Perception of oyster-based products by French consumers: the effect of processing and role of social representations

International audienceThe search for new markets in the seafood sector, associated with the question of the continuity of raw oyster consumption over generations can be an opportunity for processors to extend their ranges with oyster-based products. The twofold aim of this study was to evaluate the impact of processing and social representation on perception of oyster-based products by French consumers and to identify the best means of development in order to avoid possible failure in the market. Five products with different degrees of processing (cooked oysters in a half-shell, hot preparation for toast, potted oyster, oyster butter and oyster-based soup) were presented within focus groups and consumer tests, at home and in canteens with the staff of several companies in order to reach consumers with different ages and professional activities. The results showed that social representation had a strong impact and that behaviours were contrasted according to the initial profile of the consumer (traditional raw oyster consumers or non-consumers) and their age distribution (younger and older people). The degree of processing has to be adapted to each segment. It is suggested to develop early exposure to influence the food choices and preferences of the youngest consumers on a long-term basis

Perinatal acquisition of drug-resistant HIV-1 infection: mechanisms and long-term outcome

<p>Abstract</p> <p>Background</p> <p>Primary-HIV-1-infection in newborns that occurs under antiretroviral prophylaxis that is a high risk of drug-resistance acquisition. We examine the frequency and the mechanisms of resistance acquisition at the time of infection in newborns.</p> <p>Patients and Methods</p> <p>We studied HIV-1-infected infants born between 01 January 1997 and 31 December 2004 and enrolled in the ANRS-EPF cohort. HIV-1-RNA and HIV-1-DNA samples obtained perinatally from the newborn and mother were subjected to population-based and clonal analyses of drug resistance. If positive, serial samples were obtained from the child for resistance testing.</p> <p>Results</p> <p>Ninety-two HIV-1-infected infants were born during the study period. Samples were obtained from 32 mother-child pairs and from another 28 newborns. Drug resistance was detected in 12 newborns (20%): drug resistance to nucleoside reverse transcriptase inhibitors was seen in 10 cases, non-nucleoside reverse transcriptase inhibitors in two cases, and protease inhibitors in one case. For 9 children, the detection of the same resistance mutations in mothers' samples (6 among 10 available) and in newborn lymphocytes (6/8) suggests that the newborn was initially infected by a drug-resistant strain. Resistance variants were either transmitted from mother-to-child or selected during subsequent temporal exposure under suboptimal perinatal prophylaxis. Follow-up studies of the infants showed that the resistance pattern remained stable over time, regardless of antiretroviral therapy, suggesting the early cellular archiving of resistant viruses. The absence of resistance in the mother of the other three children (3/10) and neonatal lymphocytes (2/8) suggests that the newborns were infected by a wild-type strain without long-term persistence of resistance when suboptimal prophylaxis was stopped.</p> <p>Conclusion</p> <p>This study confirms the importance of early resistance genotyping of HIV-1-infected newborns. In most cases (75%), drug resistance was archived in the cellular reservoir and persisted during infancy, with or without antiretroviral treatment. This finding stresses the need for effective antiretroviral treatment of pregnant women.</p

Stockage des poissons fumés et ou séchés : cas de Oreochromis niloticus " Fiha saly " malgache

During storage of smoke-dried fish, various biochemical reactions can occur; they will result in product acceptability or rejection. To determine these changes, pH and humidity were measured and molds were counted on smoke-dried fish stored for 6 months. A sensory analysis was also conducted to assess the quality of the products. Infestations and losses linked to it have been estimated by counting the insects and weighing of fish batches over time. The variability in the quality of smoke-dried fish depending on the time of purchase and storage was also integrated with our study. Biochemical reactions are mainly oxidation phenomena which result in a decrease of pH and release of spoilage odors such as rancid odor (> 1.5/ 3) or sulfur, acid and moldy odors. The growth of mold (1- 36 CFU / g) due to the reabsorption of water by fish contributes to this olfactory and visual spoilage. Beyond 90 days of storage, smoke-dried fish bought in the dry season begins to be rejected (> 2/3), while the fish bought in the wet season is at the limit of acceptability (2/3) even at the beginning of storage. During the first 90 days of storage, the insect infestation generates between 10 and 60 % of losses. A salt content of 8 % appears to be effective against the infestation but contributes to the deterioration of the product when stored in rooms with higher than 65 % relative humidity.Au cours du stockage des poissons fumés/séchés, différentes réactions biochimiques peuvent intervenir et conduire à la non-acceptabilité ou rejet des produits. Pour déterminer ces changements, le pH, la teneur en eau et le nombre de moisissures ont été suivis sur des poissons fumés/séchés entreposés pendant 6 mois. Des tests sensoriels ont également été menés pour évaluer la qualité des produits. Les infestations ainsi que les pertes qui y sont liées ont été estimées en comptant les insectes et en pesant des lots de poissons au cours du temps. La variabilité de la qualité du poisson fumé/séché en fonction de la période d'achat et de stockage a également été intégrée à notre sujet d'étude. Les réactions biochimiques sont surtout des phénomènes d'oxydation qui se traduisent par une diminution du pH et le dégagement d'odeurs d'altération telles que rance (> 1,5 sur 3), soufrée, acide et moisi. L'apparition de moisissures (1 à 36 UFC/g), due à la réabsorption d'eau par le poisson, contribue à cette dégradation olfactive mais également visuelle. Au-delà de 90 jours de stockage, le poisson fumé-séché acheté en saison sèche commence à être rejeté (note > 2 sur 3), tandis que le poisson acheté en saison humide est à la limite de l’acceptabilité (note 2 sur 3), comme au début du stockage. Jusqu’à 90 jours d’entreposage, les pertes sont causées principalement par l'infestation d’insectes et varient entre10 et 60 %. Une teneur en sel de 8 % semble être efficace contre l'infestation mais contribue à la détérioration du produit lorsqu'il est stocké à des humidités relatives supérieures à 65 %

Selection of bioprotective cultures for preventing cold-smoked salmon spoilage

Biopreservation is a natural technology of food preservation, which consists of inoculating food with microorganisms selected for their antibacterial properties. The objective of this study was to select lactic acid bacteria (LAB) to improve the quality of cold-smoked salmon (CSS). In this work, different strains representative of the 4 dominant species, identified in a previous study by pyrosequencing the 16S rRNA gene, were isolated and their spoiling potential in CSS blocks, sterilized by ionization, was assessed by twelve trained panelists along the vacuum storage at 8 °C . Photobacterium phosphoreum, Brochothrix thermosphacta and Serratia proteamaculans released strong off-odors whereas the spoiling potential of Carnobacterium divergens was weaker. The spoiling capacity of Lactococcus piscium EU2241, Leuconostoc gelidum EU2247, Lactobacillus sakei EU2885, Staphylococcus equorum S030674 and 4 commercial starters was tested by the same method and 2 strains were eliminated due to off-odor production. The effect of the 6 selected LAB against the 4 specific spoiling organisms (SSOs) selected was tested by challenge tests in sterile CSS blocks. The protective effect of the LAB differed from one SSO to another and no correlation could be established between the sensory improvement, SSO inhibition, and the implantation or acidification of protective cultures (PCs). All the PCs except L. piscium reduced the off-odors released by P. phosphoreum although some of them had no effect on its growth. S. equorum, which did not grow in CSS, favored the implantation of P. phosphoreum but prevented its off-odor formation. L. piscium was the only strain that prevented the spoilage of B. thermosphacta and S. proteamaculans although it did not grow very well and did not acidify the product. L. gelidum EU2247 inhibited the growth of these 2 SSOs and lowered the pH but had no effect on the sensory quality. Finally, L. piscium was tested in 2 naturally contaminated products, with a positive effect on 1 batch. This effect was not correlated with the microbial ecosystem as determined by acultural and cultural techniques. Based on these results, the selection strategy is discussed

Lactic acid bacteria selection for biopreservation as a part of hurdle technology approach applied on seafood

As fragile food commodities, microbial and organoleptic qualities of fishery and seafood can quickly deteriorate. In this context, microbial quality and security improvement during the whole food processing chain (from catch to plate), using hurdle technology, a combination of mild preserving technologies such as biopreservation, modified atmosphere packaging and superchilling, are of great interest. Thirty-five lactic acid bacteria (LAB) belonging to the species Carnobacterium maltaromaticum, Carnobacterium inhibens, Lactococcus piscium, Leuconostoc gelidum, Vagococcus fluvialis, Vagococcus penaei and Aerococcus viridans, known to possess interesting antimicrobial activity, were chosen for their potential application as bioprotective agents as a part of hurdle technology applied to fishery products. The selection approach was based on 7 criteria including antimicrobial activity, alteration potential, resistance to chitosan coating and superchilling process, cross inhibition, biogenic amines production (histamine, tyramine) and antibiotics resistance. Antimicrobial activity was assessed against 6 common spoiling bacteria in fishery products (Shewanella baltica, Photobacterium phosphoreum, Brochothrix thermosphacta, Lactobacillus sakei, Hafnia alvei, Serratia proteamaculans) and 1 pathogenic bacteria (Listeria monocytogenes) in co-culture inhibitory assays miniaturized in 96-well microtiter plates. Antimicrobial activity and spoilage evaluation, both performed in cod and salmon juice, highlighted the existence of sensory signatures and inhibition profiles, which seem to be species related. Finally 6 LAB with no unusual antibiotics resistance profile nor histamine production ability were selected as bioprotective agents for further in situ inhibitory assays in cod and salmon based products, alone or in combination with other hurdles (chitosan, modified atmosphere packing and superchilling)

Effect of vacuum and modified atmosphere packaging on the microbiological, chemical and sensory properties of tropical red drum ( Sciaenops ocellatus ) fillets stored at 4 °C

Aims The effect of vacuum (VP – 4 °C) and CO2/N2–atmosphere (MAP – 4 °C) packaging on the quality of red drum fillets compared with whole gutted iced fish was investigated. Methods and results A metagenomic approach, bacterial enumeration and isolation, biochemical and sensory analyses were carried out. The organoleptic rejection of whole fish was observed at day 15 whereas VP and MAP fillets appeared unacceptable only after 29 days. At these dates, total mesophilic counts reached 107–108 CFU g− 1. According to Illumina MiSeq sequencing, Arthrobacter, Chryseobacterium, Brevibacterium, Staphylococcus and Kocuria were the main genera of the fresh red drum fillets. At the sensory rejection time, lactic acid bacteria (LAB), particularly Carnobacterium sp., dominated the microbiota of both types of packaging. The pH value of fresh samples was between 5.96 and 6.37 and did not vary greatly in all trials. Total volatile basic nitrogen (TVBN) and trimethylamine (TMA) concentrations were low and not represent reliable indicators of the spoilage, contrary to some biogenic amines (cadaverine, putrescine and tyramine). Conclusion Chilled packed fillets of red drum have an extended shelf-life compared to whole gutted iced fish. Overall, few differences in sensory and microbial quality were observed between the VP and MAP samples. Significance and impact of the study Next-Generation Sequencing (NGS) provided data on the microbiota of a tropical fish

Improving simultaneously the quality and safety of cooked and peeled shrimp using a cocktail of bioprotective lactic acid bacteria

Tropical shrimp is of considerable economic importance in the word but is highly perishable due to microbial and chemical degradation. Biopreservation is a food preservation technology based on the addition of “positive” bacteria able to kill or prevent the growth of undesirable microorganisms. Two strains of lactic acid bacteria (LAB) have previously been selected for a biopreservation strategy: Lactococcus piscium CNCM I-4031, for its ability to prevent the sensory deterioration of seafood and Carnobacterium divergens V41, which inhibits growth of Listeria monocytogenes. The objective was to test the association of the two strains to improve both the quality and safety of shrimp. In a first trial, the two LAB were inoculated alone or in a cocktail in cooked and peeled shrimp (CPS) Penaeus vannamei at 5 × 105 CFU/g. Chemical, sensory and microbiological analyses by culture-dependent and -independent methods were performed during storage under modified atmosphere packaging (MAP) at 8 °C. The results were compared to a non-inoculated batch. In a second trial, the same experiments were repeated in the presence of 102 CFU/g of L. monocytogenes RF191. The microbiota of CPS was composed of LAB, Shewanella spp. and Enterobacteriaceae. Brochothrix thermosphacta was not detected. L. piscium and C. divergens reached 108 and 109 CFU/g, respectively, in 7 days and did not inhibit each other when co-inoculated. L. piscium reduced L. monocytogenes by 1 Log (CFU/g) for 28 days. C. divergens had an immediate listericidal effect lasting 7 days. A regrowth of L. monocytogenes was then observed but the count was always 2 to 5 Log (CFU/g) lower than in the control. No additional or synergic effect between protective strains was observed and the cocktail had the same inhibitory effect as C. divergens alone. C. divergens was very effective at preventing the sensory deterioration of CPS. This may be related to the inhibition of Shewanella and Enterobacteriaceae. However, the panelists could detect the presence of C.divergens during the first 10 days of storage, with slight unpleasant odors and flavors. L. piscium improved the sensory quality of CPS for 14 days only. In co-culture, L. piscium eliminated the off-odors and flavors released by C. divergens in the early stage of storage and the co-culture allowed maintaining a good quality of CPS throughout the storage. Therefore, the use of a cocktail of L. piscium CNCM I-4031 and C. divergens V41 is recommended in a strategy of biopreservation of shrimp

The effect of algae diets ( Skeletonema costatum and Rhodomonas baltica ) on the biochemical composition and sensory characteristics of Pacific cupped oysters ( Crassostrea gigas ) during land-based refinement

Oyster refinement, a common practice in France, is aimed at increasing the weight of oyster tissue and influencing the taste properties of the refined oysters. Refinement usually takes place in land-based systems where the oysters are fed with relatively high concentrations of microalgae. In this study the impact of feeding Skeletonema costatum and Rhodomonas baltica on the biochemical composition and sensory characteristics of Pacific cupped oysters (Crassostrea gigas) from the Eastern Scheldt during land-based refinement was studied. After a feeding period of four and seven weeks market-sized oysters were sampled for the analysis of fatty acids, free amino acids and volatile organic compounds and for a sensory evaluation by consumers and an expert panel. The algae Skeletonema costatum showed a lower ∑ PUFA, ∑ n − 3, ∑ n − 6, C18:2n6, C18:3n3, C18:4n3, C22:6n3 content as compared with Rhodomonas baltica. These differences were also reflected in the fatty acid profile of the oysters fed with the corresponding algae diets. Furthermore, general linear model and principal component analysis showed marked differences in free amino acids and volatile organic compound content between Skeletonema, Rhodomonas fed oysters and reference oysters. For example, threonine, glutamine, leucine, histidine, (E)-2-hexenal, (E)-2octenal, (E)-2-octen-1-ol, (E,E)-2,4-octadien-1-ol, (E,Z)-3,6-nonadien-1-ol and (Z,E)-2,6-nonadienal contents were higher in Skeletonema fed oysters compared to Rhodomonas fed oysters. Sensory differences between the experimental oyster groups were shown. Skeletonema fed Pacific cupped oysters were characterized by a stronger seaweed flavor, higher perceived sweetness and a firmer texture in comparison with Rhodomonas fed oysters. Naïve consumers were only able to differentiate between Rhodomonas fed oysters and reference oysters

Characterisation of the spoilage microbiota in raw salmon (Salmo salar) steaks stored under vacuum or modified atmosphere packaging combining conventional methods and PCR-TTGE

International audienceIn order to characterise the spoilage related to microbiota of raw salmon, a combination of culture-dependent and -independent methods, including PCR-TTGE, was used to analyse 3 raw salmon batches stored for 3 days at chilled temperature in modified atmosphere packaging (MAP) (50% CO2/50% N-2) or under vacuum. Sensory evaluation, microbiological enumeration and chemical analysis were performed after 3, 7 and 10 days of storage. At the onset of spoilage, 65 bacterial isolates were picked from the plates. Thus, 13 different genera or species were identified by phenotypic and molecular tests: Serratia spp., Photobacterium phosphoreum, Yersinia intermedia, Hafnia alvei, Buttiauxella gaviniae, Pseudomonas sp., Carnobacterium maltaromaticum, Carnobacterium divergens, Lactococcus piscium, Lactobacillus fuchuensis, Vagococcus carniphilus, Leuconostoc gasicomitatum and Brochothrix thermosphacta. The PCR-TTGE profiles and band identification enabled a shift of the dominant populations during the storage to be visualised for all the batches, probably due to the temperature change and the packaging. At the beginning of storage, Pseudomonas sp. dominated the raw salmon microbiota while in the following days (7 and 10), P. phosphoreum and L piscium were identified as the main bacterial groups. This study enhances the knowledge of MAP and vacuum-packed raw salmon spoilage microbiota. (C) 2011 Elsevier Ltd. All rights reserved