Effect of water activity on the thermal stability of Thermomyces lanuginosus xylanases for process time–temperature integration

Three strains of the thermophilic fungus Thermomyces lanuginosus were used to produce β-xylanases. The thermal stability of these xylanases at low levels of water activity was studied. Isothermal inactivation experiments were performed in the temperature range of 100–130 °C. Reduction of water activity to 0.63 and as low as 0.13 had a drastic effect on the observed D and z-values. At water activity of 0.13 the D_120 °C and z-values of the three xylanases ranged from 20.4 to 37.6 min and from 23.3 to 28.9 °C, respectively. The applicability of the developed kinetic models was tested under time–temperature profiles representative of typical thermal processes. The developed systems can be applied as time–temperature integrators (TTI) at this high thermal processing range. Calculations demonstrated that the use of a triple xylanase TTI system could provide acceptable F-values prediction for z-values lower than the achieved range.     

Study of aflatoxin B1 and ochratoxin A production by natural microflora and Aspergillus parasiticus in black and green olives of Greek origin

Aflatoxin B1 (AFB1) is a carcinogenic metabolite produced by certain Aspergillus species. Ochratoxin A (OTA) is classified as "possible carcinogen" and it is a metabolite of Aspergillus ochraceus and Penicillium verrucosum. Fungi contaminate natural and processed olives which support AFB1 and OTA production. The aim of this study was to compare and investigate AFB1 and OTA production in three different varieties of damaged olives. For each variety two different treatments were applied: (1) olives with natural microflora and (2) olives inoculated with A. parasiticus after natural microflora elimination. AFB1 and OTA have been extracted simultaneously from olives, purified with immunoaffinity columns and quantitated by HPLC using fluorescence detector. The recoveries and detection limits of AFB1 and OTA were 94% and 0.15 ng AFB1 g(-1) and 102.7%, 0.41 ng OTA g(-1) respectively. Results showed that, meanwhile OTA was not found in any olive sample, AFB(1) production within the three varieties of olives with natural microflora was significantly (P< or =0.05) different regarding their substrate and time of incubation (18 days). AFB1 production in two different varieties of black olives after inoculation by A. parasiticus was not significantly higher compared with control samples. On the contrary, AFB1 production in green olives was stimulated after the 12th day. Additionally, investigation on the occurrence of AFB1 and OTA in 30 samples of olives and olive pasta from Athens market showed OTA's presence in two samples of olives contaminated at the levels of 1.18 and 1.86 ng OTA g(-1). Aflatoxin B1 was found at levels 0.15-1.13 ng AFB1 g(-1) in all samples tested.     

Säulen griechischer Tempel unter Erdbebenbeanspruchung

Columns of Greek Temples under seismic loading: Columns of ancient Greek Temples consist of accurately dressed individual blocks in total absence on binding mortars. The seismic response of such multi‐drum structures is completely different than the corresponding one of modern continuous structures. Their stability is governed by independent sliding and rocking of drums, which creates an external energy absorption mechanism. This paper presents numerical studies on the dynamic behaviour of ancient columns which exhibits a highly non‐linear response. Alternative modeling methods are used and calibrated to experimental results. It is concluded that ancient columns may be less vulnerable to seismic events compared to modern structures. The perfection of the form unified esthetical, architectural and structural requirements.     

On the importance of total polar phenols to monitor the stability of Greek virgin olive oil

A large number of virgin olive oil samples obtained from different areas in Greece were analyzed for various quality parameters. The work focuses on the colorimetric determination of total phenols with the Folin‐Ciocalteu reagent and its importance in predicting shelf life of virgin olive oil. The results indicate a good correlation of total polar phenol content with the stability of the oil. Colorimetric determination of ortho‐diphenol content does not seem to be a better means for predicting virgin olive oil stability. RP‐HPLC quantification of hydroxytyrosol and tyrosol in their free form gives poor results in the case of freshly extracted oils. It is concluded that until an easy‐to‐manage HPLC method will be available, which will quantify accurately both free and bound forms of hydroxytyrosol and other phenolics, the colorimetric method for the determination of total polar phenols remains a good practical means to evaluate the stability of virgin olive oil.     

Chain extension of recycled poly(ethylene terephthalate) with 2,2′‐(1,4‐phenylene)bis(2‐oxazoline)

The present work provides improved recycled high molecular weight poly(ethylene terephthalate) (PET) by chain extension using 2,2′‐(1,4‐phenylene)bis(2‐oxazoline) (PBO) as the chain extender. PBO is a very reactive compound toward macromolecules containing carboxyl end groups but not hydroxyl end groups. In the case of PET, where both species are present, for even better results, phthalic anhydride (PA) was added in the initial sample, before the addition of PBO. With this technique, we succeeded in increasing the carboxyl groups by reacting PA with the hydroxyl terminals of the starting polymer. From this modification of the initial PET sample, PBO was proved an even more effective chain extender. So, starting from a recycled PET with intrinsic viscosity [η] = 0.78, which would be [η] = 0.69 after the aforementioned treatment without a chain extender or M̄_n = 19,800, we prepared a PET grade having [η] = 0.85 or M̄_n = 25,600 within about 5 min. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2206–2211, 2000     

Valorization of mullet roe by-products for the production of polyunsaturated fatty acids rich oils

This work examines the potential valorization of mullet roe by-products for the production of mullet roe oil using mild processes. Three different extraction methods with potential of scale-up for the food industry, namely pressure (PE), supercritical fluid extraction (SFE), and solvent extraction (SE) are examined. Mild temperature conditions to prevent oil oxidation and (wherever applicable) food-grade solvents are used. The oil yield, the composition of oils in fatty acids by GC-FID, the level of oil oxidation (peroxide value (PV), p-anisidine value (AV), K₂₃₂ K₂₆₈, TOTOX)) and the antioxidant activity (DPPH, ABTS) are determined. SE provided the highest oil recovery, followed by SFE and PE (68%, 28% and 10% respectively). The extracted oils had a high concentration of EPA and DHA and a total of 20.7%–24.3% of identified PUFAs among the fatty acids. Oxidation was the lowest in the SFE extracted oil followed by PE, PV was <2.5 meq_O2, AV≤10 and TOTOX <15 in all examined oil samples. Further research is needed to optimize processing conditions for the increase in oil recovery.