One main objective of this study was to increase the utilization of the raw material in the rose (Rosa damascena Mill.) essential oil industry by application of membrane technologies. A new ultrafiltration-based process for green recovery of polyphenols from distilled (de-aromatized) rose petals, the primary by-product in essential oil production, was created. The process includes enzyme-assisted extraction and subsequent membrane separation for partial concentration. Following a green membrane technology strategy, the newly developed process proposes an environmentally-friendly alternative to the conventional processing, comprising organic solvent ex-traction and adsorber resin purification. The results showed that the permeate flux decreased with volume reduction ratio’s rise and increased with the transmembrane pressure and feed flow rate rises. At the beginning of the process the highest flux was with UF1-PAN membrane, but at the end of the process with UF10-PAN membrane. Total polyphenols of the retentates in-creased by 27-39% and 26-67% during ultrafiltration with UF1-PAN and UF10-PAN membrane, respectively, with the highest value obtained for UF10-PAN membrane at VRR 6. The highest concentration factor and rejection of total solids, total polyphenols, redox-active antioxidants and radical scavenging antioxidants were obtained at VRR 6 with UF10-PAN membrane. This membrane and concentration level at transmembrane pressure of 0.4 MPa and feed flow rate of 330 dm3/h are recommended to be used for application of ultrafiltration of rose-petals by-product for potential use in the food industry.

In this experimental work, the microbiological, physicochemical, organoleptic and rheological characteristics of probiotic Bulgarian yoghurts produced by ultrafiltration of goat’s milk using different volume reduction ratio (2 and 3) and several probiotic starters (MZ2f, MZ2f + Bifidobacterium bifidum BB – 87, MZ2f + Lactobacillus acidophilus LAB – 8) were studied. It was established that the dry matter, protein, fat contents, the number of lactic acid bacteria, titratable acidity and the dynamic viscosity increased and the pH decreased with the rise of volume reduction ratio during ultrafiltration. All yoghurts exhibited Bingham plastic flow behavior. We recommend to use a volume reduction ratio of 3 and MZ2f + Bifidobacterium bifidum BB – 87 to produce probiotic Bulgarian yoghurts with the highest dry matter, protein, fat contents; counts of viable lactic acid cells, viscosity and the best sensory characteristics in the range of this experiment.