# Optimizing Nigella Oil Extraction Temperature for Sustainable Production
## 1 Introduction  
The oil from _Nigella sativa_ seeds, which is also known as black cumin or Kalonji seed oil, plays a crucial role in nutrition by providing essential fatty acids, vitamins, and energy. Additionally, they hold significant value in the cosmetics and pharmaceutical industries due to the presence of phytoconstituents with medicinal properties, specifically thymoquinone (TQ) [1, 2, 3, 4, 5]. Several extraction systems are used to extract Nigella oil, including ultrasound-assisted extraction, microwave-assisted extraction, supercritical fluid extraction, mechanical extraction, Soxhlet extraction, and reflux extraction [3]. Over the past few decades, researchers have conducted comparative studies to understand the effect of these different extraction methods on Nigella oil yield and the concentration of its phytoconstituents. Their findings indicate that the oil yield and the concentration of phytoconstituents vary significantly depending on the extraction method used [6, 7, 8, 9, 10, 11, 12, 13, 14]. Among all the extraction methods, the screw press method, also known as mechanical pressing, has garnered significant attention due to its numerous advantages. These include high-quality product output, lower energy requirements, a more ecological and nontoxic approach, lower investment costs, and a comparatively simple extraction process [3, 15, 16, 17, 18]. Such benefits make the screw press method crucial for sustainable oil production by contributing to environmental preservation, resource efficiency, and economic viability. Unlike solvent extraction, which uses chemicals like hexane, the screw press method does not involve any chemical solvents. This significantly reduces the risk of environmental contamination and ensures that byproducts are free of chemical residues, making them safer for use in animal feed or as fertilizers [19; 20]. Utilizing these byproducts contributes to a circular economy, where waste is minimized and resources are continuously reused. Additionally, the low investment cost and easy handling of this method make it economically viable for small-scale producers, promoting sustainable local agriculture and production. Furthermore, the quality of oil is of prime importance and cannot be compromised. The mechanical nature of the screw press method has been reported to retain more natural nutrients and flavors in the oil, which are often lost in chemical extraction processes [20]. This results in higher quality, more nutritious oil. However, various parameters such as characteristics of the raw material (moisture content, oil content), feeding rate, extraction temperature, rotation speed of the screw, diameter of the restriction dye, and pre-treatment can affect the oil yield and the proportion of phytoconstituents in the screw press method. Therefore, it is important to identify the optimal conditions for these parameters [8; 15; 21; 22]. Some researchers have investigated the optimal conditions for screw press extraction of Nigella oil using different parameters. For instance, [PERSON] et al. applied a combination of three different feed rates, temperatures, and moisture contents to determine the ideal extraction condition in terms of oil yield and TQ [18]. [PERSON] et al. also utilized various physical parameters of the screw press oil expeller, such as nozzle size, extraction speed, diameter of the shaft screw, and extraction temperature, to identify the optimal extraction condition in terms of oil yield [8]. However, when optimizing the conditions for Nigella oil extraction, it is crucial to consider additional quality parameters, including TPC, antioxidant capacity, and fatty acid composition, in addition to oil yield and TQ content due to their significant influence in the nutritional, therapeutic, and commercial value of Nigella oil. The aim of this research was to optimize the oil yield, bioactive compounds, and fatty acids composition of screw-pressed Nigella oil by varying the temperature while keeping other parameters constant.