Abstract
Plum kernels of the “Čačanska rodna” variety, by-products from plum brandy production, were collected before and after fermentation and distillation, and used for cold-pressed oil production. Fatty acid and tocopherol contents were determined by capillary GC and HPLC, while the oxidation stability of the resulting cold-pressed oils was tested by the Rancimat method. The results showed that oleic fatty acid was dominant in the oil samples with a content of 56.6 to 61.8%, regardless of the plum kernels’ origin. The fermentation and distillation processes had a pronounced effect on the tocopherol content and oxidative stability of the resulting kernel oils. Tocopherol contents were 61.8 mg·100g-1, 87.4 mg·100g-1, 79.6 mg·100g-1 of oil, while the induction periods were 38.7, 44.4 and 33.6 hours for samples before fermentation, after fermentation and distillation, respectively. Based on the results, it could be concluded that the fermentation process increased the content of tocopherols in kernel oil whereas the high temperature during the distillation process adversely affected the tocopherol content and oxidative stability of the obtained kernel oil.
Highlights
MaterialKernels of the plum variety “Čačanska rodna” were used as starting material for the production of cold-pressed oil
Kernels from fresh plums before fermentation (PKBF) were used, as well as those extracted from different stages of the slivovitz production process, in particular, kernels separated after fermentation (PKAF) and kernels separated after distillation (PKAD)
Even though the plum kernel oil can be compared to olive oil in terms of its fatty acid composition and content, this is not the case when it comes to tocopherol content. α-tocopherol is dominant in olive oil, ranging up to 370 mg·kg-1 in content (Psomiadou et al, 2000)
Summary
Kernels of the plum variety “Čačanska rodna” were used as starting material for the production of cold-pressed oil. Plums were allowed to ferment for 13 days at 18-20 °C, while batch distillation was performed in a traditional alembic pot of 250 L for 3 hours by direct heating. The kernels were dried to 6% humidity to facilitate cold-pressing. The kernels (approximately 300 g per sample) were cold-pressed in a small-scale screw oil press (Gorenje, 2 kg·h-1 capacity, power 650 W). The temperature of the obtained oil was monitored by an IC thermometer and kept below 45 °C. After cold-pressing, the oils were kept at room temperature (22-24 °C) for 24 hours for natural sedimentation and decanted. Impact of plum processing on the quality and oxidative stability of cold-pressed kernel oil 3
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