METHOD FOR THE SURFACE DECONTAMINATION OF PACKAGED SOLID FOOD

Abstract

The invention relates to a method for the microbial decontamination of packaged solid food by means of essential oils (EOs), comprising vacuum evaporation of the EOs, and vacuum applying the EO vapours to the solid food arranged in an open container, wherein said vapours are drawn along by air or by a mixture of food-grade gases and guided to the vacuum enclosure containing the packaged food to be microbiologically decontaminated.

Claims

1. A method for the surface decontamination of packaged solid food which is performed before or during the closure of the container or before container dispatch by means of essential oils (EOs), comprising the following steps: a) evaporating the EOs in a vacuum vessel at a temperature between 20 and 150 C., such that said evaporation takes place in a time of between 1 and 40 seconds, b) applying the EO vapor to the packaged solid food located in a vacuum chamber or enclosure, wherein the generated vapor are drawn along by air or by a mixture of food-grade gases to this enclosure at a ratio of 10 to 120 mg of essential oil evaporated per liter of air or mixture of gases, this volume being measured at atmospheric pressure and a temperature of 25 C., and guided to where the food is arranged in an open container.

2. The method according to claim 1, wherein step a) is performed at an absolute pressure between 1 and 990 hPa.

3. The method according to claim 1, wherein step b) is performed at an absolute pressure between 1 and 990 hPa.

4. The method according to claim 1, wherein vacuum cooling is performed before step b).

5. The method according to claim 1, wherein the EOs used are pure EOs of a plant origin, selected from the group consisting of shoots, buds, flowers, leaves, stems, branches, seeds, fruits, roots, wood, bark, and a mixture thereof.

6. The method according to claim 1, wherein one of the components, whether or not it is the main component, of these EOs selected from terpenes, or terpenoids, or aromatic or aliphatic constituents, or a mixture thereof, or a mixture thereof with a mixture of the mentioned pure EOs, is used as an essential oil.

7. The method according to claim 1, wherein the packaged food to be decontaminated is in an open container, which is made of cardboard, wood, plastic, biodegradable plastic material or another food-grade material.

8. The method according to claim 1, wherein the food to be decontaminated is one of the following: fresh or processed solid food; food of a plant or animal origin, packaged in the form of pieces or slices; cheeses; fish that is either whole or filleted; other seafood that is either whole or in pieces; bakery products, sliced bread, bakery, pastry or confectionery goods; prepared dishes.

9. The method according to claim 1, wherein step b) is performed at a ratio of 15 to 60 mg of vaporized EOs per liter of air or mixture of gases, this volume being measured at atmospheric pressure and a temperature of 25 C.

10. The method according to claim 1, wherein in step a) the temperature is between 50 and 100 C.

11. The method according to claim 1, wherein the evaporation takes place in a time of between 1 and 30 seconds.

12. The method according to claim 2, wherein step a) is performed at an absolute pressure between 5 and 500 hPa.

13. The method according to claim 3, wherein step b) is performed at an absolute pressure between 5 and 800 hPa.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG. 1 depicts an industrial embodiment of the process for the surface decontamination of packaged solid food, where EO vapours are applied to each container, before closing or heat sealing.

[0030] FIG. 2 depicts another industrial embodiment of the process for the surface decontamination of solid food, where EO vapours are applied to several containers at the same time.

[0031] FIG. 3 depicts an industrial embodiment of the process for the surface decontamination of packaged solid food in which a continuously operating treatment tunnel is used.

[0032] FIG. 4 depicts an embodiment for the microbial surface decontamination of packaged fresh plant products, such as fruits and vegetables, previously subjected to vacuum cooling.

EMBODIMENTS

[0033] A non-exclusive embodiment of this invention is described in FIG. 1. It is an installation in which the vacuum evaporation of the EOs is carried out in the vacuum vessel 1, which is heated by a jacket 2, which can be solid (made of aluminium or another metal or alloy) or hollow and through which there flows a thermal fluid, where the heating agent can be a resistor, or water vapour, or hot water, or thermal oil, with a manual or automatic control system that allows heating the vessel 1 at a given temperature, which will depend on the type of essential oil that is used, but it must be between 20 and 150 C., preferably between 50 and 100 C.

[0034] The essential oil is metered into the vessel 1 at atmospheric pressure through a tube 3 by means of a metering pump 16 (which can be a normal metering pump or a metering micropump for small doses) taking the essential oil from a storage vessel 15. When metering the essential oil into the vessel 1, valves 14 and 18 are closed whereas valve 17 is open. Before metering, the vessel 1 is pre-heated at the desired temperature, according to the essential oil. Next, or before metering, or during metering of the essential oil into the vessel 1, a vacuum is generated by means of a vacuum pump 9 with valve 10 being opened and valve 18 closed, in a vessel 6 in which there is a container 7 with food 8 (there can optionally be several containers 7 in the vessel 6). This food can be of a plant or animal origin, including seafood, such as fish and shellfish, or it can be a prepared dish with various ingredients, or a pastry or baked good product, or any other solid food. The absolute pressure in the vessel 6 must be 1 to 200 hPa, preferably 5 to 150 hPa. Once the vacuum has been generated in the vessel 6, one valve 10 is closed and valve 18 is opened, connecting vessel 6 with vessel 1 through a tube 5. This causes an almost instantaneous evaporation of the hot essential oils because it is caused at approximately the vacuum level of the vessel 6. Next, a few seconds later, valve 14 opens (manual pressure reduction valve 13 and shutoff valve 12 for shutting off the gas cylinder 11 containing the desired mixture of gases for packaging the product in question with the most suitable modified atmosphere being open). Therefore, in just a few seconds, the EO vapours generated in 1 are drawn along by this mixture of gases until filling each container 7 containing the food 8. Next, heat sealing of the container is performed because said container has already been previously arranged in the enclosure 6 that is part of the heat sealing device.

[0035] Optionally, the installation of FIG. 1 described above can be housed in the heat sealing device 36 (indicated in FIG. 3). The dose of essential oil vapour to be added to each container, measured in milligrams (mg) of essential oil per litre of carrier gases filling each container with the food (this volume being measured at atmospheric pressure and at a temperature of 25 C.), is determined for each food and each type of mixture of EOs that is used so that it will be effective on the microbial load the food may have. With this injection of EO vapours in each container, an initial decrease in the microbial load the food may have is achieved, and this antimicrobial effect and microbial load-reducing effect produced in the food can be maintained for a certain time, throughout the shelf life thereof. The shelf life of the food is thereby prolonged, while at the same time the safety of said food is increased because the microbial load corresponding to pathogenic microorganisms is also reduced. In given cases, this antimicrobial effect can be so effective that it makes it unnecessary to use an MA. In this case, the gas used for drawing along essential oil vapours and filling the container until achieving atmospheric pressure can be air from a cylinder or from the atmosphere.

[0036] Other non-exclusive embodiments of the method of the invention are described in FIGS. 2 and 3.

[0037] FIG. 2 shows an installation in which the step for vacuum-evaporating the EOs is carried out in the vacuum vessel 20, which is heated by a jacket 28, which can be solid (made of aluminium or another metal or alloy) or hollow and through which there flows a thermal fluid, where the heating agent can be a resistor, or water vapour, or hot water, or thermal oil, with a manual or automatic control system that allows heating the vessel 20 at a given temperature, which will depend on the type of essential oil that is used, but it must be between 20 and 150 C., preferably between 50 and 100 C.

[0038] By means of a tube 3 and the metering pump 16 (which can be a normal metering pump or a metering micropump for small doses), the essential oil of storage vessel 15 is metered and introduced at atmospheric pressure into the vessel 20. Before metering and introducing the oil, the vessel 20 is pre-heated at the desired temperature, according to the essential oil to be used. During metering into the vessel 20, valves 14 and 25 remain closed, while valve 17 is open. Next, or before metering, or during metering of the essential oil into the vessel 20, a vacuum is generated in the vessel 37 by means of a vacuum pump 26 and with valve 24 open and valve 25 closed. The absolute working pressure in the vessel 20 must be between 1 hPa and 990 hPa, preferably between 5 and 200 hPa. Once the vacuum has been generated in the vessel 37, valve 24 is closed and valve 25 is opened, connecting vessel 37 with vessel 20 through tubes 5, 21, 22 and 23. This causes an almost instantaneous evaporation of the hot EOs because it is caused at approximately the vacuum level of the vessel 37. Next, a few seconds later, valve 14 opens (a manual valve 13 for communicating with the outside air through tubes 29 and 4 being open). Therefore, the EO vapours generated in 20 are drawn along by the outside air entering through 29 (this air could optionally be filtered through a highly efficient particle retaining HEPA filter, placed before valve 14, and/or it could come from a cylinder containing pressurized air until reaching and filling the vessel 37 where the containers 27 containing the food to be decontaminated are arranged). Next, the set of containers 27 could enter a tunnel 33 (like that indicated in FIG. 3, which is kept at atmospheric pressure) so that the food is in contact with the vapours during the residence time of these containers inside the tunnel 33. Then, these containers may or may not be closed by means of heat sealing or another container closure method. The food thus treated can be of a plant or animal origin, for example, vegetables and fruits that are either whole or cut up, fresh meats or cooked meat products, fish and shellfish, or any other food with different ingredients, such as prepared dishes.

[0039] FIG. 3 illustrates an installation in which the aforementioned vessel 37 can be comprised in a treatment tunnel for treating with EOs packaged solid food in open containers, such as bowls, deep trays, trays, baskets, dishes that may be more or less deep made of plastic or another food-grade material. These containers will be heat sealed, with or without MA (modified atmosphere), in a heat sealing device 36. The containers filled with product to be decontaminated are fed by belts 30 and 31 and pushed by an element 32 into a tunnel 33. To that end, a hatch 38 is opened and allows the entry of the product-filled containers into the enclosure 37 housed inside the treatment tunnel 33. This enclosure or vessel 37 would also be closed by means of the hatch 39. Optionally, this enclosure 37 could be opened by moving up the entire upper part thereof (including the ceiling and walls thereof), being separated from the base thereof, in order to let containers with food to be treated with essential oil vapours in or out.

[0040] When the vacuum is generated in the enclosure 37, the hatches 38 and 39 are closed and said enclosure or vessel 37 is completely leak-tight. Then the EO vapours are applied to the food placed in the open containers 27 (indicated in FIG. 2). The absolute pressure in the vessel 37 must be 1 to 990 hPa, preferably 5 to 200 hPa. The connection between the vessels 20 and 37 must last for a time between 1 and 60 seconds, preferably between 5 and 30 seconds. After these seconds, hatch 39 (or both hatches 38 and 39) is opened and the belt of the tunnel 33 makes the containers come out of the enclosure 37 and move forward a cycle inside the tunnel 33. Next, the belt is stopped, hatch 39 is closed and hatch 38 is opened (or both hatches 38 and 39 are kept open), allowing the entry of a new load of containers 27 filled with food into the enclosure 37 in which application of EO vapours generated in the vessel 20 is performed.

[0041] The tunnel 33 will have several forward movement and stop steps or cycles that involve residence times of the filled containers inside this tunnel of 10 s to 300 s, preferably 10 s to 120 s. The open and product-filled containers that received EO vapour treatment exit through the tunnel 33 by means of a belt 34 and are taken to the heat sealing device 36 by means of a belt 35. Optionally, this belt 35 and its intersection with belt 34 could be enclosed in a tunnel to prevent recontamination with particles from the outside air, and this tunnel covering the mentioned belt 35 could have a filtered air injection through a highly efficient particle retaining HEPA filter. The belt 34 will be closed by means of hatches 40 and 41, which will allow suctioning out the residual vapours that remain in the open containers so that they are not given off into the room in which this treatment installation defined by FIG. 3 is housed. In this installation, the EO vapours are generated in the evaporator 20 of the installation described in FIG. 2. Furthermore, to enhance the effect of the EO vapours in the surface decontamination of food, the same combination of EO vapours used in vessel 37, or another different combination with different EO vapours, can be injected together with the gases of the MA applied in the heat sealing device 36, which would have an installation like the one described in FIG. 1 for generating and applying those EO vapours. Therefore, the combination of EO vapours applied in the vessel 37 to the packaged product may have a specific effect on pathogenic microorganisms, such as E. coli, Listeria monocytogenes or Salmonella, inter alia, whereas the combination of EOs applied to the container during heat sealing by means of the installation described in FIG. 1, which would be housed in the heat sealing device 36, could be selected so that it had a specific effect on spoilage microorganisms, which will be according to the type of product, yeasts, fungi or bacteria.

[0042] As indicated above, the dose of essential oil vapour to be added in the air in the enclosure 37 for decontaminating the product in each container (measured in mg of essential oil per litre of air of this enclosure or vessel 37, and this volume of one litre being measured at atmospheric pressure and a temperature of 25 C.) is determined for each food and each type of mixture of EOs used so that it will be effective on a given microbial load (pathogenic microorganisms and/or spoilage microorganisms) the food may have. With this application of EO vapours in each container in the treatment tunnel 33, an initial decrease of the microbial load the food may have is achieved, and this antimicrobial effect and microbial load-reducing effect produced in the food can be maintained for a certain time, throughout the shelf life thereof. The shelf life of the product is thereby prolonged, while at the same time the safety of said food is increased because the microbial load corresponding to pathogenic microorganisms is also reduced.

[0043] FIG. 4 illustrates another non-exclusive embodiment of this invention. It is an industrial installation in which vacuum evaporation is performed in the vessel 20, and a vacuum application of EO vapours is performed in a vessel or enclosure 42 (right after applying a step of vacuum cooling) for the microbial surface decontamination of fresh plant products, such as, fruits and vegetables packaged in cases 43 made of cardboard, wood or plastic. The vacuum evaporation of the EOs is carried out in vacuum vessel 20, which is heated by a jacket 28, which can be solid (made of aluminium or another metal or alloy) or hollow and through which there flows a thermal fluid. The heating agent can be a resistor, or water vapour, or hot water, or thermal oil, with a manual or automatic control system that allows heating the vessel 20 at a given temperature, which will depend on the type of essential oil that is used, but it must be between 20 and 150 C., preferably between 50 and 100 C.

[0044] The essential oil is metered into the vessel 20 at atmospheric pressure through a tube 49 by means of a metering pump 46 (which can be a normal metering pump or a metering micropump for small doses) taking the essential oil from a storage vessel 48. During this metering of essential oil into the vessel 20, valves 44 and 51 are closed and valve 47 is open. Before this metering, the vessel 20 is pre-heated at the desired temperature, according to the essential oil used. Before, during or after performing the preceding metering of essential oil into the vessel 20, a vacuum is generated in the vessel or enclosure 42 by means of a vacuum pump 52 with valve 51 being closed and valve 53 open. The absolute pressure in the vessel 42 must be 1 to 500 hPa, preferably 5 to 200 hPa. Once the desired vacuum has been generated in this vessel 42, a valve 51 is opened, vacuum pump 52 being stopped and valve 53 closed, and the vessel 42 is thus connected with the vessel 20 through a tube 50. This causes an almost instantaneous evaporation of the hot EOs and the drawing along thereof, in vapour form, towards the vessel 42. Then, the EO vapours are finally drawn along by means of the air entering from the outside when the valves 44 and 45 are opened (they are opened after opening valve 51, keeping valves 47 and 53 closed). In this vessel or enclosure 42 there are a given number of containers or cases 43, which may or may not be arranged on pallets, with the food to be treated (usually of a plant origin). Once application of the EO vapours has ended, which will last 10 s to 300 s, preferably 10 s to 120 s, the enclosure or vessel 42 is then opened to discharge the packaged product into cases, and to dispatch same in refrigerated trucks.

[0045] As indicated above, the dose of essential oil vapour to be added in the air in the enclosure 42 for the decontamination of the product in each container, measured in mg of essential oil per litre of air of this enclosure or vessel 42, is determined for each product and each type of mixture of EOs used so that it will be effective on that given microbial load in connection with pathogenic microorganisms and/or spoilage microorganisms the food may have. With this application of EO vapours in each container in this vessel 42, an initial decrease of the microbial load the food may have is achieved, and this antimicrobial effect and microbial load-reducing effect produced in the food can be maintained for a certain time, throughout the shelf life thereof. The shelf life of the product is thereby prolonged, while at the same time the safety of said food is increased because the microbial load corresponding to pathogenic microorganisms is also reduced.

[0046] The constructive details relating to the hygienic design of the equipment depicted in FIG. 3 must comply with specifications for the hygienic design of food processing and packaging equipment, for example, in documents 8, 10 and 17 of the EHEDG, (EHEDG, Hygienic equipment design criteria, Second Edition, April 2004. Chipping Campden, ISBN: 0907503136, doc. 8; EHEDG: Hygienic design of closed equipment for the processing of liquid food, November 2003, Chipping Campden, doc. 10; EHEDG, Method for the assessment of in-place cleanability of food processing equipment, 3.sup.rd edition, July 2004, Chipping Campden, ISBN: 0907503179, doc 2. EHEDG: Hygienic design of pumps, homogenizers and devices in contact with liquids, 2.sup.nd edition, September 2004, Chipping Campden, ISBN: 0907503187, doc. 17), especially in relation to (1) good levels of surface polish or finish levels, such as, for example, mirror, of the internal components of this equipment (the EO vapour treatment tunnel 33 and the elements for conveying and handling product-filled containers, such as belts 30, 31, 34 and 35, and the belt of the tunnel 33); (2) rounded intersections between walls of the different components of the tunnel 33 and the heat sealing device 36; (3) components of the heat sealing stations (of the heat sealing device 36) cannot have any space that is hard to automatically clean and disinfect where dirt may accumulate; (4) no lubrication systems in the product-filled container heat sealing or conveyance region; (6) the lower part of the different regions which are kept within the product-loaded container conveyance region will have a hygienic and completely drainable design to assure that no water or washing and disinfecting solution waste are left behind when complete drainage thereof is performed during the washing and disinfecting operations. Optionally, this equipment of FIG. 3 can have an automatic washing and disinfecting system that performs washing and disinfection functions in the equipment without having to take said equipment apart.

INDUSTRIAL APPLICATIONS

[0047] The method herein described has an industrial application in the surface decontamination of the following solid, fresh or processed food: [0048] of a plant origin, such as fresh fruits and vegetables that are either whole or cut up, salads of any type and composition; [0049] of an animal origin, such as meat products in pieces or slices; cheeses in pieces or slices; fish that may or may not be whole, eviscerated, in pieces or filleted; seafood that is whole or in pieces); [0050] bakery products, such as sliced bread; [0051] pastry goods; [0052] confectionery goods that may be whole or in pieces, and [0053] prepared dishes of any type which may sustain some type of surface contamination before being packaged or once packaged and before heat sealing or closing and/or dispatch.

[0054] Specifically, this invention proposes a new industrial method for the vacuum evaporation and vacuum application of EOs in vapour form for the surface decontamination of packaged solid food before heat sealing or closing and/or dispatch.

REFERENCES

[0055] ABADIAS, M., USALL, J., ANGUERA, M., SOLSONA, C., VIAS, I. 2008. Microbiological quality of fresh, minimally-processed fruit and vegetables, and sprouts from retail establishments. International Journal of Food Microbiology 123, 121-129. [0056] ARTS F., GMEZ P., AGUAYO E., ESCALONA V., ARTS-HERNNDEZ F. 2009. Sustainable sanitation techniques for keeping quality and safety of fresh-cut plant commodities. Postharvest Biology and Technology 51, 287-296. [0057] BARBOSA, L. N., ALVES, F. C. B., ANDRADE, B. F. M. T., ALBANO, M., CASTILHO, I. G., RALL, V. L. M., JNIOR, A. F. 2014. Effects of Ocimum basilicum Linn Essential Oil and Sodium Hexametaphosphate on the Shelf Life of Fresh Chicken Sausage. Journal of Food Protection 77(6), 981-986. [0058] BASSOL, I. H. N., JULIANI, H. R. 2012. Essential oils in combination and their antimicrobial properties. Molecules, 17(4), 3989-4006. [0059] BELLETTI N, LANCIOTI R, PATRIGNANI F, GARDINI F. 2008. Antimicrobial efficacy of citron essential oil on spoilage and pathogenic microorganisms in fruit-based salads. Journal of Food Science 73, M331-M338. [0060] CAPONIGRO V., VENTURA M., CHIANCONE I., AMATO L., PARENTE E., PIRO F. 2010. Variation of microbial load and visual quality of ready-to-eat salads by vegetable type, season, processor and retailer. Food Microbiology 27, 1071-1077. [0061] FISHER K., PHILLIPS C., MCWATT L. 2009. The use of an antimicrobial citrus vapour to reduce Enterococcus sp. on salad products. International Journal of Food Science and Technology 44, 1748-1754. [0062] FISHER, K. & PHILLIPS, C. 2006. The effect of lemon, orange and bergamot essential oils and their components on the survival of Campylobacter jejuni, Escherichia coli O157, Listeria monocytogenes, Bacillus cereus and Staphylococcus aureus in vitro and in food systems. Journal of Applied Microbiology 101, 1232-1240. [0063] FRANZ, E., VAN BRUGGEN, A. H. C. 2008. Ecology of E. coli O157:H7 and Salmonella enterica in the primary vegetable production chain. Critical Reviews in Microbiology 34, 143-161. [0064] FRDER, H., MARTINS, C. G., DE SOUZA, K. I., LANDGRAF, M., FRANCO, B., DESTRO, M. T. 2007. Minimally processed vegetable salads, microbial quality evaluation. Journal of Food Protection 70, 1277-1280. [0065] GIL M. I., SELMA M. V., LPEZ-GLVEZ F., ALLENDE A. 2009. Fresh-cut product sanitation and wash water disinfection: Problems and solutions. International Journal of Food Microbiology 134, 37-45. [0066] GMEZ-LPEZ, V. M., RAGAERT, P., DEBEVERE, J., DEVLIEGHERE, F. 2008. Decontamination methods to prolong the shelf-life of minimally processed vegetables, state-of-the-art. Critical Reviews in Food Science and Nutrition 48, 487-495. [0067] GRAA A., ABADIAS M., SALAZAR M., NUNES C. 2011. The use of electrolyzed water as a disinfectant for minimally processed apples. Postharvest Biology and Technology 61, 172-177. [0068] HAN, J. H., PATEL, D., KIM, J. E., & MIN, S. C. 2014. Retardation of Listeria Monocytogenes Growth in Mozzarella Cheese Using Antimicrobial Sachets Containing Rosemary Oil and Thyme Oil. Journal of Food Science, 79(11), E2272-E2278. [0069] INOUYE, S. (2003). Laboratory of evaluation of gaseous essential oils (Part 1). The International Journal of Aromatherapy, 13, 95-107. [0070] ISSA-ZACHARIA A., KAMITANI Y., MIWA N., MUHIMBULA H., IWASAKI K. 2011. Application of slightly acidic electrolyzed water as a potential non-thermal food sanitizer for decontamination of fresh ready-to-eat vegetables and sprouts. Food Control 22, 601-607 [0071] JACXSENS, L., DEVLIEGHERE, F., DEBEVERE, J. 2001. Temperature dependence of shelf life as affected by microbial proliferation and sensory quality of equilibrium modified atmosphere packaged fresh produce. Postharvest Biology and Technology 26, 59-73. [0072] JUNTTILA, J. R., NIEMELA, S. I., HIRN, J. 1988. Minimum growth temperatures of Listeria monocytogenes and non-haemolytic listeria. Journal of Applied Bacteriology 65, 321-327. [0073] KLOUCEK, P., SMID, J., FRANKOVA, A., KOKOSKA, L., VALTEROVA, I., PAVELA, R. 2012. Fast screening method for assessment of antimicrobial activity of essential oils in vapor phase. Food Research International, 47(2), 161-165. [0074] LONCAREVIC, S., JOHANNESSEN, G. S., RORVIK, L. M. 2005. Bacteriological quality of organically grown leaf lettuce in Norway. Letters in Applied Microbiology 41, 186-189. [0075] MARTINS, P., SBAITE, P., BENITES, C., MACIEL, M. 2011. Thermal characterization of orange, lemongrass, and basil essential oils. Chemical Engineering Transactions 24, 463-468. [0076] MOREIRA, M. R., PONCE, A. G., DEL VALLE, C. E., ROURA, S. I. 2005. Inhibitory parameters of essential oils to reduce a foodborne pathogen. LWT-Food Science and Technology, 38(5), 565-570. [0077] NGUYEN-THE, C., CARLIN, F. 1994. The microbiology of minimally processed fresh fruits and vegetables. Critical Reviews in Food Science and Nutrition 34, 371-401. [0078] PAVAN DA SILVA, S. R., FRIZZO VERDIN, S. E., PEREIRA, D. C., SCHATKOSKI, A. M., ROTT, M. B., CORO, G. 2007. Microbiological quality of minimally processed vegetables sold in Porto Alegre, Brazil. Brazilian Journal of Microbiology 38, 594-598. [0079] PIANETTI, A., SABATINI, L., CITTERIO, B., PIERFELICI, L., NINFALI, P., BRUSCOLINI, F. 2008. Changes in microbial populations in ready-to-eat vegetable salads during shelf life. Italian Journal of Food Science 20, 245-254. [0080] PITTMAN C. I., PENDLETON S., BISHA B., OBRYAN C. A., BELK K. E., GOODRIDGE L., CRANDALL P. G., RICKE S. C. 2010. Activity of Citrus Essential Oils against Escherichia coli O157:H7 and Salmonella spp. and Effects on Beef Subprimal Cuts under Refrigeration. Journal of Food Science, 76(6), M433-M438. [0081] RAGAERT, P., DEVLIEGHERE, F., DEBEVERE, J. 2007. Role of microbiological and physiological spoilage mechanisms during storage of minimally processed vegetables. Postharvest Biology and Technology 44, 185-194. [0082] SCIF, G., RANDAZZO, C. L., RESTUCCIA, C., FAVA, G., GAGGIA, C. 2009. Listeria innocua growth in fresh cut mixed leafy salads packaged in modified atmosphere. Food Control 20, 611-617. [0083] SEOW, Y. X., YEO, C. R., CHUNG, H. L., YUK, H. G. 2014. Plant essential oils as active antimicrobial agents. Critical Reviews in Food Science and Nutrition, 54(5), 625-644. [0084] VALENTIN-BON, I., JACOBSON, A., MONDAY, S. R., FENG, P. C. H. 2008. Microbiological quality of bagged cut spinach and lettuce mixes. Applied Environmental Microbiology 74, 1240-1242.