Impact of Gram-negative bacteria in interaction with a complex microbial consortium on biogenic amine content and sensory characteristics of an uncooked pressed cheese

The impact of Gram-negative bacteria on sensory characteristics and production of volatile compounds as well as biogenic amines (BA) in the core of an uncooked pressed type model cheese was investigated in the presence of a defined complex microbial consortium. Eleven strains of Gram-negative bacteria, selected on the basis of their biodiversity and in vitro BA-production ability, were individually tested in a model cheese. Four out of 6 strains of Enterobacteriaceae (Citrobacter freundii UCMA 4217, Klebsiella oxytoca 927, Hafnia alvei B16 and Proteus vulgaris UCMA 3780) reached counts close to 6 log CFU g⁻¹ in the model cheese. In core of cheeses inoculated with Gram-negative bacteria, only slight differences were observed for microbial counts (Enterococcus faecalis or Lactobacillus plantarum count differences below 1 log CFU g⁻¹), acetate concentration (differences below 200 mg kg⁻¹) and texture (greater firmness) in comparison to control cheeses. Cheese core colour, odour and volatile compound composition were not modified. Although ornithine, the precursor of putrescine, was present in all cheeses, putrescine was only detected in cheeses inoculated with H. alvei B16 and never exceeded 2.18 mmol kg⁻¹ cheese dry matter. Cadaverine was only detected in cheeses inoculated with H. alvei B16, K. oxytoca 927, Halomonas venusta 4C1A or Morganella morganii 3A2A but at lower concentrations (<1.05 mmol kg⁻¹ cheese dry matter), although lysine was available. Only insignificant amounts of the detrimental BA histamine and tyramine, as well as isopentylamine, tryptamine or phenylethylamine, were produced in the cheese model by any of the Gram-negative strains, including those which produced these BA at high levels in vitro.     

Microstructural Characterization of Graphite Spheroids in Ductile Iron

The present work brings new insights by transmission electron microscopy allowing disregarding or supporting some of the models proposed for spheroidal growth of graphite in cast irons. Nodules consist of sectors made of graphite plates elongated along a ??a?? direction and stack on each other with their c axis aligned with the radial direction. These plates are the elementary units for spheroidal growth and a calculation supports the idea that new units continuously nucleate at the ledge between sectors.     

Effects of environmental factors on leucine catabolism by Carnobacterium piscicola

The metabolites from leucine degradation are involved in dry fermented sausage aroma. The catabolism of leucine by a strain of Carnobacterium piscicola was studied directly in the growth medium with 3H-labelled leucine to investigate the effect of five parameters: phase of growth, pH, oxygen, glucose and alpha-ketoisocaproic acid. Resting cells (RC) were also incubated with 3H-labelled leucine. The radioactive metabolites from leucine catabolism were analysed by high performance liquid chromatography (HPLC). At pH 5.4 and 7.2, the main metabolites detected were 3-methyl butanal, 3-methyl butanol and alpha-ketoisocaproic acid. At pH 6.5, the leucine catabolism was maximum and was characterised by a high production of 3-methyl butanoic acid. Leucine catabolism was most important during the exponential phase of growth. The addition of alpha-ketoisocaproic acid at 1%, glucose at levels of 0.5% to 2% and shaking of the growth medium increased leucine catabolism.     

FTIR-based polyphasic identification of lactic acid bacteria isolated from traditional Greek Graviera cheese

This study used a combination of phenotypic, physical (Fourier Transformed Infra-Red [FTIR] spectroscopy) and molecular (RFLP and SSCP analysis of 16S rRNA genes) methods to identify the lactic acid bacteria (LAB) flora present in traditional Greek Graviera cheese after five weeks of ripening. A total of 300 isolates collected from high dilution plates of TSAYE (incubated at 30 °C), M-17 (22 °C) and M-17 (42 °C) agar media were clustered by FTIR and then representative strains of each cluster were cross-identified blindly by all methods. Based on their FTIR spectra, 282 isolates were LAB grouped in 28 clusters. The LAB species identified and their prevalence in the cheese samples were: Lactobacillus casei/paracasei (68.8%), Lactobacillus plantarum (19.5%), Streptococcus thermophilus (8.9%), Enterococcus faecium (2.1%), and Lactococcus lactis (0.7%). Also, Staphylococcus equorum (11 isolates), Corynebacterium sp. (5 isolates) and Brevibacterium sp. (1 isolate) were recovered from TSAYE. Comparative identification results showed that phenotypic and molecular methods were in mutual agreement as regards the LAB species identified. The present polyphasic identification approach based on rapid FTIR screening of 10-fold more isolates than a previous classical identification approach allowed or improved detection of few sub-dominant species; however the predominant LAB species in the cheese samples were the same with both approaches.     

In-mouth mechanisms leading to flavor release and perception

During eating, foods are submitted to two main oral processes-chewing, including biting and crushing with teeth, and progressive impregnation by saliva resulting in the formation of a cohesive bolus and swallowing of the bolus. Texture influences the chewing behavior, including mastication and salivation, and in turn, these parameters influence texture perception and bolus formation. During this complex mouth process, flavor compounds are progressively released from the food matrix. This phenomenon is mainly dependent on the food texture, the composition and in-mouth breakdown, and on saliva impregnation and activity, but an individual's anatomical and physiological aspects characteristics should also be taken into account. This article reviews the knowledge and progresses on in-mouth processes leading to food breakdown and flavor release and affecting perception. Relationships between food texture and composition, food breakdown, oral physiology, and flavor release are developed and discussed. This review includes not only the mechanical aspects of oral physiology but also the biological aspects such as the influence of saliva composition, activity, and regulation on flavor perception. In vitro and in silico approaches are also described.     

Syntactic and semantic processing in schizophrenic patients evaluated by lexical-decision tasks.

Two lexical-decision tasks with 500-ms stimulus-onset asynchrony were conducted with 34 schizophrenic patients. This group consisted of 24 schizophrenic patients with thought disorder (TD) and 10 schizophrenic patients without thought disorder (NTD), 14 psychiatric controls (depressive illness), 20 hospitalized controls, and 20 normal controls. One lexical-decision task with semantic relations (related vs. unrelated, Experiment 1) and 1 task with syntactic relations (congruent vs. incongruent; Experiment 2) were used to evaluate processing of different lexical information. In Experiment 1, although all control groups and NTD schizophrenic patients showed semantic priming, TD schizophrenic patients did not. In Experiment 2, all groups showed a significant syntactic effect. These findings provide evidence for an abnormality in semantic processing and the preservation of syntactic processing in TD schizophrenic patients, thus suggesting a deficit in the processing of semantic information under certain conditions when compared with normal syntactic processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Morphology and Buckling of the Oxide Scale after Fe–9Cr Steel Oxidation in Water Vapor Environment

Oxidation of Metals - Under water vapor exposure at 550–560&nbsp;°C, Fe–9Cr ferritic–martensitic steels form a triplex oxide scale made of an outer magnetite layer...     

Le style parental des beaux-péres dans les familles recomposées.

Several studies have shown the importance of the stepfather-stepchild relationship in the successful adaptation of young people to stepfamilies. Indeed, when there is a good affective relationship between a stepfather and stepchild, there is a lower risk of stepchild having problems. Though it is known that the quality of this relationship has an impact, there is still a great deal of uncertainty about the best way for stepfathers to fulfill their role. This article examines how the stepfather's parenting style influences the externalised and internalised behaviour problems of young people in stepfamilies. The data were obtained from interviews with 104 adolescents (63.5 % girls; 36.5 % boys) who answered the Youth Self-Report (Achenbach, 1991), the Parental Authority Questionnaire (Buri, 1991), and the Child Parental Acceptance-Rejection Questionnaire (Rohner, 1984). The results show that the majority of young people saw their stepfather as being involved in their upbringing. More than a third of the sample considered that their stepfather was authoritarian, and another third saw him as authoritative. The young people's level of adaptation was associated with the stepfather's parenting style. Young people who saw their stepfather as being authoritative or warm particularly benefited from the relationship. (PsycINFO Database Record (c) 2010 APA, all rights reserved)