| Abstract | Cilj ovog istraživanja bio je ispitati utjecaj tretmana hladnom plazmom na fizikalno-kemijska i senzorska svojstva te aromatski profil soka jabuke i nektara višnje Maraske, te optimirati najpogodniji tretman hladnom plazmom. U prvoj fazi istraživanja svim su uzorcima određeni fizikalno-kemijski parametri (pH, električna vodljivost, temperatura, udjel suhe tvari, boja (L*, a*, b*)), udio biološki aktivnih spojeva te antioksidacijski kapacitet. Za analizu arome primijenjena je mikroekstrakcija na čvrstoj fazi (HS-SPME) i plinska kromatografija uz masenu spektrometriju (GC-MS), a senzorsko ocjenjivanje provedeno je metodom kvantitativne deskriptivne analize (QDA). Nakon provedene prve faze istraživanja, utvrđeno je kako najmanji utjecaj na fizikalno-kemijska i senzorska svojstva soka jabuke ima tretman tekućinskom plazmom s mjehurićima. Na osnovu rezultata prve faze odabran je najpogodniji tretman tekućinskom plazmom s mjehurićima, te je dizajniran puni faktorijalni plan s tri različite varijable (vrijeme tretmana, temperatura i frekvencija). Sok jabuke i nektar višnje Maraske tretirani su pri tri različita vremena (3, 6 i 9 minuta), tri temperature (30, 40 i 50 oC), te tri frekvencije (60, 90 i 120 Hz). Nakon provedenih tretmana tekućinskom plazmom s mjehurićima prema eksperimentalnom dizajnu na soku jabuke, te nektaru višnje Maraske utvrđeni su optimalni uvjeti tretmana tekućinskom plazmom s mjehurićima, prema dobivenim polinomima optimizacije, pri kojima se ostvaruju najbolji rezultati fizikalno-kemijskih i senzorskih svojstva tretiranih uzoraka, te su u najvećoj mjeri očuvani biološko aktivni spojevi. Maksimalne koncentracije fenolnih spojeva soka jabuke postižu se nakon tretmana s vremenom tretiranja u trajanju (6'), temperaturom (50 oC), te frekvencijom (60 Hz). Prema dobivenim parametrima optimizacije maksimalne koncentracije svih fenolnih spojeva višnje Maraske mogu se postići tretmanom na temperaturi od 30 oC, vremenom od 4 do 6 minuta, te frekvencijom od 60 do 70 Hz. |
| Abstract (english) | The aim of this study was to investigate the influence of cold plasma treatment on the physico-chemical and organoleptic properties of apple juice and Marasca nectar and to optimize the most suitable treatment. In the first phase in all samples were determined physico-chemical parameters (pH, conductivity, temperature, color (L *, a *, b *), total soluble solids) and the content of total phenols as well as antioxidant capacity. Analysis of aroma profile was conducted using headspace solid phase microextraction (HS-SPME) coupled with gas chromatography mass spectrometry (GC-MS) and sensory evaluation using quantitative descriptive analysis (QDA). In the first phase of research apple juice was treated in three types of reactors in which were generated gas plasma, liquid plasma with bubbles, and a combination of both in the so-called hybrid reactor, at both (positive and negative) polarities. It was found that there was no significant change in the physico-chemical composition in all three types of reactors. Liquid plasma treatment with bubbles had least impact on the physicochemical and sensory properties of apple juice, therefore was selected as the most appropriate plasma treatment for further research on apple juice and Marasca sour cherry nectar. A full factorial experimental plan was designed using three different variables (treatment time, temperature and frequency). Apple juice and nectar cherry Marasca were treated at three different times (3, 6 and 9 minutes), three temperatures (30, 40 and 50 °C), and three frequencies (60, 90 and 120 Hz). From obtained results after the liquid plasma treatment with bubbles optimal conditions were determined in order to achieve the best physico-chemical and organoleptic properties of the apple juice and Marasca sour cherry nectar. Maximum concentrations of the phenolic compounds in apple juice can be obtained at treatment time of (6'), temperature (50 °C), and at the frequency (60 Hz). According to the optimization parameters, maximum concentration of the phenolic compounds in Marasca sour cherry nectar can be achieved by plasma treatment at temperature of 30 °C, treatment time of 4 to 6 minutes, and at frequencies between of 60 and 70Hz. |
