Characterization and evaluation of the spoilage potential of Lactococcus piscium isolates from modified atmosphere packaged meat

A total of 222 psychrotrophic lactococci isolated from use-by day, modified atmosphere packaged (MAP) meat were identified to the species level by numerical analyses of EcoRI and ClaI ribopatterns and phylogenetic sequence analyses of 16S, rpoA and pheS genes. In addition, their meat spoilage potential was studied. The majority of the isolates (n=215) were identified as Lactococcus piscium, while seven isolates belonged to Lactococcus raffinolactis. L. piscium was shown to be adapted to growing in a variety of MAP meat products including broiler, turkey, pork, and minced meat from beef and pork, where they belonged to the predominating microbiota at the end of the storage. Numerical analyses of EcoRI and ClaI ribopatterns, and phylogenetic sequence analyses of rpoA and pheS genes were shown to be reliable tools in species level identification of meat lactococci. The spoilage potential of L. piscium was evaluated by inoculating representative isolates to MAP pork stored at 6 °C for 22 days. Development of spoilage population was monitored using a culture-independent T-RFLP approach. The sensory shelf life of pork inoculated with L. piscium was shortened compared to the uninoculated control. Alongside with the inoculated L. piscium isolates, Leuconostoc spp. present as initial contaminants in the samples thrived. This shows that even though lactococci were inoculated at higher levels compared to the natural microbiota, they did not occupy the niche and prevent the growth of other lactic acid bacteria.     

Casein-derived bioactive tripeptides Ile-Pro-Pro and Val-Pro-Pro attenuate the development of hypertension and improve endothelial function in salt-loaded Goto–Kakizaki rats

Increased blood pressure and plasma cholesterol concentration are the major risk factors for cardiovascular diseases. We have previously shown that fermented milk products containing casein-derived bioactive tripeptides, isoleucine-proline-proline (Ile-Pro-Pro) and valine-proline-proline (Val-Pro-Pro) partly inhibit the blood pressure increase in spontaneously hypertensive rats (SHR). In the present study, we investigated the effect of bioactive tripeptide-containing fermented milk products (with or without plant sterols) on blood pressure and vascular function in salt-loaded type 2 diabetic Goto–Kakizaki (GK) rats after 8 weeks’ treatment. The development of blood pressure was attenuated in the groups receiving tripeptide-containing products (?10 to ?12 mmHg vs. the control product group, P < 0.01). Tripeptide-containing products enhanced the impaired endothelium-dependent relaxation of mesenteric arteries. Also the role of endothelium-derived hyperpolarizing factor (EDHF) was demonstrated. Interestingly, pretreatment of arterial rings with verapamil normalized the impaired endothelial function. Endothelium-independent relaxations were similar between the groups. Furthermore, tripeptides had positive effects on renin–angiotensin–aldosterone system.     

Nanogold-Containing Catalysts for Low-Temperature Removal of S-VOC from Air

Activity and selectivity of mono- and bimetallic catalysts containing nano-particles of gold stabilized by different supports are compared in dimethyldisulfide removal from air at 150–320 °C. TiO₂-supported Au and Au–Pd samples demonstrate stable and efficient DMDS removal at temperature as low as 155 °C, with formation of the two products: SO₂ and elemental S. On the contrary, no formation of elemental S is detected in the case of Au, Au–Rh, and Au–Pd catalysts supported on HZSM-5, H-beta, or MCM-41. The most active Au–Rh/HZSM-5 catalyst demonstrates an efficient DMDS removal at 290 °C, with quantitative DMDS-to-SO₂ oxidation. Characterization of catalysts with TPR, XRD, and (XANES + EXAFS) confirms a high dispersion of the metallic phases in all catalysts under study. Specific interaction between nano-particles of gold and titanium dioxide surface could be responsible for the unusual catalytic behavior of Au/TiO₂ samples, as distinct from Au/zeolitic systems.     

Structural mechanisms leading to improved water retention in acid milk gels by use of transglutaminase

Water retention in transglutaminase (TG)-treated acid milk gels was studied and linked with the gel formation dynamics. Heat-treated skim milk with and without pre-treatment by TG was acidified at 20 °C, 30 °C and 40 °C at constant glucono-δ-lactone (GDL) level to obtain different acidification rates. Formation dynamics and structural properties of acid-induced gels were followed by rheological and near-infrared light backscattering measurements as well as microscopy. TG-treated gels showed decreased tan δ values all through the acidification, which was pronounced around the gelation point. Backscattered light intensity was lowered in TG-treated gels compared to the controls indicating that TG-treated gels were comprised of smaller aggregates. Water holding capacity (WHC) was measured by using centrifugation at selected pH points (pH 5.2, 5.0, 4.8 and 4.6) during acidification. Both acidification temperature and TG treatment had significant effects on the water retention properties of the gels. Spontaneous syneresis observed at high acidification temperatures (≥30 °C) was prevented upon TG-treatment. WHC of TG-treated gels was significantly higher compared to the control gels at all pH points. TG-treated milk gels showed a homogeneous network formed of smaller aggregate and pore sizes at the gelation point and did not show any large-scale re-organisation thereafter. Transglutaminase is likely to act as a fixative of the protein network at an early stage of gelation and thereby limiting network rearrangements that take place in acid milk gels formed at high acidification temperatures leading to contraction and subsequent wheying off.     

Plant sterols in vegetables,fruits and berries

The plant sterol contents of the most important vegetables, fruits and berries available in Finland were determined by capillary gas chromatography. The sample preparation procedure included both acid and alkaline hydrolysis to liberate sterols from their conjugates. The plant sterol contents of fresh vegetables ranged from 51 to 370 mg kg^?1 fresh weight (fw) in samples obtained from retail sale. The highest contents (>300 mg kg^?1) were measured in broccoli, Brussels sprouts, cauliflower and dill and the lowest (51 mg kg^?1) in potato. The range of sterol contents on a dry weight (dw) basis was high, 246–4100 mg kg^?1 dw. Considerable variation was also observed when individual samples of some vegetables were compared. Sitosterol was the main sterol (proportion 43–86%) in all vegetables except cucumber and spinach, in which Δ⁷‐sterols dominated. The total sterol contents were in the range 116–228 mg kg^?1 fw in all fresh fruits except avocado, which contained more sterols, 752 mg kg^?1 fw. In fresh berries the corresponding range was 60–279 m kg^?1 fw. The wild berries lingonberry and blueberry were better plant sterol sources than the cultivated berries blackcurrant, redcurrant and strawberry. In fruits and berries the proportion of sitosterol ranged from 61–93% total sterols. On the basis of the results, the contribution of vegetables, fruits and berries to the total average daily plant sterol intake was estimated to be ca 60 mg. © 2003 Society of Chemical Industry     

In vivo degradation of poly(DTE carbonate) membranes. Analysis of the tissue reactions and mechanical properties

Different bioabsorbable polymers and their co-polymers have been used to construct an optimal material for guided bone regeneration applications. Our aim was to evaluate a novel bioabsorbable material in a soft tissue environment. In this study, a poly(DTE carbonate) membrane (0.2–0.3 mm) was implanted into 20 NZW rabbits’ subcutaneous pouches for 6, 12, 24 and 52 weeks. The material was evaluated by means of histological reactions to the material and mechanical properties of the membrane. Based on this study, it can be concluded that poly(DTE carbonate) elicited a very modest foreign body reaction in the soft tissues. This reaction was uniform throughout the study. Varying amounts of calcification was seen in the fibrous capsule surrounding the implant. The number of calcified bodies did not correlate to healing time.     

High school students' perceptions of affect and collaboration during virtual science inquiry learning

This study examined affect during high school students' face‐to‐face collaborative inquiry learning in science, supported by the web‐based software Virtual Baltic Sea Explorer. Self‐reported affective states during the inquiry process in peer groups were related to evaluations of a group's collaboration and performance in three phases of interdisciplinary science inquiry (biology and chemistry). Results indicate that despite high cognitive demands, positive affect prevailed whereas negative affect was infrequent. Structural equation modelling was used to analyse the significance of affect on collaboration and group performance. The relationship between affect, collaboration, and the groups' productive outcome revealed that self‐assurance had a significant effect on collaboration and support, intertwined with scientific understanding and group performance. Furthermore, a cross‐lagged analysis showed a reciprocal relation between positive affect, scientific understanding, collaboration, and support. These outcomes contribute to the scarce literature on the nature and importance of affect in the process of face‐to‐face computer‐supported collaborative inquiry and learning in science.     

Carbon-nutrient balance hypothesis in within-species phytochemical variation ofSalix lasiolepis

Predictions of the carbon-nutrient balance hypothesis were tested using a study of within-species phytochemical variation in the arroyo willow,Salix lasiolepis. The prediction that a balance between nutrients (total protein) and carbon-based secondary metabolites (total phenols) should exist was supported using water treatment and fertilizer experiments and wild willow clones. Leaf nitrogen content and net photosynthetic rates of plants potted in soil in which parental plants grew was low, indicating that wild plants exist under relatively low nutrient status-high carbon balance conditions. The hypothesis also correctly predicted positive relationships between shoot length and phenols in glasshouse plants, wild plants, and plants in the water treatment experiment and negative relationships between shoot length and phenols in the fertilizer treatment experiment. Total phenolic glycosides, fragilin, picein, salicortin, tremulacin, and tremuloidin all correlated positively with shoot length in glasshouse plants on a carbon-biased balance, and male willows had generally lower levels of phenolic glycosides than females. Salicortin and tremulacin showed the strongest positive relationships with shoot length.