Abstract: We present a rapid and sensitive flow injection method for the determination of arginine in dietary supplements. Detection was based on the chemiluminescence reaction of arginine with alkaline hypobromite. The response is proportional to analyte concentration over the calibration range, from 2.5 x 10^-6 to 1 x 10^-4 M, and a relative standard deviation of 1% was calculated (1 x 10^-5 M, n = 12). Samples required only aqueous dilution prior to analysis, and over 100 samples could be analyzed per hour, which is superior to that achieved with conventional colorimetric and enzymatic procedures. The results obtained with the flow injection methodology were concordant with those achieved using high-performance liquid chromatography employing pre-column derivatization and fluorescence detection. Copyright © 2005 Society of Chemical Industry

Abstract: There are many chemical, microbiological and sensory indices of fish quality. Of the chemical indices, TMA-N and TVB-N are probably the most used in connection with remaining shelf-life determination. This paper reports on a study of modifications to a flow injection analysis (FIA) method necessary to make it suitable for TMA-N and TVB-N determination, specifically the optimal concentrations of NaOH and formaldehyde for releasing the volatile bases from the acidic fish extract and sequestering the non-TMA volatile bases respectively. The effects of using perchloric acid (PCA) and trichloroacetic acid (TCA) as fish extractants were also investigated. The fish species used were monkfish (Lophius piscatorius), skate (Raia clavata) and cod (Gadus morrhua). It was found that 1 M NaOH was the optimal concentration for volatile base release and that 200 g L-1 formaldehyde was adequate for non-TMA base sequestration. Use of PCA and TCA as fish extractants appeared to have no significant effect on TMA-N and TVB-N determinations.

Abstract: Structural differences in barley grains have been classified as either mealy or steely and their relative proportions have been determined using a light transflectance method in three barley samples varying in the degree of steeliness, Target being the most steely and Chariot most mealy with Blenheim being intermediate. These structural differences were found to be associated with differences in the concentration of endosperm components, particularly proteins and β-glucan. Analysis of nitrogen within the endosperm showed that protein was mainly concentrated in the embryo and distal regions with the inner, mid-endosperm containing lowest levels. As the total nitrogen (TN) of the grain increased, the mealier samples accumulated nitrogen mainly in the embryo whereas the steely sample had higher levels in the central endosperm. SDS-PAGE showed no differences in the protein banding pattern at different TN levels. Electron microscopy using immuno-gold labelling demonstrated that γ-hordeins were present in sub-aleurone and outer endosperm whereas the C-hordeins were found throughout the central endosperm. However, steely areas of central endosperm contained γ-hordeins. During malting, protein modification in Chariot was more extensive than in Target with 34kD and 97kD hordeins being completely degraded. In Chariot and Blenheim, level of β-glucan was low and it was evenly distributed throughout the endosperm. In the steelier Target, however, the amount of β-glucan was higher and was concentrated in the proximal. and distal areas of the endosperm. Steely grains (containing high concentrations of protein and β-glucan) displayed slower water distribution during steeping and later development and distribution of β-glucanase during germination. As a consequence, the steely sample achieved a lower degree of modification during malting. The structure of the endosperm, therefore, has a prime influence on the evenness of distribution of moisture and enzymes which is crucial for homogeneous modification during malting.

Abstract: Milk fat from cow and ewe milk was extracted by the method of Garcia Olmedo et al. (Anal. Bromatol., XXXI, 227) using a rotary evaporator instead of a Soxhlet extractor. Cocoa butter was extracted using the industrial process of NATRA SA (Valencia, Spain). The extracts or olive oils were homogenized with toluene in an ultrasonic bath and the homogenate injected into a carrier stream of toluene (0.95 ml/min). The carrier stream merged with a reagent stream of aqueous copper acetate/pyridine reagent of pH 6.1 (0.84 ml/min) and the solutions were mixed in a reaction coil (30 cm x 3 mm diameter). The mixed solution passed into a phase separator containing a lipophilic membrane and the copper-pyridine colored complex in the organic phase was measured spectrophotometrically at 716 nm. The calibration graph for oleic acid was linear for 0.1-5 M with reproducibility RSD (n = 12) of 1.9% at 0.3 mM and 0.8% at 2 mM. The precision RSD (n = 3) was 1.09% and recoveries were 98-101%. The effects of interferences on the method is discussed.