CHICAGO – Many people like the taste of raw – as in unpasteurized – milk. The problem, of course, is that germs may infect raw milk, so food safety regulations require that commercial milk producers heat-treat their product. But food scientists at Louisiana State University think they’ve stumbled onto a tastier way to sterilize milk. They bombard it with sound waves.
At the Institute of Food Technologists’ annual meeting, July 19, LSU graduate student Marvin Moncada Reyes presented data showing that his team in Baton Rouge successfully used sonication to knock out coliform bacteria – indicators of possible fecal germs – that can taint unpasteurized dairy products. The novel process heated milk, initially stored at 4 °C, to about 55 °C. Moncada Reyes notes this temperature is well below what the Food and Drug Administration now requires for pasteurization: a brief 15-second heating to 76 °C.
Sonication’s gentler heat can have several advantages, Moncada Reyes argues. Some milk proteins begin to denature – alter or break down – at 63 °C, changing milk’s flavor by creating new volatile compounds and eliminating others. Indeed, he observes, today’s high-temperature pasteurization leads to “a cooked flavor” in supermarket milk. The LSU scientists measured flavor compounds in the milk they tested. Although values of two key chemicals measured – dimethyl amine and dimethyl sulfide – differed little between raw and sonicated milk, the compounds' concentrations were up to 40 times higher in conventionally pasteurized milk.
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