effects of storage conditions and pet packaging on quality of edible oils in iran.
Introduction oil plays a vital role in human diet. More than 90% of the world\'s oil from vegetables, animals and marine sources is used for food or as part of it . In the food industry, there are different uses for different kinds of oil, in which rapeseed oil and sunflower oil are used for cooking. Blending oil ( Containing sunflower oil, soybean oil, cottonseed oil It is considered to be one of the current oil in the Iranian market. There are many kinds of materials for packaging. Glass, metal and different kinds of plastic used in oil packaging [34,32]. The type of packaging has a great impact on the shelf life of the oil, because the carefully processed oil may be damaged by the unelegant packaging material . PET is one of the most commonly used plastics in food packaging, covering a variety of packaging materials. Pets meet many important requirements, such as good aesthetic aspects ( Brilliant and transparent); Suitable for coloring; Good mechanical, thermal and chemical resistance; Low production cost; Short storage, easy recovery and low weight for glass bottles . Trends in the integration of modified compounds into PET Packaging Resins have evolved in order to produce containers with high definition, a variety of custom shapes, and no residual aldehyde. In addition, the addition of antioxidant stabilizer in PET increases its application in the food field, especially in the storage of vegetable oil27,34]. Important properties of packaging materials for moisture, barrier properties of oxygen and interaction between food and packaging materials have an important impact on the quality and shelf life of grease in food . Therefore, the main function of the packaging is to minimize the reaction that has a direct impact on the stability of the contained product [13,12]. The rancidity of food is one of the main reasons for the decline in quality. Sour defeat is the development of a well-off society. The taste produced by oxidation and hydrolysis that makes the food unusable . The storage capacity and shelf life of oils and fats are of concern to nutritionists, food processors, government regulators and consumers. Research on the impact of packaging on the quality of oil products shows that stability can be improved by selecting suitable packaging materials [ 22, 19, 21, 26, 5, 34, 33]. It is important to maximize the migration of substances in various plastic containers for food, depending on the speed of migration and the amount of migration compounds affecting the quality and stability of food. An additive present in a composite polymer, a fat-soluble phenol antioxidant, which may migrate to oil at a considerable speed during storage, thus affecting its stability [23,6,4]. Many studies have shown that antioxidants in packaging materials are released into oil Food included]3,25]. It is reported that due to the presence of this compound, the shelf life of some products has been extended . Shelf life and antioxidant properties of olive oil stored in glass and polyethylene (PE) [Check]20]. As a result of this study, it is easier to prevent oxidation of glass bottles that prevent oxygen from entering the oil than plastic bottles (PE). Sharma et al.  The study includes PE, polypropylene (PP) Toluene with Ding benzene (BHT) And Ding Ji yan Xiang ether (BHA) Refined sunflower oil and gutter oil combined with polyethylene during the shelf life at 37 [degrees]C. The results show that the change of peroxide value and sulfur arab acid (TBA) The presence of plastic films is significantly lower than that of blank samples . Kaya et al.  The effects of permeability and transparency of packaging materials are studied ( Glass bottles and PET bottles) Shelf life and stability of sunflower and olive oil. In this study, the oxidation stability of the oil was investigated by measuring the peroxide value. The results show that the storage stability of the oil increases according to the packaging material, color glass> transparent glass> PET . The quality of the oil can be controlled by measuring the peroxide value, acid value and sulfur acid value . Satue et al.  It is reported that the degree of oxidation of oil is usually determined by measuring the peroxide value (PV). Since this index is related to hydrogen peroxide, the main oxidation products cause sour and defeated flavor due to instability, thus converting to secondary oxidation products [19,28]. Kuchuk and karnier  The effects of PET packaging materials and various preservation conditions on the storage stability of sunflower oil were studied. The results show that, compared with the glass packaging under the above conditions, the presence of PETpackaging, oxygen, light and storage time increased the peroxide value, free fatty acid and iodine value, and the soap content [1  In this case, they were deeply impressed with reducing the stability of the oil storage. Effects of different types of plastic ( Polyethylene (PET) , PVC (PVC) Polypropylene (PP) And polystyrene (PS) Study on the stability of olive, sunflower and palm oil . The authors conclude that the cycle and temperature of the storage and packaging materials have a significant impact on the stability of the oil described above . Tawfik  The oil absorption and global migration of different types of plastic materials were studied ( PET, PVC, PP, PS) Different vegetable oils ( Olive oil, sunflower seeds and palm oil). The results show that the total migration from plastic packaging to vegetable oil depends on the type of plastic packaging and the type of oil considered. Tawfik concluded that the chain length and saturation of fatty acids would obviously affect the amount of oil absorbed by the polymer, while the migration of plastic components would not have much effect on . This study explores the effects of PET plastic sheets and various storage conditions on the distribution of fatty acids and some quality factors. Therefore, before and after the samples were stored at 25 and 45 [the distribution and quality factors of fatty acids, such as the values of peroxide, free fatty acids and iodine, and the induction perioddegrees] C. in the case of three common oils, no or no PET sheets, 20 and 60 days from miran market were investigated. Materials and methods oil and PET bottles: commercial sunflower, rapeseed and mixed oil ( Sunflower oil, soybean oil and cottonseed oil)( Add the amount of B. H. Antioxidant 100 mg/kg in all oils) Got PET bottle from Savola Behshahr, Tehran. Iran. Chemical solvents from Merck. , Germany. Sample Preparation: after measuring the specific surface on the bottle, cut them into 14 pieces of the same size ( Their surface is 6 [cm. sup. 2]). Pieces are placed in 250 ml glass containers, and the glass containers are poured with oil of up to 150 ml volume, so that good separation is always maintained between test pieces, and completely immersed in each type of oil. Glassware containing test pieces are stored at  and 45degrees] C. 20, 60 days 【33]. Since all samples are stored in dark places and sealed containers ( 250 ml in glassware) The light and oxygen parameters of all samples have similar effects. Control temperature and record data through data recorders (Ruskar, England). Glassware fitted with oilsonly is placed under the same conditions as a blank sample. Repeat each treatment four times. Chemical test: used to determine the distribution of fatty acids, a type- Determination of FID method  Used as a practical method. Gas chromatography system ( Germany Agilent Technology model 6890N) Flame ionization detector (FID) And HP88 columns with specifications of 100 m * 250mm * 0. 2m [1,2] Used as a practical method. Column temperature increased from 170 to 190 [degrees] Cin5 minutes 0. 5[degrees] C/min, keep at this temperature for 20 minutes, the detector temperature is [degrees] C, the carrier gas is helium at 0. 7 ml/min, pressure 10 PSI, sample intake 1 microliter [1,7]. By using the ymmat system ( Metrohm model 734, Switzerland)and AOCS(Cd 12b-92) The induction period test is completed at 110 [degrees]C . Calculate the iodine value according to the mathematical formula given in AOCS (Cd 1c-85) , Directly from the oil fatty acid spectrum (Firestone, 1994). In oxidation and rancidity, oxygen is formed by oil and peroxide. Degree of over-oxygen formation (Peroxide Value) Calculation According to AOCS (Cd8-63). The determination of free fatty acids is made by AOCS (Cd 3d-63). Statistical analysis: four experiments were conducted for each sample. Two analyses were performed from the test sample at each specific time interval. Statistical analysis ( The mean and standard division are calculated at each time interval, so analyzed with SPSS ver. 17 (SPSSInc. Michigan Avenue, Chicago, USA) And Minitab version. 11. 12 (MinitabInc. , USA). Results and discussion tables 1, 2 and 3 show the fatty acid composition of sunflower oil and mixed oil ( Sunflower seeds, soybeans and cottonseed oil) Storage on 25 th and 45 th for 20 days and 60 days before and after canolaoil [degrees]C. As the results show, it is observed that there are some minor changes in the number of saturated and unsaturated fatty acids in the above oils. The main fatty acids in sunflower oil are palm acid 7. 74(%)Fatty acid 23. 37(%) Fatty acid 61. 76(%) And flax acid. 63(%) After storage, the content of the above fatty acids changes slightly. As an example, the outline of these flower oils is changed to soft-fat acid 8. 7(%)Fatty acid 25. 15(%) , And fatty acids 57. 83(%) 60 days after 45 [storage]degrees]C. Results The amount of poly-unsaturated fatty acids such as fatty acids was reduced, and the amount of mono-unsaturated fatty acids and saturated fatty acids such as fatty acids and soft fatty acids was increased. The most striking fatty acids in the mixed oil include soft fatty acid 9. 43(%)Fatty acid 23. 80(%) Fatty acid 58. 00(%) And flax acid. 42(%) Some minor changes were observed after storage, similar to sunflower oil. It shows that the composition of fatty acids changed to soft fatty acid 9. 63(%), Acid 24. 79(%) , And 55 fatty acids. 56(%) 60 days after 45 [storage]degrees]C. Among the vegetable oils with this initial fatty acid characteristic: soft fatty acid 5. 07(%), Acid 56. 01(%) Fatty acid 20. 94(%) , Flax acid. 15(%) After storage under the same conditions, minor changes in the distribution of fatty acids were observed. The passage of time and the rise of temperature lead to the break of 2 cis double bonds and convert them into single and non-heavy bonds, geometric heterogeneity of different shapes (such as Cis or Trans) the dialogue between and local heterogeneity (such as Iso) causes the above changes . Since all samples are stored in dark places and sealed containers ( Glassware 250 ml) The light and oxygen parameters of all samples have similar effects. According to the results shown in Figure 1, the presence or absence of plastic parts has no significant effect on the distribution of fatty acids 1. significantly reduced (P [ Less than or equal to]0. 05) Observed during the induction period (IP) In the above oil, 20 days and 60 days after storage on the 25 th and 45 th [degrees]C. Of these oils, the induction cycle of canola is the largest, because this oil contains a large amount of oil fatty acids (Single saturation) Since the mixed oil contains different types of fatty acids, such as unsaturated fatty acids, the induction cycle of the mixed oil is minimal. Significant differences (P [ Less than or equal to]0. 05) The induction period was observed in the presence or absence of plastic parts. These differences indicate the effect of plastic debris on shortening the induction cycle and are related to previous studies 14,21]. In the case of mixed oil, the induction period decreased significantly after 60 days of 45 [degrees] C makes the oil useless considering the mixing oil standard ( Maximum 8 hours of authorization for entry period)[16,15,17]. The results show that canola oil has the largest induction cycle compared to other oils. As shown in the figure. 2. there is a significant increase in sunflower oil and blending oil (P [ Less than or equal to]0. 05) Value in peroxide (PV) After 20 and 60 days of 25 and 45 [degrees] C. in the case of the presence or absence of the PET sheet, but in canola oil, there is only a significant effect of time and temperature (P [ Less than or equal to]0. 05) At peroxidevalue. Mixed oil containing different types of fatty acids; Due to the large number of unsaturated fatty acids, the peroxide value is rapidly formed. Due to the presence of a large number of natural antioxidants and mono-unsaturated fatty acids, the formation rate of peroxide in sunflower oil and vegetable oil is slower than that in mixed oil [21,18,4] However, during and after storage, the efficiency of natural antioxidants was reduced, the amount of monounsaturated fatty acids decreased, and the value of peroxide in sunflower oil and vegetable oil increased compared with the original oil. In the absence of plastic parts, sunflower and vegetable oil increased significantly (p[ Less than or equal to]0. 05) After 20 days and 60 days, at 45 [degrees]C. In contrast, PVs have changed at the end of the storage period, and PVs have increased due to the release of pro-oxidation compounds such as aldehyde from plastic fragments. In addition, it is also stimulated by an increase in temperature. Previous investigations confirmed the results. 14,9,21,11]. The maximum authorized value of peroxide in sunflower oil, rapeseed oil and mixed oil in Iran\'s national standard is 2. 5, 2. 0 and 5. According to these values, 0 meq/kg, sunflower oil stored at 45 [degrees] C. rapeseed oil stored in 45 [during the two storage periods]degrees] C. 60 days stored in 45 [and mixed oil]degrees] C. 20 days with plastic parts, 60 days with plastic parts and without plastic parts, because it is not used [16,1517]. The results show that canola oil has the smallest PV at the end of the storage period compared to other oils. Iodine value (IV) As shown in the figure, reduce during storage3. The content of unsaturated fatty acids has a direct effect on IVs. Due to the presence of unsaturated fatty acids in mixed oil and sunflower oil, IVs in sunflower oil and mixed oil decreased significantly (P [ Less than or equal to]0. 05)  60 days laterdegrees] C. with or without pets. It was observed that the iodine value of vegetable oil changed slightly after decreasing. Results related to previous investigations32]. Amount of free fatty acids (FFA%) Under different storage conditions, as shown in the figure. 4. It is generally believed that during storage, partial hydrolysis of the oil has occurred, thus increasing the content of free fatty acids. A significant increase (P [ Less than or equal]0 . 05) In fa % stored for 20 days and 60 days, at 25, 45 [degrees] C. in the above oil, the effect of temperature and time on the formation of free fatty acids is shown and the previous study [13,29,9,11]. FFA % increased significantly (P [ Less than or equal to]0. 05) In the case of the presence or absence of plastic parts in the oil. Lower molecular acids are released from plastic fragments, which are caused by elevated temperature. These results are consistent with previous studies. 13]. In the Iranian national standard, the maximum allowable content of free fatty acids in sunflower seeds, rapeseed and mixed oil is 0. 2, 0. 2 and 0. Therefore, the mixed oil stored in 45 [1%]degrees] C 20 days and 60 days of deterioration with and without plastic parts [15,16,17]. It should be noted that the presence of free fatty acids increases hydrolysis, leading to deterioration of the oil and making the oil unsuitable for human consumption. The results showed that the free fatty acid content of canola oil was the highest compared with other oils. Conclusion: in the examination of mass factors such as fatty acid spectrum, free fatty acid, peroxide value, induction period and iodine value, there are obvious results. With the increase of storage time and temperature, the presence of PET tablets will have a certain impact on fa %, PV, induction period and iodine value. It is concluded from this study that the stability of vegetable oil depends on the type of oil and its initial physical and chemical properties, storage time and temperature, and the type of packaging (PET and Glass). In addition, with the increase of storage temperature and time, the deterioration rate of vegetable oil is accelerated and the stability is limited. The results showed that the quality of ofoil decreased after high temperature storage (45[degrees]C) Long storage time. Therefore, in order to prevent deterioration, the oil packaged in the PET bottle should be stored at a temperature below 25 [degrees]C. If the temperature rises (T