at 1709 cm(-1).     

Thermal degradation of sucralose and its potential in generating chloropropanols in the presence of glycerol

Sucralose, a polychlorinated synthetic high-intensity sweetener is being increasingly used in relatively large amounts in baked products under high temperature environments. This necessitates understanding its thermal decomposition and studying the consequences of hydrogen chloride release from sucralose and its ability to chlorinate various food related ingredients such as glycerol to generate chloropropanols a potentially toxic class of compounds. Studies conducted on the thermal degradation of sucralose under dry heating conditions have indicated that the glycosidic cleavage occurs through the formation of a galactopyranosyl cation contrary to sucrose where fructofuranosyl cation dictates the major breakdown products. Consequently the major product detected was levoglucosenone and its precursor. Subsequent degradation of the two monosaccharide derivatives causes dehydrochlorination and dehydration reactions to produce furan-related products. In addition, pyrolysis of sucralose in the presence of glycerol generated significant amounts of 3-monochloropropanediol and 1,2- and 1,3-dichloropropanols based on the relative intensities of their chromatographic peaks which amounted to 15% of the total chromatographic peak area.     

Prediction of Process Lethality through Measurement of Maillard-Generated Chemical Markers

ABSTRACT: Direct measurement of time-temperature exposure of the center of particulate foods is often impractical to establish. Currently, foods are overheated to ensure sterility when their process lethality is difficult to estimate. Indirect measurements using chemical markers can overcome these difficulties. A novel approach that correlates marker yields to process lethality, rather than to microbial destruction, was developed. This was achieved through controlled heating of the sample at various time intervals to further induce marker formation and calculate the lethality values. When the data were plotted as marker yield against lethality and were subsequently extrapolated, the x- and y-axes intercepts yielded information regarding the original process lethality and initial marker yield.     

Use of the Microwave-Assisted Process in extraction of fat from meat, dairy, and egg products under atmospheric pressure conditions

Fat from meat, dairy, and egg products was extracted by using Microwave-Assisted Process (MAP) technology under atmospheric pressure conditions. Fat content was determined gravimetrically after extraction with microwaves and organic solvents that are transparent to microwaves relative to the sample. (In situ hydrolysis was performed for dairy and egg products.) Fat from the food sample migrated completely to the extractant when samples were irradiated with focused microwave for a total of 3 min for meat products, 1 min for dairy products, and 4 min for egg products. Unlike current methods used for determining fat in meat products, the microwave-assisted method does not require a dry sample, because moisture in the sample (around 75%) enhances the efficiency of extraction. No preprocessing was required for meat samples other than homogenization, which is critical, as it is for other current methods. In addition to speed and ease of use, the features of this technology are low solvent consumption, low energy consumption, reproducibility, and recoveries similar to or even better than those of conventional extraction methods.