Chemical characterization of hull-less pumpkin seed oil press-cake

Abstract

The utilization of agricultural waste products to produce food has recently received increased attention, not only to minimize waste disposal problems, but to help maximize potential resources and production of new and novel food products. The objective of this study was to characterize the pumpkin oil press-cake, a by-product of the pumpkin seed oil pressing process. The cakes were obtained by pressing the domestic variety of hull-less pumpkin seeds (Cucurbita pepo L.) "Olinka". Two pressing processes were applied: using a continual screw press in cold-pressed oil manufacturing and hydraulic press in the virgin pumpkin oil pressing process. In order to assess the suitability of this by-product, proximate analyses of the samples were conducted to determine the residual oil and water contents, as well as proteins, carbohydrates, crude fibers and ash using official methods of analysis. The residual oil was also analyzed in order to determine its nutritive quality. The obtained results showed that two kinds of oil press-cakes were significantly different in terms of oil and water contents. The press-cake obtained using a screw press had higher water content (8.30 ± 0.40%) and lower residual oil content (13.41 ± 1.48%), compared to the press-cake obtained using a hydraulic press (3.94 ± 0.65% water content and 18.18 ± 9.44% residual oil). In addition, the pumpkin press-cakes had a substantial amount of high quality proteins. The protein content of the press-cake obtained using a screw press was 67.09 ± 3.08 % d.m., while the protein content in the cake obtained using a hydraulic press was 59.20 ± 5.13% d.m. Results have also confirmed that the residual oil, regardless of the pressing method used, was of high quality, especially in terms of the high content of the essential omega-6 (linoleic fatty acid) and gamma tocopherols. The obtained results confirmed that both press-cakes can be used in different applications as value-added, functional ingredients for food manufacture.