This doctoral dissertation investigated the possibility of using butternut squash (Cucurbita moschata) to obtain highly valuable pectic polysaccharides. Pectic polysaccharides were obtained by conventional acid extraction, enzyme-assisted acid extractions and enzymatic extractions, and subsequently characterized. In general, the yield of pectic polysaccharide, compared to conventional acid extraction (60.6 mg/gDM), was increased when the acid step was preceded by enzymatic treatment. On the other hand, yields of enzymatic extractions were similar or lower compared to the acid extraction. The highest extraction yield (104.4 mg/gDM) was obtained after acid extraction assisted by xylanase, cellulase and amylase.With the use of enzymes for the extraction of butternut squash pectic polysaccharides, it was possible to obtain up to 3 times higher galacturonic acid content than in conventional acid extraction; the highest galacturonic acid content was determined in the sample obtained in amylase-assisted acid extraction (84.4 g/100 g). The same was true for the content of homogalacturonan, and the opposite for rhamnogalacturonan-I. After the degree of methoxylation was determined, all pectic polysaccharides, except the acid-extracted one, were classified as low methoxylated pectins. The application of acid in the extraction of pectic polysaccharides from butternut squash had a negative effect on the content of total phenols, antioxidant and iron(II)-chelating activities. The highest content of total phenols was determined in the sample extracted with cellulase and xylanase (1.16 mg FK/g). In-vitro antioxidant activity was the highest in the sample extracted with cellulase, xylanase and amylase (2.42 mM TE/100 g), and the highest Fe2+-chelating activity in the sample extracted with amylase (2.13 mM EDTA/100 g). By measuring the molar mass, it was determined that the acid-extracted pectic polysaccharides were more prone to aggregation in their solution and that the enzymatically extracted samples on average had lower molar mass than the acid extracted samples. The viscosity of pectic polysaccharides was more affected by the type of enzyme used for extraction than whether acid was used for that purpose; the highest viscosity was measured in samples obtained with the help of amylase. The solubility of pectic polysaccharides was the highest among all pectic polysaccharides where xylanase and cellulase were used in the enzymatic extraction step (more than 77%). Additionally, pectic polysaccharides isolated by different extraction techniques were subjected to modifications with endo-polygalacturonase and pectin-methylesterase (individually or combined) to obtain pectic polysaccharides and oligosaccharides with changed characteristics and properties. Determination of the Michaelis-Menten constant of endo-polygalacturonase showed that this enzyme had the highest affinity for the samples extracted with the use of acid; endo-polygalacturonase showed the highest affinity for the pectic polysaccharide obtained in amylase-assisted acid extraction (KM = 13.3 mg/mL), which was in accordance with the greatest decrease in Mw and viscosity of samples extracted in this way. Modification by endo-polygalacturonase had a positive effect on increasing antioxidant and Fe2+-chelating activity.Modification with pectin-methylesterase led to de-esterification of all pectic polysaccharides; the degree of methoxylation in most samples was reduced 3.5 times on average. After modification with this enzyme, molar mass and viscosity increased in most samples, and the greatest intensity of these changes was observed in samples obtained without the use of acid. The antioxidant activities of pectin-methylesterase-modified pectic polysaccharides were higher than those of the corresponding unmodified samples, with the greatest change in the sample extracted in conventional acid extraction where this activity doubled.After examining the effect of the combined action of endo-polygalacturonase and pectin-methylesterase on pectic polysaccharides from butternut squash, it was concluded that the intensity of reduction in molar mass and viscosity was almost twice as high as the reduction of these properties after modification with endo-polygalacturonase alone. Modification with combined enzymes led to two-fold increases in ABTS and iron(II)-chelating activities of all modified pectic polysaccharides than the increases observed after modification with endo-polygalacturonase alone. The greatest increase was observed after the modification of acid-extracted pectic polysaccharide; antioxidant and Fe2+-chelating activity increased 4.2 and 44 times, respectively. Furthermore, the potential of acid-extracted pectic polysaccharide from butternut squash to be used for the preparation of complex coacervates with ovalbumin and gelatin was also investigated. The yield of coacervation was higher with gelatin than with ovalbumin. Also, coacervates with gelatin had up to 3 times greater mechanical stability than coacervates with ovalbumin, but their stability in simulated gastrointestinal conditions was two times lower than the stability of coacervates with ovalbumin.