This work aimed to quantify the impact of aw and fat content of dry-cured ham on the Log reduction of Salmonella enterica by high pressure (HP). Dry-cured ham with adjusted aw (0.86–0.96) and fat ...content (10–50%) was inoculated with S. enterica and pressurised (347–852MPa, 5min/15°C), following a Central Composite Design. Polynomial regression indicated a significant impact of pressure and aw on S. enterica HP-lethality. By lowering aw a clear piezoprotection was observed. At low aw (0.88) the S. enterica reduction was little affected by increasing pressure (e.g. 2.3 to 3.2 Logs at 450 to 750MPa, respectively). At the highest aw the estimated inactivation ranged from 3.3 to 8.9 Logs at 450 to 750MPa, respectively. No significant piezoprotective effect on S. enterica was recorded by the fat content. The relevance of food characteristics on the HP-lethality of S. enterica indicate the need to validate the HP effectiveness on the specific product.
•A product oriented approach was applied to quantify the effect of aw and fat on S. enterica HP- lethality.•The empirical response surface methodology was applied as the modeling procedure.•The piezoprotection of aw was quantitatively stronger at increasing pressure.•The effect of fat was not significant, thus this factor was not included in the model.•Process criteria for cold-pasteurisation to meet the safety standards were estimated.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The aim of this study was the evaluation of the effects of pure citral and citron essential oil on microbial spoilage and growth and survival of pathogenic microorganisms during storage. They were ...added in the syrup of industrial ready‐to‐eat fruit salads stored at 9 °C. Both citral (25 to 125 ppm) and citron essential oil (300, 600, 900 ppm) were able to prolong the microbial shelf life of the fruit‐based salads. The essential oil gave excellent results, avoiding the undesirable effects attributable to the cytotoxicity of citral. Citron essential oil doubled the time needed for the wild microflora to reach concentrations able to produce a perceivable spoilage in condition of thermal abuse (9 °C). The same essential oil had reduced effects on the survival of Gram‐negative species Salmonella Enteritidis and Escherichia coli, but showed a strong inhibition toward the Gram‐positive pathogen Listeria monocytogenes.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The aim of the work was to develop and validate a model of the inactivation of
Listeria monocytogenes on dry-cured ham by high hydrostatic pressure (HHP) processing, as a function of the ...technological parameters: intensity, length and fluid temperature. Dry-cured ham inoculated with
L. monocytogenes was treated at different HHP conditions (at 347–852 MPa; for 2.3 to 15.75 min; at 7.6 to 24.4 °C) following a central composite design. Bacterial inactivation was assessed in terms of logarithmic reductions of
L. monocytogenes counts on selective media. According to the best fitting and most significant polynomial equation, pressure and time were the most important factors determining the inactivation extent. The significance of the quadratic term of pressure and time indicated that little effect was observed below 450 MPa, whereas holding time longer than 10 min did not result in a meaningful reduction of
L. monocytogenes counts. Temperature did not show significant influence at the range assayed. The model was validated with results obtained from further experiments and bibliographical data within the range of the experimental domain. The accuracy factor and bias factor were within the proposed acceptable values indicating the suitability of the model for predictive purposes, such as prediction of the process criteria to meet the Food Safety Objectives. The results of this work may help food processors to select optimum processing conditions of HHP.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
High pressure processing (HPP) is a promising food preservation technology as an alternative to thermal processing for microbial inactivation. The technological parameters, the type of microorganism, ...and the food composition can greatly affect the microbicidal potential of HPP against spoilage and pathogenic microorganisms. Presently, the number of available models quantifying the influence of food characteristics on the pathogen inactivation is scarce. The aim of this study was to model the inactivation of Listeria monocytogenes CTC1034 in dry-cured ham, as a function of pressure (347–852MPa, 5min/15°C), water activity (aw, 0.86–0.96) and fat content (10–50%) according to a Central Composite Design. The response surface methodology, based on the equation obtained with a stepwise multivariate linear regression, was used to describe the relationship between bacterial inactivation and the studied variables. According to the best fitting polynomial equation, besides pressure intensity, both aw and fat content exerted a significant influence on HP-inactivation of L. monocytogenes. A clear linear piezoprotection trend was found lowering the aw of the substrate within the whole range of tested pressure. Fat content was included in the model through the quadratic term and as interaction term with pressure, resulting in a particular behavior. A protective effect due to the presence of high fat content was identified for pressure treatments above ca. 700MPa. At lower pressure, higher inactivation of L. monocytogenes occurred by increasing the fat content above 30%. The results emphasize the relevant influence of intrinsic factors on the L. monocytogenes inactivation by HPP, making necessary to assess and validate the effectiveness of HPP on specific food products and consequently set process criteria adjusted to each particular food product.
•A product oriented approach was applied to assess the effect of aw and fat on L. monocytogenes HP-inactivation.•The empirical response surface methodology was applied as the modeling procedure.•A linear piezoprotection was observed by lowering the aw values of dry-cured ham.•The protective effect of fat was dependent on the pressure level.•Process criteria for cold-pasteurization to meet the safety standards were estimated.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Minimally processed fruits are an important area of potential growth in rapidly expanding fresh cut produce. However, the degree of safety obtained with the currently applied preservation methods ...seems to be not sufficient. The interest in the possible use of natural compounds to prevent microbial growth has notably increased in response to the consumer pressure to reduce or eliminate chemically synthesized additives in foods. The aim of this work is to give an overview on the application of natural compounds, such as hexanal, 2-(E)-hexenal, hexyl acetate and citrus essential oils, to improve the shelf-life and the safety of minimally processed fruits as well as their mechanisms of action.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
High pressure processing (HPP) is a promising food preservation technology as an alternative to thermal processing for microbial inactivation. The technological parameters, the type of microorganism, ...and the food composition can greatly affect the microbicidal potential of HPP against spoilage and pathogenic microorganisms. Presently, the number of available models quantifying the influence of food characteristics on the pathogen inactivation is scarce. The aim of this study was to model the inactivation of Listeria monocytogenes CTC1034 in dry-cured ham, as a function of pressure (347-852MPa, 5min/15°C), water activity (a
, 0.86-0.96) and fat content (10-50%) according to a Central Composite Design. The response surface methodology, based on the equation obtained with a stepwise multivariate linear regression, was used to describe the relationship between bacterial inactivation and the studied variables. According to the best fitting polynomial equation, besides pressure intensity, both a
and fat content exerted a significant influence on HP-inactivation of L. monocytogenes. A clear linear piezoprotection trend was found lowering the a
of the substrate within the whole range of tested pressure. Fat content was included in the model through the quadratic term and as interaction term with pressure, resulting in a particular behavior. A protective effect due to the presence of high fat content was identified for pressure treatments above ca. 700MPa. At lower pressure, higher inactivation of L. monocytogenes occurred by increasing the fat content above 30%. The results emphasize the relevant influence of intrinsic factors on the L. monocytogenes inactivation by HPP, making necessary to assess and validate the effectiveness of HPP on specific food products and consequently set process criteria adjusted to each particular food product.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
To quantify the inactivation of Serratia liquefaciens exerted by high pressure processing (HPP), slices of dry-cured ham were inoculated and processed combining different levels of technological ...parameters: pressure (347–852 MPa), time (2.3–15.8 min) and temperature (7.6–24.4 °C) according to a central composite design. Bacterial inactivation, as logarithmic reduction, indicated that S. liquefaciens was relatively sensitive to HPP. Six log reductions were achieved in a total of 10 trials combining pressures of 600 MPa or above with different holding times and temperatures. The inactivation of S. liquefaciens was analysed through the multiple regression analysis to generate a second order polynomial equation. Pressure and time were the two factors which significantly determined the inactivation of S. liquefaciens on dry-cured ham. Temperature did not significantly affect the lethality of the process. The response surface methodology was used to determine optimum process conditions to maximize the inactivation of S. liquefaciens in the experimental range tested. The maximum inactivation of S. liquefaciens in dry-cured ham was achieved by combining a pressure of 650 MPa with a holding time of 8 min. Combinations above these values (i.e. 750 MPa for 13 min) would not significantly improve the lethality of the process.
► Serratia liquefaciens was relatively sensitive to HPP on dry-cured ham. ► S. liquefaciens inactivation on dry-cured ham depended on pressure and holding time. ► The temperature (7.6–24.4 °C) did not significantly affect the process lethality. ► More than 6-log reductions can be obtained at pressures from 600 MPa. ► Process criteria to reduce pathogens allow the inactivation of S. liquefaciens.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
This research was conducted to determine the biogenic amine (BA) and ethyl carbamate (EC) concentrations in commercial Primitivo wine samples and the influence of the use of malolactic starter ...culture on concentrations of these potentially hazardous compounds in this wine. One hundred sixty bottles of wine from eight producers in the Apulia region of southern Italy were purchased at retail and analyzed. The most common BAs were histamine, 2-phenylethylamine, tyramine, cadaverine, putrescine, spermine, and spermidine. Putrescine (derived from ornithine) was the most abundant BA in all commercial Primitivo wines (5.41 to 9.51 mg/liter), 2-phenylethylamine was detected in only two commercial wines (at less than 2.12 mg/liter), and histamine was found at concentrations of 1.49 to 16.34 mg/liter. The concentration of EC in commercial Primitivo wine was 6.81 to 15.62 ppb, which is not considered dangerous for human health. Malolactic fermentation (MLF) affected the concentrations of BAs and EC differently. For EC, no significant differences were detected between samples of wine produced by spontaneous fermentation and wine that was inoculated malolactic starter. Mean EC concentrations were 12 and 14 ppb in two batches tested (always 18 ppb or less), regardless of whether the malolactic starter was added. Although present at trace levels in wine before the MLF, histamine accumulated during the MLF process, regardless of whether the malolactic starter was added. However, the increase in histamine was higher in wines without the malolactic starter. The concentrations of putrescine and cadaverine increased after MLF, especially in the wine that spontaneously fermented. The use of a selected malolactic starter resulted in reductions in BA concentrations in wine produced by this guided MLF compared with wine produced by spontaneous MLF.
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CEKLJ, GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The effect of high pressure processing parameters on the inactivation of a potentially virulent Enterococcus faecalis strain inoculated on sliced dry-cured ham was investigated. The response surface ...methodology was applied in combination with a central composite design of the technological parameters: including pressure (347–852MPa), length of the treatment (2.3–15.8min) and temperature (7.6–24.4°C). Bacterial inactivation, as logarithmic reductions of Enterococcus spp. counts, was modeled through the backward stepwise procedure. According to the best fitting and most significant polynomial equation, pressure and time were the factors determining the Enterococcus inactivation, while temperature was not statistically significant. E. faecalis showed a notable resistance to high pressure processing, similar to that reported for Staphylococcus aureus and higher than the baroresistance of pathogens such as Listeria monocytogenes or Salmonella. To achieve 4 log reduction of E. faecalis on dry-cured ham, pressures from 750MPa for at least 9.5min would be required.
The results of this work can help food processors to set optimum technological parameters of high pressure processing to inactivate undesired microorganisms in food.
► The effect of technological parameters pressure, time and fluid temperature was mathematically modeled. ► Pressure and holding time were the significant factors included in the polynomial equation. ► E. faecalis on dry-cured ham showed a high baroresistance. ► 4 log reduction requires pressures of 750MPa (for 9.5min) or higher. ► The model can be a useful tool for the optimization of HPP in the food industry.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The aims of this work were to identify and characterize for some important technological properties the yeast species present throughout the ripening process of Pecorino Crotonese, a traditional ...cheese produced in a well defined area of Southern Italy. In particular, the strain technological properties considered include fermentation/assimilation of galactose and lactose, assimilation of lactate and citrate in the presence of different NaCl concentrations, hydrolysis of butter fat, skim milk, gelatine and casein, production of brown pigments in cheese agar and ability to produce biogenic amines. High yeast levels were recorded in cheese samples already after 5
h of brining (about 5
log
cfu/g) and these concentration remained constant during ripening. The yeast isolates belonged to restrict number of yeast species. While
Kluyveromyces lactis and
Saccharomyces cerevisiae were isolated prevalently in the first stages of Pecorino Crotonese production,
Yarrowia lipolytica and
Debaryomyces hansenii dominated during the later stages of maturation. Otherwise, the latter two were very NaCl resistant species. In fact,
D. hansenii strains conserved the ability to assimilate lactose and galactose in the presence of 10% NaCl, while almost all the strains of
Y. lipolytica isolated assimilated citrate and lactate up to 7.5% NaCl.
Y. lipolytica isolates evidenced also the highest proteolytic and lipolytic activities and the capability to catabolize tyrosine producing brown pigment. In addition they resulted in the highest aminobiogenic potential decarboxylating ornithine, phenylalanine, tyrosine and lysine. However, they were not able to produce histamine, biogenic amine produced by three strains of
D. hansenii.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
