Infl uence of process parameters and composition of the oil phase on rheological properties of mayonnaise

Sažetak Poznavanje reoloških svojstava hrane od velikog je značenja bilo da se radi o postizanju određenih svojstava hrane ili o vođenju procesa pri proizvodnji hrane. U ovom radu istraživan je utjecaj procesnih parametara (brzina rotacije rotora homogenizatora, vrijeme pripreme majoneze) i sastava uljne faze na reološko ponašanje majoneze. Mehanički proces homogenizacije majoneze proveden je kod 10 000, 12 000 i 15 000 o/min. i vremenu 3 i 8 min. pri sobnoj temperaturi. Majoneza sadrži 70% ulja sa različitim udjelima suncokretovog ulja i Olys ulja. Mjerenja reoloških svojstava provedena su na rotacijskom viskozimetru (DV- III + Digital Rheometer-Brookfield Engineering Laboratories, USA) sa koncentričnim cilindrima pri temperaturama 10 oC i 25 oC. Iz dobivenih podataka izračunati su reološki parametri koefi cijent konzistencije, indeks tečenja i prividna viskoznost. Rezultati istraživanja su pokazali da brzina rotacije rotora homogenizatora, vrijeme trajanja procesa pripreme majoneze i sastav uljne faze utječu na reološka svojstva. Homogenizacijom kod veće brzine rotora nastaje majoneza sa većom konzistencijom i viskoznosti. Dolazi do formiranja većeg broja kapljica ulja manjeg promjera i bolje disperzije u vodenoj fazi emulzije. Porastom udjela Olys ulja u uljnoj fazi povećava se viskoznost i konzistencija majoneze pripremljene kod 15 000 o/min. Homogenizacijom majoneze tijekom 8 min. kod 12 000 o/min. dolazi do porasta viskoznosti i konzistencije.The knowledge of rheological properties of food is very important both for achieving specifi c food properties and for controlling the food production process. In this study we investigated the eff ect of process parameters (rotation speed of the rotor homogenizers, time of preparation of mayonnaise) and the oil phase composition on the rheological behavior of mayonnaise. The mechanical process of homogenization of the mayonnaise was conducted in 10 000, 12 000 and 15 000 rpm and the time 3 and 8 min. at room temperature. Mayonnaise contains 70% of oil with diff erent proportions of sunfl ower oil and Olys oil. Rheological tests were carried out in a controlled rotational viscometer (DV- III + Digital Rheometer - Brookfi eld Engineering Laboratories, USA) with concentric spindles at 10 °C and 25 °C. From the obtained data, rheological parameters: consistency coeffi cient, fl ow behavior index and apparent viscosity were calculated. The results of research showed that homogenization speed, preparation time and the composition of oil phase have infl uence on rheological properties of mayonnaise. The result of homogenization at the higher speed of the rotor is mayonnaise with greater consistency and viscosity. There appears a formation of greater number of oil droplets with minor diameter, which are more dispersible in water phase of emulsion. The higher proportion of Olys oil in the oil phase increases the viscosity and consistency of mayonnaise prepared at 15 000 rpm. Homogenization of mayonnaise for 8 min. at 12 000 rpm increases viscosity and consistency