Modelling the effect of temperature and CO 2 on microbial spoilage of chilled gilthead seabream fillets

The effect of temperature (0-15°C) and CO 2 (0-80%) on the growth of spoilage bacteria (total viable count, Pseudomonas sp. and lactic acid bacteria) in marine cultured gilthead seabream fillets was studied and kinetically modelled using an Arrhenius type equation. Pseudomonas sp. dominated the spoilage microflora of aerobically packed fillets whereas LAB defined spoilage at the MAP conditions. Modified atmosphere packaging led to a significant shelf-life extension of fillets, in terms of microbial growth and organoleptic deterioration. The preservative effect of CO 2 was greater as the CO 2 concentration in the atmosphere increased. Under this context, MAP can practically extend the shelf life of chilled gilthead seabream fillets. The growth of LAB was modelled as a function of temperature and CO 2 concentration in modified atmosphere packaging. The applicability of the models was validated at fluctuating temperature conditions. The nominal maximum CO 2 concentration (CO 2,max) for growth and the specific growth rate (k ref) at T ref (4°C) in the absence of carbon dioxide were determined to be 98.3% and 0.015 h -1, respectively. The activation energy parameter of the model, which indicates the temperature dependence of the growth rates, was 101.0 kJ/mol showing a strong dependence of LAB growth on storage temperature. Based on organoleptic acceptability the end of shelf life coincided with 10 7/g Pseudomonas sp. and 10 6/g lactobacilli for aerobically and MAP stored samples respectively. Based on the developed models this translates to 7, 8, 12 and 32 days of shelf life at 5°C and 0, 20, 50 and 80% CO 2 respectively

Modelling the effect of temperature and CO2 on microbial spoilage of chilled gilthead seabream fillets

The effect of temperature (0-15°C) and CO 2 (0-80%) on the growth of spoilage bacteria (total viable count, Pseudomonas sp. and lactic acid bacteria) in marine cultured gilthead seabream fillets was studied and kinetically modelled using an Arrhenius type equation. Pseudomonas sp. dominated the spoilage microflora of aerobically packed fillets whereas LAB defined spoilage at the MAP conditions. Modified atmosphere packaging led to a significant shelf-life extension of fillets, in terms of microbial growth and organoleptic deterioration. The preservative effect of CO 2 was greater as the CO 2 concentration in the atmosphere increased. Under this context, MAP can practically extend the shelf life of chilled gilthead seabream fillets. The growth of LAB was modelled as a function of temperature and CO 2 concentration in modified atmosphere packaging. The applicability of the models was validated at fluctuating temperature conditions. The nominal maximum CO 2 concentration (CO 2,max) for growth and the specific growth rate (k ref) at T ref (4°C) in the absence of carbon dioxide were determined to be 98.3% and 0.015 h -1, respectively. The activation energy parameter of the model, which indicates the temperature dependence of the growth rates, was 101.0 kJ/mol showing a strong dependence of LAB growth on storage temperature. Based on organoleptic acceptability the end of shelf life coincided with 10 7/g Pseudomonas sp. and 10 6/g lactobacilli for aerobically and MAP stored samples respectively. Based on the developed models this translates to 7, 8, 12 and 32 days of shelf life at 5°C and 0, 20, 50 and 80% CO 2 respectively

Modelling the effect of temperature and CO 2 on microbial spoilage of chilled gilthead seabream fillets

The effect of temperature (0-15°C) and CO 2 (0-80%) on the growth of spoilage bacteria (total viable count, Pseudomonas sp. and lactic acid bacteria) in marine cultured gilthead seabream fillets was studied and kinetically modelled using an Arrhenius type equation. Pseudomonas sp. dominated the spoilage microflora of aerobically packed fillets whereas LAB defined spoilage at the MAP conditions. Modified atmosphere packaging led to a significant shelf-life extension of fillets, in terms of microbial growth and organoleptic deterioration. The preservative effect of CO 2 was greater as the CO 2 concentration in the atmosphere increased. Under this context, MAP can practically extend the shelf life of chilled gilthead seabream fillets. The growth of LAB was modelled as a function of temperature and CO 2 concentration in modified atmosphere packaging. The applicability of the models was validated at fluctuating temperature conditions. The nominal maximum CO 2 concentration (CO 2,max) for growth and the specific growth rate (k ref) at T ref (4°C) in the absence of carbon dioxide were determined to be 98.3% and 0.015 h -1, respectively. The activation energy parameter of the model, which indicates the temperature dependence of the growth rates, was 101.0 kJ/mol showing a strong dependence of LAB growth on storage temperature. Based on organoleptic acceptability the end of shelf life coincided with 10 7/g Pseudomonas sp. and 10 6/g lactobacilli for aerobically and MAP stored samples respectively. Based on the developed models this translates to 7, 8, 12 and 32 days of shelf life at 5°C and 0, 20, 50 and 80% CO 2 respectively

Monitoring the effect of high pressure and transglutaminase treatment of milk on the evolution of flavour compounds during lactic acid fermentation using PTR-ToF-MS

In this study, the effects of thermal or high hydrostatic pressure (HHP) treatment of a milk base in the absence or presence of a transglutaminase (TGase) protein cross-linking step on the flavour development of yoghurt were investigated. The presence of several tentatively identified volatile flavour compounds (VOCs), both during the enzymatic treatment and the lactic acid fermentation of the milk base, were monitored using a proton transfer reaction time-of-flight mass spectrometer (PTR-ToF-MS). The formation of the major flavour compounds (acetaldehyde, diacetyl, acetoin, and 2-butanone) followed a sigmoidal trend described by the modified Gompertz model. The HHP treatment of milk increased significantly the volatile compound formation rate whereas it did not affect the duration of the lag phase of formation, with the exception of acetaldehyde and diacetyl formation. On the contrary, the TGase cross-linking of milk did not significantly modify the formation rate of the volatile compounds but shortened the duration of the lag phase of their formatio

Rheological, textural, physicochemical and sensory profiling of a novel functional ice cream enriched with Muscat de Hamburg (Vitis vinifera L.) grape pulp and skins

The scope of the present work was the development of an ice cream containing substantial amount of phenolic compounds by substituting sucrose by a Muscat de Hamburg grape pulp and skin matter (GPSM)-enriched bulking agent at the level of 25 to 100% w/w. Sucrose replacement by GPSM reinforced the pseudoplastic and thixotropic character of the ice cream mixes imparting weak gel-like properties (G′ > G′′). Oscillatory thermo-mechanical analysis revealed the occurrence of a β-relaxation peak at − 17 to − 12.8 °C, whilst a slight depression of the freezing point was observed. The increase in GPSM solids resulted in a significant increase in the instrumental hardness and overrun of ice cream samples, whilst it enhanced their meltdown resistance. Although GPSM boosted the nutritional value and flavour profile of the ice cream, when sucrose substitution exceeded 50%, undesirable sensory characteristics, such as coarse/grainy texture, bitterness and astringency, were detecte

Mead fermentation monitoring by proton transfer reaction mass spectrometry and medium infrared probe

Mead is a traditional alcoholic beverage similar to wine, but obtained by the fermentation of a diluted solution of honey. The rate of fermentation is generally monitored by the measurement of a set of physicochemical variables such as pH, titratable acidity, Brix degrees, sugars and ethanol concentration. This work aims at developing a new monitoring method for alcoholic fermentations that is based on two on-line approaches: a proton transfer reaction mass spectrometry (PTR-MS) and a fibre optic coupled attenuated total reflection (FTIR-ATR) spectroscopy. Microfermentations are performed on 100 mL musts in isothermal conditions at 20 °C. Musts consist on diluted honey solutions (24 Bx) with pollen (0.4 % w/v) and yeast (Saccharomyces cerevisiae subsp. bayanus). The effect of flavour enhancers [chilli (Capsicum annuum), clove (Eugenia caryophyllata) and a mixture of both] on the rate of fermentation was also evaluated. The results show that clove inhibits fermentation, whereas chilli increases the rate of fermentation. PTR-MS and FTIR-ATR are simple, fast and nondestructive techniques able to monitor the fermentation process without the need of sample preparation, extraction or pre-concentration steps