Observations on the Instability of the Protein Phase of Frozen Concentrated Milk

Reviews of the progress of Dairy Science: Frozen concentrated milk

“…found little effect of temperature for whole milk, but significant differences when skim milk was considered under similar (but not identical) conditions. These results for skim milk are in agreement with those of Doan & Warren (1947) for skim milk concentrate and suggest that there is an optimum heating temperature around 65 °C. Braatz & Winder (1959) expanded these observations and patented a combined heat treatment which was optimal (Braatz & Winder, 1962).…”

“…Although each investigator used slightly differing heat treatments, the destabilization seems to have been associated with conditions where some denaturation of the whey proteins would be expected to occur (Davies & White, 1959). Typically, after treatment at temperatures above 66 °C, the stability of the milk during frozen storage was poor and this is in complete agreement with the results of Doan & Warren (1947). Below 66 °C, there are varying results.…”

“…The more limited data of Rose & Tessier (1954) do not appear to fit this pattern as closely, but this may be because Rose & Tessier (1954) examined temperature effects in the high subfreezing range ( -7 to -18 °C) where Koschak et al (1981) found that a maximum of instability occurred. When the limited data (in many cases only two points) from other sources were considered, it was found that the slope of the Arrhenius plot remained close to the linear portion of the curve obtained from the data of other workers (Doan & Warren, 1947;Desai et al 1961;Wells & Leeder, 1963;El-Negoumy & Boyd, 1965).…”

“…Heating has been carried out before concentration, after concentration and in combination. There is complete unanimity that high heat treatments are deleterious (Doan & Warren, 1947;Wildasin & Doan, 1951;Tamate et al 1966;Kadan, 1967). Although each investigator used slightly differing heat treatments, the destabilization seems to have been associated with conditions where some denaturation of the whey proteins would be expected to occur (Davies & White, 1959).…”

Changes in Concentrated Milk During Frozen Storagea

“…The nature of the changes occurring in the proteins of milk during frozen storage has not been studied extensively, although it is accepted that the flocculent protein precipitate that forms is primarily the caseinate system (Webb and Hall, 1935 ;Doan and Warren, 1947 ;Christianson, 1953 ;Wells and Leeder, 1963). Electrophoretically, no differences have been detected between normal and precipitated casein (Christianson, 1953;Wells and Leeder, 1963).…”