Use of Time-Temperature Indicators as Quality Control Devices for Market Milk

Abstract

i-Point TTM and 3M Monitormark time-temperature indicators were evaluated for their use as quality monitors for market milk. i-Point indicators exhibiting a life span of 10 d at 4.4°C. 8 d at 6.8°C and 6.5 d at 10°C and 3M Monitormark having a response temperature of 5°C and a 14 d maximum exposure time were selected. Fresh HTST pasteurized commercial market milk was stored at 4.4,6.8 or 10°C. Time temperature indicators, activated at the time of storage of milk were followed daily at the three storage temperatures for color development in i-Point TTM and index number in 3M Monitormark. Milks were evaluated for bacterial numbers and acceptability at selected time intervals. Milks generally remained acceptable approximately 4 d after the end of the life span of i-Point indicators at 10°C and more than 10 d at 4.4 °C. 3M Monitormark exhibited insensitivity in the temperature range of 4–10°C. This integration of time as well as temperature makes it possible to replace the sell-by-date on market milk with i-Point TTM indicator to more effectively monitor quality.