Characterization of Italian Cheeses Ripened Under Nonconventional Conditions

International audience; Four Italian cheeses (Casciotta di Urbino, Barricato San Martino, Vento d'Estate, and Ubriaco di Raboso) nonconventionally ripened under different plant materials (walnut leaves, herbs, hay, and wine by-products, respectively) were compared for compositional, microbiological, biochemical, and volatile profile characteristics. Mean values for gross composition were rather similar. Because primary starters were not used for manufacture, the endogenous lactic acid bacteria were mainly present (7.0 to 9.0 log10 cfu/g). Except for Lactobacillus paracasei and Leuconostoc mesenteroides, which were commonly identified in 3 cheeses, Lactococcus lactis, Enterococcus sanguinicola, Lactobacillus brevis, Enterococcus durans/Enterococcus faecium, Lactobacillus plantarum, and Weissella cibaria/Weissella confusa were variously found in the 4 cheeses. Random amplification of polymorphic DNA-PCR analysis showed the biodiversity among the strains, and the species of lactobacilli were in part grouped according to their origin. As shown by the principal component analysis of reverse-phase fast protein liquid chromatography data for the pH 4.6-soluble fractions and by the determination of free AA, the secondary proteolysis of Barricato San Martino and Vento d'Estate mainly differed from the other 2 cheeses. Purge-and-trap and solid-phase microextraction were coupled with gas chromatography-mass spectrometry to determine volatile compounds. Vento d'Estate showed the highest levels of almost all chemical classes, and Casciotta di Urbino was characterized by a very low level of volatile components. Esters, ketones, and terpenes were the chemical classes that mainly differentiated the cheeses. Several volatile compounds seemed to be released directly from the plant materials used for ripening, especially terpenes for Vento d'Estate cheese. The lowest level of volatile free fatty acids was found in Casciotta d'Urbino, in which rennet paste was not used during manufacture. The highest concentration of free fatty acids, especially butyric and caproic acids, was found in Vento d'Estate cheese

Conditions de production du lait et qualités sensorielles des fromages

Ce texte fait partie du dossier : Systèmes d’élevage et typicité des produits laitiers

Use of autochthonous mesophilic lactic acid bacteria as starter cultures for making Pecorino Crotonese cheese: Effect on compositional, microbiological and biochemical attributes

The use of selected autochthonous mesophilic lactic acid bacteria as starter cultures was investigated according to the traditional protocol for making Pecorino Crotonose (PC). Leuconostoc mesenteroides subsp. mesenteroides 2A, Lactobacillus casei 23C and Lactobacillus plantarum 18C (Autochthonous Starter, AS1) and Leuc. mesenteroides subsp. mesenteroides 2A, and L. casei 25D and 16A (AS2) were isolated and identified from aged ewes’ milk PC cheeses, selected based on several enzymatic activities, and used as starter cultures. As shown by the in vitro kinetic of acidification, selected starter cultures had suitable capabilities to acidify. The manufacture of PC cheeses was carried out at an industrial plant scale. A control cheese (CC) was also made, using commercial starters consisting of mesophilic and thermophilic species. Ripening lasted 105 days at 10 °C. A poly-phasic approach was used to compare cheeses during manufacture and ripening, mainly based on pyrosequencing of the 16S rRNA targeting DNA, proteolysis and volatile component analyses. Compared to CC, both autochthonous starter cultures slightly affected the gross chemical composition of PC cheese. The cell density of thermophilic starters of CC progressively decreased throughout ripening. Plate count and RAPD-PCR showed that the cell number of autochthonous lactobacilli cultures of PC cheeses, made with AS1 and AS2, was almost constant throughout ripening and abundantly higher than that observed in CC. As shown by culture-independent analysis, the OTUs found during ripening varied depending on the manufacture with or without autochthonous starter cultures. The major chemical differences among cheeses were the concentration of free amino acids and the synthesis of some key volatile components (e.g., 2-methyl-1-propanol, 2-methyl-1-butanol, isobutyric, isovaleric, and isocaproic acids). Compared to CC, the use of AS1 positively affected the overall cheese quality

Spatial Distribution of the Metabolically Active Microbiota within Italian PDO Ewes' Milk Cheeses.

Italian PDO (Protected Designation of Origin) Fiore Sardo (FS), Pecorino Siciliano (PS) and Pecorino Toscano (PT) ewes' milk cheeses were chosen as hard cheese model systems to investigate the spatial distribution of the metabolically active microbiota and the related effects on proteolysis and synthesis of volatile components (VOC). Cheese slices were divided in nine sub-blocks, each one separately subjected to analysis and compared to whole cheese slice (control). Gradients for moisture, and concentrations of salt, fat and protein distinguished sub-blocks, while the cell density of the main microbial groups did not differ. Secondary proteolysis differed between sub-blocks of each cheese, especially when the number and area of hydrophilic and hydrophobic peptide peaks were assessed. The concentration of free amino acids (FAA) agreed with these data. As determined through Purge and Trap (PT) coupled with Gas Chromatography-Mass Spectrometry (PT-GC/MS), and regardless of the cheese variety, the profile with the lowest level of VOC was restricted to the region identified by the letter E defined as core. As shown through pyrosequencing of the 16S rRNA targeting RNA, the spatial distribution of the metabolically active microbiota agreed with the VOC distribution. Differences were highlighted between core and the rest of the cheese. Top and bottom under rind sub-blocks of all three cheeses harbored the widest biodiversity. The cheese sub-block analysis revealed the presence of a microbiota statistically correlated with secondary proteolysis events and/or synthesis of VOC

Criblage des bactéries lactiques en fonction de leur cinétique de réduction : approche méthodologique

Les bactéries lactiques (BL) sont des micro-organismes importants dans l'industrie alimentaire pour la fabrication de produits fermentés ou comme probiotiques. Parmi les BL, certaines espèces sont capables de réduire le potentiel d’oxydoréduction (Eh) jusqu’à des valeurs négatives alors que d'autres non [1]. Cette diversité d'activité réductrice retrouvée chez les BL permet l'utilisation de souches sélectionnées apportant des valeurs de réduction optimales nécessaires à la qualité globale des produits laitiers [2–6]. Les principaux mécanismes impliqués sont les groupes thiol exofaciaux, la NoxE NADH Oxydase et le mécanisme mettant en jeu la chaîne de transport d'électrons [7,8,9].Actuellement, il existe différentes façons de comparer les BL en fonction de leurs propriétés réductrices. Cachon et al 2002 [10] ont proposé une Méthode de mesure Potentiométrique de l'Activité Réductrice (MPAR) par suivi des cinétiques en milieu liquide grâce à des sondes redox. Michelon et al 2013 [11] ont proposé la Méthode cOlorimétrique de mesure de la CApacité Réductrice (MOCAR) par criblage sur milieu solide. Par rapport à MPAR, MOCR permet le criblage d'un grand nombre de souches en peu de temps. Cependant, cette méthode est binaire et discrimine relativement mal les souches d’une même espèce. Par conséquent, nous avons développé une nouvelle méthode, Méthode de mesure par Absorbance de l’Activité Réductrice (MAAR) afin de différencier les souches en gardant la simplicité de MOCAR mais avec la pertinence de la cinétique de réduction bactérienne obtenue avec MPAR. Pour cela, un milieu chimiquement défini a été mis au point pour suivre l’absorbance dans le temps. Onze souches de BL pures ainsi que 3 ferments de L. lactis commerciaux ont été testés avec MAAR et comparés avec la méthode de référence MPAR en utilisant l’interface iCinac. Les paramètres discriminatoires obtenus à partir de la cinétique avec MAAR ont permis de différencier les souches pures d’une même espèce et les starters de la même manière qu’avec MPAR. Cette nouvelle méthode de criblage permet : (1) de différencier simultanément plusieurs souches d’une même espèce en fonction de leur activité réductrice ; (2) la comparaison de souches intra-genre. Ainsi, une utilisation combinée des criblages MOCAR et MAAR permettrait de cribler rapidement plus de souches de BL en fonction de leur potentiel de réduction.References[1]. M Brasca., S. Morandi, R. Lodi, A. Tamburini of J Appl Microbiol, 2007, 10.1111/j.1365-2672.2007.03392.x[2]. V. Caldeo, JA. Hannon, DK. Hickey, D. Waldron, MG. Wilkinson, TP. Beresford of J Dairy Res, 2016, 10.1017/S002202991600056X[3]. F. Martin, N. Cayot, C. Vergoignan, L. Journaux, P. Gervais, R. Cachon of Food Res Int, 2010, 10.1016/j.foodres.2009.09.032[4]. F. Martin, R. Cachon, K. Pernin, J. De Coninck, P. Gervais, E. Guichard of J Dairy Sci, 2011, [5]. S. Nouaille, L. Rault, S. Jeanson, P. Loubière, Y. Le Loir, S. Even of Appl Environ Microbiol 2014, 10.1128/AEM.02287-14[6]. S. Abraham, R. Cachon, B. Colas, G. Feron, J. De Coninck of Int Dairy J, 2007, 10.1016/j.idairyj.2006.12.010[7]. D. Michelon, S. Abraham, B. Ebel, J. De Coninck, F. Husson, G. Feron of FEBS J, 2010, 10.1111/j.1742-4658.2010.07644.x[8]. S. Tachon, JB. Brandsma, M. Yvon of Appl Environ Microbiol, 2010, 10.1128/AEM.02120-09 [9]. C. Roussel, B. Ebel, E. Munier, D. Michelon, F. Martin-Dejardin, E. Beuvier, J. De Coninck, P. Gaudu, R. Cachon of Food Res Int, 2022, 10.1016/j.foodres.2022.111154[10]. R. Cachon, S. Jeanson, M. Aldarf, C. Divies of Le lait, 2002, 10.1051/lait:2002010[11]. D. Michelon, S. Tachon, B. Ebel, J. De Coninck, G. Feron, P. Gervais, M. Yvon, R. Cachon of J Biosci Bioeng, 2013, 10.1016/j.jbiosc.2012.09.01

Screening of lactic acid bacteria based on their reduction kinetics

International audienceLactic Acid bacteria (LAB) are widespread in the dairy industry for their use as starters and probiotics. They are able to reduce redox potential (E h) of food matrices, influencing oxidation-reduction reactions involved in the organoleptic quality of the product and also preventing the development of undesired microflora. Amongst LAB, some species are able to reduce E h below negative values while others do not [1]. This diversity of reducing activity found in LAB allows the use of selected strains providing optimal reduction values necessary to the overall quality of food dairy products. Currently, there are different ways to compare LAB based on their reducing properties. Cachon et al., 2002 proposed the Potentiometry Reduction Activity Method (PRAM) by monitoring E h in liquid medium with redox probes, and the comparison of the maximum reduction rate (Vmax r), and the time to reach Vmax r. Michelon et al., 2013 proposed the cOlorimetric Reduction CApacity Method (ORCAM), a screening method on solid medium. This later takes advantage over PRAM to allow screening of a lot of strains in a short time. Nevertheless, this method is relatively non-discriminatory between LAB strains belonging to the same species. Consequently, we developed a new method, the Absorbance Reducing Activity Method (ARAM), in order to differentiate strains by keeping the simplicity of ORCAM but with the relevance of bacterial reduction kinetics obtained with PRAM. To validate this new screening method, PRAM using iCinac interface was carried out in parallel as reference method

In vivo sodium release and saltiness perception in solid lipoprotein matrices. 1. Effect of composition and texture

Reducing the sodium content in foods is complex because of their multidimensional sensory characteristics and the multifunctionality of sodium chloride. The aim of this study was to elucidate how food composition may influence in-mouth sodium release and saltiness perception. Lipoprotein matrices (LPM) were produced using milk constituents and characterized by means of rheological measurements, texture, and taste sensory profiles. Texture and taste perceptions were affected differently by variations in the salt level, dry matter, and fat contents. Composition and textural changes also modified temporal sodium release and saltiness perception recorded in five subjects, but the effects varied as a function of the salt content. The water content mainly appeared to influence the amount of sodium released, whereas saltiness perception was mainly related to fat content. Elasticity, coating, and granularity were found to be correlated with temporal sodium release and/or saltiness parameters