| Abstract [eng] |
Rational utilisation of biomass, which occurs as a secondary product in the process of recycling raw plant material, is a relevant issue. Currently the biggest emphasis is on the ultrasound application for plantbased protein treatment within lower temperatures (< 50 ˚C). The aim of this thesis is to evaluate the functional features of flaxseed protein extract after dry fractionation, their changes after the ultrasound treatment using different levels of pH and their potential use in bioprocesses as well as the manufacture of hydrated gel. In the beginning of the experiment there were two stages of dry separation used to get the protein-rich fractions of flaxseed: (i) combined separating (aero-dynamical separation and sieving fractionation) and (ii) separation based on geometric features. Combined separation was found to be more effective and simpler allowing to get up to 35 % more protein on average in the extracted flaxseed fractions (d ≤ 0,315 mm; 0,315 < d ≤ 0,500 mm). These fractions were found to contain the highest level of fat (17,28 %; 7,51 % respectively). Ultrasound treatment of flaxseed protein fractions (850 kHz; 2 W/cm2) increased soluble protein contents by 2,80 % compared to baseline. Analysis of albumins and globulins within flaxseed protein fractions using SDS-PAGE electroferosis technique in a range of 8,000 and 220,000 D, revealed the impact of ultrasound treatment on the qualitative changes of protein. In all cases, higher ultrasound effects on protein substances have been observed on albumin fractions than on globulins by initiating especially lower molecular weight (< 12,000 D) protein formation. The further analysis also includes ultrasonication impact on functional properties of flaxseed protein fractions. Using 15 % solution of flaxseed protein fractions, gel formed more effectively and had a more intense colour during high frequency ultrasonic treatment (850 kHz, 0,9 W/cm2 and 1,3 W/cm2) rather than low frequency (37 kHz, 2 W/cm2). Emulsion formation capacity within albumin fractions was lower with the highest ultrasound intensity used on samples (850 kHz; intensity – 2 W/cm2) compared with the lower intensities (0,9 W/cm2, 1,3 W/cm2). Emulsion formation capacity was found to be related to pH and it was the highest within acidic medium (pH 3). Positive ultrasound impact and significant increase of foam formation capacity within globulin fractions was found to be using the lowest ultrasound intensity (0,9 W/cm2) and pH 7. Ultrasonic treatment (850 kHz, intensity – 0,9 W/cm2) of flaxseed protein fractions increased growth of their lactic acid bacteria (LAB). Flaxseed protein fractions in all stages of fermentation (after 6, 22 and 30 hours) were a better medium for cultivation of L. paracasei than P. pentosaceus (KTU 05–9). While applying ultrasonic treatment of flaxseed protein fractions (duration – 30 min), it allowed to use higher quantity of lyophilised raspberry additive (5%) for gel preparation and hence increase its effect on gel quality. |
