RESUMEN
In this study, in situ-expressed metabolic routes of Brochothrix (B.) thermosphacta and Carnobacterium (C.) divergens were evaluated based on a metatranscriptomic dataset from bacteria growing on MAP chicken meat (O2/CO2; N2/CO2). Both species exhibited no (C. divergens) or minor transcription regulation (B. thermosphacta) within their main metabolic routes in response to different atmospheres. Both employ pathways related to glucose and ribose. Gluconeogenesis from lipid-borne glycerol is active in the progressing lack of carbohydrates. Pyruvate fates in both species comprise lactate, ethanol, acetate, CO2, formate, C4-compounds and H2O2 (only B. thermosphacta). Both species express genes for a minimal aerobic respiratory chain, but do not possess the genetic setting for a functional citric acid cycle. While products of carbohydrate and glycerol metabolism display mild to medium sensorial off-characteristics, predicted end products of their amino acid metabolism comprise, e.g., isobutyrate and isovalerate (B. thermosphacta) or cadaverine and tyramine (C. divergens) as potent spoilage compounds.
Asunto(s)
Brochothrix/fisiología , Carnobacterium/fisiología , Microbiología de Alimentos/métodos , Embalaje de Alimentos/normas , Carne/microbiología , Transcriptoma , Animales , Atmósfera , Recuento de Colonia Microbiana , Peróxido de Hidrógeno/metabolismo , Aves de CorralRESUMEN
This study examined the growth characteristics of Listeria monocytogenes as affected by a native microflora in cooked ham at refrigerated and abuse temperatures. A five-strain mixture of L. monocytogenes and a native microflora, consisting of Brochothrix spp., isolated from cooked meat were inoculated alone (monocultured) or co-inoculated (co-cultured) onto cooked ham slices. The growth characteristics, lag phase duration (LPD, h), growth rate (GR, log(10) cfu/h), and maximum population density (MPD, log(10) cfu/g), of L. monocytogenes and the native microflora in vacuum-packed ham slices stored at 4, 6, 8, 10, and 12 °C for up to 5 weeks were determined. At 4-12 °C, the LPDs of co-cultured L. monocytogenes were not significantly different from those of monocultured L. monocytogenes in ham, indicating the LPDs of L. monocytogenes at 4-12 °C were not influenced by the presence of the native microflora. At 4-8 °C, the GRs of co-cultured L. monocytogenes (0.0114-0.0130 log(10) cfu/h) were statistically but marginally lower than those of monocultured L. monocytogenes (0.0132-0.0145 log(10) cfu/h), indicating the GRs of L. monocytogenes at 4-8 °C were reduced by the presence of the native microflora. The GRs of L. monocytogenes were reduced by 8-7% with the presence of the native microflora at 4-8 °C, whereas there was less influence of the native microflora on the GRs of L. monocytogenes at 10 and 12 °C. The MPDs of L. monocytogenes at 4-8 °C were also reduced by the presence of the native microflora. Data from this study provide additional information regarding the growth suppression of L. monocytogenes by the native microflora for assessing the survival and growth of L. monocytogenes in ready-to-eat meat products.
Asunto(s)
Brochothrix/fisiología , Recuento de Colonia Microbiana , Manipulación de Alimentos/métodos , Listeria monocytogenes/crecimiento & desarrollo , Carne/microbiología , Animales , Antibiosis , Técnicas de Cocultivo , Seguridad de Productos para el Consumidor , Contaminación de Alimentos , Embalaje de Alimentos/métodos , Humanos , Cinética , Refrigeración , Porcinos , TemperaturaRESUMEN
Rosemary essential oil (REO) contains bioactives having antioxidant and antimicrobial properties. This work investigated the effect of REO combined with modified atmosphere packaging conditions (MAP), in our case, aerobic, vacuum or high O2, to extend the shelf life of beef. Beef slices were wrapped in special three-layer sheets of packaging material, some with a coating of REO (active packaging, AP), and some without REO (non active packaging, NAP), and stored at 4°C for 20days. The use of REO proved efficacious in every storage condition, as seen in the lower counts of psychrotrophics, Brochothrix thermosphacta, Pseudomonas spp., and Enterobacteriaceae in AP meat compared to NAP meat. Sensory and colourimetric analyses showed that the best packaging conditions were high-O2 atmosphere in combination with REO. Based on microbiological data, shelf life of beef was 5-6days for AP samples packaged under aerobic conditions and 14-15days for AP samples in high-O2 conditions.
Asunto(s)
Embalaje de Alimentos/métodos , Conservación de Alimentos/métodos , Aceites Volátiles/administración & dosificación , Carne Roja/análisis , Refrigeración/métodos , Rosmarinus , Animales , Atmósfera/análisis , Brochothrix/efectos de los fármacos , Brochothrix/fisiología , Bovinos , Recuento de Colonia Microbiana/métodos , Microbiología de Alimentos/métodos , Aceites Volátiles/aislamiento & purificación , Componentes Aéreos de las Plantas , Carne Roja/microbiología , VacioRESUMEN
The performance of a multispectral imaging system has been evaluated in monitoring aerobically packaged beef filet spoilage at different storage temperatures (0, 4, 8, 12, and 16°C). Spectral data in the visible and short wave near infrared area (405-970nm) were collected from the surface of meat samples and correlated with microbiological data (log counts), for total viable counts (TVCs), Pseudomonas spp., and Brochothrix thermosphacta. Qualitative analysis (PLS-DA) was employed for the discrimination of meat samples in three microbiological quality classes based on the values of total viable counts, namely Class 1 (TVC<5.5log10CFU/g), Class 2 (5.5log10CFU/g
Asunto(s)
Manipulación de Alimentos , Microbiología de Alimentos/métodos , Carne/microbiología , Imagen Óptica/normas , Animales , Brochothrix/fisiología , Calibración , Bovinos , Recuento de Colonia Microbiana , Pseudomonas/fisiología , Análisis de Regresión , Reproducibilidad de los Resultados , TemperaturaRESUMEN
This study investigated the sensory quality and physicochemical evolution (pH, glucose, l-lactic acid, biogenic amine, free amino-acids and volatile compounds) during storage at 8°C of cooked peeled shrimp inoculated with the specific spoilage bacteria Brochothrix thermosphacta alone or mixed with the protective strain Lactococcus piscium CNCM I-4031. Growth of both bacteria was monitored at regular intervals during storage by microbial counts and the thermal temperature gradient gel electrophoresis (TTGE) technique. Bacterial counts showed that L. piscium and B. thermosphacta inoculated at 7 log CFU/g and 3 log CFU/g were well adapted to shrimp, reaching a maximum level of 9 log CFU/g after 4days and 10days respectively. In mixed culture, the growth of B. thermosphacta was reduced by 3.2±0.1 log CFU/g. The TTGE technique allowed monitoring the colonisation of the strains on the shrimp matrix and confirming the dominance of L. piscium in mixed culture throughout the experiment. Sensory analysis confirmed that B. thermosphacta spoiled the product after 11days, when its cell number attained 8 log CFU/g with the emission of strong butter/caramel off-odours. This sensory profile could be linked to the production of 2,3 butanedione, cyclopentanol, 3-methylbutanol, 3-methylbutanal, 2-methylbutanal, 4-methyl-3-chloro-3-pentanol and ethanol, which were produced in more significant quantities in the B. thermosphacta batch than in the batches in which the protective strain was present. On the contrary, TVBN and TMA were not suitable as quality indicators for B. thermosphacta spoilage activity. In the products where the protective L. piscium strain was present, no adverse effect on sensory quality was noted by the sensory panels. Moreover, biogenic amine assessment did not show any histamine or tyramine production by this strain, underlining its safety profile. Both strains produced lactic acid (1850mg/kg in L. piscium and B. thermosphacta batch on days 3 and 10 respectively; 3830mg/kg on day 7 in mixed culture) and the pH decrease from 6.6±0.0 to 5.9±0.1 was similar in all batches. Lactic acid production or competition for free amino-acid was not involved in the inhibition mechanism; however rapid glucose consumption by L. piscium could partially explain the growth limitation of the spoilage micro-organism. This study demonstrated the spoilage characteristic of B. thermosphacta and the usefulness of L. piscium as a bioprotective culture for tropical cooked peeled shrimp without any adverse effect on the sensory quality of the product.