Application of whey protein isolates and zein in system of alginate carriers for encapsulation of ginger (Zingiber officinale) polyphenols

Zbog svojih ljekovitih svojstava đumbir (Zingiber officinale) ima dugu tradiciju primjene u medicini, a u novije vrijeme ti se pozitivni zdravstveni učinci potkrjepljuju sve većim brojem podataka o njegovom bogatom bioaktivnom sastavu. Budući da nema dostupnih podataka o inkapsulaciji polifenola đumbira, cilj ovog rada bio je istražiti učinkovitost inkapsulacije polifenolnih ekstrakata đumbira metodom ionskog geliranja te odrediti utjecaj sastava nosača na učinkovitost inkapsulacije. Kao nosač za imobilizaciju korišten je čisti alginat te kombinacije alginata s izolatima proteina sirutke i zeinom. Dobivenim česticama određen je udjel vode, fizikalno-kemijske i morfološke karakteristike, učinkovitost inkapsulacije polifenola i zadržavanja antioksidacijskog kapaciteta, kao i profili otpuštanja polifenola i antioksidacijskog kapaciteta u simuliranim gastrointestinalnim uvjetima. Dobiveni rezultati pokazali su da je dodatak izolata proteina sirutke u alginatni nosač rezultirao tvorbom manjih čestica, a dodatkom zeina dobivene su veće čestice, dok su obje vrste proteina uzrokovale smanjenje tvrdoće čestica, njihove elastičnosti te udjela vode. Dodatkom proteina povećala se inkapsulacijska učinkovitost i zadržavanje antioksidacijskog kapaciteta te usporilo otpuštanje polifenola iz njihovog sastava. Najefikasnijim nosačem pokazao se alginat u kombinaciji sa zeinom s učinkovitošću inkapsulacije polifenola od 93,05%, najvišim zadržavanjem antioksidacijskog kapaciteta (86,79% određeno ABTS metodom i 89,67% određeno DPPH metodom) i kontinuiranim otpuštanjem polifenola iz čestica.Due to its medicinal properties ginger (Zingiber officinale) has a long tradition of application in medicine and in more recent times those positive effects on health are being substantiated by growing number of facts about its rich bioactive composition. Since there are no available information about encapsulation of ginger polyphenols, the aim of this thesis was to investigate encapsulation efficiency of ginger polyphenolic extracts using the method of ionic gelation and to determine the influence of composition of carriers on encapsulation efficiency. Pure alginate and combinations of alginate with whey protein isolates and zein were used as carriers for immobilization. The acquired hydrogel beads had their water content, physical, chemical and morphological properties, encapsulation and retention of antioxidant capacity efficiency, as well as the release profiles of total polyphenols and antioxidant capacity in simulated gastrointestinal conditions determined. The results showed that the addition of whey protein isolates in the alginate-based carrier resulted in formation of smaller particles, and the addition of zein particles resulted in bigger particles, while both proteins caused decreased hardness, elasticity and water content in the particles. The addition of proteins increased the encapsulation efficiency and retention of antioxidative capacity and slowed the release of polyphenols. The most efficient carrier was alginate in combination with zein with encapsulation efficiency of 93,05%, highest retention of antioxidation capacity (86,79% measured by ABTS method and 89,67% measured by DPPH method), and a continuous release of polyphenols from beads