Dulcineia Ferreira

Use of FT-IR spectroscopy to follow the effect of processing in cell wall polysaccharide extracts of a sun-dried pear

The sun-dried pear is a traditional Portuguese food product with unique organoleptic characteristics. In order to understand the modifications that occur during the drying process, cell wall extracts were prepared from dried and fresh tissues. Cell wall polymers were solubilised from the CWM by sequential extraction with aqueous solutions of CDTA, Na 2 CO 3 . and KOH, with increasing strengths, to leave the cellulosic residue. The polysaccharides present in the different extracts were characterised by sugar analysis and by FT-IR spectroscopy in the region between 1200 and 850 cm -1 . The spectra analysis followed by chemometrics allowed us to distinguish the fresh from the sun-dried pear extracts in CDTA, Na 2 CO 3 , and KOH precipitates. These extracts contain pectic polysaccharides rich in GalA and Xyl-rich hemicellulosic polysaccharides (xylans). The selection of the most important wavenumbers allowed us to identify the spectral region related to GalA in pectic polysaccharide extracts in the range between 1120 and 990 cm -1 . This study shows the potential of the FT-IR spectroscopy and multivariate information in the discrimination of cell wall extracts from dried and fresh pears.

Study of the Solar Drying of Pears

ABSTRACT Four pear cultivars originating from Portugal (‘Amêndoa’, ‘Amorim’, ‘Carapinheira Branca’ and ‘S. Bartolomeu’) were dried in a solar drier, following a traditional sun drying method normally used in Portugal for the production of dried pears. The temperature and relative humidity inside the drier were recorded hourly throughout the whole process, while the moisture loss in the pears was evaluated with a variable frequency along the drying process, according to the drying rate. From the results obtained, it was possible to conclude that the conditions inside the drier are very favorable to drying, with periods in which the atmosphere is characterized by very high temperatures and very low relative humidities. Furthermore, the drying rates of the four cultivars of pears used in this study were investigated and it was observed that all of them present a similar kinetic behavior, thus enabling the use of alternative cultivars for the production of dried pears.

Evaluation of Textural Properties in Apples of Regional Varieties

Regional varieties of apples present an endogenous patrimony that should be preserved and promoted to guarantee biodiversity of genetic resources. In the present work, Texture Profile Analysis (TPA) was performed to apples of fourteen different regional varieties, having in consideration the spatial geometry of the fruits, and the textural parameters: hardness, adhesiveness, springiness, cohesiveness, and chewiness were assessed. The samples to perform the TPAs were obtained from different locations in the fruit–external and internal–and considering axial and radial orientations. The results of these analysis performed allowed us to conclude that the apples from regional varieties showed different textural properties among themselves. Furthermore, it was generally observed that hardness does not vary much according to the internal or external location of the sample, but varies quite significantly according to the orientation, being generally higher for the axial measurements. From the present work, it was possible to conclude that, in terms of textural properties, the varieties studied showed important differences.

Composition of regional Portuguese apple cultivars in different harvest years.

In the present study, apples of regional cultivars originating from Portugal were compared in terms of some chemical properties during three consecutive harvest years. It was possible to conclude that these regional cultivars of apples were generally sweeter and contained more minerals than other cultivars described in the literature. The data revealed that the acid, protein, and mineral content depended on the apple cultivar. The acid content varied notably with the 2004, 2005, and 2006 harvests. For total sugar or protein content, the variations observed were comparatively smaller. In the 2004 and 2005 harvests, the sugar and protein contents were similar but differ from the 2006 harvest. In respect to mineral content, the 2004 harvest registered the highest differences, and this was also the year when the apples had the highest maturation index, calculated as the sugar/acid ratio.

Properties of Regional Portuguese Apple Cultivars Produced in Conventional and Organic Modes

The present study involved examining the physical and chemical attributes of seven regional Portuguese apple cultivars. The apples analyzed were produced in two different production modes: conventional and biological, to verify in the extent to which these variables influenced the results. The data obtained enabled us to conclude that the chemical properties: moisture content, total and reducing sugars, protein, and ash, were influenced by the production mode in different ways, depending on the cultivar. As to the textural properties estimated, the results showed that the cultivar ‘Lila’ was the one that presented the greatest similarity when comparing the conventional with the biological modes of production. Furthermore, it was possible to observe that the production mode did not significantly influence the fiber content in the cultivars of apples analyzed.