of Packaging Materials and Refined Sunflower Oil

Transcription

1 Food Sci. Technol. Res., 10 (3), , 2004 The Effect Stability of of Packaging Materials and Refined Sunflower il Storage Condition on the xidative R. RAMEZANI Department of Food Science and Technology, Agricultural School, Shiraz University, Shiraz, 71444, Iran Received March 29, 2004; Accepted June 22, 2004 In this research, refined sunflower oil was packed at various packaging materials namely: yellow PET (polyethylene terephtalate) bottles, clear PET bottles, yellow HDPE (high density polyethylene) containers and metal cans. Randomly selected packaged sunflower oils samples were packed in carton as dark condition and secondary container. The samples were stored at room temperature (26.9'C) for 365 days. At 45 days intervals, the peroxide values of stored samples were determined. Every 180 days the samples were analyzed for TBA and anisidine values. In order to determine the effect of storage temperature, some samples were stored at 38'C under dark condition for a period of 56 days. At 7 days intervals, the peroxide value of samples was determined. The results indicate that at room temperature, increase in peroxide value, thiobarbituric acid (TBA), anisidine value and totax value were significantly (p < 0.05) higher in sunflower oil stored in HDPE containers as compared to PET (yellow, clear) bottles and metal cans. No significant differences were observed in the capability of PET bottles and metals cans to protect the oil against the deterioration effect of primary and secondary oxidation. At 38'C, significant differences on peroxide value of sunflower oil in HDPE containers in comparison to the other packaging materials were observed (p < 0.05). The results indicate that, the estimated shelf life for sunflower oil in HDPE containers at room temperature were less than 180 days and decreased to 35 days at 38'C. Where as, the shelf life of sunflower oil in PET (yellow, clear) bottles and metal cans were estimated to be more than 365 days at room temperature. It seems that PET bottles and metal cans are suitable containers for sunflower oil that protect oil against oxidative deterioration, where as the HDPE container with the low oxidative stability is unsatisfactory. Keywords: sunflower oil, oxidative stability, storage condition, polyethylene terephtalate, high density polyethylene, metal cans. Introduction ne of the most important parts of oil processing is packaging that protects the product from point of manufacture through usage by consumer. Package affects on shelf life of the oil in such away that carefully processed oil may be damaged by improper selection of packaging materials. Shelf life is a duration period between packing a product and using it, for which the quality of the product remain acceptable to the product user. Environmental factors such as light, gaseous atmosphere, temperature and moisture can affect the stability of oil (1eo 1983, 1985). The best-known effect of oxygen on deterioration is the promotion of the rancidity of fats. xidation is a main problem for polyunsaturated oil. There have been a number of studies on the oxidative stability of oils in various packaging materials. Some investigators concluded that, metal cans, amber glass and green glass bottles gave the greatest oxidative stability to refined palm oil kept in dark condition (27 :~: 1'C), and where as polyethylene film was unsatisfactory (Nkpa shirazu. ac, ir et al. 1992). Some reports on palm oil quality in different film packaging material indicate that the quality deterioration of palm oils was more pronounced when they stored under 30-40% relative humidity and 45'C (Narasimhan et al. 2001). During long-term storage of soybean oil in plastic bottles (polyvinyl chloride and acrylonitrile) and glass bottles (clear and amber), it was concluded that the oil in plastic containers could serve as an alternative to clear glass bottles (Warner and Mounts 1984). Some studies on the storage quality of sunflower oil in different packaging materials indicated that the oil in glass and steel containers had better qualities than the others (Jaimand and Rezaee 1995). At room temperature, refined sunflower oil remains stable in high-density polyethylene (HDPE) bottles and sealed tin for two years (Semwal and Arya 1992). Some reports indicate that the storage lives of sunflower oil in polyethylene terephthalate (PET), clear glass and color glass bottles under 10 w fluorescence lamp were 10.4, and 11.8 mo. at 10'C and 4.8, 5.1 and 6.5 mo. at 20'C, respectively (Kaya and Tekin 1993). The effect of various packaging materials (clear PET, yellow PET, HDPE and metal can) and light condition on storage stability of refined sunflower oil indicate that yellow PET with the lowest light

2 The Effect of Packaging Materials and Storage Condition on the xidative Stability of Refined Sunflower il 351 transmittance properties ( nm) and peroxide value (when exposed to four 20 w fluorescent lamp) proved to be the most suitable container for sunflower oil (Ramezani and Karbassi 2002). Kinetic study on the autoxidation of sunflower oil indicate that the autoxidation reaction occurs faster in sunflower oil in glass than in PET polymer container and faster than in the darkness of the metal container (Topaller et al. 1997). The effect of polyethylene and polypropylene films on the storage stability of sunflower and groundnut oil at 37'C indicate that, reduction in rate of autoxidation was more pronounced in the presence of antioxidant incorporated film (sharma et al. 1990). Storage stability of sunflower oil in the presence of oxygen-scavenging film that contain polyfuryloxirane was more than oil stored without the film, or than film stored with 0.02% BHT (Maloba et al. 1996). In lran, the plastic containers, such as high density polyethylene (HDPE), polyethylene terephthalate (PET) and metal cans are common for packaging of fats and oils. These containers are packed in carton as a secondary packaging to provide total opacity and light protection. The increase in use of plastic containers for oil, motivated the present study to compare the effect of packaging materials (clear PET, yellow PET, HDPE and metal can) and storage conditions (at room temperature and 38'C under dark condition) on oxidative stability of refined sunflower oil. Materials and Methods Materials Chemicals Chemicals such as acetic acid, chloroform, sodium iodide, sodium thiosulfate, 1-butanol, 2-thiobarbituric acid, iso-octane and p-anisidine were obtained from E. Merck Chemical Co. (Frankfurter Strass 250, 6100 Darmstadt, Germany). Samples Sunflower oil was extracted, refined and packaged by Shiraz Nargase il Company. Packaging materials were manufactured by lran Fila and Shiraz Nargase il Co. as follow: yellow PET bottle, clear PET bottle, yellow HDPE container and metal can. 72 samples for each packaging materials in totally of 288 samples in various packaging materials were prepared. Method s Storage condition 1-Ninty four samples of randomly selected packaged sunflower oil (26 samples of each packaging materials) were packed in carton as a secondary con- tainer and dark condition. They were stored in room temperature for 365 days. Relative humidity and temperature of storage condition were recorded instrumentally (thies, Germany). At 45 days interval, 12 samples were removed from storage, shaken vigorously and analyzed for peroxide value (PV) determination in duplicate (A..C.S 1990). Stored samples during storage periods of, 180 and 365 days were analyzed for thiobarbituric acid (TBA) and anisidine value (AV) (A..C.S 1 990). The total oxidation value (total) was calculated from the relationship (Rossel 1989): Totax = 2 (PV) + AV 2-Various packaged refined sunflower oil was stored in air oven (gallenkamp V-160 Model, England) at 38'C under dark condition for a period of 56 days. Every 7 days, peroxide value of stored samples was determined (A..C.S 1990). The thickness of films was determined by measuring 10 thicknesses with micrometer. The density of the films was determined by weighing a known area of films, and calculating (Paine & Paine 1992). Statistical analysis The data were statistically analyzed by analysis of variance and compare means by LSD test (SPSS for windows statistical software package). Results Sunflower oil in various packaging materials stored in environmental condition with the average temperature of 26.9'C and relative humidity of 36.6%. The results of peroxide value of refined sunflower oil stored at room temperature are shown in Table 1. As it shows, the peroxide value of sunflower oil in HDPE containers were increased sharply while in the other containers this value increased gradually. Peroxide value of sunflower oil in HDPE containers changed markedly during storage for a period of 45 days and this value was more than 10 meq/kg after 225 days. During 365 days of storage, the mean of peroxide value of sunflower oil in HDPE in comparison to the other packaging material was significantly different (p < 0.05), while the means comparison of peroxide value in clear PET, yellow PET and metal cans weren't significantly different. TBA analysis of stored sunflower oil samples is shown in Fig. 1. At interval of, 180 and 365 days of storage, TBA value of refined sunflower oil in various Packaging Table 1. Peroxide formation is sunflower oil stored in the dark at room temperature (26.9'C). Peroxide value (meq 02/kg oil)(1) Packaging material Storage period (days) o Clear PET(2) 1.05 :!: 0.0la 1.41 :!: 0.05a 1.74 i 0.08a 2.13 d: 0.06a Yellow PET(2) 1.06 :!: 0.02" 1.41 :!: 0.05" 1.56 :~: 0.06" 2.12:!:.06a HDPE(3) 1.06 :!: 0.0la 2.32 :!: 0.22b 3.28 :!: 0.42b 6.28 :!: 0.53b Metal can 1.06 :!: 0.0la 1.45 :t 0.09a 1.83 :t: 0.25a 2.31 :!: 0.39* 2.90 :!: 0.02a 2.91 :!: 0.02" 8.57 :!: 0.97b 2.80 :!: 0.23* (1) Mean :~: SD. Values in each column with the same superscript are not significantly different (p < 0.05, LSD) (2) PET (polyethylene terephthalate) (3) HDPE (High density polyethylene) d: 0.07a 3.35 :!: 0.06a 3.02 :!: 0.02" 3.22 :~: 0.16" :!: 0.37b 17.3 i 0.77b 3.15 :!: 0.08" 3.54 :!: 0.15" 3.67 :!: 0.1la 4.00 :t 0.15a 3.7 :!: 0.10" 3.98 :!: 0.18" i: 0.6lb 30.9 :~: 0.70b 4.01 :!: 0.08* 4.39 :!: 0.1*

3 352 R. RAMEZANI o 02 J ~(:1> <00 1 H Storage 1 80 periods (days) 365 E~] HDPE ~ Metal can Fig. 1. Thiobarbituric acid value in refined sunflower oil stored at room temperature (26.9'C) and dark condition. In each storage period, means of values with similar letters are not significantly different (p < 0.05, LSD). Abbreviations as in Table I. materials were increased. Any significant differences weren't observed in TBA of sunflower oil in PET (yellow, clear) and metal containers where as the TBA value of sunflower oil in HDPE containers as a compared to the other packaging materials, were significantly different (p < 0.05). Anisidine values of stored refined sunflower oil in various ~ o 10 c:f > o 8 c I' 6 co Z 4 < 2 Storage 1 80 periods (days) 365 E~ HDPE ~ Metal can Fig. 2. Anisidine value in refined sunflower oil stored at room temperature (26.9'C) and dark condition. In each storage period, means of values with similar letters are not significantly different (p < 0.05, LSD). Abbreviations as in Table 1. tainers gave the highest increase in anisidine value, while no significant differences were found in anisidine value of sunflower oil in PET and metal containers. The combined effect of the peroxide and anisidine value of sunflower oil can be evaluated by total oxidation value (Totax). The results are shown in Fig. 3. There is a significant difference in the total oxidation value for oil packaged in HDPE. packaging materials are shown in Fig. 2. During storage periods, anisidine values of packaged sunflower oils were increased. At 365 days, refined sunflower oil in HDPE cono :: 75 > ~a:l Fo ~ aa aa I :~i~~~i ~ I ai b }:1. i: i:iii a B a b 'J~EF:.., Storage 1 80 Periods (days) 365 E~I HDPE ~ Metal can Fig. 3. Total oxidation value in refined sunflower oil stored at room temperature (26.9'C) and dark condition. In each storage period, means of values with similar letters are not significantly different (p < 0.05, LSD). Abbreviations as in Table I. * 5- The peroxide value of sunflower oil stored at 38'C (Table 2) indicate that peroxide value of refined sunflower oil samples in various packaging materials were increased steadily during 56 days of storage. The limiting peroxide value specified by lran standard (1993) was used to determine the keeping quality of sunflower oil. The shelf life estimated in this way to be less than 35 days for sunflower oil in HDPE containers and less than 56 days for PET (yellow, clear) and metal cans. Significant differences in peroxide value of sunflower oil in HDPE containers in comparison to the other packaging materials were observed (p < 0.05). Where as the means comparison of the peroxide value of sunflower oil in PET (yellow, clear) and metal cans weren't significantly different. The tests carried out on plastic packaging materials must be chosen to examine those properties which are relevant to the application. Table 3 Iists the properties of plastic packaging films. Table 2. Peroxide formation is sunflower oil stored in the dark at 38'C. Packaging material Clear PET(2) 1.04 :!: 0.01* Yellow PET(2) 1.08 :t 0.06* HDPE(3) I. 10 :!: 0.09* Metal can 1.09 :!: 0.07* Peroxide value (meq 02/kg oil)(1) Storage period (days) o :!: 0.05' 2.5 :!: 0.12" 1.68 :!:.03* 2.69 :!: 0.10" 2.77 :!:0.1lb 3.94:!:0.3lb 1.63 :!:0.01* 2.58 :!:0.13" 3.98 :!: 0.37* 4.21 :!: 0.12* 6.71 :!: 0.43b 4.25 :!: 0.48* (1) Mean :!: SD. Values in each column with the same superscript are not significantly different (p < 0.05, LSD) (2) PET (polyethylene terephthalate) (3) HDPE (High density polyethylene) 4.84 :!: 0.12* 5.23 :!: 0.21" 6.02 :!: 0.34* 7.05 :!: 0.58" 8.00 :~: 0.19" 4.93 :!: 0.l' 5.49 :!: 0.21" 6.12 :!: 0.15* 7.13 :!: 0.16* 8.28 :!: 0.33* 7.93 :!: 0.14b 8.72 :!: 0.28b 9.64 :!: 0.94b :!: 0.67b ll.35 :!: 0.53b 5.25 :!: 0.24" 5.91 :!: 0.34* 6.39 :!: 0.65" 7.38 :!: 0.73" 8.08 :!: 0.28"

4 The Effect of Packaging Materials and Storage Condition on the xidative Stability of Refined Sunflower il 353 Table 3. Some properties of plastic packaging materials(1). Packaging materials Density (kg/m3) Thickness (mm) Light(4) ( nm) (5) 2 Clear PET(2) Yellow PET(2) HDPE(3) 1376 i ~ ~ d: d: :!: :!: :t ~ 1.56 } (1) Mean t SD (2) Polyethylene terephthalate (3) High density polyethy lene (4) Light transmissions is percenta e of light passing through wall thickness (Ramezani & Karbassi 2002) (5) xygen transmission rate = cm~/25 um2/d./atm./at 23125'C, 50% RH. (Paine & Paine 1992) Discussion Deterioration of lipid foods as a result of oxidation is a particulate problem for polyunsaturated oils, such as sunflower oil. Peroxide is considered to be the first product formed in oils by the oxidation process. Peroxide value is a good guide to judge about the quality of oil (Rossel 1989). Peroxide value of refined sunflower oil stored in dark condition at room temperature (Table 1) and 38'C (Table 2) indicate that the packaging containers such as, yellow and clear PET bottles and metal cans gave the greatest protection of sunflower oil against oxidative deterioration. Where as the highest peroxide value was recorded for the sunflower oil packaged in HDPE containers. The limiting peroxide value specified by FAIWH (Codex standard 1992) and lran standard ( 1993) for refined sunflower oil is 10 meq/kg and 7 meq/kg, respectively. According to the lran standard, the estimated shelf life of sunflower oil in HDPE containers at room temperature was less than 180 days, while for the other packaging containers were more than 365 days (Table 1). At 38'C, the shelf life decreased to less than 35 days for sunflower oil in HDPE containers and less than 49 days in PET (yellow, clear) and metal cans (Table 2). This would indicate that the HDPE containers gave the least protection of sunflower oil against oxidation deterioration. Although the peroxide value doesn't give information about secondary oxidative products, they can be used as an indicator for oil quality. The TBA test is another empirical method frequently used for the detection of lipid oxidation, it relates to the level of aldehyde present in the oil by the reaction of malonaldehyde with TBA (Guillen-sans and Guzman-chozas 1998) and a representative parameter for the secondary oxidation step (Angelo 1996). Anisidine value determine the level of aldehyde, principally, 2-alkenals (Rossel 1989). This research clearly shows that TBA (Fig. 1), anisidine value (Fig. 2) and totax value (Fig. 3) of sunflower oil in HDPE containers were increase significantly (p < 0.05). It is evident that PET (yellow, clear) and metal containers gave the greatest protection to the sunflower oil against secondary oxidative deterioration. No significant differences were found in the capability of PET bottles and metal cans to protect the sunflower oil against the deleterious effects of secondary oxidation (Figs. 1-3). Based on all these determination of peroxide value, TBA, anisidine value and totax value some trends have clearly emerged. Firstly, the packaging material enhances the rate of deterioration of the oil. The deteriorative parameters responsible for the low shelf life of sunflower oil in HDPE containers may be considered to be high oxygen permeability (Table 3). Actually, one of the criteria to choose the packaging materials is the knowledge of the permeability of the polymeric material to the gases and vapors of the environment. Some of the structural parameters of the polymer play a major role in their effect on permeability (Jasse et al. 1994). xygen is the most critical factors affecting the quality of oils. It may access the oil by permeation of the wall of the container. The quantity of gas transmitted is, inversely proportional to the thickness of the film (Paine and Paine 1992). Although, the wall thickness of HDPE container is more than PET, but PET barrier properties are also superior to HDPE (Table 3). The rate at which a gas will pass through a permeable membrane is controlled by several factors, some governed by the properties of membrane. Different plastic resins block oxygen at different rates (Leo 1983, 1985). PET has a good gas barrier but oxygen transmission rate in HDPE is relatively high (Johansoon and Leufven 1994 Table 3). Therefore, PET is a suitable plastic container for contact with edible oil and provides an adequate oxygen barrier. The technological progress has provided PET material with properties of complete barrier for gas exchange (Robichon and Savina 1996). The prospects for developing PET resin for bottles in a world are good and should increase over the next years at a rate which is detrimental to glass and metal container (Chretien 1996). Also, oxidative deterioration can often be prevented or minimized by limiting the access of the product to oxygen through the selection of the packaging materials (Caudill 1996). Secondly, other deteriorative parameters responsible to predict shelf life are storage temperature. The storage stability of sunflower oil decreases as the storage temperature increased from 26.9'C to 38'C. The peroxide value of sunflower oil in HDPE containers at room temperature (Table 1) and 38'C (Table 2) were increased significantly. As a result of type of polymer in HDPE containers and high oxygen permeability, shelf life of sunflower oil in HDPE containers at 38'C was less than 35 days. Temperature may have double effect; it affects the rate of oxidation of fats and modifies the barrier properties of plastic container (Hine 1987). Temperature and relative humidity as environmental factors may affect the barrier characteristics of the packaging materials (Johansoon and Leufven 1 995). The influence of temperature on their diffusion behavior may

5 354 lead to the variation of permeation through polymeric packaging (Jasse 1994). Diffusion and permeability increase with temperature (Leo 1985). Light transmittance characteristics of packaging materials (Table 3) indicate that, HDPE container exclude light at wavelengths of But permeability of HDPE to oxygen is fairly high so where oxidation is likely to be a problem, they are not suitable. Edible oil often will be filled into primary containers such as plastic bottles which are then packaged within protective cartons. In this case the secondary container provided by the carton, minimize the light transmittance requirements that must be met by the primary container and provides total opacity and light protection for the period of time in which the shipper used. Conclusion It is undisputedly clear that PET bottles and metal cans are suitable containers for packaging of sunflower oil. PET bottles clearly exhibited their superiority as packaging materials for sunflower oil. In order to minimize oxidative deterioration of sunflower oil after production and distribution, it is most preferable that the sunflower oil be packaged in PET and stored under dark condition. The leakage of air through poor seals in metal cans and HDPE containers, make superiority of PET bottles as a seamless container. The highest oxidative deterioration was recorded for the sunflower oil packaged in HDPE containers. Any packaging material that is used for edible oil must have provided a barrier compatible with the oil product. Shelf life and stability are directly related to the oxygen permeability of packaging material. It is important to determine the desired shelf life of the edible oils and then select the packaging material, for institutional trade, it may be preferable to use a low cost material with a low oxygen barrier property. The same edible oil packaged in high oxygen barrier material would allow a retail shelf life of longer. Acknowledgments The authors thank the research council of Shiraz University for the grant supporting of this project (No. 75-AG ), Shiraz Nargase il Company for providing the packaged refined sunflower oil, and also H. Essfandiyari for chemical analysis. Ref erences Angelo, A.J. St. (1996). Lipid oxidation in foods. Crit. Rev. Food Sci. and Nutr., 36, A..C.S. (1990). "fficial Methods and Recommended Practices of the American il Chemists Society". American il Chemists Society. Illinois, U.S.A. Methods Cd 8.53, Cd 19-90, Cd Caudill, V. (1996). Packaging. "Bailey's Industrial il and Fat Products," ed. by Y.H. Hui. A Wiley. Interscience Publication, John Wiley and Sons, New York. U.S.A, p Chretien, G. (1996). Molded plastic containers for foodstuff packagmg In "Food Packagmg Technology," ed by G. Bureau & J.-L. Multon. VCH Publisher, New York, USA, Vol. I, p Codex Standard for Edible Sunflower Seed il. (1992). 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