Basic concept of the present study was to examine ochratoxin A (OTA) presence in Greek grapes on the field, during winemaking and at the final product, wine. Finally the project was an attempt to integrate approaches for controlling the responsible fungus (Aspergillus carbonarius) in Greece, together with ways to eliminate presence of OTA in wine. To this end the effect of water activity (aw), and other important environmental factors such as temperature, pH and strains and their interactions on growth/OTA production were studied. Greek A. carbonarius isolates grew optimally at 30-35ºC and 0.96 aw, while maximum OTA production occurred under suboptimal growth conditions (15-20ºC & 0.93-0.96 aw). Greek isolates examined in the present study were more xerotolerant than others of the Mediterranean basin. Studies were performed in organic and non-organic vine grape production systems in an attempt to correlate the presence of total Aspergillus section Nigri and ochratoxigenic A. carbonarius strains with meteorological conditions and geographical localization. Besides the studies on ecophysiology and in the field, growth data were fitted to several predictive models in order to contribute to the evaluation of solutions that can be practically used in Greece for protecting production from OTA contamination. The effect of temperature and aw on the growth of A. carbonarius strains could be satisfactorily predicted under the experimental conditions studied, and the proposed boundary models for growth/no growth and toxin/no toxin production could serve as a useful tool. Another component of the present thesis was the investigation of OTA content in Greek wines and the correlation of the results with the origin of production, the year of production, the colour and type, and other vinification techniques. This showed that Greek red, rosé and white wines had lower levels and incidences of contamination than wines from other countries of the Mediterranean basin. Moreover, Greek wines were below the European limit of 2.0 μg L-1. Although contamination with the mycotoxigenic fungus was rather high, most of the samples contained low levels of OTA. The key areas of concern were the results from the southern regions of Greece, mainly Peloponnese and Aegean Islands, especially for the dessert type ones. In order to understand the partitioning of OTA during vinification and clarification processes in Greek wines, an experimental vinification process was performed using different fermentation techniques (presence or absence of artificially inoculated OTA, A. carbonarius, starter yeasts). The general trend for the evolution of OTA concentration throughout the vinification process was a decrease of the initial concentration which was more significant in the first days of fermentation when acceleration of yeast population took place. This data has been integrated to produce a prevention management strategy in Greece to minimise OTA contamination in the grape-wine chain.

Freshness and safety of muscle foods are generally considered as the most important parameters for the food industry. It is crucial to validate and establish new rapid methods for the accurate detection of microbial spoilage of meats. In the current thesis, the microbial association of meat was monitored in parallel with the chemical changes, pH measurements and sensory analysis. Several chemical analytical techniques were applied to explore their dynamics on quantifying spoilage indicators and evaluate the shelf life of meat products. The applied analytical methods used were Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, image analysis, high performance liquid chromatography (HPLC) and gas chromatography/mass spectroscopy (GC/MS). The first component of the study was designed to evaluate the potential of FTIR spectroscopy as a rapid, reagent-less and non-destructive analytical technique in estimating the freshness and shelf life of beef. For this reason, minced beef samples survey from the Greek market), beef fillet samples stored aerobically (0, 5, 10, 15 and 20ºC) and minced beef samples stored aerobically, under modified atmosphere packaging (MAP) and active packaging (0, 5, 10, and 15ºC), were analysed with FTIR. The statistical analysis from the survey revealed that the impact of the market type, the packaging type, the day and the season of purchase had a significant effect on the microbial association of mince. Furthermore, the Principal Components Analysis (PCA) and Factorial Discriminant Analysis (FDA), applied to the FTIR spectral data, showed discrimination of the samples based on freshness, packaging type, the day and season of purchase. The validated overall classification accuracies VCA) were 61.7% for the freshness, 79.2% for the packaging 80.5% for the season and 61.7% for the day of purchase. The shelf life of beef fillets and minced beef was evaluated and correlated with FTIR spectral data. This analysis revealed discrimination of the samples regarding their freshness (VCA 81.6% for the fillets, 76.34% for the mince), their storage temperature (VCA 55.3% and 88.1% for the fillets and mince, respectively) and the packaging type (VCA 92.5% for the mince). Moreover, estimations of the different microbial populations using Partial Least Squares Regression (PLS-R) were demonstrated (e.g. Total viable counts-TVC: RMSE 1.34 for the beef fillets and 0.72 for the mince). Cont/d.

Fresh meat is exposed to various factors which cause microbiological contamination during handling, processing, packaging and storage. Furthermore, the storage conditions applied may affect the microbial association of the product and consequently the spoilage process. Therefore, the purpose and importance of this study was to identify areas that should be addressed to monitor the succession of bacterial communities during storage of raw meat. The improvement of the microbiological quality and safety of meat was also studied. Cont/d.

No description available.

No description available.

The purpose of this project was to conduct an investigation into the development of a soy cheese with acceptable texture. The effects of heat treatment, different oils/fat and reducing and non-reducing sugars on the soy protein isolate (SPI) and SPI curd were studied. The physico-chemical, biochemical and textural properties of three types of soy cheese were compared: (1) glucono-8-lactone (GDL) induced, (2) bacterially fermented and (3) GDL-induced and fermented. The results indicate that the fermentedGDL- cheese had the most acceptable texture. Heat treatment of SPI at neutral pH caused it to denature partially and increased the storage modulus and hardness of subsequently GDL-induced gels. Subsequent heat treatment of the acidic gels further significantly enhanced the storage modulus and gel hardness. The SPI emulsion containing palm stearin showed higher emulsifying stability, emulsifying activity, protein adsorption and denaturation degree than the emulsions containing sunflower and soy oil at neutral pH. The acidified emulsion gel containing palm stearin was significantly harder than the control (without fat), whereas emulsion gels containing sunflower and soy oil were softer than the control. Glucose, lactose and sucrose increased the onset denaturation temperature of SPI, resulting in decreased gel hardness and stiffness at acidic pH. At neutral pH, both reducing and non-reducing sugars increased the emulsifying activity of SPI emulsions and decreased the emulsifying stability and protein adsorption at oil/water interface. The Maillard reaction took place between SPI and glucose and lactose, resulting in increased gelation of SPI and decreased emulsifying activity at neutral pH. Chemical analysis indicated that disulfide bonds were involved in maintaining the structure ofthe gels. Furthermore, evidence was found of other types of covalent bonds besides disulfide bonds in acidic gels formed by glycated SPI.

The raffinose family oligosaccharides (RFO) are alpha-galactosyl derivatives of sucrose, and the most common are raffinose, stachyose and verbascose. Raffinose is found exclusively in the embryo. Embryos and endosperms of barley (Hordeum vulgare. Cv. Golden Promise) were studied throughout their development and into maturity to investigate the 'relationships among a-amylase, carbohydrate, abscisic acid (ABA), raffinose synthesis pathway and the onset of desiccation tolerance. The onset of desiccation tolerance corresponds to an increase in starch, a-amylase, raffinose and a decrease in monosaccharides, stachyose and sucrose in the embryo of immature grains. A 5 fold increase was observed between 3-4 W.P.A of raffinose. 4-5 W.P.A, in the embryo a-galactosidase increases from 0.125 - 0.54 U/dry wt. The increase of raffinose precedes by a week the rise in a.:.galactosidase. In immature embryos, compared to the control without ABA, raffinose and galctose slightly increaSed and myo-inositol and glycerol decreased. ABA induced the down regulation of photochrome Band glutathione S-transferases. During imbition of mature grains in the embryo raffinose, melibiose and stachyose decreased to undetectable by 28, 17 and 17 h respectivlty however, sucrose increased. In the dormant samples metabolism fluctuated only slightly'. Galactose and raffinose was only present in dormant grain. Germination percentage was adversely influenced by salt and osmotic stress (PEG). Expression of raffinose synthase increased after 5 and 48 h of NaCI treatment and at 30°C during dehydration and re-hydration. The gene was also detected throughout 5 days of germination. In summary, water deficit stress caused pronounced effects on carbohydrate metabolism in barley embryos.RFO,s and glycerol were generally depressed by all stress treatments, which suggests RFO's may not playa direct role in inducing tolerance in embryo tissues.

No description available.

The robustness of industrial grain whisky fermentation is influenced by environmental stresses that affect the performance of distiller's yeast, and have an effect on its sugar usage and ethanol. production. Among changes that occur during ferinentation is an increase in temperature and ethanol concentrations, which both are known to cause a stress response in. yeast. In order to understand the yeast response, I used proteomics technology to quantify levels of identified proteins during industrial fermentations. Increased levels of stress proteins and proteases were among the significant changes in the soluble proteome of distiller's yeast, as the fermentations progressed. The proteomic data set was complemented with an expression analysis of-selected yeast genes, which included a detailed analysis of genes and proteins involved in sugar uptake and metabolism. Proteomics technology was also used to study molecular differences in distiller's yeast that occurred when changing the volumetric scale from industrial (400,000 1) to laboratory (0.5 1), and in a second series of experiments, increasing the yeast pitching rate from 1 g- L to 4 g L. The results showed that up-regulation of proteases was not observed at laboratory scale, and increasing pitching rate led to a significant:increase in . the levels of heat shock proteins during fermentation. The mitochondrial proteome of distiller's yeast was also investigated at 30 min and 48 h of laboratory fermentations, leading to quantification of mitochondria-associated proteins that may be important for metabolism and/or yeast survival under fermentative conditions. Gene deletion of the HSP26 gene in distiller's yeast revealed that four copies were present, and ploidy analysis confirmed that distiller's yeast indeed is a tetraploid strain. The deletion of the HSP26 gene did not influence yeast sensitivity against lactic acid, acetic acid, ethanol or oxidative stress. Interestingly, prolonged fermentations (>72 h) with IlHSP26 mutants showed that ethanol yield was reduced compared to wild type cells.

Peat is used as a source of flavour compounds in Scotch malt whisky production when it is burned during malt kilning. The aim of this project was to establish whether peats from different locations in Scotland are chemically distinct and could consequently impm1 variations in flavour to m:t1t whisky. Peat s:lI11ples from four geographical locations (Islay, Orkney, St fergus and Tomintoul) were distinguished by Fourier Transform Infrared (FT-IR) spectroscopy. Analysing peat samples using Curie point pyrolysis in cOll1bination with Gas Chromatography-r-.lass Spectrometry (Py-GC-MS) showed that peats from Islay and St fergus were rich in lignin derivatives while those from Orkney and Tomintoul had higher levels of carbohydrate derivatives. Also, Islay and Orkney peats were rich in nitrogen-containing hcterocycles and :Iromatic hydrocarbons respectively. A labol':ltory-scale pealillg)rocess was developed :lI1d malt was prepared using peat from the fClllr locations. 'j'his .11alt was mashed and ll.'rmented and the wash distilled on a laboratory-scale. Analysis by GC-MS showed that some peatderived compounds such as lignin-derived syringols were not transferred to the spirit. Nevertheless, principal components analysis of the GC-MS data revealed that the spirits grouped into a similar pattern as that derived from the peat analyses. Assessment of the spirits by sensory panel revealed significant flavour differences; in particul:lr spirits prepared with Islay peats were distingdished by burnt an.! smoky aromas. These lindings indicate that if distillers change the source or their peat, either through choice or by necessity, they must take into account the possible inth:ence that this could ha\(~ on the flavour character of their product.