Studies on the induction of heat stability in evaporated milk by preheating: effects of milk concentration, homogenization and whey proteins

Abstract

When milk was preheat-treated after either evaporation or homogenization with fat present the degree of heat stability induced in the resulting evaporated milk (EM) was considerably less than with the normal process in which the preheat treatment was carried out first. When the preheat treatment was carried out after both evaporation and homogenization, no heat stability was induced by the preheat treatment. Removal of the whey protein fraction from the milk increased the heat stability of both the EM homogenized before preheat treatment and the EM made by the normal process.

Heat stability of concentrated skim milk as a function of heating time and temperature on a laboratory scale – Improved methodology and kinetic relationship

“…Despite this, major influencing factors on heat stability of concentrated and unconcentrated milk could be unravelled. Especially pHdependency of HCT as well as the effects of different mineral composition of the serum phase, whey protein denaturation and technological pre-treatments such as various preheat treatments of the milk used and the effect homogenisation were investigated (McCrae, Hirst, Law, & Muir, 1994;Newstead, Conaghan, & Baldwin, 1979;Sweetsur & Muir, 1982;Tan-Kintia & Fox, 1999;Whiteley & Muir, 1996). Nevertheless, the reaction kinetics eventually leading to the formation of large particles should be further addressed.…”

Invited review: Heat stability of milk and concentrated milk: Past, present, and future research objectives

“…3) Differences in composition of milk, resulting either from the stage of lactation, the genetics of an individual cow, or seasonal variation due to herd synchronization (Holm et al, 1932;White and Davies, 1958;Rose, 1961a,b;Davies and White, 1966b;Holt et al, 1978b;Sweetsur and Muir, 1982;Singh and Tokley, 1990;Pouliot and Boulet, 1991;Chen et al, 2015). 4) The improvement or modification of the heat stability of milk and concentrated milk by pre-and postprocessing, processing sequence, additives, or milk fortification (Webb and Holm, 1932;Bell and Webb, 1943;Rose, 1962;Morrissey and O'Mahony, 1976;Muir and Sweetsur, 1976;Fox and Hearn, 1978a,b;Newstead et al, 1979;Pearce, 1979;Fox, 1981;Hardy et al, 1985;Dalgleish et al, 1987a,b;Augustin and Clarke, 1990;Singh and Tokley, 1990;Pouliot and Boulet, 1991;McCrae et al, 1994;O'Connell and Fox, 1999a;Tan-Kintia and Fox, 1999;Huppertz et al, 2004;Vyas and Tong, 2004;Singh et al, 2007;Sievanen et al, 2008;Omoarukhe et al, 2010;Lewis et al, 2011;de Kort et al, 2012;On-Nom et al, 2012;Chen et al, 2015). 5) Mechanistic insights into the factors affecting heat-induced coagulation…”

“…Usual preheating conditions for milk used vary widely and are more of an empirical nature than directed due to a full understanding of the underlying mechanisms. Heating conditions resulting in a notable increase in heat stability are 90°C for 10 min, 110 to 120°C for 1 to 5 min, 140°C for 5 s, or 130 to 150°C for 1 to 5 min Newstead et al, 1979;Singh and Tokley, 1990;Fox et al, 2015). Concentration of milk by evaporation at 55 to 85°C led to a shift in the heat stability maximum to a more acidic pH, due to possible heat-induced changes in milk depending on residence time and temperatures of the milk in the evaporator compared with concentration of milk by RO (Dumpler and Kulozik, 2015).…”

Milk protein-carbohudrate interactions in sterilised milk products

“…A statistically significant correlation between fj-lactoglobulin levels and maximum or minimum CT was also observed, providing more evidence for the importance of whey protein. These results were later confirmed by Morrissey (1969a), Fox & Hoynes (1975) and Newstead et al (1977). The type of coagulation was related to the ß-lactoglobulin content in milk (Carvalho, 1977b), and the latter was related to the genetic variant (Aschaffenburg and Drewry, 1957;Rose, 1962;Lontie, 1964;Feagan et al, 1972;Carvalho 1977a;) Initially, Rose (1962), postulated that ßlactoglobulin was the only whey protein that could destabilize milk in the region of the minimum, but Fox & Hearn (1978b) showed that α-lactalbumin could also introduce pH sensitivity, whilst the addition of the structurally similar bovine serum albumin had a more pronounced destabilizing effect.…”

“…The same author pointed out that the addition of serum protein to serum-protein-free micelles increased the heat stability of an otherwise very unstable system. This effect was offset by forewarming (85-90°C), prior to serum protein addition Increasing levels of Ca ++ and Mg ++ in the serum accentuated the destabilizing effect of forewarming (Morrissey & O'Mahony, 1976) (Newstead et al, 1977;Sweetsur & Muir, 1980c).…”