Crystallisation and glass transition behaviour of Chilean raisins in relation to their sugar compositions.

The effects of sugar component ratio, water fraction, and storage conditions on crystallisation and glass transition temperature (Tg) of three Chilean dried raisins were examined by using differential scanning calorimetry (DSC), polarised light microscopy and X-ray diffraction (XRD) techniques. Thompson, Flame and Golden raisins differed in fructose:glucose and glucose:water ratios, impacting on their measured Tgs (P < 0.05) and propensity of sugaring. The ratios of fructose:glucose (1:3, 1:2 and 1:1) and glucose:water (1.7, 1.9 and 2.1) also influenced the measured Tgs (P < 0.05) and sugaring of fructose-glucose-water model solutions. Measurement of Tgs in the raisins as a function of water activity (aw 0.11-0.74) showed that water acts as a strong plasticiser decreasing the Tgs (-16.4 to -61.6 °C). XRD results revealed that sugaring in Thompson raisins was delayed at low temperatures (5 & 15 °C) compared to that stored at 25 °C. The refrigeration may be a simple approach to delay the sugaring in raisins.

Effect of the pre-treatment and the drying process on the phenolic composition of raisins produced with a seedless Brazilian grape cultivar.

The grape is an important fruit regarding economic and health benefit parameters, because of its large consumption around the world and their bioactive phenolic compounds. The drying process of BRS Morena grapes, whether pre-treated or not with olive oil for producing raisins, resulted in qualitative and quantitative changes in their phenolic composition (anthocyanins, flavonols, stilbenes, hydroxycinammic acid derivatives, flavan-3-ols and proanthocyanidins). The raisins with the pre-treatment preserved more anthocyanins and proanthocyanidins than the raisins not pre-treated. Moreover, the total dehydration time accelerated by approximately 40% in the raisins pre-treated. Therefore, the production of raisins of BRS Morena grapes pre-treated with olive oil as a natural surfactant constitutes an interesting process from both the industrial and health points of view, because of the remarkable reduction in the processing time and the preservation of high concentrations of flavonoids, which have important claims to health benefits from biological activities.

Diversity of black Aspergilli isolated from raisins in Argentina: Polyphasic approach to species identification and development of SCAR markers for Aspergillus ibericus.

Aspergillus section Nigri is a heterogeneous fungal group including some ochratoxin A producer species that usually contaminate raisins. The section contains the Series Carbonaria which includes the toxigenic species Aspergillus carbonarius and nontoxigenic Aspergillus ibericus that are phenotypically undistinguishable. The aim of this study was to examine the diversity of black aspergilli isolated from raisins and to develop a specific genetic marker to distinguish A. ibericus from A. carbonarius. The species most frequently found in raisins in this study were Aspergillus tubingensis (35.4%) and A. carbonarius (32.3%), followed by Aspergillus luchuensis (10.7%), Aspergillus japonicus (7.7%), Aspergillus niger (6.2%), Aspergillus welwitschiae (4.6%) and A. ibericus (3.1%). Based on inter-simple sequence repeat (ISSR) fingerprinting profiles of major Aspergillus section Nigri members, a sequence-characterized amplified region (SCAR) marker was identified. Primers were designed based on the conserved regions of the SCAR marker and were utilized in a PCR for simultaneous identification of A. carbonarius and A. ibericus. The detection level of the SCAR-PCR was found to be 0.01 ng of purified DNA. The present SCAR-PCR is rapid and less cumbersome than conventional identification techniques and could be a supplementary strategy and a reliable tool for high-throughput sample analysis.

Ochratoxin A in raisins samples marketed in São Paulo, Brazil / Ocratoxina A em amostras de uva passa comercializadas em São Paulo, Brasil

The present study aimed to evaluate a methodology for analyzing ochratoxin A (OTA) in raisins samples marketed in São Paulo, Brazil. OTA was extracted with methanol:water (80:20, v/v) and diluted with phosphate buffer solution, and purified through an immunoaffinity column. OTA was separated and quantified using HPLC with fluorescence detection. The established detection and quantification limits were 0.24 and 0.80 ng/g, respectively. The recoveries values were 81.6, 80.4 and 81.9%, and the relative standard deviations (RSD) were 6.0, 4.3, and 6.1 % at 2.0, 5.0 and 10.0 ng/g levels, respectively. Of twenty black raisin samples analyzed 10 (50 %) contained OTA at levels ranging from 1.3 to 39.1 ng/g. All of twenty-two white raisin samples showed no contamination with OTA.

O presente estudo teve como objetivo avaliar uma metodologia para análise de ocratoxina A (OTA) em amostras de uva passa comercializadas em São Paulo, Brasil. A OTA foi extraída com metanol: água(80:20, v/v) e diluída com solução tampão fosfato, utilizando-se coluna de imunoafinidade para purificação da amostra. A OTA foi separada e quantificada por meio de CLAE com detector de fluorescência. Os limites de detecção e de quantificação estabelecidos foram respectivamente de 0,24 e 0,80 ng/g. Os valores de recuperação foram 81,6; 80,4 e 81,9% e os coeficientes de variação foram 6,0; 4,3 e 6,1 % respectivamente para os níveis de 2,0; 5,0 e 10,0 ng/g. De um total de vinte amostras de uvas passas pretas, 10 (50 %) continham OTA na faixa de concentrações de 1,3 a 39,1 ng/g. Todas as vinte e duas amostras de uvas passas brancas não apresentaram contaminação por OTA.