| Sažetak | Osušeni plod naranče sve se više koristi u izradi hortikulturnih dekoracija, a njegova održivost kroz dulji vremenski period ključna je. Karakteristična boja ploda naranče, kao i dimenzije ploda značajno se mijenjaju ovisno o procesu sušenja, a prilikom čega najveći utjecaj pokazuju temperatura i vrijeme sušenja. Boja je jedan od ključnih vizualnih svojstava osušene sirovine, a njena stabilnost ovisno o uvjetima stajanja značajno se degradira. Svime navedenim, proces sušenja potrebno je optimizirati. U posljednje vrijeme razvijaju se suvremene tehnologije koje uključuju upotrebu ultrazvuka visokog intenziteta kao predtretmana sušenju, a koji pokazuje niz prednosti prilikom upotrebe. Skraćeno vrijeme, energetska učinkovitost, te ponajviše očuvanje organoleptičkih, fizikalnih i nutritivnih svojstava neke su od najvećih prednosti upotrebe ultrazvuka kao predtretmana sušenju. Stoga je i cilj ovog istraživanja bio utvrditi promjenu boje, dimenzije i stabilnost osušenog ploda naranče ovisno o predtretmanu ultrazvukom visokog intenziteta. Ploške naranče prosječne debljine 4 mm neposredno prije sušenja u konvekcijskom sušioniku podvrgnute su tretmanu ultrazvukom u tri intervala: 5, 10 i 15 minuta. Od fizikalnih svojstava određena je boja ploški CIELAB metodom, te veličina (duljina i širina, mm) pomičnim mjerilom. Fizikalna svojstva osušenih ploški praćena su u periodu čuvanja od 2 mjeseca. Istraživanjem je pokazano da predtretman ultrazvukom pozitivno djeluje na očuvanje L* i a* kromatskih parametara sušenih ploški naranče, odnosno predtretman je pogodovao očuvanju specifičnog obojenja naranče, očuvana je svjetlina i karakteristično narančasto obojenje. Najbolji učinak ultrazvuka u očuvanju svjetline uzorka postignut je tretmanom u trajanju od 5 i 10 minuta, dok je duže vrijeme predtretmana (15 minuta) negativno utjecalo na L* i b* parametre. U odnosu na kontrolni uzorak čuvan dva mjeseca, uzorak tretiran ultrazvukom 5 minuta imao je višu L* vrijednost čime je dokazano pogodno djelovanje predtretmana ultrazvukom na očuvanje boje u periodu čuvanja. Što se tiče promjena duljine i širine ploda kod uzoraka predtretiranih ultrazvukom, značajnije promjene nisu uočene. Svime navedenim, može se zaključiti kako je ultrazvuk visokog intenziteta kao predtretman sušenju značajno pozitivno utjecao na očuvanje fizikalnih svojstava sirovine, a čime se u konačnici postiže dobivanje kvalitetnijeg finalnog proizvoda iskoristivog i u dekorativne svrhe dostupnog kroz duži period. |
| Sažetak (engleski) | Dried orange fruits are increasingly used for making decorations, where their shelf life over a long period of time is crucial. The characteristic colour of orange fruit, as well as the dimensions of the fruit, change significantly depending on the drying process, with temperature and drying time having the greatest influence. Colour is one of the most important visual characteristics of the dried raw material, and its stability is significantly affected depending on storage conditions. For all these reasons, the drying process must be optimized. Recently, modern technologies have been developed that involve the use of high-intensity ultrasound as a pre-treatment for drying, which brings a number of advantages. Time saving, energy efficiency and, above all, preservation of organoleptic, physical, and nutritional properties are one of the major advantages of using ultrasound as a pre-treatment for drying. Therefore, the objective of this study was to determine the change in colour, size, and stability of dried oranges as a function of pre-treatment with high-intensity ultrasound. Orange slices with an average thickness of 4 mm were subjected to ultrasonic treatment immediately before drying in a convection dryer at three intervals: 5, 10, and 15 minutes. Based on the physical properties, the colour of the samples was determined using the CIELAB method and the size (length and width, mm) was determined using a sliding scale. The physical properties of the dried orange samples were monitored during the storage period of 2 months. The research showed that the pre-treatment with ultrasound had a positive effect on the preservation of the colour parameters L* and a* of the dried orange slices, i.e. the pre-treatment favoured the preservation of the specific colour of the orange, the brightness and the characteristic orange colour were preserved. The best effect of ultrasound in preserving the brightness of the sample was obtained at a treatment time of 5 and 10 minutes, while a longer pre-treatment time (15 minutes) had a negative effect on the parameters L* and b*. Compared to the control sample stored for two months, the sample treated with ultrasound for 5 minutes had a higher L* value, proving the beneficial effect of pre-treatment with ultrasound on colour retention during the storage period. As for the changes in the length and width of the fruits in the samples pre-treated with ultrasound, no significant changes were observed. It can be concluded that high-intensity ultrasound as a pre-treatment for drying has a significantly positive effect on the preservation of the physical properties of the raw material, which ultimately leads to a higher quality end product that can be used for decorative purposes and is available for a longer period of time. |
