Primjena ultrazvuka visokog intenziteta kao predobrade za unaprijeđeno sušenje jabuke sorte "Granny smith"

master's thesis

• Title (english): Application of high intensity ultrasound as pretreatment for enchanced drying of apple cultivar "Granny smith"
• Author: Ana Žutić
• Mentor: Mladen Brnčić (mentor)
• Granter: University of Zagreb; Faculty of Food Technology and Biotechnology; (Department of Process Engineering); (Laboratory for Unit Operations); Zagreb
• Defense date and country: 2010-07-13, Croatia
• Scientific / art field, discipline and subdiscipline: BIOTECHNICAL SCIENCES; Food Technology

Abstract

Postupci sušenja, koji su od velikog značaja za prehrambenu industriju, većinom se temelje na upotrebi toplinske energije. Takve metode mogu dovesti do negativnih promjena u strukturi, teksturnim i senzorskim svojstvima hrane. Upotreba ultrazvuka visokog intenziteta kao predobrade sušenju obećava jer djeluje manje negativno na glavne karakteristike i kvalitetu proizvoda. Cilj ovog rada bio je proučiti kako primjena ultrazvuka visokog intenziteta različitih amplituda utječe na vrijeme sušenja komadića jabuka te na njihovu boju, strukturu i teksturna svojstva. Koristio se ultrazvučni uređaj maksimalne nominalne snage 400 W i frekvencije 24 kHZ, a predtretman se provodio ultrazvukom amplituda 25 %, 75 %, 50 % i 100 %. Sušenje uzorka provodilo se u infracrvenoj sušari pri temperaturi od 80 ˚C, do uspostave ravnotežnog stanja. Dobiveni rezultati pokazuju da primjena ultrazvuka različitih amplituda skraćuje vrijeme sušenja i povećava difuzivnost vode zbog tvorbe mikroskopski velikih kanalića na površini i unutar uzorka. Toplinska analiza pokazuje da se primjenom ultrazvuka visokog intenziteta ne uništava stanično tkivo jabuke. Boja tretiranih uzoraka prihvatljiva je u usporedbi sa bojom netretiranih. Tvrdoća uzoraka postupno opada sa povećanjem duljine i intenziteta tretiranja ultrazvukom, za razliku od elastičnosti koja ostaje nepromijenjena.

Abstract (english)

Drying processes, which have a great significance in food industry are often based on the use of thermal energy. Such methods may lead to the negative changes in structure, texture and sensory characteristics of foods. The use of high-intensity ultrasound as pretreatment for drying is very promising because it can act without affecting the main characteristics and quality of the products. The aim of this work was to investigate the impact of high-intensity ultrasound of different amplitudes on drying the pieces of apple, as well on their colour, structure and texture. Ultrasound device working at a frequency of 24 kHz with a power capacity about 400 W was used for ultrasound pretreatment. The amplitudes used were 25 %, 50 %, 75 % and 100 %. Drying was preformed in infrared dryer, at the temperature of 80 ˚C. The results show that the use of different amplitudes of ultrasound reduces the time of drying and increases water diffusivity due to the formation of microscopic channels in apple structure. Thermal analysis showes that high-intensity ultrasound does not induce brakedown of the apple tissue, despite the formation of microscopic channels. The colour of the ultrasound treated samples is acceptable as compared to untreated. Hardness of samples gradually drops with increase of intensity and duration of ultrasonic treatment, while elasticity of samples remains the same.

• Keywords: jabuka; ultrazvuk visokog intenziteta; infracrveno sušenje; toplinska analiza
• Keywords (english): apple; high-intensity ultrasound; infrared drying; thermal analysis
• Language: croatian
• URN:NBN: urn:nbn:hr:159:246851
• Study programme: Title: Food Technology; specializations in: Food Engineering; Course: Food Engineering; Study programme type: university; Study level: graduate; Academic / professional title: diplomirani inženjer prehrambene tehnologije; smjer prehrambeno inženjerstvo (diplomirani inženjer prehrambene tehnologije; smjer prehrambeno inženjerstvo)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Access restricted to students and staff of home institution
• Created on: 2017-08-28 11:01:32