Combined effects of antimicrobial coating, modified atmosphere packaging, and gamma irradiation on Listeria innocua present in ready-to-use carrots (Daucus carota)

Safety achievement and shelf-life prolongation of poultry breast meats by polylactic acid active packaging and gamma-irradiation

Active packaging incorporated with volatile oils is a promising technology to extend the shelf-life of perishable food. Therefore, the present work aimed at producing composite pouches based on polylactic acid incorporated with a mixture of lemongrass and cumin essential oils (PLA/mix oil). The effect on the shelf-life of fresh poultry breasts was determined on samples packaged in the PLA/mix oil alone and in combination with gamma-irradiation, and stored under refrigeration through microbiological, physicochemical, and sensorial analyses. The effect of active packaging and gamma-irradiation on artificially inoculated foodborne bacteria (Escherichia coli O157:H7 ATCC 25922, Salmonella Enteritidis, Listeria monocytogenes ATCC 35152) in poultry breasts was evaluated. When compared to control, poultry breast samples packaged in the PLA/mix oil and irradiated at 4 kGy alone decreased microbial count, maintained colour and pH values, and increased TBARS index at a lower rate, thus extended the shelf-life by 21 and 14 d, respectively. However, the combination of PLA/mix oil and gamma-irradiation at 2 kGy (PLA/mix oil + 2 kGy) was more effective in decreasing all microbial counts and extending the shelf-life by more than 28 d. Initial load of S. Enteritidis, E. coli, and L. monocytogenes inoculated in poultry breasts decreased by 3.03, 2.98, and 3.19 log CFU/g, respectively, after 3 d of storage in PLA/mix oil packaging, while the combination between PLA/mix oil and gamma-irradiation at 2 kGy (PLA/mix oil + 2 kGy) caused a synergistic impact with an increase in radiosensitivity of S. Enteritidis, E. coli, and L. monocytogenes by 3.53, 4.47, and 4.23 log CFU/g, respectively, after one day of storage as compared to the control. Active packaging (PLA/mix oil) alone and in combination with gamma-irradiation can be considered an innovative technology that could have a major effect on the prolongation of shelf-life and safety of poultry breast meats. Moreover, this new technology represents a promising alternative to commercial and unsustainable plastic films.

The Effects of Novel Thermal and Nonthermal Technologies on the Properties of Edible Food Packaging

Edible packaging is influenced by factors such as formulation, production technology, and solvent and additive properties. With the increase in the request for coating and film quality, appropriate form, and high product safety and storage period, various technologies such as high hydrostatic pressure, irradiation, ultrasound, high-pressure homogenization, cold plasma, and microwave have been reviewed. The present study states definitions and mechanisms of novel technologies. The experimental condition, packaging matrix, and the results pertaining to the effects of these technologies on various types of edible packaging is also discussed. The most of the matrix used for packaging was whey protein, soy protein isolate, chitosan, and gelatin. The technologies conditions such as power, frequency, time, temperature, dose, pressure, and voltage can have a significant influence on the application of them in film and coating. Therefore, finding the optimum point for the features of the technologies is important because improper use of them reduces the properties of the edible packaging.

Essential Oil Nanoemulsions and their Antimicrobial and Food Applications

The consumer awareness for secure insignificantly handled food has constrained the food dealers either to decrease the measure of chemically synthetic antimicrobial substances or to replace them with natural ones. Essential oils (EO) extracted from edible, therapeutic and herbal plants have been well recognized as natural antimicrobial additives. As characteristic then viable antimicrobials, EO have been progressively observed towards control of foodborne microbes and progression of nourishment wellbeing. It is ordinarily hard to achieve high antimicrobial vulnerability when mixing with EO in nourishment based items because of low dissolvability of water and interactive binding. Subsequently, the delivery system of nanoemulsion-based EO is emerging as aviable solution to control the growth of foodborne pathogens. Lipophilic compounds are distributed uniformly in the aqueous phase with the help of nanoemulsion technique. Therefore, the nanoemulsion formulation is generally comprised of mainly three constituents i.e. oil phase, aqueous and a surfactant. Nanoemulsions droplet average diameters should below 100 nm. According to previous studies, the clove, cinnamon and thyme oil nanoemulsions which were formulated with non ionic surfactants (Spans and Tweens) were having droplet size less than 100nm. The current review emphases on essential oil based nanoemulsions which are prepared with different ingredients which hence, enhance the antimicrobial action in food items.

Effects of natural antimicrobials with modified atmosphere packaging on the growth kinetics of Listeria monocytogenes in ravioli at various temperatures

The objective of this study was to investigate the antimicrobial effects of cultured sugar/vinegar (CSV) blend and nisin to control the risk of Listeria monocytogenes in ready to cook (RTC) ravioli. Ravioli dough was prepared with 0.1, 0.3, 0.5, 1% CSV blend and 0.1, 0.2, and 0.3% nisin. Inoculated spinach or artichoke raviolis with 2.0 ± 0.5 log cfu/g of L. monocytogenes were packed aerobically or using modified atmosphere packaging (MAP), and then stored at 4, 10, 17, and 24 °C for 60 days. Growth kinetic parameters of the observed data fit well to the Baranyi equation. Ravioli with spinach filling materials yielded a higher risk than that with artichoke. L. monocytogenes was able to survive in ravioli with artichoke, but did not grow. The addition of 1% CSV blend or 0.3% nisin in spinach ravioli with the combination of MAP effectively controlled the growth of L. monocytogenes at the temperature below 10 °C. The organoleptic quality of spinach ravioli was not also affected by the application of 1% CSV blend. Therefore, the CSV blend can be recommended to improve the microbial safety and quality of natural RTC ravioli at retail market.

Practical applications

The risk of ravioli was affected by the filling materials of ravioli at retail market. Addition of 1% cultured sugar/vinegar blend in dough substantially contributes to the extension of shelf-life of MAP spinach raviolis. classification and regression tree analysis results indicate that refrigeration temperature is the main control factor to affect lag time and growth rate, while packaging method is critical for maximum population density.

Effect of combined long-term starvation and γ-irradiation on membrane fatty acids and cell surface hydrophobicity of Salmonella enterica serovar Typhimurium

This study was carried out to explore the adaptive mechanisms of Salmonella enterica serovar Typhimurium, in particular the implication of fatty acids (FA) in the remodeling of membrane lipid composition to overcome the combined effects of long-term starvation and γ-irradiation stresses. In addition, cell surface hydrophobicity was also evaluated. The bacterial strains (control and starved) were treated with a nonlethal γ-irradiation dose of 0.5 kGy and sublethal doses of 1 kGy. Gas chromatography analysis showed that the FA composition of starved and γ-irradiated cells was modified. However starvation combined with γ-irradiation induced more modifications in the FA composition than γ-irradiation or starvation alone. Indeed, the unsaturated FA-to-saturated FA ratio decreased significantly for both strains compared with γ-irradiated cells, as main consequence of the cyclic FA formation. Our results showed that starvation, irradiation, or combined stresses significantly influenced the hydrophobicity, and this may have affected the virulence state of Salmonella Typhimurium cells. This study represents one of the few to demonstrate the modifications on bacterial membrane as a cellular response to survive to the ionizing radiation combined with long-term starvation stress.

Edible packaging materials

Research groups and the food and pharmaceutical industries recognize edible packaging as a useful alternative or addition to conventional packaging to reduce waste and to create novel applications for improving product stability, quality, safety, variety, and convenience for consumers. Recent studies have explored the ability of biopolymer-based food packaging materials to carry and control-release active compounds. As diverse edible packaging materials derived from various by-products or waste from food industry are being developed, the dry thermoplastic process is advancing rapidly as a feasible commercial edible packaging manufacturing process. The employment of nanocomposite concepts to edible packaging materials promises to improve barrier and mechanical properties and facilitate effective incorporation of bioactive ingredients and other designed functions. In addition to the need for a more fundamental understanding to enable design to desired specifications, edible packaging has to overcome challenges such as regulatory requirements, consumer acceptance, and scaling-up research concepts to commercial applications.

Effect of antimicrobial coatings on the radiosensitization of Escherichia coli, Salmonella typhimurium, and Listeria monocytogenes in fresh broccoli

Radiosensitization of Listeria monocytogenes, Escherichia coli, Salmonella Typhimurium, and aerobic microflora was evaluated in broccoli florets coated by antimicrobial coatings and treated with different doses of γ-radiation. Broccoli florets were inoculated with aerobic microflora isolated from broccoli and with pathogenic bacteria (L. monocytogenes, E. coli, and Salmonella Typhimurium) at 10(6) CFU/ml. Inoculated florets were then coated with methylcellulose-based coating containing various mixtures of antimicrobial agents: organic acids plus lactic acid bacteria (LAB metabolites), organic acids plus citrus extract, organic acids plus citrus extract plus spice mixture, and organic acids plus rosemary extract. Coated florets were irradiated with various doses (0 to 3.3 kGy), and microbial analyses were conducted to calculate the D(10)-value and relative sensitivity. All antimicrobial coatings had almost the same effect of increasing the radiosensitivity of L. monocytogenes (from 1.31 to 1.45 times) to γ-irradiation. The coating containing organic acid plus citrus extract was the most efficient formulation for increasing the radiosensitization of E. coli and aerobic microflora, by 2.40 and 1.76 times, respectively, compared with the control without the antimicrobial coating. The coating containing organic acids plus LAB metabolites was the most effective formulation for increasing the radiosensitization (by 2.4 times) of Salmonella Typhimurium. Results suggest that the spice extract, when mixed with organic acids and citrus extract, might protect E. coli and aerobic microflora from the effects of γ-irradiation.

Response of Bacillus cereus to gamma-irradiation in combination with carvacrol or mild heat treatment

Carvacrol and mild heat treatment were tested for their efficiency to increase the radiosensitivity of Bacillus cereus in broth. The bacterium was treated with gamma-irradiation alone or in combination with carvacrol at its minimal inhibitory concentration or mild heat treatment for 10 min at 45 degrees C. The effects of this combination of treatments were studied on various parameters: the bacterial viability, the modifications of the cell morphology with scanning electron microscopy (SEM), the cellular fatty acids composition of the membrane quantified by gas chromatography, the intracellular and extracellular adenosine 5'-triphosphate (ATP) concentrations, and the DNA degradation. Combined treatments resulted in additive or synergistic effects as compared to gamma-irradiation alone. A significant modification (P < or = 0.05) of the fatty acid composition and unsaturation ratios was observed. Pretreatment with mild heat or carvacrol before irradiation disturbed the membrane integrity of B. cereus and induced a significant decrease (P < or = 0.05) of the intracellular ATP concentration. SEM observations revealed that the cell membrane was more severely affected with combined treatment than irradiation alone. The electrophoresis analysis showed that DNA degradation by combined treatments was greater than the gamma-irradiation alone.

Effect of gamma radiation and oregano essential oil on murein and ATP concentration of Listeria monocytogenes

The effects of gamma radiation and of oregano essential oil alone or in combination with radiation on murein composition of Listeria monocytogenes and on the intracellular and extracellular concentration of ATP were evaluated. The bacterial strain was treated with two radiation doses, 1.2 kGy to induce cell damage and 3.5 kGy to cause cell death. Oregano essential oil was used at 0.020 and 0.025% (wt/vol), which is the MIC. All treatments had a significant effect (P < or = 0.05) on the murein composition, although some muropeptides did not seem to be affected by the treatment. Each treatment influenced differently the relative percentage and number of muropeptides. There was a significant correlation (P < or = 0.05) between the reduction of intracellular ATP and increase in extracellular ATP, following treatment of the cells with oregano oil. The reduction of intracellular ATP was even more important when essential oil was combined with irradiation, but irradiation of L. monocytogenes alone induced a significant decrease (P < or = 0.05) of the internal ATP without affecting the external ATP. Transmission electron microscopic observation revealed that oregano oil and irradiation have an effect on cell wall structure.