Effect of different packing treatments on the microbiological and physicochemical characteristics of untreated green olives of the Conservolea cultivar

Microbiological, physicochemical and organoleptic changes were studied in non‐pasteurised samples of untreated green olives cv Conservolea stored at 20 °C for 180 days under different preservation treatments (acidified brine and modified atmospheres). The microbial flora consisted of lactic acid bacteria and yeasts, while no enterobacteria and pseudomonads were enumerated in any package. Although no thermal treatment was applied to the packages, no sediment formation was observed due to the growth of propionic bacteria. Olives packed in brine supplemented with 0.3% lactic and 0.3% citric acids presented the highest acidity, the lowest brine and flesh pH and the lowest dark brine colour as measured by the parameter A₄₄₀?A₇₀₀. Olives packed in modified atmospheres (vacuum, 40% CO₂/30% O₂/30% N₂ and air) presented a progressive loss of fruit firmness and colour with time. At the end of the storage period, olives packed in aerobic conditions and 40% CO₂/30% O₂/30% N₂ presented the lowest firmness and skin colour and were unacceptable to the panellists. The best quality characteristics were maintained in vacuum‐packed olives, as indicated by the higher organoleptic scores. Firmness degradation followed first‐order kinetics (r² > 0.980) and the expected shelf‐life was 23, 15 and 9 months for olives packed in vacuum, 40% CO₂/30% O₂/30% N₂ and air respectively. Copyright © 2004 Society of Chemical Industry     

Selection of potential probiotic lactic acid bacteria from fermented olives by in vitro tests

The present study aims to evaluate the probiotic potential of lactic acid bacteria (LAB) isolated from naturally fermented olives and select candidates to be used as probiotic starters for the improvement of the traditional fermentation process and the production of newly added value functional foods. Seventy one (71) lactic acid bacterial strains (17 Leuconostoc mesenteroides, 1 Ln. pseudomesenteroides, 13 Lactobacillus plantarum, 37 Lb. pentosus, 1 Lb. paraplantarum, and 2 Lb. paracasei subsp. paracasei) isolated from table olives were screened for their probiotic potential. Lb. rhamnosus GG and Lb. casei Shirota were used as reference strains. The in vitro tests included survival in simulated gastrointestinal tract conditions, antimicrobial activity (against Listeria monocytogenes, Salmonella Enteritidis, Escherichia coli O157:H7), Caco-2 surface adhesion, resistance to 9 antibiotics and haemolytic activity. Three (3) Lb. pentosus, 4 Lb. plantarum and 2 Lb. paracasei subsp. paracasei strains demonstrated the highest final population (>8 log cfu/ml) after 3 h of exposure at low pH. The majority of the tested strains were resistant to bile salts even after 4 h of exposure, while 5 Lb. plantarum and 7 Lb. pentosus strains exhibited partial bile salt hydrolase activity. None of the strains inhibited the growth of the pathogens tested. Variable efficiency to adhere to Caco-2 cells was observed. This was the same regarding strains' susceptibility towards different antibiotics. None of the strains exhibited β-haemolytic activity. As a whole, 4 strains of Lb. pentosus, 3 strains of Lb. plantarum and 2 strains of Lb. paracasei subsp. paracasei were found to possess desirable in vitro probiotic properties similar to or even better than the reference probiotic strains Lb. casei Shirota and Lb. rhamnosus GG. These strains are good candidates for further investigation both with in vivo studies to elucidate their potential health benefits and in olive fermentation processes to assess their technological performance as novel probiotic starters.     

A comparison of Raman and FT-IR spectroscopy for the prediction of meat spoilage

In this study, time series spectroscopic, microbiological and sensory analysis data were obtained from minced beef samples stored under different packaging conditions (aerobic and modified atmosphere packaging) at 5 °C. These data were analyzed using machine learning and evolutionary computing methods, including partial least square regression (PLS-R), genetic programming (GP), genetic algorithm (GA), artificial neural networks (ANNs) and support vector machines regression (SVR) including different kernel functions [i.e. linear (SVR_L), polynomial (SVR_P), radial basis (RBF) (SVR_R) and sigmoid functions (SVR_S)]. Models predictive of the microbiological load and sensory assessment were calculated using these methods and the relative performance compared. In general, it was observed that for both FT-IR and Raman calibration models, better predictions were obtained for TVC, LAB and Enterobacteriaceae, whilst the FT-IR models performed in general slightly better in predicting the microbial counts compared to the Raman models. Additionally, regarding the predictions of the microbial counts the multivariate methods (SVM, PLS) that had similar performances gave better predictions compared to the evolutionary ones (GA-GP, GA-ANN, GP). On the other hand, the GA-GP model performed better from the others in predicting the sensory scores using the FT-IR data, whilst the GA-ANN model performed better in predicting the sensory scores using the Raman data. The results of this study demonstrate for the first time that Raman spectroscopy as well as FT-IR spectroscopy can be used reliably and accurately for the rapid assessment of meat spoilage.     

The Local Bootstrap for Periodogram Statistics

A bootstrap procedure for the periodogram of a weakly dependent stationary sequence is proposed. The method works by locally resampling the periodogram ordinates and does not require estimation of the spectral density and of frequency domain residuals obtained by means of initial smoothing. Asymptotic properties of the proposed bootstrap procedure are studied and consistency is proved for interesting classes of statistics including ratio statistics, kernel estimates of the spectral density and parameter estimates. Some practical aspects concerning the implementation of the method are also discussed.     

Effect of technological parameters on the characteristics of kasseri cheese made from raw or pasteurized ewes' milk

Two groups of kasseri cheese (pasta filata type) were manufactured from raw or pasteurized ewes' milk, without starter cultures. Cheeses of each group were divided into two subgroups: the first was ripened and stored at 4°C and packaged in plastic film; the second ripened and stored at 15°C and coated with paraffin wax. Milk pasteurization and technological parameters had a significant effect on the pH ( P  < 0.05), while only technological parameters had an effect on the total solids content. At day 120, the range of mean cfu/g counts for the mesophilic aerobic flora was 9.5 × 10⁷−1.4 × 10⁸; for the thermophilic streptococci, the range was 2.6 × 10⁷−7.6 × 10⁷; and for the thermophilic bacilli, 9.8 × 10⁶−1.7 × 10⁷. Changes in the N fractions became significant after 30 days of ripening. For mature 120-day-old cheeses, the percentage of total N soluble at pH 4.6 was 22.7%–22.9% in raw milk cheeses and 19.0%–21.7% in pasteurized milk cheeses. The percentage of total N soluble at 12% TCA was 10.1%–12.2% in raw milk cheeses and 7.3%–11.5% in pasteurized milk cheeses; the percentages of total N soluble at 5% PTA were 3.1%–4.0% and 2.6%–3.6%, respectively. The residual α_s-casein percentages at day 120 ranged between 63% and 78% of the respective area at day 1; the residual β-casein ranged between 67% and 75%. There were some characteristic differences in the reverse phase-HPLC peptide profiles of the four cheeses. In general, the effect of the different ripening conditions was more pronounced in cheeses made from pasteurized milk.     

Purification and characterization of chymosin and pepsin from kid

The objective of this work was to study the characteristics of the gastric aspartic proteinases chymosin and pepsin which are constituents of the kid rennet. The two enzymes were extracted from abomasal tissue of one kid from a local indigenous breed, separated from each other by DEAE-cellulose chromatography and then were purified by gel filtration and anion-exchange chromatography. The molecular weights of the purified kid chymosin and pepsin as determined by gel filtration were 36 kDa and 40 kDa respectively. The isoelectric point of kid chymosin was as multiple forms of 3-6 zones at pH 4.6-5.1, while that of kid pepsin was at pH < or =3.0. Kid pepsin contained 0.37 molecules phosphorous per molecule and was totally inhibited by 5 muM pepstatin A, being more sensitive than kid chymosin. Both enzymes were almost equally as proteolytic as calf chymosin on total casein at pH 5.6. Kid pepsin activity was more pH and temperature dependent than kid chymosin activity. In comparison with the calf chymosin temperature sensitivity, the order of increased sensitivity was: calf chymosin 相似文献   

Testing the Fit of a Vector Autoregressive Moving Average Model

Abstract. A new procedure for testing the fit of multivariate time series model is proposed. The method evaluates in a certain way the closeness of the sample spectral density matrix of the observed process to the spectral density matrix of the parametric model postulated under the null and uses for this purpose nonparametric estimation techniques. The asymptotic distribution of the test statistic is established and an alternative, bootstrap‐based method is developed in order to estimate more accurately this distribution under the null hypothesis. Goodness‐of‐fit diagnostics useful in understanding the test results and identifying sources of model inadequacy are introduced. The applicability of the testing procedure and its capability to detect lacks of fit is demonstrated by means of some real data examples.     

Role of sigma B factor in the alkaline tolerance response of Listeria monocytogenes 10403S and cross-protection against subsequent ethanol and osmotic stress

Many of the considerable abilities of Listeria monocytogenes to persist and grow in a wide range of adverse environmental conditions are thought to be at least partly under the control of the alternative sigma factor (sigmaB), encoded by the sigB gene. However, little is known about the role of this master regulon in the impressive ability of Listeria to persist and grow under conditions of alkaline pH. In this study, Northern blot analysis of parent Listeria mRNA revealed that alkali adaptation (pH 9.5 for 1 h) significantly increased the expression of sigB-derived mRNA. The study included a comparison of the relative survival of mid-exponential populations of adapted and nonadapted parent type (sigmaB expressing) and mutant (not sigmaB expressing, deltasigB) Listeria strains during subsequent alkaline (pH 12.0), osmotic (25% NaCl, wt/vol), or ethanol (16.5%) stress. Alkali-adapted parent strains were more resistant to pH 12.0 than were adapted deltasigB type strains, but both alkali-adapted parent and deltasigB strains were more resistant to pH 12.0 than were nonadapted strains. Alkali-adapted parent strains were more resistant to osmotic stress than were adapted deltasigB type strains. No significant differences in viability were observed between alkali-adapted parent and deltasigB strains after ethanol stress, suggesting that cross-protection against osmotic stress is mediated by sigmaB whereas cross-protection against ethanol is sigmaB independent. Overall, alkali-induced cross-protection against osmotic and ethanol challenges may have serious implications for food safety and human health because such stress conditions are routinely used as part of food preservation and surface cleaning processes.     

Formulation and characterization of novel temperature sensitive polymer-coated magnetic nanoparticles

The objective of this research was to develop novel polymer coated magnetic nanoparticles for controlled drug delivery applications. To form these novel nanoparticles, silane-coated magnetic nanoparticles (MNPs) were used as a template for a free radial polymerization of three monomers, N-isopropylacrylamide, acrylamide, and allylamine (NIPA-AAm-AH), on the surface of MNPs. Transmission electron microscope results indicated that the size of the NIPA-AAm-AH coated MNPs was approximately 100 nm. To investigate the chemical composition and chemical state of our nanoparticles, FTIR and XPS were used. Results from chemical analysis illustrated the presence of the constituent functional groups of the NIPA-AAm-AH coated MNPs. In addition, the magnetic properties of different layers on the MNPs, analyzed by SQUID, indicated a decrease in saturation magnetization after each layer of coating. The nanoparticles were successfully conjugated to fluorescent PEG to prolong their circulating half life. Furthermore, bovine serum albumin (BSA) was used in order to investigate the protein release profile of the nanoparticles as a function of the temperature. The protein release profile indicated that the NIPA-AAm-AH coated MNPs have a significantly higher percent release at 41 degrees C compared to those of 4 degrees C and 37 degrees C, which demonstrates their temperature sensitivity. In the future, the release profile of therapeutic drugs from nanoparticles at various temperatures and pHs as well as targeted capability of the synthesized nanoparticles for possible applications in controlled and targeted delivery will be investigated.     

MRI mediated, non-invasive tracking of intratumoral distribution of nanocarriers in rat glioma

Nanocarrier mediated therapy of gliomas has shown promise. The success of systemic nanocarrier-based chemotherapy is critically dependent on the so-called leaky vasculature to permit drug extravasation across the blood-brain barrier. Yet, the extent of vascular permeability in individual tumors varies widely, resulting in a correspondingly wide range of responses to the therapy. However, there exist no tools currently for rationally determining whether tumor blood vessels are amenable to nanocarrier mediated therapy in an individualized, patient specific manner today. To address this need for brain tumor therapy, we have developed a multifunctional 100?nm scale liposomal agent encapsulating a gadolinium-based contrast agent for contrast-enhanced magnetic resonance imaging with prolonged blood circulation. Using a 9.4?T MRI system, we were able to track the intratumoral distribution of the gadolinium-loaded nanocarrier in a rat glioma model for a period of three days due to improved magnetic properties of the contrast agent being packaged in a nanocarrier. Such a nanocarrier provides a tool for non-invasively assessing the suitability of tumors for nanocarrier mediated therapy and then optimizing the treatment protocol for each individual tumor. Additionally, the ability to image the tumor in high resolution can potentially constitute a surgical planning tool for tumor resection.