New universal indicator

Abstract

The results may be summarized as follows:1.When cream was held at 50° F. it changed from first to second grade in from 11 to 16 or more days. At 70° F. it changed in from 3 to 10 days, and at 90° F. in from 1 to 4 days. The time required for the cream to change from first to third grade varied from 4 to more than 16 days as the temperature was varied by 5° intervals between 50 and 90° F.2.The cream soured in from 1 to 6 days, souring more rapidly as the storage temperature increased. Stale flavors were most prevalent at low storage temperatures after several days (4–14) holding. Putrid flavors were detected at high or low temperatures but not at intermediate temperatures (60–75° F.). Bitter flavor varied widely in time of appearance (1–14 days) but apparently was retarded at low temperatures. Unclean flavor appeared early. Rancidity was not detected in cream stored at 50 to 55° F. but appeared in from 3 to 9 days at other storage temperatures. With one exception cheesy flavor appeared only at temperatures of 65° F. or above. Yeastiness appeared in from 4 to 5 days at temperatures of 85 and 90° F., but as storage temperatures were reduced development of this flavor was retarded.3.At the lower storage temperatures (50 and 60° F.) the cream was regarded as second grade at lower levels of acidity than when the cream was stored at higher temperatures. At 60° F. the acidity of poor cream increased only slightly faster than that of good cream, the maximum being 0.7 per cent in 4 days and remained the same thereafter. At 70 and 90° F. the rate of acid development in the poor cream was much greater than in the good cream, the rate of acid development being dependent on the storage temperature. Addition of starter to poor cream increased the rate of acidity development at all temperatures, being greatest at the higher temperature.4.The hydrogen-ion concentration of the cream decreased rapidly during the first 2 days to a value of pH 4.6, after which the rate of decrease was less. The pH values revealed little information not indicated by tests for total acidity.5.Formol titrations of cream held at 60° P. indicated that protein decomposition was less in good cream than in poor cream. At higher storage temperatures proteolysis was accelerated, but the difference between the rate in poor and good cream was more marked at lower temperatures. Addition of starter to poor cream caused an increase in the formol titration at all temperatures. Data presented raises a question regarding the validity of the formol titration as an index of undesirable conditions.6.Practically no yeasts or molds developed in cream held for 16 days at 50° F. At temperatures of 70° F. or above mold and yeast development increased rapidly.