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Effect of High Temperature Heat Treatment of Milk on the Ammonia Content¹

Maryland Agricultural Experiment Station, College Park

ABSTRACT

The application of the phenol-hypochlorite colorimetric procedure for determining ammonia revealed that, when milk was heated at 96°C., production of ammonia averaged 0.96 mg. per cent per hour for milk heated in an open flask and 1.25 mg. per cent per hour for milk heated in sealed cans.

The heating of milk under conditions to cause the milk to brown and to develop a caramel flavor resulted in increases in the ammonia content approximating 1.5 to 2 mg. per cent.

It is doubtful that the cooked flavor of milk may be correlated directly with ammonia production, although there was some indication that extremely shall quantities of ammonia were produced at 80°C. Certainly, a more sensitive method for ammonia measurement than the one used in this study would need to be utilized to establish with certainty any relationship between the critical temperature for cooked flavor production and the simultaneous production of ammonia. Heating temperatures as high as 95°C. for momentary periods produced only small quantities of ammonia.

The non-casein nitrogen is the major source of ammonia produced by high heat treatment.

¹ Scientific paper no. A292, contribution no. 2242 of the Maryland Agricultural Experiment Station (Dairy Department).

² Present address: Department of Agriculture, Athens, Greece.

³ Present address: Department of Dairy Technology, The Ohio State University, Columbus.

⁴ Present address: Department of Dairy Industry, University of Wisconsin, Madison.