Milk heating

Fig. 10. Free2e drying profiles for A, whole milk, and B, nonfat milk. Heat was transmitted by radiation from heated wires above the fro2en milk which rested in a transparent plastic tray. (-----------------------) is the induction period. Total pressure was 33 Pa (0.25 mm Hg).

The predominant amines found in cheese are tyramine, cadaverine, putrescine and histamine (Table 6.6) (Stratton et ah, 1991 Silla Santos, 1996 Novella-Rodriguez et ah, 2002 Novella-Rodriguez et al., 2003). Biogenic amine levels may vary between types of cheese as well as within the varieties themselves. The differences within a variety of cheese may be due to a number of factors, including manufacturing processes, bacterial counts in the milk, heat treatments used, use of starter cultures, and the duration and conditions of the ripening process (Stratton et al., 1991 Pinho et al., 2001 Novella-Rodriguez et al., 2003). 

Effect of milk heating on peptide formation during cheese ripening... 

Rose, D. and Tessier, H. (1959) Composition of ultrafiltrates from milk heated at 80 to 230°F in relation to heat stability. J. Dairy Sci., 42, 969-80. 

Figure 9.14 The denaturation of the total ( ) and individual whey proteins in milk, heated at various temperatures for 30 min /l-lactoglobulin ( ), a-lactalbumin (O). proteose peptone ( ), immunoglobulins (A), and serum albumin ( ) (from Webb and Johnson, 1965).

Figure 9.17 Exposure of sulphydryl groups by heating milk at 75 (O). 80 ( ), 85 (A) or 95 (A) °C de-aerated milk heated at 85°C ( ) (from Jenness and Patton, 1959).

Table 9.3 Substances making a strong contribution to the flavour of indirectly heated UHT milk, those contributing to differences in flavour of milk heat-treated in different ways, and those used in a synthetic UHT flavour preparation (from Manning and Nursten, 1987)...

In addition to the general decrease in viscosity with increasing temperature, heating milk can also influence its rheology by heat-induced denatura-tion of cryoglobulins and/or other whey proteins. Concentration of milk, e.g. by ultrafiltration, prior to heating results in a greater increase in f/app than in milk heated before concentration. 

Gould, I. A. and Frantz, R. S. 1945. Some relationships between pH, titrable acidity, and the formol titration in milk heated to high temperatures. J. Dairy Sci. 28, 387-399. 

Glycopeptides have been found in milk at temperatures above 50 °C (Hindle and Wheelock 1970), and peptides similar to macropeptides from chymosin (EC 3.4.23.4) hydrolysis are produced in milk heated to 120°C for 20 min (Alais et al 1967). Under severe ultra-high-temper-... 

Sweetsur, A. W. M. and White, J. C. D. 1974. Studies on the heat stability of milk protein. I. Interconversion of type A and type B milk heat-stability curves. J. Dairy Res. 41, 349-358. 

Solutions are prepared of (a) 1 gram of paraphenylenediamine in 50 c.c. of water and (6) 1% hydrogen peroxide solution, diluted with five times its volume of water and acidified with a few drops of very dilute sulphuric acid (1 c.c. of the cone, acid per litre). From 5 to 10 c.c. of the milk are treated with a drop of (b) and 2 drops of (a). With raw milk or milk which has not been heated above 78°, an intense blue coloration is formed immediately. With milk previously heated to 78-80°, a bluish-green coloration forms after a few moments. Milk heated above 8o° gives no coloration, or at most a scarcely perceptible violet. 

Unsweetened evaporated milk. Heat the unopened can in a 40—60°C water bath for 2h, shaking vigorously every 15min. Remove from bath, allow to cool to room temperature, open, and thoroughly stir the contents. 

Sweetened condensed milk. Heat the unopened can in a water bath at 30—40°C, open, remove entire contents and stir thoroughly until sample is homogeneous. 

Figure 19.5. Resistance to penetration of a yoghurt gel as a fiinetion of the degree of p-lg (genetie variant B) denaturation resulting from milk heating pre-treatment sm skim milk, wm whole milk (Dannenberg 1986).

Guinee, T.P., O Callaghan, D.J., Pudja, P.D., and O Brien, N., Rennet coagulation properties of retentates obtained by ultrafiltration of skim milks heated to different temperatures, Int. Dairy J., 6, 581, 1996. 

UHT milk and evaporated milk Heat stability, emulsifying... 

Coat s milk is sometimes fed to infonts, particularly those who are sensitive to cow s milk. Coat s milk contains very little folate. Nicol and Davis (N4) found goat s milk to contain only 7 compared with 52 pg/liter in cow s milk. Heating the milk reduced the folate in the goat s milk to 1 p.g/liter and halved that in the cow s milk. 

Casein resins Burnt milk, heated horn or burning hair... 

Oldfield, D.J. Haijinder, S. Michael W.T., Kevin, N.P. Kinetics of denaturation and aggregation of whey protein in skim milk heated in an ultra-high temperature (UHT) pilot plant. International Dairy Journal, 1998, 8, 311—318. 

Fig. 2 Evolution of casein (CN), a-lactalbumin (a-La), and (3-lactoglobulin ((3-Lg) contents in raw milk heated for 5 min at defined temperatures (n = 5).

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