Pressure Low Temperature Treatment of Milk
According to recent research, high-pressure, low-temperature processing of milk could extend its shelf life without affecting flavour.
According to recent research, high-pressure, low-temperature processing of milk could extend its shelf life without affecting flavour. Most milk is heated at 72oC for 15 seconds to rid it of microbes, providing it a shelf life of about 20 days under refrigeration.
Ultra-high temperature processing of milk at 135-150oC for 3-5 seconds extends its shelf life to about six months at room temperature. But the technique can give the beverage an unpleasant cooked aroma derived from volatile sulfur compounds, aldehydes, and methyl ketones. Such compounds limit the milk’s consumer appeal.
The high temperature treatment favours the formation of hexanal, heptanal, and nonanal, but the low temperature treatment does not. The high-temperature treatment also produces more hydrogen sulfide. Dr. Michael C. Qian and his colleagues at Oregon State University are trying to find a remedy for the situation by studying the effect of pressures as high as 620 megapascals (about 90,000 psi) on milk flavour.
Using methods such as solid phase microextraction, gas chromatography, and pulsed-flame photometric detection, the researchers found that the impact of high-pressure processing on the volatile composition of milk is almost negligible at 25oC but significant at 60oC.
