The rebodying of stirred yoghurt: interactions between proteins

Abstract

The aim of the present study was to identify the nature of bonds established between protein particles after stirring that are responsible for the texture improvement of stirred yoghurts, called rebodying. Using a constant model yoghurt at pH 4.4, the effects of changes in the physicochemical conditions at stirring were studied on the subsequent rebodying. Short term rebodying was measured as the changes in viscoelastic properties at 4 degrees C during 20 h after stirring, while long-term rebodying was measured as the viscosity changes during 28 d storage at 4 degrees C. Moreover, stirred gels obtained from either set gels that were allowed time or not for ionic equilibration were compared. Increasing or decreasing ionic strength did not change the properties of stirred gels. Calcium chloride addition significantly decreased G'0 h, G'20 h and tan20 h but did not induce changes in the gel microstructure as observed by confocal scanning microscopy. Yoghurt rebodying could not be explained by fulfilling ionic equilibrium. Moreover, N-ethyl maleimide addition had no effect on the stirred yoghurt. Attractive electrostatic and disulphide interactions were not involved in the gel rebodying and increasing calcium concentration in the set gel limited rebodying.

Rheological properties of stirred yoghurt as affected by gel pH on stirring, storage temperature and pH changes after stirring

“…The increase in G 0 after stirring was found as a two-stage process. G 0 increased first rapidly for 2 h then slowly for at least the following 22 h (result not shown), in accordance with other authors (Arshad et al, 1993;Cayot et al, 2003;Renan et al, 2008aRenan et al, , 2008b.…”

Use of modified whey protein in yoghurt formulations

“…Yoghurt viscosity increased by a factor of w5 during the storage period, while relaxation rate decreased from 74 to 65% (data not shown). Viscosity increase during storage was more important than that reported by Renan et al (2008). In the present study, apparent viscosity was measured with a T-type sensor with minimal gel disturbance.…”

“…Yoghurt apparent viscosity increased in the first and third week storage through a mechanism called rebodying or structure recovery. According to Renan et al (2008), short term rebodying it thought to be due to cooling and formation of elastic bonds between protein particles, while long-term rebodying is ascribed to over-acidification. Yoghurt viscosity increased by a factor of w5 during the storage period, while relaxation rate decreased from 74 to 65% (data not shown).…”

Studying stirred yogurt microstructure using optical microscopy: How smoothing temperature and storage time affect microgel size related to syneresis

“…As well, van Marle (1998) and Körzendörfer et al (2018) found a relationship between larger microgels and higher induced syneresis results, suggesting that microgel size and syneresis are related. After shearing, the gel rebodying occurs during cold storage: the broken gel structure is modified, new structures build up, and yogurt viscosity increases (Cayot et al, 2003;Renan et al, 2008Renan et al, , 2009. Some authors have introduced the idea that microgels may affect stirred yogurt viscosity depending on their characteristics and interactions in the gel network.…”