Search

The objective of this work is to study the effect of the rapeseed oil content on the physical properties of whey protein emulsion films. For this purpose, whey protein films with the addition of 0, 1, 2 and 3 % of rapeseed oil, and glycerol as a plasticizer were obtained by the casting method. Film-forming emulsions were evaluated and compared using light scattering granulometry. The Sauter mean diameters (d32) of lipid droplets in film-forming solutions showed an increasing trend when increasing the oil volume fractions. The inclusion of rapeseed oil enhanced the hydrophobic character of whey protein films, reducing moisture content and film solubility in water. All emulsified films showed high lightness (L*≈90). Parameter a* decreased and parameter b* and total colour difference (ΔE) increased with the increase of the volume fractions of oil. These results were consistent with visual observations; control films were transparent and those containing oil opaque. Water vapour sorption experimental data at the full range of water activity values from 0.11 to 0.93 were well described with Peleg’s equation (R2≥0.99). The tensile strength, Young’s modulus and elongation at break increased with the increase of rapeseed oil volume fraction, which could be explained by interactions between lipids and the protein matrix. These results revealed that rapeseed oil has enormous potential to be incorporated into whey protein to make edible film or coating for some food products. The mechanical resistance decreased with the addition of the lipids, and the opacity and soluble matter content increased., Svrha je ovoga rada bila ispitati utjecaj dodatka repičinog ulja u različitim volumnim udjelima na fizikalna svojstva filmova izrađenih od proteina sirutke. Filmovi su pripremljeni u kalupima lijevanjem emulzija dobivenih od proteina sirutke s dodatkom 0, 1, 2 ili 3 % repičinog ulja te glicerola kao plastifikatora. Raspodjela veličine čestica emulzije određena je metodom laserske difrakcije, te je utvrđeno da se s povećanjem volumnog udjela ulja povećao srednji Sauterov promjer (d32) lipidnih kapljica. Dodatkom repičinog ulja povećala se hidrofobnost, a smanjio udjel vlage u filmovima te njihova topljivost u vodi. Sve su emulzije bile vrlo svijetle (L*≈90), a pri većim volumnim udjelima ulja smanjila se vrijednost parametra a*, a povećali vrijednost parametra b* i ukupna razlika u boji (ΔE). Rezultati su bili u skladu s onima dobivenim vizualnim pregledom: kontrolni uzorci filmova bili su prozirni, dok su oni s dodatkom ulja bili mutni. Ispitana je sposobnost upijanja vode filmova, a dobiveni su podaci u rasponu aktiviteta vode od 0,11 do 0,93 dobro opisani pomoću Pelegove jednadžbe (R2≥0,99). Povećanjem volumnog udjela repičinog ulja povećali su se vlačna čvrstoća, Youngov modul elastičnosti i istezljivost filmova, vjerojatno uslijed povezivanja lipida s proteinima. Rezultati pokazuju da se dodavanjem repičinog ulja emulzijama dobivenim od proteina sirutke može proizvesti jestivi film ili omotač za koje postoji velika mogućnost primjene u prehrambenoj industriji. Dodatkom lipida smanjili su se mehanički otpor i prozirnost filmova, a povećao udjel topljivih tvari.