| Abstract [eng] |
The aim of this research was to evaluate the influence of cranberry pomace extracts on the physicochemical properties and digestibility of yogurt. In the research, cranberry pomace extract was fractionated into high (HMW) and low molecular weight (LMW) fractions of compounds, which differed in the quantity of proanthocyanidins and certain monomeric anthocyanidins. 1813.95 ± 11.04 mg/100 g of proanthocyanidins was detected in the extract of HMW fractions and 60.31 ± 0.60 mg/100 g in the extract of LMW fractions. The extracts differed in antioxidant and antimicrobial activity. The DPPH radical scavenging capacity of the LMW fraction was 102 ± 0.02 mg TE/g and that of the HMW fraction was 305 ± 0.01 mg TE/g. The HMW fraction was characterized by inhibition of lactic acid bacteria as measured by the transparent zone formed in the agar medium and by their growth curve during the storage. Due to these properties, fermenting milk with HMW extract failed to produce yogurt. When researching the properties of milk mixtures with the extracts, it was found that the formation of new covalent and non-covalent bonds between milk proteins, HMW, and phenolic compounds of unfractionated cranberry extract caused the enlargement of milk protein particles, an increase in viscosity in the milk mixtures and yoghurt made from them, and shortening the duration of acid coagulation of proteins. As the amount of the extract increased, the viscosity of the yogurt increased. However, the LMW extract had no effect on the particle size and viscosity of the proteins of the milk mixtures and yogurt produced from them. After in vitro digestibility studies of aqueous solutions of cranberry extracts, their mixtures with milk and yogurt made from the mixtures, according to the release of free α-amino groups, the digestion rate of milk proteins was evaluated, while the bioavailability of phenolic compounds of the extract was assessed according to the release of phenolic compounds and proanthocyanidins, the bioavailability index, and the antioxidant activity at different stages of gastrointestinal and small intestinal digestion. During the digestion of all fractions of the cranberry pomace extracts, it was found that the total phenolic compounds and proanthocyanidins significantly reduce. This had a negative effect on their bioavailability and antioxidant properties. It was also found that during the digestion, the milk proteins adversely affect the release and bioavailability of the phenolic compounds of the cranberry extracts and in particular the release and bioavailability of the proanthocyanidins. The lowest bioavailability of phenolic compounds (17.74%) and proanthocyanidins (4.10%) and the lowest degree of milk protein hydrolysis (15.41 ± 0.21%) were found in the milk mixtures with the LMW cranberry extract fraction. Summarizing the results of the research, it is recommended using an extract containing lower molecular weight phenolic compounds in the production of yogurt enriched with the cranberry extract. . |
