ویژگی‌های فیزیکی و شیمیایی روغن استخراج شده از بافت‌های چربی شترمرغ (نژاد گردن مشکی کانادایی)

Introduction: The ostrich (Struthio canelus) is the largest and oldest bird in the world and belongs to the Ratite family, which is unable to fly and is adapted to living in hot areas and barren lands. Birds of this family are characterized by low-fat meat and low cholesterol. Ostrich oil makes up about 15% of their total body weight (Basuny et al., 2017) that is mainly composed of triglycerides and is free of phospholipids. Ostrich oil is a relatively new and very valuable source of animal fats, which in recent years has received special attention to the use of it in pharmaceutical and food industries. Today, ostrich oil is mostly used for health, cosmetic and also medicinal purposes. Little researches has been carried out on its use orally and there is no comprehensive information about the properties of adipose tissue oil in different parts of ostrich body. Therefore, the aim of this study was to investigate the physical and chemical properties of oil extracted from different parts of ostrich body and introduce it as a new source of edible fat.
Materials and Methods: In this study, adipose tissue from 3 parts (front of the heart, front of the chest and lower abdomen) were obtained from ostrich breeding farm (Karaj, Iran). Oil extraction was carried out according to wet melting method by using rotary evaporator at 80°C for 2 hrs. Then some physical and chemical properties of the extracted oil such as fatty acid composition, cholesterol and total sterol, tocopherol composition, melting point, refractive index, color and induction period were investigated. The fatty acid composition of oils was determined by employing a gas chromatograph equipped with a DEGS capillary column (60 m × 0.25 mm i.d.) and a flame ionization detector. Sterols and tocopherols were identified by gas chromatography and high performance liquid chromatography methods respectively. Refractive index of oils was determined by using a refractometer and color of samples were analysed by application of Lovibond. The induction period was performed on a Metrohm Rancimat apparatus model 743 at 110 °C with an air flow of 20 L/h. All the experiments and/or measurements were carried out in triplicate order. The data were statistically analyzed using the Statistical Analysis System software package on replicated test data. Analyses of variance were performed by application of an ANOVA procedure. Significant differences between the means were determined using the Duncan multiple range test.
Results and discussion: Based on the results, the highest amount of oil extracted from the abdominal parts (62.45%), front of the chest (40.35%) and front of the heart (38.58%) respectively. The main saturated and unsaturated fatty acids of extracted oils were palmitic and oleic acids respectively. The results of total saturated and unsaturated fatty acids in oil samples indicated that the highest amount of total saturated fatty acids was observed in oil obtained from the front of the heart (34.59%) and the lowest amount was observed in lower abdominal oil (33.72%) (P<0.05). The highest amount of unsaturated fatty acids was related to the lower abdomen oil (66.28%) and the lowest amount was in the front of the chest oil (65.44%) (P<0.05). The ratio of polyunsaturated fatty acids to saturated fatty acids (PUFA/SFA) in the oils of front of the heart, front of the chest and lower abdomen were 0.59, 0.61 and 0.65, respectively. The results of total sterol and cholesterol in the oil samples showed that the highest amount of total sterol (125.91 mg/100 g) and cholesterol (95.82 mg/100 g) were obtained in the oil of front of the heart. The highest levels of delta tocopherol (0.98 mg/100 g) were in the oil of anterior cardiac. The highest levels of alpha tocopherol (2.45 mg/100g) and beta tocopherol (0.87 mg/100g) were obtained in anterior thoracic oil. The samples were not different significantly in terms of gamma tocopherol and gamma tocotrienol. Melting point (29.31°C in all samples), refractive index (1.45 in all samples), yellow (35 Lovibond) and red (2 Lovibond) colors in the oils of the front of the heart, front of the chest and lower abdomen did not show significant differences. The highest induction period was obtained in the oil of front of the heart (11.58 hours) and the lowest stability was related to abdominal part (11.44 hours), Therefor no significant difference was observed between the induction period of the samples (P<0.05).
Conclusion: In this study, the results of the analysis of fatty acids in the studied oils showed that the composition of ostrich oil fatty acids in the lower abdomen, front of the heart and in front of the chest are the same and only their amounts were evaluated differently. According to the obtained results, ostrich oil can be considered as a valuable oil in the food industry due to its high content of essential fatty acids and tocopherol compounds, low cholesterol and good stability.