Chemical changes during high-temperature short-time treatment of milk in an industrial-scale plant

A study on the effects of HTST pasteurisation on milk in an industrial indi rect UHT plant was carried out. Heat treatments at 105-125 degrees C for 2 s were applied. Heat load in milk was evaluated by the determination of dif ferent thermal indicators such as lactulose, furosine and undenatured whey proteins. At 105 degrees C beta-lactoglobulin suffered a 90% of denaturatio n whereas no formation of lactulose was detected. Heat treatments carried o ut at 125 degrees C caused a 97% of beta-lactoglobulin denaturation and lac tulose formation up to 140.2 mg/l. Furosine formation increased with temper ature obtaining, at the most severe heat treatment, similar level to UHT mi lks. At 105 and 110 degrees C, undenatured beta-lactoglobulin seems to be t he most appropriate indicator to assess the heat load in milk, however lact ulose is indeed a better indicator than undenatured beta-lactoglobulin to m onitor the heating conditions applied when temperatures are higher than 110 degrees C.