Document Type : Research Article
Authors
Ferdowsi University of Mashhad
Abstract
Introduction: Evening primrose (Oenothera biennis L.) is a relatively new oilseed crops with high value which its oil is the most important source of gamma linolenic acid. In this study, seed of Evening primrose was stored in different temperature and packaging materials to improve the content and quality of its oil.
Materials and Methods: In order to study the effect of packaging, storage temperature and storage period on Evening primrose seed oil properties, a split-plot in time experiment was conducted on the basis of completely randomized design at 32 treatments and three replications. Treatments included four levels of storage period (3, 6, 9 and 12 months) as main plot, four levels of packaging (Paper with 0.15 mm, Aluminum with 0.12 mm, PolyVinylChloride (PVC) with 0.09 mm and Cellophane with 0.07 mm thickness) and two levels of temperature (4 °C and Ambient temperature (20 °C)) as sub plots. Seed packages of 100 grams stored in plant physiology laboratory of horticulture department of Ferdowsi university of Mashhad from May 2014 to May 2015. After each period of storage seed oil (extracted by soxhelet) acid and peroxide value were examined as oil quality index. The statistical analysis was performed using the JMP software version 8 and data means were compared using LSD test’s in 5% level of probability. Acid and peroxide value were measured according to standards of EEC REG 2568/91 and AOCS cd 8-53, respectively.
Results and Discussion: Based on the results, the simple effect of temperature, packaging material and storage time was significant on all the properties of evening primrose oil. Before storage, seed oil content was 16.45% (w/w) but after three months of storage the oil content increased to 19.75% w/w. From third month of storage until 9th a sharp decline was observed, and the oil content was 12.71 % w/w at the end of 9th months. Finally the seed oil content slightly increased until 12thmonth. Before storage, acid and peroxide value were reported 1.16 (mg KOH/g oil) and 2.4 (meq O2/Kg oil), respectively. During storage, acid value showed descending trend so that at the end of 6 and 12 months storage obtained 1.08 and 0.96 mg KOH/g oil, respectively. Oil peroxide value after third months reached to 3.14 (meq O2/Kg oil) and its maximum (9.82 meq O2/Kg oil) was detected at the end of storage period. Ambient temperature in terms of oil content and 4 °C in terms of oil quality were optimum condition for Oenothera seed storage. Seeds samples which packed in paper and cellophane material showed the most oil content (17.29% and 16.75%, respectively). Cellophane packaging in terms of acid (0.89 mgKOH/g oil) and peroxide value (5.05 meq O2/Kg oil) was diagnosed the best packaging material to preserve the quality of the oil during storage. Interaction between storage temperature and storage period on oil percentage was significant at 1%. The highest oil percentage (59/22%) was detected after three months of storage at ambient temperature. Interaction between packaging and storage temperature on acid value of evening primrose seed oil was significant at 1% as aluminum packaging at ambient temperature and paper packaging in both temperatures had the highest acid value (1.15 and 1.11mg KOH/g oil, respectively). The lowest acid value (0.82 mg KOH/g oil) was detected in cellophane packaged seeds at 4°C temperature. Interaction between packaging material and storage period on acid value of evening primrose seed oil was significant at 1%. The highest acid value (1.24 mg KOH/g oil) obtained after six months in paper packaged seeds and seeds samples which packed in cellophane material had the lowest acid value (0.72 mg KOH/g oil) after nine months of storage. Interaction between storage temperature and storage period on acid value of evening primrose oil was significant at 1%. The highest acid value (1.11mgKOH/g oil) was detected after 12 months of storage at ambient temperature. At the end of 12th months at 4 °C temperature, the lowest acid value (0.81mg KOH/g oil) was reported. Interaction between packaging material, storage temperature and storage period on acid value of evening primrose seed oil was significant at 1% as paper packaged seeds after six months of storage at 4°C temperature and cellophane packaged seeds after 12 months of storage at ambient temperature showed the highest acid value (1.34 mg KOH/g oil). The end of 9th months in cellophane packaged seeds at both temperature, the lowest acid value (0.72 mg KOH/g oil) obtained. Interaction between packaging material and storage period on peroxide value of evening primrose oil was significant at 1% as paper packaged seeds after 12 months of storage had the highest peroxide value (11meq O2/Kg oil). Seeds samples which packed in PVC and cellophane material after three months showed the lowest peroxide value (2.15 and 1.85 meq O2/Kg oil, respectively). Interaction between storage temperature and storage period on peroxide value of evening primrose oil was significant at 1%. The highest peroxide value (10.01meq O2/Kg oil) was detected after 12 months of storage at ambient temperature. After three months of storage at 4°C temperature the lowest peroxide value (2.65 meq O2/Kg oil) obtained. Interaction between packaging material, storage temperature and storage period on peroxide value of evening primrose seed oil was significant at 1% as paper packaged seeds after 12 months of storage at 4°C temperature had the highest peroxide value (12 meq O2/Kg oil). The lowest peroxide value (1.60 meq O2/Kg oil) was detected in cellophane packaged seeds after three months of storage at 4 °C temperature.
Conclusion: Overall, evening primrose seed storage in paper and cellophane packaging during three months at ambient temperature to improve the content of oil was desirable. Seed storage in paper packaging at ambient temperature after12 months, reduced oil quality. Seeds samples which packed in PVC and cellophane material at 4°C temperature preserved the quality of evening primrose oil.
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