Effects of high-intensity ultrasound on physical, chemical and microbiological properties of whey

Sirutka predstavlja visokovrijedan nusproizvod koji zaostaje nakon izdvajanja kazeina i mliječne masti tijekom sirenja. Dugo je vremena smatrana otpadnim produktom u sirarstvu dok se posljednjih godina bilježi porast proizvodnje napitaka na bazi sirutke kao i raznih drugih proizvoda koji nastaju izdvajanjem sirutkinih proteina i drugih sastojaka sirutke. Također u posljednje vrijeme raste trend minimalno procesirane hrane, a kao jedan od načina minimalnog procesiranja se javlja ultrazvuk. Cilj ovog rada je bio ispitati kako tretman ultrazvuka visokog intenziteta utječe na svojstva sirutke od kojih su ispitivani: viskoznost, električna vodljivost, veličina čestica, titracijska kiselost, pH, ukupan broj mikroorganizama, te udio proteina i senzorske karakteristike sirutke. Ispitivanjem je utvrđeno da ultrazvuk ima povoljan utjecaj na sirutku jer smanjuje broj mikroorganizama i poboljšava senzorske karakteristike. Sve to ukazuje na to da bi ultrazvuk mogao biti zamjena komercijalnim tretmanima sirutke.Whey is a highly valuable by-product which lags after the separation of casein and fat during cheesemaking. For a long time it was considered to be a waste product but in the last few years there has been an increase in the production of whey-based beverages and as well as a variety of other products made of whey protein and other whey component. Also recently is growing a trend of minimally processed food. As one type of minimal processing occurs ultrasound. The aim of this thesis was to assay how treatment of high intensity ultrasound affects the properties of whey from which were tested: viscosity, electrical conductivity, particle size, titratable acidity, pH, and total number of microorganisms, protein content and sensory properties. The study found that ultrasound has favorable effect on the whey as it reduces the number of microorganisms and improves sensory characteristics. All this indicates that ultrasound could be a good alternative to commercial whey treatments