# Changes in Selected Properties of Cold-Pressed Oils Induced by Natural Plant Additives
## 1 Introduction  
Cold-pressed oils are extracted from seeds and fruits of oil-bearing plants with fat content higher than 15%. An exception is oil pressed from amaranth seeds, which contains 4.9-8.1% of fat [1]. According to the Codex Alimentarius, these vegetable oils and edible fats are extracted by mechanical pressing at low temperature. The products can be purified by rinsing with water, sedimentation, filtration, or centrifugation [2]. Cold-pressing oil extraction is a relatively common method based on the use of hydraulic or screw presses equipped with a cooling system. The method is a very simple and ecologically clean technology and does not require significant investment and energy inputs; consequently, it has gained popularity [3]. Given their content of highly active antioxidants (tocopherols, polyphenols, carotenoids, squalene), n-3 and n-6 polyunsaturated fatty acids, and bioactive sterols, cold-pressed oils can be classified as functional foods. Because of their characteristic aroma and flavor, they are most often added to potatoes, octtage cheese, or salad dressings. In addition to their traditional use, they are also applied as an enrichment in some products (e.g., mayonnaise and bread) with various bioactive compounds [4].  
An undesirable phenomenon affecting the oils is the decline in their nutritional value during long-term storage. The most substantial changes in the chemical and organoleptic properties of these products are induced by reactions with oxygen [5]. The degradation rate and oil stability depend, for example, on fatty acid composition, oil extraction method, and oxygen concentration, as well as on the presence of free fatty acids, mono- and diacylglycerols, transition metal ions, phospholipids, enzymes, pigments, and antioxidants [6].  
One of the methods to prevent unfavorable changes occurring during storage of fats involves combining oils with aromatic ingredients, such as herbs, spices, or seasoning vegetables (e.g., garlic and chili pepper), especially those with high antioxidant potential due to high total phenolic and flavonoid content [7]. This primarily increases the oxidative stability of the mixture [5]. In addition, the content of ingredients, such as vitamin C, provitamin A, carotenoids, capsaicin (chili pepper) [8], phenolic acids, and flavonoids, contributes to the increase in the nutritional value of oils. It improves the parameters beneficial for human health. These additives have been reported to exert a protective role against certain cancers, prevent gastric ulcers, stimulate the immune system, prevent cardiovascular diseases, and protect against age-related macular degeneration and cataract [9; 10].  
Because the antioxidant activity of these additives (garlic and chili pepper) has not yet been reported in the oils, the present study aimed to determine the effect of addition of garlic and chili pepper (as a source of natural antioxidants that could increase the shelf life and avoid changes in the fatty acid composition of the sample in terms of the degree of lipid oxidation, peroxide value (PV), and oxidative stability) on the chemical properties of cold-pressed oil from selected seeds after 2, 4, and 6 weeks of storage at 10 \(\pm\) 1 \({}^{\circ}\)C.