Evaluation of heat‐induced changes in Spanish commercial milk: hydroxymethylfurfural 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 μm, the function of the correlation line was, y=0.47x−0.089 (r=0.958, P<,0.005).

A comparative study of lipid and hypochlorous acid induced oxidation of soybean proteins

“…This was, moreover, evidenced by the results obtained for the total lysine determined after complete acid hydrolysis, where only 5e13% lysine residues losses were observed at pH 5.8 and 8, respectively (Table 2). This was obviously due to the conversion of the chloramines of the lysine 3-amino group to the native lysine during the strong acid digestions applied (Nightingale et al, 2000). Although expected that the monochloramines of the 3-amino groups of the lysine residues would decarboxilate and loose ammonia leading to carbonyls formation, we observed that they led to only limited amounts of carbonyls, which is also in line with previous reports (Domigan, Charlton, Duncan, Winterbourn, & Kettle, 1995).…”

“…The loss of reactive lysine was monitored using derivatization with ortho-phthaldialdehyde (OPA) in the presence of 2-mercaptoethanol (2-ME) which yields a fluorescent product with a maximum excitation wavelength of 340 nm and emission of 450 nm (Ferrer et al, 2003) and b-casein was used to prepare a calibration curve (Morales, Romero, & Jimenez Perez, 1996).…”

Fluorometric determination of chemically available lysine: Adaptation, validation and application to different milk products

“…In the same line, a 10-15% greater blockage of lysine in sterilized versus UHT milk is mentioned by Finot et al [36] and Anantharaman and Finot [2]. Morales et al [37] report a loss of L 2% in UHT milk and L 6% in in-bottle sterilized milk. The fact that sterilization modifies whey proteins to a greater extent than the UHT processes could explain the above-mentioned differences [38,39].…”

The FAST index – A highly sensitive indicator of the heat impact on infant formula model

“…In our system, HMF was not detectable in raw IF, but its concentration rapidly increased with temperature starting from 87°C. The IF model heated for 9.5 min contained 2.54, and 7.35 lM HMF at 110°C, the latter being in the range of concentrations described for UHT milk (Morales, Romero, & Jimenez-Perez, 1996. Surprisingly however, HMF levels reported in commercial IF were much lower, 0.60-1.29 lM (Albala-Hurtado, Veciana-Nogues, Marine-Font, & Vidal-Carou, 1998;Chávez-Servín, Castellote, & López-Sabater, 2006), although a higher HMF concentration would be expected than in UHT milk, because of the higher lactose content in IF than in cow's milk.…”