Search results for "Veterinary Science"
showing 10 items of 2359 documents
Effect of oxidoreduction potential on aroma biosynthesis by lactic acid bacteria in nonfat yogurt
2011
; The aim of this study was to investigate the effect of oxidoreduction potential (Eh) on the biosynthesis of aroma compounds by lactic acid bacteria in non-fat yogurt. The study was done with yogurts fermented by Lactobacillus bulgaricus and Streptococcus thermophilus. The Eh was modified by the application of different gaseous conditions (air, nitrogen, and nitrogen/hydrogen). Acetaldehyde, dimethyl sulfide, diacetyl, and pentane-2,3-dione, as the major endogenous odorant compounds of yogurt, were chosen as tracers for the biosynthesis of aroma compounds by lactic acid bacteria. Oxidative conditions favored the production of acetaldehyde, dimethyl sulfide, and diketones (diacetyl and pen…
Production of a cheese model for sensory evaluation of flavour compounds
1995
Summary - A cheese model used to perform sensory evaluation of flavour compounds extracted from various cheese varieties was made with caseins, low heat milk powder, deodorized milk fat, NaCI and renne!. Its composition and physicochemical properties were close to mature hard cheese, apart from a lower dry matter content and sodium concentration, and a higher lactose concentration. Its preparation was established in arder to avoid drainage for at least 24 h, which should allow the incorporation of not only sorne lipophilic substances such as aromas but also some water-soluble substances such as amino acids and peptides. The rheological behaviour of the cheese model measured by a compression…
A study on texture-taste-aroma interactions: physico-chemical and cognitive mechanisms
2009
International audience; Texture–taste, texture–aroma and aroma–taste interactions were examined in custard desserts varying in viscosity (at identical composition), sucrose level and aroma nature. All reciprocal interactions were investigated, with each binary interaction addressed through an independent sensory study. Rheological, in vivo aroma release and sucrose release measurements were run in parallel to control for a possible physico-chemical origin of these interactions. Observed interactions were found to be dependent upon the nature of the sensory modalities involved; physico-chemical mechanisms could only in some instances entirely explain these interactions. Taste and aroma did n…
Determination of taste-active compounds of a bitter camembert cheese by omission tests
2001
The taste-active compounds of a Camembert cheese selected for its intense bitterness defect were investigated. The water-soluble fraction (WSE) was extracted with pure water and fractionated by successive tangential ultrafiltrations and nanofiltration. The physicochemical assessment of these fractions led to the construction of a model WSE which was compared by sensory evaluation to the crude water-soluble extract, using a panel of 16 trained tasters. As no significant difference was perceived, this model WSE was then used directly or mixed with other cheese components for omission tests. Among the main taste characteristics of the WSE (salty, sour, umami and bitter), bitterness was found t…
Effect of the association of surface flora on the sensory properties of mould-ripened cheese
1997
Summary - In cheese, flavour and taste are, in great part, generated by the starters during the ripening stage. Proteolysis and lipolysis are the first steps of the elaboration of a large number of taste and odour compounds directly invol ved in the sensory quality of cheeses. The pathways used by the microorganisms to produce flavour compounds are still unclear in many cases. It would be useful for the starter-producing industry to have screening criteria permitting diversification of the starter quality, and for the cheese industry to know which strain to associate to obtain cheeses with specifie sensory properties. The production of experimental cheeses with different associations of sur…
Inactivation of lactococcal aromatic aminotransferase prevents the formation of flora aroma compounds from aromatic amino acids in semi-hard cheese
1999
The enzymatic conversion of aromatic amino acids to aroma compounds plays a role in the formation of an undesirable floral aroma in Cheddar-like cheeses. In lactococci, the first step of aromatic amino acid degradation is a transamination, catalysed by an aromatic aminotransferase (AraT). We observed previously that in vitro, araT inactivation prevented degradation of aromatic amino acids and decreased degradation of Met and Leu. In this study we evaluated the effect of araT inactivation in Lactococcus lactis on flavour development in St. Paulin-type cheese. The degradation of amino acids was monitored by using radiolabelled amino acids and the volatile compounds formed were analysed by GC-…
Effect of growing area on tocopherols, carotenoids and fatty acid composition ofPistacia lentiscusedible oil
2014
International audience; In this investigation, we aim to study, for the first time, the effect of the growing area on tocopherols, carotenoids and fatty acid content of Pistacia lentiscus fixed oil. Fruits were harvested from eight different sites located in the north and the centre of Tunisia. Tocopherols, carotenoids and fatty acid content of the fixed oils were determined. The highest carotenoid content was exhibited by Feija oil (10.57 mg/kg of oil). Oueslatia and Tabarka oils displayed the highest alpha-tocopherol content (96.79 and 92.79 mg/kg of oil, respectively). Three major fatty acids were determined: oleic, palmitic and linoleic acids. Oleic acid was the main fatty acid presenti…
New results in the volatile odorous compounds of French cheeses
1990
Les composes volatils odorants de 5 fromages a pâte persillee (3 roqueforts fabriques avec des souches de Penicillium roqueforti differentes, 1 Bleu des Causses et 1 Bleu d'Auvergne) ont ete extraits, separes par chromatographie en phase gazeuse et analyses par spectrometrie de masse. Cent vingt neuf composes ont ete identifies et quantifies
Sensory analysis: methodological aspects relevant to the study of cheese
1997
Bien que certaines caracteristiques sensorielles puissent etre apprehendees par des mesures instrumentales, la methode la plus directe, a savoir celle utilisant l'homme comme instrument de mesure, reste la plus exacte. La mesure instrumentale ne peut s'y substituer que si les donnees ainsi obtenues sont bien correlees aux donnees sensorielles. Dans ce texte, les differents aspects de la mise en place et de la realisation des essais sensoriels visant a obtenir une description des produits sont exposes. L'attention est attiree sur les procedures et precautions necessaires pour l'obtention de mesures sensorielles fiables, condition indispensable a la reconnaissance de l'analyse sensorielle com…
Mise au point et validation d'une technique d'extraction des arômes du beurre permettant de conserver la typicité de l'odeur des produits
1998
L'obtention d'un extrait representatif de l'odeur d'un aliment est une etape essentielle de l'analyse de ses composes d'arome. Dans le cas du beurre, deux techniques d'extraction ont ete comparees du point de vue de la qualite des extraits obtenus, avec l'aide d'un jury de degustateurs : une technique d'extraction sous vide et une technique d'extraction a l'eau. Les extraits obtenus par distillation sous vide, purement aqueux, ne sont pas representatifs des beurres d'origine. Neanmoins, ils en restituent toutes les qualites odorantes lorsqu'ils sont reincorpores au sein d'une emulsion comparable a celle du beurre. Les aromes extraits sont alors evalues dans un contexte tenant compte de leur…