Srećko Tomas

Effect of extraction conditions on the extractability of phenolic compounds from lyophilised fig fruits (Ficus carica L.).

Effect of Extraction Conditions on the Extractability of Phenolic Compounds from Lyophilised Fig Fruits (Ficus Carica L.) In this work the influence of 50-80% (v/v) aqueous ethanol and the temperature of extraction (25-80°C) on the extractability of total phenolics, total flavonoids and total proanthocyanidins from different fig fruits was investigated. The best extraction conditions (80%, v/v aqueous ethanol, 80°C) obtained in the experiments with lyophilised Ficus carica L. cv. Šaraguja were used while performing the extraction of phenolic compounds from other fig varieties (Bružetka bijela, Crnica, Bjelica and Termenjača). The antioxidant capacity was measured in all fig fruits as well. It has been shown that the temperature of extraction and ethanol to water ratio have a statistically significant influence on the extraction of phenolic compounds from fig fruits variety Šaraguja. The highest content of phenolic compounds was found in fig variety Crnica while the lowest one in fig variety Bjelica. According to the results obtained in this study, fig fruits can be considered as a natural source of phenolic compounds with good antioxidant capacity.

Characterization and differentiation of monovarietal grape marc distillates on the basis of varietal aroma compound composition.

To investigate the varietal aroma compound composition of monovarietal grape marc distillates made from six different varieties (Vitis vinifera L.) in the region of Istria (Croatia), 30 samples were subjected to GC/MS and GC/FID analysis. A total of 73 compounds were identified: 45 monoterpenes, 20 sesquiterpenes, 3 diterpenes, and 5 C(13)-norisoprenoids. The largest number and the highest concentration of monoterpenes were found in Muscat Blanc, followed by Rose Muscat of Porec (Muskat ruza porecki) distillates, which were both characterized as highly aromatic. Lower, but still significant monoterpenol content was determined in distillates made from Istrian Malvasia (Malvazija istarska) grape marc. Chardonnay, Cabernet Sauvignon, and Teran distillates exhibited poorer monoterpene profiles, while Teran distillates contained elevated sesquiterpene concentrations. It was concluded that investigated monovarietal grape marc distillates significantly differ in varietal aroma compound composition. Stepwise linear discriminant analysis provided efficient discrimination models, and extracted various monoterpenes, sesquiterpenes and C(13)-norisoprenoids as important differentiators of distillates according to varietal origin.

Cold Pressing and Supercritical CO2 Extraction of Hemp (Cannabis sativa) Seed Oil

In a past few decades the variety of hemp Cannabis sativa L. was unfairly neglected because of the similarity with the kind of hemp that is illegal and is used as a narcotic. The objective of this study was to evaluate the oil extraction process from Cannabis sativa seeds by cold pressing followed by extraction with supercritical CO2. In pressing experiments, the response surface methodology was conducted in order to study the effects of temperature, frequency and nozzle size on oil recovery and quality parameters. The optimal condition to obtain the highest oil recovery and the best oil quality within the experimental range of the variables studied was at temperature of 60 °C, frequency of 20 Hz and using nozzle of ID 6 mm. The residual oil in the press cake was totally extracted by supercritical CO2 in newly designed and built supercritical fluid extraction system. The oregano essential oil was the most effective in protecting the oil from oxidative deterioration.

Simulation, calculation and possibilities of energy saving in spray drying process

In this work some possibilities to improve the conventional spray drying process using programming in Excel as a calculation tool have been presented. The program gives a simple description of the drying process using thermodynamic calculations of heat and mass balance. Using the program it is possible to reduce operating costs and to improve capacity per unit of drying equipment. The minimization of energy consumption during the drying operation can be achieved by recycling exhaust air. The maximum theoretical range of recirculation is 60%. The fuel oil saving rate depends linearly on the rate of recirculation, and the theoretical maximum fuel oil saving is approximately 14%. Ecological issues were also considered as well, since decreased fuel consumption lowers harmful gas emission to the environment. All necessary data are represented in the process flow sheet, which is used for a better understanding of the drying process optimisation.

Influence of Temperature and Drying Time on Extraction Yield of Phenolic Compounds from Grape Pomace Variety “Portogizac”

The influence of drying temperature (60 °C, 70 °C, 80 °C) and fluid-bed drying time (90 min, 135 min, 180 min) on the extraction yield of phenolic compounds and antioxidant activity of extracts were investigated. The content of phenolic compounds and antioxidant activity of extracts obtained from wet grape pomace (WGP) were 73.83 mgGAE gdb–1, 42.24 mgCE gdb–1, 30.53 mg gdb–1, and 0.35 ginhDPPH gdb–1 for total phenolic compounds (TPC), total flavonoids (TF), total extractible proanthocyanidins (TPA), and antioxidant activity (AA), respectively. The applied drying conditions caused the reduction of content of all phenolic compounds down to 13.2 %, 43.1 %, 15.3 % and 21.0 % for TPC, TPA, TF and AA, respectively. The most abundant individual phenolic compound in grape pomace extracts was catechin (5.14 – 8.52 mg gdb–1). The highest content of observed compounds was retained when applying drying temperature below 70 °C for 90 minutes.