This study is concerned with the effect of the process of roasting of naked pumpkin seeds prior to their pressing on the chemical composition and oxidative stability of the extracted oil. Ground seeds were roasted at temperatures of 90, 110, and 130°C for 30 and 60 min, according to the traditional technology of production of roasted pumpkin oil. Depending on the roasting conditions of the seeds, this treatment resulted in a significant increase of the contents of phospholipids (from 0.005 to 0.463%), total phenolic compounds (from 4.63 to 19.60 mg/kg), and total tocopherols (from 265.79 to 350.98 mg/kg) in oil. Higher contents of these minor components enhanced the oxidative stability of the oil, i.e., increased the induction period (from 4.50 to 12.93 h). However, at the same time, the applied thermal treatment generated an increase in the primary and secondary oxidation products, resulting in higher Totox values that could lower the quality of the oil.

The production of cold-pressed oil from nonroasted naked pumpkin seeds by pressing with screw presses started in the Republic of Serbia at the end of 1990s. This oil has the characteristic flavour of raw-dried seeds, and is a specific product of this region. The oil samples were prepared by pressing naked pumpkin seeds and pumpkin seeds with the hulls in a 3:2 ratio using a screw press. The changes of the oil sensory characteristics, basic chemical quality and oxidative stability were followed over a 2-year period. The results obtained showed that the oil sensory quality was stable during the first 12 months of storage, after which the flavour became musty. Although the chemical quality of the oil deteriorated to some extent, both the acid and peroxide values satisfied the legislative minimum during the whole investigation time. The oxidative stability of oil determined by a Rancimat apparatus was good, although the induction period after 2 years decreased by 25-40%. To ensure the use of only the highest quality oil, a 12-month shelf life is recommended.

Prolonged storage of frozen berries had some impact on the quality of the oils compared to the fresh sample. Free fatty acid content (FFA) and peroxide values (PV) increased in blackberry oil (BO) (from 1.18 to 3.54% oleic acid) and in raspberry oil (RO) (from 2.66 to 8.84% oleic acid). PV values were higher in the RO (increased from 4.82 to 13.97 mmol/kg) than in the BO (increased from 3.73 to 11.14 mmol/kg). Both oils were very high in omega‐6 FA (%): 63.66 ± 0.49 for BO and 54.94 ± 0.18 for RO, and omega‐3 FA (%): 14.77 ± 0.42 for BO and 32.38 ± 0.38 for RO, with their ratio of 1.8 and 4.5. Both oils have shown a very high level of α, β + γ, and δ‐tocopherols. Much higher levels of campesterols and stigmasterols were found in the BO, while the content of β‐sitosterols was much higher in the RO. Total phenolic content was much higher in the BO (∼27%). Our results demonstrated that pomace, despite longterm frozen storage, is a good raw material for oil extraction, as its oil composition remains stable. Chemical characteristics suggested that oils are of high quality and a possible source of functional ingredients. Practical applications: Pomace is a fruit processing waste, which is currently underutilized, and not used much for food production. Blackberry and raspberry seed pomaces that mostly consist of seeds are generated in large quantities. Both seed oils are of high quality and rich in essential omega fatty acids and very high content of bioactive compounds such as tocopherols, phenols, sterols, and carotenoids that have antioxidant properties. Due to their nutritional and antioxidant properties they are considered value‐added products that can be successfully used for functional and nutraceutical food products. The oils have high levels of oleic, omega‐6, and omega‐3 fatty acids and bioactive compounds including tocopherols, phenols, sterols, and carotenoids. Based on the research results, prolonged storage (8 months) of frozen blackberries and raspberries in sealed plastic bags at −18°C before further processing and use of the pomace as a by‐product can be recommended to the food industry.

This study is concerned with the determination of technological quality characteristics of dried pomaces, i.e. blackberry and raspberry seeds, along with the quality parameters, content of total carotenoids and chlorophyl and transparency of crude extracted oil (using organic solvent). Blackberry seeds (Rubus fruticosus L.) were obtained from a domestic variety Čačanska bestrna, while the raspberry seeds (Rubus idaeus L.) were of the variety Willamette. Oil content of the blackberry pomace was 13.97 and 14.34%, while the oil content of the raspberry pomace was 13.44 and 14.33% on dry basis (d.b.). In regard to technological characteristics of the pomaces, i.e. volumetric and specific weight, no considerably difference was found. However, a weight test for 1000 seeds showed a significant difference in weight: 3.5 g (d.b.) for the blackberry pomace and 1.5 g for the raspberry pomace (d.b.). Proximate analysis of blackberry seed oil showed that this oil had better quality since the FFA value was 3.43% (sample B1) and 3.53% (sample B2), while the peroxide value was 8.89 and 11.16 mmol/kg, respectively. Raspberry seed oil had higher FFA (8.59 and 8.83% for sample R1 and R2) and peroxide values (13.99 and 13.84 for sample R1 and R2) than the blackberry seed oil. Crude extracted blackberry seed oil had a brown-greenish color due to the high total chlorophyll content (around 3000 mg/kg dissolved in cyclohexane). Raspberry seed oil had a dark yellowishorange color, due to lower chlorophyll content (around 200 mg/kg) compared to the blackberry seed oil, while the content of total carotenoids was slightly higher in this oil (around 40 mg/kg) compared to the blackberry seed oil (33 mg/kg). [Projekat Ministarstva nauke Republike Srbije, br. TR 31014: Development of the new functional confectionery products based on oil crops

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