Evaluation of heat-induced changes in Spanish commercial milk: HMF and available lysine content

Abstract

Hydroxymethyfurfural (HMF) content and loss of available lysine were measured as indices of heat damage in various Spanish commercial milks (pasteurized, UHT sterilized and in-bottle sterilized milks) with similar processing dates. HMF level was determined by the traditional colorimetric procedure and by the reversed-phase HPLC method. Available lysine was measured by an alternative method with o-phthaldialdehyde as fluorescent marker. A significative relationship has been found between the HMF content and loss of available lysine and both are suitable for use as heat-induced indices. When loss of lysine (y) was expressed as percentage and HMF (x) as ¿m, the function of the correlation line was, y=0.47x¿0.089 (r=0.958, P<,0.005).