Microencapsulation of Red Grape Juice by Freeze Drying and Application in Jelly Formulation

Svrha je ovoga rada bila proizvesti nove prehrambene proizvode obogaćene bioaktivnim sastojcima iz koncentriranog soka od crvenog grožđa, mikroinkapsuliranog pomoću sušenja zamrzavanjem u otopini izolata proteina sirutke i kitozana. Dobiven je prah s učinkovitošću enkapsulacije od (86,1±4,0) %, masenih udjela antocijana (izraženih kao ekvivalenti cijanidin-3-O-glukozida) od (1,4±0,2) mg/g, ukupnih polifenola (izraženih kao ekvivalenti galne kiseline) od (3,3±0,6) mg/g i flavonoida (izraženih kao ekvivalenti katehina) od (1,6±0,5) mg/g. Konfokalnom laserskom mikroskopijom otkriveno je da su flavonoidni pigmenti bili umotani u matriks, dok su antocijani tvorili velike i kompaktne nakupine. Mikroinkapsulirani prah je zatim upotrijebljen za proizvodnju želea. Novi prehrambeni proizvodi imali su zadovoljavajući maseni udjel antocijana, i to od (0,03±0,01) do (0,12±0,02) mg/g, dok se udjel flavonoida nije bitno promijenio. Svi želei su imali znatnu antioksidacijsku aktivnost. Rezultati ispitivanja probavljivosti in vitro potvrdili su je da tijekom simulirane probave došlo do polaganog otpuštanja antocijana iz hrane u želucu, a zatim znatnog otpuštanja bioaktivnih sastojaka u crijevima. Dodatak mikroinkapsuliranog praha znatno je smanjio tvrdoću, kohezivnost i elastičnost želea, što je dovelo do destabilizacije strukture gela i smanjenja privlačnih sila između komponenata matriksa. Sensorska analiza pokazala je da su panelisti preferirali uzorak želea pripremljen od grožđanog soka.The aim of this work is to obtain new food products enriched with bioactive compounds from concentrated grape juice microencapsulated by freeze drying using a whey protein isolate- chitosan system. The obtained powder showed an encapsulation efficiency of (86.1±4.0) %, with an anthocyanin mass fraction (expressed as cyanidin-3-O-glucoside equivalent) of (1.4±0.2) mg/g, while the total polyphenolic (expressed as gallic acid equivalents) and flavonoid (expressed as catechin equivalents) mass fractions were (3.3±0.6) and (1.6±0.5) mg/g, respectively. The confocal laser microscopy revealed the presence of the flavonoid pigments wrapped inside the matrix, whereas the anthocyanins were grouped into large and compact clusters. The microencapsulated powder was used for jelly formulation. The new food formulations have a satisfactory anthocyanin mass fraction ranging from (0.03±0.01) to (0.12±0.02) mg/g, while no significant differences were observed in flavonoid content. All the value-added jelly showed appreciable antioxidant activity. The in vitro digestibility results confirm a slow release of anthocyanins from the food matrices during simulated gastric digestion and a significant release of the bioactive compounds into the gut. The addition of microencapsulated powder caused a significant decrease in firmness, cohesiveness and springiness, leading to the destabilization of the gel structure, while reducing the attraction forces between the matrix components. The sensorial analysis indicated that the panellists preferred the sample with grape juice the most