EVALUATION OF HEAT-INDUCED CHANGES IN SPANISH COMMERCIAL MILK - HYDROXYMETHYLFURFURAL AND AVAILABLE LYSINE CONTENT

Hydroxymethyfurfural (HMF) content and loss of available lysine were m easured as indices of heat damage in various Spanish commercial milks (pasteurized, UHT sterilized and in-bottle sterilized milks) with simi lar processing dates. HMF level was determined by the traditional colo rimetric procedure and by the reversed-phase HPLC method. Available ly sine was measured by an alternative method with o-phthaldialdehyde as fluorescent marker. A significative relationship has been found betwee n the HMF content and loss of available lysine and both are suitable f or use as heat-induced indices. When loss of lysine (y) was expressed as percentage and HMF (x) as mu M, the function of the correlation lin e was, y = 0.47x - 0.089 (r = 0.958, P < 0.005).