Exploring the Diversity of Biofilm Formation by the Food Spoiler Brochothrix thermosphacta.

Brochothrix thermosphacta is considered as a major spoiler of meat and seafood products. This study explores the biofilm formation ability and the biofilm structural diversity of 30 multi-origin B. thermosphacta strains using a set of complementary biofilm assays (biofilm ring test, crystal violet staining, and confocal laser scanning microscopy). Two major groups corresponding to low and high biofilm producers were identified. High biofilm producers presented flat architectures characterized by high surface coverage, high cell biovolume, and high surface area.

Plate waste increases with the number of foods proposed: An exploratory experimental study in adolescents' school canteens.

The objective of this exploratory study was to examine whether the number of foods offered has an impact on plate waste and meal satisfaction in adolescents' school canteens. The plate waste of 247 French students was estimated during two school lunches, the only variation being the number of starters offered (3 versus 6). Plate waste was assessed by the weight of food left on the tray. Students had to complete a short questionnaire regarding their general satisfaction with the meal. The results indicated that limiting the number of starters provided from 6 to 3 choices led to a decrease of Plate waste (-28.1 g) (p < .0001), and a modest increase in Meal satisfaction (p = .02). They suggest that limiting the number of food choices in school canteens reduces plate waste, while not diminishing satisfaction with the meal.

Optimization of an O2-balanced bioartificial pancreas for type 1 diabetes using statistical design of experiment.

A bioartificial pancreas (BAP) encapsulating high pancreatic islets concentration is a promising alternative for type 1 diabetes therapy. However, the main limitation of this approach is O2 supply, especially until graft neovascularization. Here, we described a methodology to design an optimal O2-balanced BAP using statistical design of experiment (DoE). A full factorial DoE was first performed to screen two O2-technologies on their ability to preserve pseudo-islet viability and function under hypoxia and normoxia. Then, response surface methodology was used to define the optimal O2-carrier and islet seeding concentrations to maximize the number of viable pseudo-islets in the BAP containing an O2-generator under hypoxia. Monitoring of viability, function and maturation of neonatal pig islets for 15 days in vitro demonstrated the efficiency of the optimal O2-balanced BAP. The findings should allow the design of a more realistic BAP for humans with high islets concentration by maintaining the O2 balance in the device.

Effect of the Manufacturing Process on the Microbiota, Organoleptic Properties and Volatilome of Three Salmon-Based Products.

Lightly preserved seafood products, such as cold-smoked fish and fish gravlax, are traditionally consumed in Europe and are of considerable economic importance. This work aimed to compare three products that were obtained from the same batch of fish: cold-smoked salmon (CSS) stored under vacuum packaging (VP) or a modified atmosphere packaging (MAP) and VP salmon dill gravlax (SG). Classical microbiological analyses and 16S rRNA metabarcoding, biochemical analyses (trimethylamine, total volatile basic nitrogen (TVBN), biogenic amines, pH, volatile organic compounds (VOCs)) and sensory analyses (quantitative descriptive analysis) were performed on each product throughout their storage at a chilled temperature. The three products shared the same initial microbiota, which were mainly dominated by Photobacterium, Lactococcus and Lactobacillus genera. On day 28, the VP CSS ecosystem was mainly composed of Photobacterium and, to a lesser extent, Lactococcus and Lactobacillus genera, while Lactobacillus was dominant in the MAP CSS. The diversity was higher in the SG, which was mainly dominated by Enterobacteriaceae, Photobacterium, Lactobacillus and Lactococcus. Although the sensory spoilage was generally weak, gravlax was the most perishable product (slight increase in amine and acidic off-odors and flavors, fatty appearance, slight discoloration and drop in firmness), followed by the VP CSS, while the MAP CSS did not spoil. Spoilage was associated with an increase in the TVBN, biogenic amines and spoilage associated VOCs, such as decanal, nonanal, hexadecanal, benzaldehyde, benzeneacetaldehyde, ethanol, 3-methyl-1-butanol, 2,3-butanediol, 1-octen-3-ol, 2-butanone and 1-octen-3-one. This study showed that the processing and packaging conditions both had an effect on the microbial composition and the quality of the final product.

Sensopeptidomic Kinetic Approach Combined with Decision Trees and Random Forests to Study the Bitterness during Enzymatic Hydrolysis Kinetics of Micellar Caseins.

Protein hydrolysates are, in general, mixtures of amino acids and small peptides able to supply the body with the constituent elements of proteins in a directly assimilable form. They are therefore characterised as products with high nutritional value. However, hydrolysed proteins display an unpleasant bitter taste and possible off-flavours which limit the field of their nutrition applications. The successful identification and characterisation of bitter protein hydrolysates and, more precisely, the peptides responsible for this unpleasant taste are essential for nutritional research. Due to the large number of peptides generated during hydrolysis, there is an urgent need to develop methods in order to rapidly characterise the bitterness of protein hydrolysates. In this article, two enzymatic hydrolysis kinetics of micellar milk caseins were performed for 9 h. For both kinetics, the optimal time to obtain a hydrolysate with appreciable organoleptic qualities is 5 h. Then, the influence of the presence or absence of peptides and their intensity over time compared to the different sensory characteristics of hydrolysates was studied using heat maps, random forests and regression trees. A total of 22 peptides formed during the enzymatic proteolysis of micellar caseins and influencing the bitterness the most were identified. These methods represent simple and efficient tools to identify the peptides susceptibly responsible for bitterness intensity and predict the main sensory feature of micellar casein enzymatic hydrolysates.

Use of random forest methodology to link aroma profiles to volatile compounds: Application to enzymatic hydrolysis of Atlantic salmon (Salmo salar) by-products combined with Maillard reactions.

To use salmon protein hydrolysates as food ingredients and to mask the fish odor, Maillard reactions were associated with enzymatic production of hydrolysates. The study explored an original approach based on regression trees (RT) and random forest (RF) methodologies to predict hydrolysate odor profiles from volatile compounds. An experimental design with four factors: enzyme/substrate ratio, quantity of xylose, hydrolysis and cooking times was used to create a range of enzymatic hydrolysates. Twenty samples were submitted to a trained panel for sensory descriptions of odor. Hydrolysate volatile compounds were extracted by means of Headspace Solid Phase MicroExtraction (HS-SPME) and analyzed using gas chromatography/mass spectrometry (GC-MS). The results showed that RT and RF methodologies can be useful tools for predicting an entire sensory profile from volatile compounds. Four main volatile compounds made it possible to separate hydrolysates into five groups according to their specific sensory profile. 2,5-dimethylpyrazine, 1-hydroxy-2-propanone and 3-hydroxy-2-pentanone were identified as the main predictors of the roasted odor, whereas methanethiol was associated with a mud odor. These results also suggest the appropriate process conditions for obtaining a typical roasted odor.

Can instrumental characterization help predicting sour taste perception of wheat sourdough bread?

Sourdough bread is known to have a characteristic sour taste. To guarantee consumer acceptability, sour taste should be monitored to assure constant bread quality. However, little is known about bread sour taste perception, especially how it evolves during tasting, neither if some simple measurements could help predict it. The aims of this study were to characterize the evolution of sour taste perception during bread tasting and to determine which bread instrumental variables can be correlated to it. For that purpose, eight types of bread were made with different sourdoughs and baking processes to obtain wide ranges of acidity, density and Fermentation Quotient. Bread were characterized by instrumental methods (i.e. pH, Total Titratable Acidity, organic acid content and density measurements) and their sour taste was determined by Quantitative Descriptive Analysis and a dynamic method called Progressive Profiling. As a result, it appeared that breads were perceived as significantly different throughout tasting. The "sour taste profile" was globally similar among breads with the highest intensity reached at the swallowing point. Progressive Profiling seemed then an efficient and simple method to evaluate the intensity of food organoleptic properties as well as the persistence after swallowing. Surprisingly, bread acetic acid content and Fermentation Quotient showed no effect on sour taste perception. Conversely, from all the physicochemical characteristics monitored, bread pH correlated with sour taste the most, explaining up to 97% of sour taste variations. Measuring bread pH could therefore constitute a quick and easy way to predict bread sour taste perception in research and industry.

Comprehensive sensory and chemical data on the flavor of 16 red wines from two varieties: Sensory descriptive analysis, HS-SPME-GC-MS volatile compounds quantitative analysis, and odor-active compounds identification by HS-SPME-GC-MS-O.

This paper describes data collected on 2 sets of 8 French red wines from two grape varieties: Pinot Noir (PN) and Cabernet Franc (CF). It provides, for the 16 wines, (i) sensory descriptive data obtained with a trained panel, (ii) volatile organic compounds (VOC) quantification data obtained by Headspace Solid Phase Micro-Extraction - Gas Chromatography - Mass Spectrometry (HS-SPME-GC-MS) and (iii) odor-active compounds identification by Headspace Solid Phase Micro-Extraction - Gas Chromatography - Mass Spectrometry - Olfactometry (HS-SPME-GC-MS-O). The raw data are hosted on an open-access research data repository [1].

Genotypic and phenotypic characterization of the food spoilage bacterium Brochothrix thermosphacta.

Microbial food spoilage is responsible for significant economic losses. Brochothrix thermosphacta is one of the major bacteria involved in the spoilage of meat and seafood. Its growth and metabolic activities during food storage result in the production of metabolites associated with off-odors. In this study, we evaluated the genotypic and phenotypic diversity of this species. A collection of 161 B. thermosphacta strains isolated from different foods, spoiled or not, and from a slaughterhouse environment was constituted from various laboratory collections and completed with new isolates. A PCR test based on the rpoB gene was developed for a fast screening of B. thermosphacta isolates. Strains were typed by MALDI-TOF MS, rep-PCR, and PFGE. Each typing method separated strains into distinct groups, revealing significant intra-species diversity. These classifications did not correlate with the ecological origin of strains. The ability to produce acetoin and diacetyl, two molecules associated with B. thermosphacta spoilage, was evaluated in meat and shrimp juices. The production level was variable between strains and the spoilage ability on meat or shrimp juice did not correlate with the substrate origin of strains. Although the B. thermosphacta species encompasses ubiquitous strains, spoiling ability is both strain- and environment-dependent.

Effect of Salt Reduction on Children's Acceptance of Bread.

Salt reduction is becoming a major concern for public authorities, especially in cereal products. As childhood is important for the development of healthy eating habits, this study aimed to formulate salt-reduced breads with satisfying sensory properties for children. Sourdough and an artisanal bread-making process were used to compensate the flavor loss due to salt reduction. French breads (FBs) made with sourdough and artisanal processing were compared with white breads (WBs). Two salt levels were applied (1.2 and 1.8 g /100 g flour). To determine their acceptability and characterization, the four breads were assessed (i) by an adult panel (n = 39) according to cohesiveness, overall odor intensity, overall aroma in the mouth and saltiness intensity and (ii) a panel of children (n = 100, aged 6 to 11 years) according to overall liking and saltiness intensity. Finally, consumption by children (n = 89, aged 6 to 11 years) was measured during school lunch to evaluate the acceptability of salt reduction in a real consumption context. Both formulation and salt level induced physical and sensory changes in breads perceived by adults. They described WB as less dense, cohesive, and aromatic but more odorant than FB. Saltiness differences were perceived by adults but not by children. Children showed a preference for the saltiest breads and the FB but these drivers of preference were not confirmed during consumption measurements. These results shed new light on how natural solutions to enhance the flavor of bread can reduce its salt level while maintaining acceptability. PRACTICAL APPLICATION: Salt reduction in bread could be compensated by the use of sourdough and an artisanal bread-making process. These methods allow an improvement of the nutritional quality of breads while maintaining their acceptance by young consumers by favoring the development of appealing organoleptic characteristics (aroma, texture). These methods are natural, easy to implement, and could be adapted to other fermented products in order to improve their nutritional quality.

The effect of organic wheat flour by-products on sourdough performances assessed by a multi-criteria approach.

In this study, we determined the effect of organic (i) flour ash content (1%-1.4%) and (ii) flour by-product addition (bran, shorts and germ) on sourdough performances. After five consecutive back-sloppings, sourdough was used for bread-making and its bread-related properties were assessed. No effect of flour composition factors (i & ii) on sourdough lactic acid bacteria and yeasts were highlighted. Nonetheless, they greatly altered lactic acid and acetic acid sourdough contents from 6.9 to 17.4 g/kg and from 0.9 to 2.2 g/kg, respectively. The flour ash content (i) had a significant and positive effect on sourdough acidity and CO2 production. Bread made with sourdough with a high ash content had a significantly higher acidity and specific volume. These physicochemical differences between breads were perceived by sensory evaluation in a significant way. Sourdough supplemented (ii) with germ had higher lactic acid and carbon dioxide contents than sourdough supplemented with bran and shorts. Hence, flour composition, combining ash content and flour by-products, appears to be an effective factor to obtain a better control of sourdough performances.

Free Sorting and Association Task: A Variant of the Free Sorting Method Applied to Study the Impact of Dried Sourdough as an Ingredienton the Related Bread Odor.

This paper presents a new variant of the free sorting method developed to analyze the relationship between dried sourdough (DSD) and corresponding DSD-bread (bread) odors. The comparison of DSD and bread sensory characteristics is complicated due to their specific features (for example, acidity for DSD and a characteristic "baked bread" aroma for breads). To analyze them at the same time, this study introduces a new variant of the free sorting method, which adds an association task between DSD and bread after those of free sorting and verbalization. This separation makes it possible to change the product between tasks. It was applied to study the impact of 6 European commercial DSDs on their related DSD-bread. According to our results, this methodology enabled an association between different kinds of products and thus underlined the relationship between them. Moreover, as this methodology contains a verbalization task, it provides product descriptions. Compared with the standard free sorting method, free sorting with an association task gives the distance (i) between DSDs, (ii) between breads, and (iii) between DSDs and breads. The separation of product assessment through sorting and association avoids the separation of products according to their category (DSD or bread).

The predominance of Lactobacillus sanfranciscensis in French organic sourdoughs and its impact on related bread characteristics.

Fourteen bakeries located in different regions of France were selected. These bakers use natural sourdough and organic ingredients. Consequently, different organic sourdoughs used for the manufacture of French bread were studied by the enumeration of lactic acid bacteria (LAB) and 16S rRNA sequencing of the isolates. In addition, after DNA extraction the bacterial diversity was assessed by pyrosequencing of the 16S rDNA V1-V3 region. Although LAB counts showed significant variations (7.6-9.5log10CFU/g) depending on the sourdough studied, their identification through a polyphasic approach revealed a large predominance of Lactobacillus sanfranciscensis in all samples. In ten sourdoughs, both culture and independent methods identified L. sanfranciscensis as the dominant LAB species identified. In the remaining sourdoughs, culture methods identified 30-80% of the LAB as L. sanfranciscensis whereas more than 95% of the reads obtained by pyrosequencing belonged to L. sanfranciscensis. Other sub-dominant species, such as Lactobacillus curvatus, Lactobacillus hammesii, Lactobacillus paralimentarius, Lactobacillus plantarum, Lactobacillus pentosus, and Lactobacillus sakei, were also identified. Quantification of L. sanfranciscensis by real-time PCR confirmed the predominance of this species ranging from 8.24 to 10.38log10CFU/g. Regarding the acidification characteristics, sourdough and related bread physico-chemical characteristics varied, questioning the involvement of sub-dominant species or L. sanfranciscensis intra-species diversity and/or the role of the baker's practices.

Understanding aroma release from model cheeses by a statistical multiblock approach on oral processing.

For human beings, the mouth is the first organ to perceive food and the different signalling events associated to food breakdown. These events are very complex and as such, their description necessitates combining different data sets. This study proposed an integrated approach to understand the relative contribution of main food oral processing events involved in aroma release during cheese consumption. In vivo aroma release was monitored on forty eight subjects who were asked to eat four different model cheeses varying in fat content and firmness and flavoured with ethyl propanoate and nonan-2-one. A multiblock partial least square regression was performed to explain aroma release from the different physiological data sets (masticatory behaviour, bolus rheology, saliva composition and flux, mouth coating and bolus moistening). This statistical approach was relevant to point out that aroma release was mostly explained by masticatory behaviour whatever the cheese and the aroma, with a specific influence of mean amplitude on aroma release after swallowing. Aroma release from the firmer cheeses was explained mainly by bolus rheology. The persistence of hydrophobic compounds in the breath was mainly explained by bolus spreadability, in close relation with bolus moistening. Resting saliva poorly contributed to the analysis whereas the composition of stimulated saliva was negatively correlated with aroma release and mostly for soft cheeses, when significant.

Odour quality of spray-dried hens' egg powders: the influence of composition, processing and storage conditions.

This study aimed to determine whether compositional or processing parameters have an influence on the odour quality of egg powders. The parameters tested were: whole egg vs. egg yolk, polyunsaturated fatty acid (PUFA) enrichment, spray-drying temperature (160°C vs. 180°C), production scale (industrial vs. pilot plant), storage temperature (15°C vs. 30°C) and time (1, 2, 4 and 8 months). The quality of egg powders was evaluated by sensory analysis using free sorting, and by gas chromatography coupled to mass spectrometry and olfactometry. PUFA enrichment and spray-drying temperature do not affect the odour of egg yolk powders. There are significant differences between the odour of whole-egg and egg-yolk powders as well as between powders produced on an industrial scale or in a pilot plant. An increase in the odour intensity of egg powders was observed during storage, while unpleasant odours were perceived when the egg powders were stored at 30°C.

In vivo sodium release and saltiness perception in solid lipoprotein matrices. 2. Impact of oral parameters.

This study aimed to investigate the relationships between sodium release, saltiness, and oral parameters during the eating of lipoprotein matrices (LPM). Sodium release and saltiness relative to 10 LPM were recorded during normal mastication by five subjects with differing oral parameters (chewing efficiency and salivary flow rate). The LPM samples varied in composition (dry matter, fat, salt, and pH levels) and represented a broad range of hardness. Mastication was recorded using electromyography simultaneously with sensory assessment. Differences in chewing behavior could explain most of the variability in sodium release and saltiness among subjects. Subjects with a higher chewing force and lower salivary flow rate experienced higher levels of sodium release and saltiness. In terms of the LPM, sodium release and saltiness were affected by either chewing behavior or food composition.

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.

Improvement of the identification of four heavy metals in environmental samples by using predictive decision tree models coupled with a set of five bioluminescent bacteria.

A primary statistical model based on the crossings between the different detection ranges of a set of five bioluminescent bacterial strains was developed to identify and quantify four metals which were at several concentrations in different mixtures: cadmium, arsenic III, mercury, and copper. Four specific decision trees based on the CHAID algorithm (CHi-squared Automatic Interaction Detector type) which compose this model were designed from a database of 576 experiments (192 different mixture conditions). A specific software, 'Metalsoft', helped us choose the best decision tree and a user-friendly way to identify the metal. To validate this innovative approach, 18 environmental samples containing a mixture of these metals were submitted to a bioassay and to standardized chemical methods. The results show on average a high correlation of 98.6% for the qualitative metal identification and 94.2% for the quantification. The results are particularly encouraging, and our model is able to provide semiquantitative information after only 60 min without pretreatments of samples.

Experimental design methodology for the preparation of carbonaceous sorbents from sewage sludge by chemical activation--application to air and water treatments.

The objective of this study is to optimize experimental conditions of sorbent preparation from sewage sludge using experimental design methodology. Series of carbonaceous sorbents have been prepared by chemical activation with sulfuric acid. The sorbents produced were characterized, and their properties (surface chemistry, porous and adsorptive properties) were analyzed as a function of the experimental conditions (impregnation ratio, activation temperature and time). Carbonaceous sorbents developed from sludge allow copper ion, phenol and dyes (Acid Red 18 and Basic Violet 4) to be removed from aqueous solution as well as VOC from gas phase. Indeed, according to experimental conditions, copper adsorption capacity varies from 77 to 83 mg g(-1), phenol adsorption capacity varies between 41 and 53 mg g(-1) and VOC adsorption capacities (acetone and toluene) range from 12 to 54 mg g(-1). Each response has been described by a second-order model that was found to be appropriate to predict most of the responses in every experimental region. The most influential factors on each experimental design response have been identified. Regions in which optimum values of each factor were achieved for preparation of activated carbons suitable for use in wastewater and gas treatments have been determined using response surfaces methodology. In order to have a high mass yield and to minimize the energetic cost of the process, the following optimal conditions, 1.5 g of H2SO4 g(-1) of sludge, 700 degrees C and 145 min are more appropriate for use of activated carbon from sludge in water and gas treatments.

New gas chromatography-olfactometric investigative method, and its application to cooked Silurus glanis (European catfish) odor characterization.

A new gas chromatography-olfactometric method, gas chromatography-global olfactometry omission detection (GC-GOOD), was applied to dynamic headspace odor extracts of Silurus glanis (European catfish). The GC-GOOD method is based on the omission test theory and uses a gas chromatograph coupled with a three-way valve and an a flame ionization detector. The GC-GOOD method enabled the identification of key families of volatile compounds in the S. glanis global odor and the elucidation of the interactions occurring between these families. Significant main effects were observed for the families of volatile compounds exhibiting cooked odor, grassy odor and alcohol, solvent and plastic odors. Omission of these families involved a loss of odor similarity.