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Sušenje predstavlja najpoznatiji i najučinkovitiji način konzerviranja namirnica te je jedan od najčešćih toplinskih procesa obrade hrane. MeĎutim, postupci sušenja mogu dovesti do negativnih promjena u strukturi, teksturnim i senzorskim svojstvima hrane. Nove netoplinske metode obrade namirnica sve se više koriste kao nadopuna ili zamjena standardnim metodama koje koristi prehrambena industrija. Primjena ultrazvuka visokog intenziteta predstavlja novu metodu netoplinske obrade hrane i zbog svojeg djelovanja na staničnu strukturu se koristi kao metoda predobrade ili obrade namirnice prije sušenja. Cilj ovog rada bio je ispitati utjecaj ultrazvuka kao predobrade na sušenje uzoraka buče te ih usporediti sa uzorcima netretiranih ultrazvukom. Koristio se ultrazvučni ureĎaj sa kupelji maksimalne snage 1580 W, frekvencije 37 kHz i amplitude 100%. Sušenje uzoraka provodilo se u vakuum sušari pri temperaturi od 40ºC tijekom 180 minuta. Dobiveni rezultati pokazali su da je ultrazvuk visokog inteziteta učinkovit kao metoda obrade prije sušenja zbog očuvanja glavnih karakteristika proizvoda. TakoĎer, smanjenjem tlaka povećava se učinak vakuum sušenja pa je tako najveći učinak postignut pri najniţem tlaku. Isto tako duţe vrijeme tretiranja rezultira većim utjecajem ultrazvuka na tretirani uzorak, pri čemu ne dolazi do promjene izgleda uzoraka. Drying is the most famous and effective method of preserving foodstuff and is one of the most common heat treatment of food. However, such methods may lead to the negative changes in structure, texture and sensory characteristics of foods. New non-thermal technologies for processing of foodstuff is more and more used as replacement or supplement to standard thermal technologies used in food industry. Application of high-intensity ultrasound in food processing presents a novel non-thermal method and because of its impact on the cellular matrix is used as a pretreatment method for drying of foodstuff. The aim of this work was to examine the impact of ultrasound as a pretreatment on drying samples of squash and compare them with ultrasound untreated samples. Ultrasound device working at a frequency of 37 kHz with a power capacity of 1580 W and amplitude 100% was used for ultrasound pretreatment. Drying was performed in a vacuum dryer, at the temperature of 40ºC during 180 minutes. The results showed that high-intensity ultrasound is efficient as a pre-drying method for preserving the main characteristics of the product. Also, the effect of the vacuum drying increases by reducing the pressure, so the best effect is achieved at the lowest pressure. Longer treatment time results in a greater impact of the ultrasound on the treated sample, which doesn't change the appearance of the samples. |
