Browsing by Author "Lydakis, Dimitrios"

Now showing 1 - 4 of 4
  • Thumbnail Image
    ItemOpen Access
    Attribute analysis and quality assessment of extra virgin olive oil produced in Sitia, Crete, Greece
    (Cranfield University, 2011) Kalarchakis, Ioannis; Zafiropulos, Vassilis; Fragkiadakis, Georgios A.; Lydakis, Dimitrios
    In this study, extra virgin olive oil produced in the mountainous organic semi- intensive production systems of Krya (Sitia, Crete, Greece) was under investigation in different stages of production. The region is characterized by high altitude, sloping and difficulty to access systems that are considered as high risk of abandonment but its sustainability has extreme survival importance for the local population that consists of producers and suppliers that strive daily to improve this product. The study focuses in principles of cultivation, quality control and marketing in order to assess the production systems of Krya in comparison with other regions. Data suggest that dominant crop practices in the area is harvesting with hand–held mechanical harvesters (100%) and soil cultivation with ploughshares attached to different sizes of tractors, irrigation is applied in most systems in Krya, Pruning and fertilization is also practiced in variable degrees. Temperature measured during different stages of processing seems to have reached 27°C to 35°C suggesting a drop in quality because of high temperature effect to phenolic content. Samples obtained from Krya groves have produced olive oil that was classified as Extra virgin olive oil based in sensory and chemical tests, with average free acidity scores lower than 0.4 %, with average peroxide scores lower than 12 meq/L and K270 index scores lower than 0,15. Sensory results suggest olive oils with high medium fruitiness (< 6) and light sense of bitterness and pungency (< 3) with no defects (0). Several tools are proposed for better evaluation of the standard cultivation practices, sensory characteristics are displayed in specific graph models and the total quality of olive oil is calculated based in specified formula that combined both chemical and sensory results. Based in the Total quality index score formula twenty-four samples obtained from Krya and comparative organic systems are compared with popular olive oils currently dominating the Greek and Cretan market. Finally this study suggests options for improvement of the production stages of cultivation, process and post harvest management that may increase the success of the product and maintain the productivity in the region aiming to become competitive in the global market.
  • Thumbnail Image
    ItemOpen Access
    Ecology of A.carbonarius and ochratoxin A production in vine fruits and control in the production chain
    (Cranfield University, 2008-01) Pateraki, Marianthi G.; Magan, Naresh; Lydakis, Dimitrios
    This study examined black aspergilli, especially A. carbonarius and A. niger and ochratoxin A (OTA) contamination of grapes, during drying and industrial processing of dried vine fruits. This was complemented by studies on potential control using preservatives and physical factors such as modified atmospheres. Fungal population kinetics were determined in relation to grapes at harvest, and during drying at three different altitudes (sea level: 0-200 m; medium level: 250-500 m; high level: >500 m) in two seasons. At pre-harvest, A. niger aggregate species were the predominant fungal species while A. carbonarius was occasionally isolated, in both years studied. Both altitude and bunch position affected black aspergilli population dynamics. Overall, they were increased during drying. However, both black aspergilli groups were mostly isolated, at low and medium altitudes (<500 m). OTA contamination was influenced by bunch position, although altitude did not significantly influenced amounts. The fungal biodiversity was decreased during sun-drying of sultanas. The widest diversity of species occurred at the sea level. However, A. niger aggregate, were dominant during drying. Time of drying and altitude significantly influenced fungal loads of black aspergilli. In contrast, OTA production (ca 0.001 - 0.0025 μg g - 1 ) was not significantly influenced by altitude and drying time. Shannon Index of Biodiversity (H), for pre-harvest and pos-harvest studies, was determined for the first time. A. niger aggregate (ca 5.0 Log10 CFUs g -1 ) was predominant during industrial processing, while A. carbonarius was only isolated at low levels (1.5-2.0 Log10 CFUs g -1 ). Heat treatment (up to 90 o C) appeared to be the key-procedure for the elimination of fungal populations. In the contrary, SO2 treatment did not statistically alter fungal population dynamics. OTA contamination was not significantly affected by industrial processing. In vitro studies conducted on both White Grape Juice Medium (WGJM) and in sultanas with strains of A. carbonarius originated from Cretan sultanas and compared with a strain isolated from Italian wine grapes. They examined the impact of sodium metabisulphite (NaMBS), elevated CO2 (up to 50%) concentrations and aw levels, on black aspergilli spore germination, growth and OTA production. Moreover, fungal interactions in vitro and in situ were also investigated. In general, spore germination occurred over a wide range of sodium metabisulphite concentrations, although germ tube extension was significantly controlled. At ≥ 750 mg L -1 NaMBS, no spore germination was observed while both mycelial growth and OTA production were completely inhibited. Medium concentrations of NaMBS (≤ 250 mg L -1 ) enabled optimum spore germination, growth and OTA production (x 0.965 aw). The efficacy of controlled atmospheres x aw showed that there was very little inhibitory effect on spore germination. However, both germ tube extension and fungal growth were inhibited by 50% CO2. After 10 days, growth was not as effectively controlled. Aw had a bigger effect on OTA production than modified atmospheres. In situ experiments on sultanas confirmed these results. Competition and dominance of A. carbonarius over other fungal species showed that aw and temperature influenced Indices of Dominance and OTA production. In vitro and in situ, OTA production by A. carbonarius was significantly influenced by the fungal competitor used.
  • Thumbnail Image
    ItemOpen Access
    The influence of farming systems on the incidence of Aspergillus carbonarius in viticultural products
    (Cranfield University, 2013-02) Kontaxakis, Emmanouil A.; Magan, Naresh; Lydakis, Dimitrios
    In viticulture, the most effective way to prevent or reduce the ochratoxin A (OTA) contamination of viticultural products is the control of ochratoxigenic fungal species, and especially Aspergillus carbonarius, the predominant produce of ochratoxin A in these products. In the present study, conducted in the years 2010, 2011 and 2012, in Heraklion Prefecture (Crete, Greece), the influence of the different farming systems that are applied in the Cretan vineyards, on the incidence of A. carbonarius in grapes and soil, and hence the potential of OTA contamination of viticultural products, were examined. The impact of different cultivar characteristics, cultivation techniques (trellis system, nutrition and irrigation management, fungicides treatments) and area of cultivation was also investigated. Cont/d.
  • Thumbnail Image
    ItemOpen Access
    Study of phenolic content and antioxidant activity of Greek red and white wines by means of classical methods and FTIR
    (Cranfield University, 2015) Strataridaki, Argiro E.; Aldred, David; Lydakis, Dimitrios
    Phenolic and antioxidant contents of wines are very important in terms of both flavour attributes and health benefits. Changes occur during ageing of wine in containers (e.g. wooden barrels) in relation to their antioxidant activity and phenolic content. Vilana, Dafni, Kotsifali and Mandilari single variety Cretan wines, were vinificated to determine their antioxidant activity and phenolic content Wines were aged in different containers after two vinifications. Changes in the above characteristics were determined every three months for a twelve month period. Stainless steel with and without oenosticks containers, American oak, French oak, Acacia and Chestnut barrels were used for wine ageing. As far as phenolic and antioxidant contents are concerned, ageing of wine in chestnut barrels, Kotsifali and Mandilari (red wines) and in Acacia barrels for Vilana and Dafni (white wines), gave the best results, achieving the highest phenolic content and antioxidant activity after 12 months of ageing. The phenolic fingerprints of Vilana, Dafni, Kotsifali and Mandilari wines were determined for the first time. The phenolic fingerprint of wines has been recently used for the authentication and discrimination of red wines. In this study, attempt has also been made to use the phenolic fingerprint of white wines, for authentication. Differences were observed in Kotsifali and Mandilari (red wines) and in Vilana and Dafni (white wines) directly after vinification, allowing their discrimination. Also the changes in their phenolic fingerprints were monitored during ageing in different containers for a 12 month period. The effect of hydroxytyrosol and oleuropein on wine spoilage induced by acetic acid bacteria was also determined. Hydroxytyrosol was better than oleuropein in controlling the increase of volatile acidity, causing wine spoilage. Wines treated with 0.5mg/l hydroxytyrosol showed control of volatile acid production, and may be a promising alternative to sulphites in wine production in the future. Finally, extracts obtained from olive oil mills and winery by-products were used in Vilana vinification instead of sulphites and antioxidant activity and phenolic content of the wines determined.