# Changes in Collagen across Pork Tenderloin during Marination with Rosehip Nanocapsules
## 1 Introduction  
Pork production is a dynamic and growing industry that produces 33% of the total meat consumption of animal meat in the population's diet, with differences between continents. The main nutrients in pork are proteins with essential amino acids, fats with essential fatty acids, vitamins, minerals, and other health-promoting compounds such as antioxidants [1]. One of the most important proteins is myofibrillar protein, which constitutes 55 to 60% of the total meat proteins or 10% of the weight of skeletal muscle. Meat proteins play a significant role in determining the quality of muscle products because they are responsible for the functional characteristics of meat and meat products, impart textural and emulsifying properties, and have gel-forming and water-holding abilities [2, 3]. Another important protein is collagen, which plays a significant role in the tenderness of meat and meat products; it is the major structural protein of connective tissue [4, 5]. However, the contribution of collagen characteristics to tenderness may differ between species, age, and gender [6]. It has been reported that the collagen present in muscles is approximately 1.5-10% of its dry weight [7]. The functional characteristics of these proteins are mainly affected by the processing conditions, for example, ionic strength, pH, and temperature [2], affecting the tenderness and biological value of the meat. Different chemical reactions occur during the processing and storage of meat due to molecular interactions as a result of thermal treatment or the addition of additives. For this reason, other methods, both physical and chemical, have been developed to preserve meat. These methods not only aim to maintain quality but also consider sensory and nutritional features as well as consumer appeal. There is a growing demand for natural-origin preservation systems and minimally processed meat products with longer shelf lives [8]. Mariation is one of the chemical methods used for improving meat tenderization [8]. However, acid marination improves the tenderization and flavoring of treated meat, causing meat fibers to swell [4; 9] through collagen and myofibrillar solubility and muscle protein swelling [10]. Various ingredients have been incorporated into marinades to preserve and improve tenderness and flavor. Using nanoparticles to enhance the release of antibacterial and antioxidant compounds could be an option to improve meat products' quality. In recent investigations, functional and bioactive nanoparticles in meat and meat products have been used to enhance the nutritional benefits by reducing saturated fats and salts [10]. Rosehip oil is an active compound that can be used as a natural additive in meat during marination. It is obtained from the seeds of the pseudo fruit _Rosa canina_ L. It has shown a powerful natural antioxidant capacity due to the content of ascorbic acid, carotenoids, and phenolic compounds [11; 12]. In addition, this oil is rich in linoleic (54%), linoleic acid (19.37%), and other polyunsaturated fatty acids (19.50%). Phytosterols (\(\beta\)-sitosterol), in particular, have important functional properties that can potentiate the beneficial effects of consumption. This oil is important because, due to its phenolic compounds, it has a greater antioxidant capacity than other vegetable oils, such as grape seed oil and pomegranate seed oil. Rosehip oil also has a higher level of linolenic acid than vegetable oils, such as canola and soybean, which are the primary dietary sources of linolenic acid [13]. A problem with this oil is its high content of linoleic and linolenic acids, which are vulnerable to lipid oxidation [14]. The entrapment of rosehip oil in nanocapsules increases its stability and can be used for meat marination. Nanoencapsulation protects oil against fatty acid oxidation and modifies its release time. Little information is available on the use of nanoparticles in marination and meat quality preservation [10].