The effect of small amounts of chlorine on the reduction time of milk.

IT would be expected that the addition of chlorine to milk, as hypochlorite or in some other form, would increase the reduction time. Further consideration will show that a large number of variables are involved—the amount of chlorine, the age of the milk sample at the time of addition, the form in which chlorine is added, the age of the sample when tested, the period which has elapsed since the addition of chlorine, the number and kinds of bacteria present, and the temperature. It would be difficult to assess the relative importance of each and all of the factors in a single experiment, and the object of the experiments described in this paper was to ascertain the minimum amount of chlorine which significantly increases the reduction time of the sample. Wilson (1938) tested fifteen samples, of which four had reduction times of less than 20 min. Part of each sample was stored in the refrigerator. Six different chlorine compounds were used in concentrations ranging from 25 to 400 parts per million of available chlorine. Chlorine water was the most and Milton the least effective as judged by the increase in reduction time (E^T.). Cold storage reduced the effect of the chlorine, and the increase in B.T. was also less in the case of the four poor-quality samples (R.T. less than 20 min.) An increase of about 30 min. was given for the better class samples by 25 p.p.m. av. Cl, and of about 10 min. for the other four samples. Chlorine could be tasted in all cases when 100 p.p.m. av. Cl was present and Milton could be detected at 50 p.p.m. Anderson (1938) also made trials. An inspection of his results suggested that occasionally as little as 5 p.p.m. av. Cl might affect the reduction time, and 50-100 p.p.m. av. Cl could be detected by taste in milk and cream. Wright & Anderson (1938), however, state that even 200 p.p.m. av. Cl half an hour after adding, cannot be detected by odour. They also suggest that amounts of less than 50 p.p.m. av. Cl have no preservative effect (apparently measured as keeping quality). Wilson (1938) found that the average increase in keeping quality for eleven samples was 1 hr. 27 min. when chlorine in the formof Milton was added to give a concentration of 25 p.p.m. av. Cl. In an attempt to measure the interaction of storage temperature, age on adding chlorine and concentration of chlorine, Barkworth (1940) prepared twenty-five subsamples from .each sample. Chlorine Was added at 0, 5 and 10 p.p.m. either at 10.0 a.m. or at 5.0 p.m., using samples of morning milk.