# The Study of Thermal Properties of Blackberry, Chokeberry and Raspberry Seeds and Oils
###### Abstract  
The seeds of berry fruits are a component of fruit waste occurring in the production process. Circular economy rules focus on decreasing the amount of waste produced and reusing by-products when it is possible. To determine the possible applications of the studied fruit industry wastes, the thermal properties of berry seeds and of oil extracted from the tested material were examined. Differential scanning calorimetry (DSC), modulated differential scanning calorimetry (MDSC), and thermogravimetry (TG) of blackberry, chokeberry, and raspberry seeds were carried out. The properties of oil extracted in the Soxhlet apparatus were studied by pressure differential scanning calorimetry (PDSC), TG, and gas chromatography (GC) measurements. The results show that berry seeds lipids are from different melting fraction groups with a dominance of low-melting fraction, which consists of mono- and polyunsaturated fatty acids. There are also occurring residues of carbohydrates and inorganic, thermostable substances in the studied seeds. A GC analysis of oil confirms that the polyunsaturated fatty acids (PUFA) are most abundant and amount to 78.72 \(\pm\) 0.06% in blackberry seed oil, 73.79 \(\pm\) 0.14% in chokeberry seed oil, and 82.74 \(\pm\) 0.03% in raspberry seed oil. The PDSC study showed that the most oxidative stable oil is blackberry seed oil, followed by raspberry and chokeberry seed oils. According to the obtained results, berry seeds can be used as a source of oil in food or other production chains. However, more detailed characteristics of berry seed oils are needed to determine their applicability. f 2 but generally, they are rich in seeds and skins of fruits. For example, the seeds content in powdered chokeberry pomace was found to be 22.1% [6]. Seeds of berry fruits may be a source of high-quality oil with a high content of polyunsaturated fatty acids (PUFA), which are significant from a nutritional point of view [7; 8]. Especially significant is the abundance of \(\alpha\)-linolenic and linoleic acids, which are classified as essential fatty acids and must be delivered by food to humans [9]. The oils also contain monounsaturated fatty acids (MUFA) and a limited percentage of saturated fatty acids (SFA) [7; 8]. However, a high PUFA content results in the lower oxidative stability of oils which may affect the application of berry seed oils. High topcpherd abundance in berry seed oils [7; 8] may have a preventive role in the oxidation process, but only at lower temperatures, due to topcpherd's ability to promote oxidation in high temperatures [10]. To define possible ways of berry seeds usage, it is reasonable to study the properties of seeds and the oil obtained from them. Thermal properties are the most adequate parameters to determine the usefulness of seeds as a source of oil. Differential scanning calorimetry (DSC) and modulated differential scanning calorimetry (MDSC) are applicable tools to describe the thermal transitions of examined samples in micro-scale. They provide information about thermodynamic and kinetic characteristics dependent on the temperature of the material. In food products analysis, DSC helps determine the transitions resulting from the specific composition of foods because different groups of nutrients are specified by various transitions. Considering lipids, it is possible to analyze first-order transitions, e.g., the transformation of the crystalline structures or melting, and also second-order transitions, e.g., setting crystalline structures. That information can be helpful in the determination of the shelf life of products and their rheological properties [11]. Modulated scanning calorimetry is useful in determining the glass transition, which is a parameter describing the transition of a substance from a glassy state to a gummy state. This parameter is specific for a given material and depends on its composition.