Role of gelatin in low fat stirred yogurt and its possible replacement

Abstract

Stabilizers have been widely used in yogurts to provide good stability and desirable texture, gelatin being the most preferred choice because of its multiple functions (i.e. gelling,-melt-in-mouth‖ and surface activity). However, gelatin is not universally accepted due to some religious beliefs and potential contamination with viruses and prions. Hence, finding an alternative to gelatin has always been of considerable interest to both the dairy industry and academia. In this thesis, a systematic study on the role and replacement of gelatin type B in yogurt was carried out. The main methodologies used in this research were rheology, scanning electron microscopy, texture analysis, water holding capacity (WHC) measurement and sensory evaluation. Firstly, the effects of gelatin concentration, pH and addition of milk proteins (whey protein isolate [WPI], milk protein concentrate [MPC] and skim milk powder [SMP]) on the properties of pure gelatin were studied. Higher gelatin concentrations led to stronger gels. Rheological properties of the gelatin gels were independent of pH from 4.6 to 8.0, but the fracturability and microstructure of the gels were greatly influenced; gelation was inhibited at pH 3.0. SMP and MPC significantly enhanced the storage modulus (G′) of gelatin gels and changed their microstructure, while WPI showed a negative effect on G′ and caused no modification of microstructure. Gelatin A was briefly compared with gelatin B; results similar to those for gelatin B were obtained, except that gelatin A gel was more susceptible to extreme pH and addition of milk protein.