Rheological and structural properties of differently acidified and renneted milk gels

Abstract

In this study we assessed the rheological and structural properties of differently acidified and renneted milk gels by controlling pH value and renneting extent. Skim milk were exactly renneted to 4 extents (20, 35, 55, and 74%) and then direct acidified to the desired pH (4.8, 5.0, 5.2, 5.5, 5.8, and 6.2), respectively. Rheological properties were assessed by dynamic rheological measurements, structural properties were studied by spontaneous whey separation and confocal laser scanning micrograph, and protein interactions were studied by dissociation test. Results showed that minimally renneted milk samples (20 and 35%) formed weak gels with low storage modulus, and the acidification range within which gels could form was narrow (pH ≤ 5.2). Highly renneted milk samples formed more gels with high storage modulus. The results of this study revealed that acidification determined the structural properties of highly renneted milk gels. As pH increased from 5.0 to 6.2, highly renneted milk gels had lower loss tangent, decreased spontaneous syneresis, and smaller pores. For both the low and high rennetings, divalent calcium bonds contributed less at low pH than at high pH. In conclusion, renneting increased the pH range suitable for gel formation; acidification determined the spontaneous syneresis and microstructure of highly renneted milk gels.

Effects of Size and Stability of Native Fat Globules on the Formation of Milk Gel Induced by Rennet

“…Rheological experiments were carried out with a stress‐controlled rheometer AR1500 (TA Instrument Ltd., New Castle, Del., U.S.A.) according to the method of Liu and others (). Measurements were taken using a conical concentric cylinder geometry (5920 μm fixed gap, 15 mm outer radius, 14 mm inner radius, and 42 mm height).…”

Modifications of structures and functions of caseins: a scientific and technological challenge

“…Extensive information are described in different reviews and book chapters (Horne 1999). From a general point of view, at acid pH, the heat stability is decreased whereas the rennet coagulation is improved with a decrease in the coagulation time (Van Hooydonk et al 1986;Famelart et al 1996;Liu et al 2014a). …”

Physicochemical, textural and rheological properties of probiotic yogurt fortified with fibre-rich pineapple peel powder during refrigerated storage

“…bulgaricus, and reinforced by disulphide crosslinks between denatured whey proteins and k-casein molecules. Yogurt gel firmness mainly depends on the strength of the three-dimensional network of milk proteins, which is in turn governed by total solids content, acidification rate and proteolytic activity of employed cultures (Lee & Lucey, 2004Liu et al, 2014). Furthermore, the yogurt culture may be co-cultured with probiotic bacteria to enhance physiological functionalities of yogurt (Kailasapathy, Harmstorf, & Phillips, 2008).…”