ЗВІТ З НДР 29-81 ЗА 2007 – 2009 Р Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel MareUniversity - Suceava Volume XI, Issue 1 – 2012 54 IN VES T IG AT IO N O F TH E PRO C ESS O F S TOR IN G P ACK AG ED PUM PK IN IN MOD IFIED A TM OSPHE R E *Stefan STEFANOV1, Hristo HRISTOV1, Donka STOEVA1, Zapryana DENKOVA1, Radosveta NIKOLOVA1 1University of Food Technologies, Plovdiv, Bulgaria, stvstefanov@yahoo.com *Corresponding author Received 10 December 2011, accepted 5 February 2012 Abstract: The article presents experimental studies with packaged in modified atmosphere and stored refrigerated grated pumpkin and chopped pumpkin. We have used three types of gas environment: 30% СО2 / 70% N; 100%СО2 and vacuum. We have drawn up time temperature curves during refrigerator storage. We have defined the variation of СО2 in the packages during storage. On the base of microanalysis we have defined the shelf life. Keywords: modified atmosphere, cold storage, shelf life, pumpkin 1. Introduction Fruits and vegetables are still alive after being harvested. Their shelf-life is defined by several factors, such as harvest ripeness, store temperature, content of the gas environment, type and material of the packaging, availability of microorganisms and others [1, 2, 3, 4]. Their storing in refrigeration units increase the possibility of longer quality lasting periods of the products. The packaging in modified atmosphere is one of the ways for additional increase the shelf-life (1) or allows their storing at higher temperature. The defining of shelf-life of a product is a complex investigation of the store temperature, the gas environment content and microflora. The aim of the present work is to define the most suitable out of the three gas environment types for storing of grated pumping and chopped pumpkin at same refrigeration temperature. 2. Materials and methods For packaging of grated pumpkin and intact pieces of pumpkin is used semi automatic packaging machine Tray sealer Fibosa with two trays – Fig. 1. Figure 1. Chamber of the packaging machine with packaging trays Figure 2. Control desk of the packaging machine mailto:stvstefanov:@yahoo.com Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel MareUniversity - Suceava Volume XI, Issue 1 – 2012 55 Polypropylene (PP) trays with dimensions 130 x 215 mm (fig. 3) are used for packaging. The upper foil, which seals the tray has high stoppage effect on gases and vapours. It is multi ply Lintop PP DAN. This is a foil, which has very high stoppage effect on oxygen, carbon dioxide and water vapours. The values of oxygen permeability are under 15 cm3/m2.24h.bar at 23oC and RH 0% according to ASTM D 3965, the values of carbon dioxide permeability are under 75 cm3/m2.24h.bar at 23oC and RH 0% according to ASTM D 3965 and the values of water vapours permeability is under 3 g/m2.24h.bar at 23oC and RH 85% according to ISO 2528. The foil thickness is 50 μm and the basis weight is 46 g/m2. The strength characteristics are defined according to ASTM D882. The sealing temperature of the upper oil to the base, which can be PP as well as PE, is 170 °С. Figure 3. Packaging tray Figure 4. Upper foil Lintop PP DAN The grated pumpkin and intact pieces pumpkin is packed in three different packages in condition of each gas environment, as the sealing seams are visually inspected. One of them is put aside for microbiological analysis as a control sample and the rest are put in a refrigerator „Liebherr” CT2841and are stored in refrigeration conditions. The reading and registration of the temperature is done by R.I.C.S. (Remote Integrated Control System) EVCO ITALY, which has 5 separate temperature probes – Pt, placed as it is shown on Fig. 5. During storage the gas environment content is measured by portable gas analyzer PBi Dansenzor „CheckPoint”. After expiration of the 5 days set storage period of the pumpkin, we separate the microbiological availability by the following methods: - BDS EN ISO 4833:2004 Microbiology of food and animal feeding stuffs - Horizontal method for the enumeration of microorganisms - Colony-count technique at 30 degrees C ; - BDS EN ISO 7954:2002 Microbiology -- General guidance for enumeration of yeasts and moulds -- Colony count technique at 25 degrees C yeasts and molds; The reading and registration of the temperature is done by the temperature probes of R.I.C.S. which are located in the following zones (Fig. 5) Figure 5. Location of the temperature probes 1 lower part; 2,4,5 central part; 3 in the room. 3. Results and Discussion The temperature variation in the refrigerator CT 2841 Liebherr has been followed for the whole store period and we Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel MareUniversity - Suceava Volume XI, Issue 1 – 2012 56 have presented data for only two days (48 hours), because during the next days the temperature has no variations(Fig.3 and 4) Figure 6.Store temperatures during the first day Figure 7.Store temperatures during thesecond day The packaged pumpkin is stored in the central zone of the refrigerator (sensor 2, 4 and 5). We can see on fig. 6 that the upper part of the refrigerator (sensor 3) has the highest temperature variation. This is observed only during the first 10 hours, until the input packages are cooled down. The average temperature of the stored pumpkin for the whole period is 5.5 оС, but the shelf life is defined by the maximal temperature of 6.5 оС. The breathing of fruits and vegetables is a biochemical process, related to evolving heat and carbon dioxide. The higher store temperature is related with more intensive breathing of the packaged fruits. This means reduction of O2 quantity and increasing the СО2 quantity in packages, made of high barrier property materials. Using the gas analyzer we reported the СО2 content of each sample during the separate days of the refrigerator storage (5,5 ± 1оС). You can see the results for the CO2 content in Table 1. Fig. 8 and Fig.9 graphic of CO2 content at storing in vacuum packaging of intact and grated pumpkin. Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel MareUniversity - Suceava Volume XI, Issue 1 – 2012 57 Table 1 Pumpkin, packaged with upper foil Lintop Packaging environment content Condition of the pumpkin № of sample CO2, content % Third day Fourth day Air grated 1 2,4 2,9 Vacuum intact 2 2,6 3,3 intact 3 2,5 3,1 grated 4 3 3,2 intact 5 3,1 4,4 intact 6 2,9 3,7 intact 7 2,5 2,8 30% CO2 :70% N2 intact 8 3,7 4,6 intact 9 11,1 10,6 grated 10 14,8 13,5 intact 11 4,5 5,8 100% CO2 intact 12 7,6 7,2 grated 13 43,6 39,3 intact 14 39,7 31,5 intact 15 7,8 4,0 intact 16 10,7 9,6 intact 17 9,3 8,9 Figure 8. CO2 content in packages with intact pieces of pumpkin (upper foil Lintop ) packaged in vacuum Figure 9. CO2 content in packages with grated pumpkin (upper foil Lintop ) packaged in vacuum During storage in vacuum in grated condition as well as intact pieces condition of the pumpkin we observer similar СО2 content variation. The breathing is an aerobic process which is sopped in case of oxygen absence it is stopped. In our case the process is due to the incoming through the foil oxygen and even the bigger surface of the grated pumpkin has no effect. On Fig. 10 and 11 we can see a graphic of the СО2 content of packages with gas environment of grated and intact pieces of pumpkin. Figure 10. CO2 content in packages of pumpkin (upper foil Lintop ) Packaged in gas environment 30% CO2 :70% N2 Figure 11. CO2 content in packages of pumpkin (upper foil Lintop )Packaged in gas environment 100% CO2 Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel MareUniversity - Suceava Volume XI, Issue 1 – 2012 58 On the graphics of Fig 10 and 11 we can see the decreasing СО2 in the packages, as in the case with the grated pumpkin the breathing process is more intensive and the СО2 content is higher in the end of the storage period. When storing fruits and vegetables, for better quality of the end product it is necessary to observe the microbiological pollution as well as the maintaining of low temperature. We can see on table 2 experimental results from microflora of pumpkin (grated and intact) packaged in different gas environment: 100% СО2, 70:30% N2: СО2 and vacuumed after 5 days storing in refrigerator (5,5 ± 1оС). Table 2.Packaging of pumpkin Grated pumpkin Intact pumpkin Total microbial counts, CFU/g Yeasts and molds, CFU/g Total microbial counts, CFU/g Yeasts and molds, CFU/g 100% СО2 7,7. 103 over 10 1,87. 103 over 10 30% СО2 / 70% N2 3,1. 104 10 7,5. 104 over 10 Vacuum 1,6. 104 over 20 over 104 over 10 Figure 12.Total microbial counts in grated pumpkin after refrigerator storing(5,5±1оС) 5 days Figure 13. Yeasts and molds content in grated pumpkin after refrigerator storing(5,5±1оС) 5 days On table 2 and Fig. 12 and 14 we can see that gas environment containing 100% СО2, is more suitable for packaging grated pumpkin or intact pumpkin pieces, because the СО2 itself has antimicrobial effect. When it is mixed with N2 its effect is being reduced. The less suitable for such products with high aqua activity aw is packaging in vacuum – Fig. 13 Figure 14. Total microbial counts in intact pumpkin pieces after refrigerator storing (5,5 ± 1оС) 5 days Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel MareUniversity - Suceava Volume XI, Issue 1 – 2012 59 4. References [1]. STEFANOV ST. at all. Explore options to extend the berries by store packaging in modified atmosphere. International Conference “Biotechnologies, Present and Food Engineering, “Stefan cel Mare” University of Suceava, Romania. Fourth edition, November, 19-20, 2010. [2]. STEFANOV ST., N. ARABADJIEVA, А. HRISTOVA, Z. DENKOVA, Y. STEFANOVA, CH. SAZDOV – Prilojenie na perforirani folia za opakovane na sveji plodove v modifizirana atmosfera. NAUCHNI TRUDOVE NA RUSENSKIA UNIVERSITET - 2010, tom 49, seria 9.2. str. 50 (in Bulgarian) [3]. STEFANOV ST., H. HRISOV, G. KOSTOV, Y. STEFANOVA, CH. SAZDOV, N. ARABADJIEVA, D. STOEVA. Sahranenie na opakovani hranitelni producti v modifizirana atmosfera. NAUCHNI TRUDOVE NA RUSENSKIA UNIVERSITET - 2009, tom 48, seria 9, str. 125-129. (in Bulgarian) [4]. STEFANOV ST., N. ARABADJIEVA, А. HRISTOVA, Y. STEFANOVA, Z. DENKOVA, CH. SAZDOV Opakovaneto v modifizirana atmosfera sp. “Propak”, ISSN 1313-0986, br. 6, ХІІ, 2010 г. Str. 20-26. (in Bulgarian)