Structural, mechanical and enzymatic study of pectin and cellulose during mango ripening.

Mango is an important crop worldwide, with a postharvest loss that is huge due to its climacteric behaviour. This study evaluated the softening of Tommy Atkins mangos during the ripening process. Ripening index (RPI) shown a decrease from 9.18 ±â€¯0.14 to 4.75 ±â€¯0.47. The enzymatic activity agreed with physicochemical parameters and with the structural and mechanical changes. Three pectin fractions were isolated from the mango cell wall: water soluble (WSP), chelator soluble (CSP) and diluted alkali soluble (DASP) pectin. The Younǵs modulus (E) of the primary cell wall was evaluated, it decreased from 1.69 ±â€¯1.02 to 0.39 ±â€¯0.16 MPa, which could be attributed to the softening of the fruit. A linear fit correlation between E and RPI was found. X-ray and confocal laser scanning microscopy analysis showed the changes occurred in the mango cell wall structure during maturation. Novelties of current study can be helpful in the use of mango wastes to obtain cellulose.

Combining FT-IR spectroscopy and multivariate analysis for qualitative and quantitative analysis of the cell wall composition changes during apples development.

The aim of this work was to quantitatively and qualitatively determine the composition of the cell wall material from apples during development by means of Fourier transform infrared (FT-IR) spectroscopy. The FT-IR region of 1500-800 cm(-1), containing characteristic bands for galacturonic acid, hemicellulose and cellulose, was examined using principal component analysis (PCA), k-means clustering and partial least squares (PLS). The samples were differentiated by development stage and cultivar using PCA and k-means clustering. PLS calibration models for galacturonic acid, hemicellulose and cellulose content from FT-IR spectra were developed and validated with the reference data. PLS models were tested using the root-mean-square errors of cross-validation for contents of galacturonic acid, hemicellulose and cellulose which was 8.30 mg/g, 4.08% and 1.74%, respectively. It was proven that FT-IR spectroscopy combined with chemometric methods has potential for fast and reliable determination of the main constituents of fruit cell walls.

Role of the support material on laser desorption/ionization mass spectra.

We report the results of experimental studies on the effects of sample supports in laser desorption/ionization mass spectrometry (LDI-MS). LDI time-of-flight (TOF) mass spectra obtained for C(60) and insulin samples deposited onto standard stainless steel substrate and/or onto some non-metallic materials (glass, scotch tape, floppy disc foil, Teflon foil, photocopy film), all recorded under identical, typical experimental conditions, have been compared with regard to their intensity and quality. The LDI investigations show that compared with stainless steel, glass and floppy disc foil sample supports boost (2-3.5 times) ion yields for C(60)(+) and C(60)(-) ions, respectively. The stainless steel and scotch tape sample supports are the best for the mass resolution of positive ions and the formation of (C(60))(n)(-) (n