Influence of added lyophilized butter serum on the heat stability of unconcentrated and concentrated bovine milk

Abstract

The influence of added lyophilized butter serum on the heat stability of milk was investigated. The addition of lyophilized serum from salted butter to unconcentrated skimmed milk (SM) reduced the heat coagulation time (HCT) at, and increased the pH of, the maximum in the pH–HCT profile and caused disappearance of the minimum. NaCl had similar effects on the heat stability of SM as lyophilized salted butter serum, whereas lyophilized serum from unsalted butter had little effect. The addition of lyophilized salted butter serum to concentrated skimmed milk (CSM) also shifted the pH of maximum heat stability to a higher value and, at certain concentrations, increased the maximum HCT; similar effects were obtained on addition of NaCl, but lyophilized serum from unsalted butter had little effect. These results suggest that the effects of lyophilized serum from salted butter on the heat stability of SM or CSM are due primarily to the presence of a high level of NaCl in this serum.

Effect of NaCl on some physico-chemical properties of concentrated bovine milk

“…A shift in the pH of maximum HCT of 2 Â or 3 Â concentrated milk to a more alkaline value on adding NaCl (Figs. 1 and 2) was also observed by Huppertz and Fox (2006); similar changes have also been observed for unconcentrated milk (Fox & Nash, 1979;Grufferty & Fox, 1985;Huppertz & Fox, 2006). Heat-induced dissociation of micellar k-casein is the main factor promoting heatinduced coagulation of casein micelles in concentrated milk in the pH-range 6.5-6.9 (see Singh, 2004;Singh, Creamer, & Newstead, 1995).…”

“…Furthermore, no minimum was observed in the pH-HCT profile of milk containing 420 mmol L À1 NaCl (Fox & Nash, 1979;Grufferty & Fox, 1985;Huppertz & Fox, 2006). Huppertz and Fox (2006) reported that adding 85 or 170 mmol L À1 NaCl to concentrated milk (18%, w/v, total solids) shifted the pH of maximum heat stability to a higher value and increased the maximum HCT. Since there is little further information on NaCl-induced changes in the physico-chemical properties of concentrated milk, the aim of the studies reported in this communication was to investigate the influence of added NaCl on the heat and ethanol stability, zeta potential, mineral balance, pH and casein micelles size of concentrated milk.…”

“…As a result, several properties of milk are altered, e.g., the rennet coagulation time of milk is increased (Famelart et al, 1999;Grufferty & Fox, 1985;Van Hooydonk et al, 1986;Zoon et al, 1989) and the ethanol stability is reduced (Horne & Parker, 1983). The maximum heat coagulation time (HCT) of unconcentrated milk is increased and shifted to a higher pH value by adding 50-100 mmol L À1 NaCl (Grufferty & Fox, 1985;Huppertz & Fox, 2006), but X200 mmol L À1 NaCl caused considerable destabilization throughout the pH-range assayed (6.4-7.4;Fox & Nash, 1979;Grufferty & Fox, 1985;Morrissey, 1969). Furthermore, no minimum was observed in the pH-HCT profile of milk containing 420 mmol L À1 NaCl (Fox & Nash, 1979;Grufferty & Fox, 1985;Huppertz & Fox, 2006).…”

“…The maximum heat coagulation time (HCT) of unconcentrated milk is increased and shifted to a higher pH value by adding 50-100 mmol L À1 NaCl (Grufferty & Fox, 1985;Huppertz & Fox, 2006), but X200 mmol L À1 NaCl caused considerable destabilization throughout the pH-range assayed (6.4-7.4;Fox & Nash, 1979;Grufferty & Fox, 1985;Morrissey, 1969). Furthermore, no minimum was observed in the pH-HCT profile of milk containing 420 mmol L À1 NaCl (Fox & Nash, 1979;Grufferty & Fox, 1985;Huppertz & Fox, 2006). Huppertz and Fox (2006) reported that adding 85 or 170 mmol L À1 NaCl to concentrated milk (18%, w/v, total solids) shifted the pH of maximum heat stability to a higher value and increased the maximum HCT.…”