[ca] Aquest treball busca estudiar el préssec produit a la zona de Lleida. A la present tesis doctoral s'ha caracteritzat el préssec cultivat i transformat a la zona de Lleida en lo relatiu al seu contingut en compostos volàtils i fenòlics, a mes de la presencia de micotoxines i els punts de partida per a la definició d'estrategies per a la seva mitigació. Per això, s'ha treballat a la caracterització dels compostos volàtils de 17 varietats de préssec, pavia, nectarina i paraguià (préssec pla). S'han detectat 22 compostos volàtils als mateixos, essent les pavies les mes riques en compostos de la familia de les lactones, essent el valor mes alt d'aquests compostos el trobat en Baby Gold GC58 per a la gamma-Decalactona de 0,152 ± 0,018 ppm. En 12 de les varietats seleccionades, s'ha estudiat la concentració de compostos fenòlics pressent a les fraccions de llavor, ós, polpa i pell, i entre diversos estats fenològics com la flor. S'ha aconseguit trobar diferencies significatives entre les diferents families de préssec, pavia, nectarina i paraguaià (préssec pla) i comprobar que la fracció pell es la més rica en compostos polifenòlics, encara que es en estadi de flor quan es troben els valors mes alts de compostos polifenòlics, arribant a valors en en flor de Nectarina Big Top de 9378,60 ± 1656,76 ppm de polifenols totals quantificats a l'estudi front a valors de 5449,66 ± 1387,96 ppm en pell de la varietat Summer Lady, per exemple. A més, s'ha demostrat l'incidència de micotoxines, particularment aflatoxines, en les fruites estudiades i s'han investigat els origens de la mateixa. S'ha investigat la micobiota pressent al préssec, essent la mateixa Aspergillus flavus i Aspergillus parasiticus (sección Flavi) , i Penicillium spp., Alternaria spp., Eurotium spp., Aspergillus sección Nigri, Monilinia spp., Cladosporium spp., Rhizopus spp. i Fusarium spp. En aquesta microbiota, les especies productores d'aflatoxina (Aspergillus flavus y Aspergillus parasiticus (sección Flavi)) han sigut aïllades i estudiat el seu comportament en medis de cultiu estándar (PDA i DRB) així com en 2 medis de cultiu en base préssec desenvolupats especificament per a la present tesis. S'ha aconseguit determinar que la temperatura òptima de producción d'aflatoxina es trova en el marge de 25 a 30°C, i que en 48 hores es poden obtenir nivells de toxina que poden ocasionar el problema detectat. S'ha plantejat una hipótesis segons la qual el moment mes probable d'infecció seria l'estat fenològic de flor.

[en] Lleida's grown peaches have a lot of studies about the species which are used on the region, but Little work has been done on the interesting compounds that are part of it. Also, in the late years, companies from the area have been detecting problems which were thought of being linked with dry fruit more than with peaches. At this doctoral thesis we have characterized peaches which are grown at Lleida region, and also transformed peach products on its content on volatile and phenolic compounds, and also presence of mycotoxins and starting points to define strategies for its mitigation. With this aim, we have worked on characterization on volatile compounds for 17 varieties of peach, pavia, nectarine and paraguayo (flat peach). 22 compounds have been detected on them, being pavias the richest ones in compounds of the lactone family, with highest value on them the one found at Baby Gold GC58 for gamma-Decalactone of 0,152 ± 0,018 ppm. On 12 of the selected varieties, concentration of phenolic compounds which are present at fractions of seed, stone (kernel), pulp and peel (skin), and also phonologic stages as flower, have been studied. We have found significant differences between families of peach, pavia, nectarine and paraguayo (flat peach), and confirm that the peel fraction is the richest in polyphenolic compounds, but it's at the stage of flower when highest values of polyphenolic compounds can be found, reaching values at Nectarina Big Top flower of 9378,60 ± 1656,76 ppm of total polyphenols quantified on this study against values of 5449,66 ± 1387,96 ppm on the peel of Summer Lady variety, as an example. Also, it has been proven mycotoxin incidence, in particular aflatoxins, on the studied fruits and the origins of this toxins have been studied. We have looked out for the mycobiota which is present at peach, being it Aspergillus flavus and Aspergillus parasiticus (section Flavi) , and Penicillium spp., Alternaria spp., Eurotium spp., Aspergillus section Nigri, Monilinia spp., Cladosporium spp., Rhizopus spp. and Fusarium spp. In this microbiota, aflatoxin producing species (Aspergillus flavus and Aspergillus parasiticus (section Flavi)) have been isolated and their behavior studied on standard culture media (PDA and DRB) and in two peach based media that have been developed specifically for this thesis. We have been able to determine that the optimal aflatoxin production temperature it's between 25 and 30°C, and that in 48 hours levels of aflatoxin that can create the detected problem can be reached. An hypothesis has been formed that states that the most probable time for infection of Aspergillus flavus and Aspergillus parasiticus (section Flavi) would be the flowering stage, causing during the life spam of the fruit the problem of aflatoxins.