An NMR study on internal browning in pears

Internal browning in pears (Pyrus communis L. cv. Blanquilla) has been studied by NMR and MRI in order to develop a non-destructive procedure for on-line disorder identification. For NMR relaxometry, disordered tissue shows higher transverse relaxation rates compared to sound tissue, especially at higher magnetic field strength and for long pulse spacing. Membrane alteration and therefore tissue disintegration, as well as water evaporation, appear to be the main causes of this response. Correlation between relaxation times and diffusion showed that the proton pools in disordered tissue are grouped into a smaller number of populations compared to sound tissue, also highlighting cell decompartmentation in disordered tissue. At a macroscopic level, fast low angle shot MR images, effective transverse relaxation-weighted (TR 11 ms and TE 3.7 ms) and proton density-weighted (TR 7.6 ms and TE 2.5 ms), were acquired for pears at a rate of 54 mm/s. Images have been discriminated for internal breakdown according to histogram characteristics. Up to 94 and 96% of pears, respectively, were correctly classified in the former and the latter type of images. In this study a minimum value of 12% of tissue affected by breakdown was always clearly identifie

Application of FTIR spectroscopy for the determination of virgin coconut oil in binary mixtures with olive oil and palm oil.

Rapid Fourier transform infrared (FTIR) spectroscopy combined with attenuated total reflectance (ATR) was applied for quantitative analysis of virgin coconut oil (VCO) in binary mixtures with olive oil (OO) and palm oil (PO). The spectral bands correlated with VCO, OO, PO; blends of VCO and OO; VCO and PO were scanned, interpreted, and identified. Two multivariate calibration methods, partial least square (PLS) and principal component regression (PCR), were used to construct the calibration models that correlate between actual and FTIR-predicted values of VCO contents in the mixtures at the FTIR spectral frequencies of 1,120–1,105 and 965–960 cm−1. The calibration models obtained were cross validated using the “leave one out” method. PLS at these frequencies showed the best calibration model, in terms of the highest coefficient of determination (R 2) and the lowest of root mean standard error of calibration (RMSEC) with R 2 = 0.9992 and RMSEC = 0.756, respectively, for VCO in mixture with OO. Meanwhile, the R 2 and RMSEC values obtained for VCO in mixture with PO were 0.9996 and 0.494, respectively. In general, FTIR spectroscopy serves as a suitable technique for determination of VCO in mixture with the other oils

Preliminary investigation into the geographical origin differentiation of saffron (Crocus sativus L.) by multi-element (HCN) stable isotope analysis

A simple solvent extraction was performed to remove the majority of the lipid in saffron and eliminate any variability in isotopic composition due to variable lipid content. The global hydrogen, carbon and nitrogen (HCN) stable isotope composition of the defatted dry mass fraction was measured by elemental analyses and high temperature conversion coupled to an Isotope Ratio Mass Spectrometer. The objective of this study was to differentiate the geographical origin of saffron coming from different countries (Greece, Italy, Iran and Spain) by measuring the stable isotopic composition of the bio-elements hydrogen, carbon and nitrogen. Also a chemical characterization of 28 saffron samples was carried out by UV-Vis, HPLC and GC analysis

A comparison of mid-infrared and raman spectroscopies for the authentication of edible oils

Robust, routine, and rapid instrumental methods for the determination of the authenticity of edible oils, and the detection of adulteration, are continually being sought. In this paper, we compare mid-infrared and Raman spectroscopies for their ability to discriminate between oils of differing botanical origin and for their ability to detect added adulterants. Furthermore, we used sufficient numbers of samples to permit a comparison of some of the chemometric methods (linear discriminant analysis, artificial neural networks) available and looked at the results obtained when the two spectroscopic datasets were combined. We show that mid-infrared spectroscopy, in combination with linear discriminant analysis, gave the best classification rates and adulteration detection levels compared to Raman or combined data

Effects of sample heating in FT-Raman spectra of biological materials

The effects of laser-induced sample heating and fluorescence of biopolymers in Fourier transform-Raman spectroscopy were investigated. It was shown that these two phenomena are essentially independent of each other. Methods of quantifying the laser-induced heating were developed and it was shown that measurement of the thermal emission generated by the sample is not sufficient to determine its temperature. The use of a marker compound mixed with the test sample to estimate the sample temperature was explored. Monitoring the temperature-dependent phase transitions of NH4NO3 provided a crude indication of a minimum sample temperature. However, using sulphur as a marker and exploiting the relationship between the intensities of its anti-Stokes and Stokes bands, it was possible to estimate the sample temperature with greater confidence. Using these techniques it was shown that sample temperatures could easily reach approximately 400 K under normal laser power inputs. Such temperatures are likely to be damaging to biological samples and it is concluded that great care must be exercised when using FT-Raman

Allergens of the cupin superfamily

The cupin family comprises a family of proteins possessing a common beta-barrel structure that is thought to have originated in a prokaryotic ancestor. This structural motif is found as a single domain in fungal spherulins, fern sporulins and the germins/oxalate oxidase proteins of plants, while the globular storage proteins of plants, called legumins (11 S) and euvicilins (7 S), are two-domain cupins. The 11 S globulins are hexameric heteroligomeric proteins of M (r) approximately 360000, with each subunit comprising an acidic 30000-40000- M (r) polypeptide that is disulphide-linked to a 20000- M (r) basic polypeptide. A number of cupins have been identified as major plant food allergens, including the 7 S globulins of soybean (beta-conglycinin), peanut (conarachin; Ara h 1), walnut (Jug r 2) and lentil, and the 11 S globulins of peanut (arachin; Ara h 3), soybean (glycinin) and possibly also coconut and walnut. Other members of the cupin superfamily have not been identified as allergens, with the exception of one germin (germination-specific protein) from pepper. Cupins are generally very stable proteins. A summary of our current knowledge of allergenic seed storage globulins will be presented, together with an overview of cupin structure and stability properties, as illustrated by the allergenic soya globulins, glycinin and beta-conglycinin