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Ferrand M.,Institute Of Lelevage | Huquet B.,Institute Of Lelevage | Bouvier F.,French National Institute for Agricultural Research | Caillat H.,French National Institute for Agricultural Research | And 6 more authors.
Electronic Journal of Applied Statistical Analysis | Year: 2011

To know and to control the fine milk composition is an important concern in the dairy industry. The mid-infrared (MIR) spectrometry method appears to be a good, fast and cheap method for assessing milk fatty acid profile with accuracy. Although partial least squares (PLS) regression is a very useful and powerful method to determine fine milk composition from spectra, the estimations are often less accurate on new samples coming from different spectrometers. Therefore a genetic algorithm (GA) combined with a PLS was used to produce models with a reduced number of wavelengths and a better accuracy. Number of wavelengths to consider is reduced substantially by 5 or 10 according the number of steps in the genetic algorithm. The accuracy is increased on average by 9% for fatty acids of interest. © 2011 Università del Salento.

Michalski M.C.,INSA Lyon | Genot C.,French National Institute for Agricultural Research | Gayet C.,CNIEL | Lopez C.,Agrocampus Ouest | And 7 more authors.
Progress in Lipid Research | Year: 2013

On a nutritional standpoint, lipids are now being studied beyond their energy content and fatty acid (FA) profiles. Dietary FA are building blocks of a huge diversity of more complex molecules such as triacylglycerols (TAG) and phospholipids (PL), themselves organised in supramolecular structures presenting different thermal behaviours. They are generally embedded in complex food matrixes. Recent reports have revealed that molecular and supramolecular structures of lipids and their liquid or solid state at the body temperature influence both the digestibility and metabolism of dietary FA. The aim of the present review is to highlight recent knowledge on the impact on FA digestion, absorption and metabolism of: (i) the intramolecular structure of TAG; (ii) the nature of the lipid molecules carrying FA; (iii) the supramolecular organization and physical state of lipids in native and formulated food products and (iv) the food matrix. Further work should be accomplished now to obtain a more reliable body of evidence and integrate these data in future dietary recommendations. Additionally, innovative lipid formulations in which the health beneficial effects of either native or recomposed structures of lipids will be taken into account can be foreseen. © 2013 Elsevier Ltd. All rights reserved.

Rolet-Repecaud O.,French National Institute for Agricultural Research | Berthier F.,French National Institute for Agricultural Research | Beuvier E.,French National Institute for Agricultural Research | Gavoye S.,Actilait | And 4 more authors.
LWT - Food Science and Technology | Year: 2013

Proteolytic milk-clotting enzymes are extracted from various sources (animals, plants, fungi) and processed according to various methods that are specific to each manufacturer or cheese-maker. Chemical composition and polypeptide patterns of 24 milk-clotting preparations from animal and fungal sources: 10 commercial rennets, 9 artisanal calf rennets, 2 recombinant chymosin preparations and 3 microbial preparations, were compared in order to identify differences according to both their manufacturing process and their source. The preparation from. Cryphonectria parasitica had the highest ammonia and small peptide content. Commercial rennets and preparations from. Rhizomucor miehei had the highest NaCl and pH values while artisanal rennets had the lowest and recombinant chymosins were intermediate. In comparison with the other commercial preparations, commercial rennets had the highest variability in chemical composition and their polypeptide profiles showed numerous protein bands ranging from 15 kDa to 197 kDa, like artisanal rennets. Protein composition of commercial rennets revealed the presence of bovine serum albumin, either native or degraded, and degraded chymosin. The results indicated that the source of coagulating enzymes and the conditions applied for enzyme extraction led to specific chemical compositions, polypeptide patterns and protein composition which are described in this article. © 2012 Elsevier Ltd.

Falentin H.,French National Institute for Agricultural Research | Falentin H.,Agrocampus Ouest | Postollec F.,ADRIA Developpement | Parayre S.,French National Institute for Agricultural Research | And 8 more authors.
International Journal of Food Microbiology | Year: 2010

Bacterial communities of fermented foods are usually investigated by culture-dependent methods. Real-time quantitative PCR (qPCR) and reverse transcription (RT)-qPCR offer new possibilities to quantify the populations present and their metabolic activity. The aim of this work was to develop qPCR and RT-qPCR methods to assess the metabolic activity and the stress level of the two species used as ripening cultures in Emmental cheese manufacture, Propionibacterium freudenreichii and Lactobacillus paracasei. Three small scale (1/100) microbiologically controlled Emmental cheeses batches were manufactured and inoculated with Lactobacillus helveticus, Streptococcus thermophilus, P. freudenreichii and L. paracasei. At 12 steps of cheese manufacture and ripening, the populations of P. freudenreichii and L. paracasei were quantified by numerations on agar media and by qPCR. 16S, tuf and groL transcript levels were quantified by RT-qPCR. Sampling was carried out in triplicate. qPCR and RT-qPCR assessments were specific, efficient and linear. The quantification limit was 103 copies of cells or cDNA/g of cheese. Cell quantifications obtained by qPCR gave similar results than plate count for P. freudenreichii growth and 0.5 to 1 log lower in the stationary phase. Bacterial counts and qPCR quantifications showed that L. paracasei began to grow during the pressing step while P. freudenreichii began to grow from the beginning of ripening (in the cold room). Tuf cDNA quantification results suggested that metabolic activity of L. paracasei reached a maximum during the first part of the ripening (in cold room) and decreased progressively during ripening (in the warm room). Metabolic activity of P. freudenreichii was maximum at the end of cold ripening room and was stable during the first two weeks in warm room. After lactate exhaustion (after two weeks of warm room), the number of tuf cDNA decreased reflecting reduced metabolic activity. For L. paracasei, groL cDNA were stable during ripening. For P. freudenreichii, groL1 gene was highly-expressed during acidification, while groL2 gene highly expression was only observed at the end of the ripening stage after lactate (carbon substrate of P. freudenreichii) exhaustion. The potential use of 16S and tuf genes for the normalization of cDNA quantification throughout an Emmental cheese manufacture is discussed. For the first time, specific gene expression was performed by RT-qPCR yielding metabolic activity and stress response evaluation for L. paracasei and P. freudenreichii in cheese. © 2010 Elsevier B.V.

Couvert O.,European University of Brittany | Couvert O.,147 Rue Of Luniversite | Pinon A.,Institute Pasteur Of Lille | Pinon A.,147 Rue Of Luniversite | And 22 more authors.
International Journal of Food Microbiology | Year: 2010

A stochastic modelling approach was developed to describe the distribution of Listeria monocytogenes contamination in foods throughout their shelf life. This model was designed to include the main sources of variability leading to a scattering of natural contaminations observed in food portions: the variability of the initial contamination, the variability of the biological parameters such as cardinal values and growth parameters, the variability of individual cell behaviours, the variability of pH and water activity of food as well as portion size, and the variability of storage temperatures. Simulated distributions of contamination were compared to observed distributions obtained on 5 day-old and 11 day-old cheese curd surfaces artificially contaminated with between 10 and 80 stressed cells and stored at 14 °C, to a distribution observed in cold smoked salmon artificially contaminated with approximately 13 stressed cells and stored at 8 °C, and to contaminations observed in naturally contaminated batches of smoked salmon processed by 10 manufacturers and stored for 10 days a 4 °C and then for 20 days at 8 °C. The variability of simulated contaminations was close to that observed for artificially and naturally contaminated foods leading to simulated statistical distributions properly describing the observed distributions. This model seems relevant to take into consideration the natural variability of processes governing the microbial behaviour in foods and is an effective approach to assess, for instance, the probability to exceed a critical threshold during the storage of foods like the limit of 100. CFU/g in the case of L. monocytogenes. © 2010 Elsevier B.V.

Falentin H.,French National Institute for Agricultural Research | Falentin H.,Agrocampus Ouest | Henaff N.,ADRIA Developpement | Le Bivic P.,French National Institute for Agricultural Research | And 12 more authors.
Food Microbiology | Year: 2012

For Emmental manufacture two kinds of adjunct culture are added: (i) thermophilic lactic acid bacteria (starters) such as Lactobacillus helveticus (LH), and Streptococcus thermophilus (ST) growing the first day of the manufacture and (ii) ripening culture. ST and LH have a key role in curd acidification and proteolysis at the beginning of the manufacture but are considered to be lyzed for a great part of them at the ripening step. The aim of this work was to assess the metabolic activity of these bacteria throughout manufacture and ripening. During Emmental cheesemaking, LH and ST were subjected to i) population quantification by numerations and by quantitative PCR (qPCR) ii) reverse transcription (RT) Temporal Temperature Gel Electrophoresis (TTGE) iii) transcript quantification by RT-qPCR targeting 16S rRNA, tuf and groL mRNAs to evaluate bacterial metabolic activity. During ripening, ST and LH numerations showed a 2.5 log 10 loss of culturability whereas qPCR on pelleted cells revealed only one log 10 of decrease for both of these species. 10 9 ST and 10 8 LH cells/g of cheese still remained. They contained a stable number of 16S transcript and at least 10 6 copies of mRNAs per 10 9 cells until the end of ripening. These results prove the unexpected persistency of thermophilic lactic acid bacteria starters (ST and LH) metabolic activity until the end of ripening and open new perspectives in term of their involvement in the quality of cheeses during ripening. © 2011 Elsevier Ltd.

PubMed | Actilait, French National Institute for Agricultural Research and University Paris Est Creteil
Type: Journal Article | Journal: Journal of dairy science | Year: 2013

Mid-infrared (MIR) spectrometry was used to estimate the fatty acid (FA) composition in cow, ewe, and goat milk. The objectives were to compare different statistical approaches with wavelength selection to predict the milk FA composition from MIR spectra, and to develop equations for FA in cow, goat, and ewe milk. In total, a set of 349 cow milk samples, 200 ewe milk samples, and 332 goat milk samples were both analyzed by MIR and by gas chromatography, the reference method. A broad FA variability was ensured by using milk from different breeds and feeding systems. The methods studied were partial least squares regression (PLS), first-derivative pretreatment + PLS, genetic algorithm + PLS, wavelets + PLS, least absolute shrinkage and selection operator method (LASSO), and elastic net. The best results were obtained with PLS, genetic algorithm + PLS and first derivative + PLS. The residual standard deviation and the coefficient of determination in external validation were used to characterize the equations and to retain the best for each FA in each species. In all cases, the predictions were of better quality for FA found at medium to high concentrations (i.e., for saturated FA and some monounsaturated FA with a coefficient of determination in external validation >0.90). The conversion of the FA expressed in grams per 100mL of milk to grams per 100g of FA was possible with a small loss of accuracy for some FA.

Cogan T.M.,Teagasc | Goerges S.,Naturkost Ernst Weber GmbH | Gelsomino R.,SA Coca Cola Services N.V. | Larpin S.,Millipore | And 16 more authors.
Microbiology Spectrum | Year: 2014

Comprehensive collaborative studies from our laboratories reveal the extensive biodiversity of the microflora of the surfaces of smear-ripened cheeses. Two thousand five hundred ninety-seven strains of bacteria and 2,446 strains of yeasts from the surface of the smear-ripened cheeses Limburger, Reblochon, Livarot, Tilsit, and Gubbeen, isolated at three or four times during ripening, were identified; 55 species of bacteria and 30 species of yeast were found. The microfloras of the five cheeses showed many similarities but also many differences and interbatch variation. Very few of the commercial smear microorganisms, deliberately inoculated onto the cheese surface, were reisolated and then mainly from the initial stages of ripening, implying that smear cheese production units must have an adventitious "house" flora. Limburger cheese had the simplest microflora, containing two yeasts, Debaryomyces hansenii and Geotrichum candidum, and two bacteria, Arthrobacter arilaitensis and Brevibacterium aurantiacum. The microflora of Livarot was the most complicated, comprising 10 yeasts and 38 bacteria, including many gram-negative organisms. Reblochon also had a very diverse microflora containing 8 yeasts and 13 bacteria (excluding gram-negative organisms which were not identified), while Gubbeen had 7 yeasts and 18 bacteria and Tilsit had 5 yeasts and 9 bacteria. D. hansenii was by far the dominant yeast, followed in order by G. candidum, Candida catenulata, and Kluyveromyces lactis. B. aurantiacum was the dominant bacterium and was found in every batch of the 5 cheeses. The next most common bacteria, in order, were Staphylococcus saprophyticus, A. arilaitensis, Corynebacterium casei, Corynebacterium variabile, and Microbacterium gubbeenense. S. saprophyticus was mainly found in Gubbeen, and A. arilaitensis was found in all cheeses but not in every batch. C. casei was found in most batches of Reblochon, Livarot, Tilsit, and Gubbeen. C. variabile was found in all batches of Gubbeen and Reblochon but in only one batch of Tilsit and in no batch of Limburger or Livarot. Other bacteria were isolated in low numbers from each of the cheeses, suggesting that each of the 5 cheeses has a unique microflora. In Gubbeen cheese, several different strains of the dominant bacteria were present, as determined by pulsed-field gel electrophoresis, and many of the less common bacteria were present as single clones. The culture-independent method, denaturing gradient gel electrophoresis, resulted in identification of several bacteria which were not found by the culture-dependent (isolation and rep-PCR identification) method. It was thus a useful complementary technique to identify other bacteria in the cheeses. The gross composition, the rate of increase in pH, and the indices of proteolysis were different in most of the cheeses. © 2014 American Society for Microbiology.

Sauvageot F.,Campus University | Herbreteau V.,Actilait | Berger M.,Insudiet | Dacremont C.,Campus University | Dacremont C.,University of Burgundy
Food Quality and Preference | Year: 2012

Fifteen groups of participants in nine laboratories performed triangle tests with two pairs of soft drinks. Groups differed in practice level with triangle tests: eight groups of 60 consumers who were not used to triangle test, three groups of qualified assessors who have already performed a few triangle tests, and four groups of trained assessors with a more extensive practice of triangle tests; qualified and trained groups included 9 or 18 assessors. The soft drinks were made from syrups at two levels of dilution in order to achieve about 55% of correct responses to test for difference and about 40% of correct responses to test for similarity. Participants performed three replicated tests with each pair of drinks, except the groups of 9 assessors who performed six replicated tests. When testing for difference, large inter-groups differences were observed. One consumer group and one trained group from two different laboratories failed by far to reach the critical number of correct responses leading to demonstrate a significant difference between products. For similarity test, all consumer groups demonstrated a significant similarity whereas two qualified groups and one trained group did not. This is explained by a slightly higher level of performance for qualified and trained assessors compared to consumers. © 2011 Elsevier Ltd.

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