New Trends for the Evaluation of Heat Treatments of Milk

Abstract

Milk is generally very rich in nutrients and this may lead it to be an ideal growth environment for many microorganisms, including pathogens, so effective measurements aiming to ensure total microbiological safety of milk and minimize the risk to human health are needed. Milk heat treatments are the most common practices carried out to inhibit the microbial growth; therefore it is necessary to have analytical procedures that are more and more up-to-date and capable of detecting the effectiveness of the heat treatments. Most of the reference and official methods to assess heat treatment in milk are based on the evaluation of the modifications of some milk components following the thermal process, such as the determination of enzyme activities (alkaline phosphatase and lactoperoxidase), whey proteins, Maillard reaction compounds (generally furosine), and lactulose. Besides the most common techniques (liquid and gas chromatography, capillary electrophoresis, or spectroscopy) used for the detection of single thermal indicators, new approaches, such as chemometric studies or more recent techniques, including size-exclusion chromatography with online electrospray mass spectrometry or stable isotope ratio mass spectrometry, are discussed in this review in order to evaluate heat treatment in milk.

Application of Spectroscopic Techniques to Evaluate Heat Treatments in Milk and Dairy Products: an Overview of the Last Decade

“…2 a Total number of scientific articles published on the application of spectroscopic techniques for monitoring thermal treatments in milk. The data was traditional sterilization employs temperatures ranging from 110 to 120°C and times ranging between 20 and 40 min (Ali et al, 2019;Birlouez-Aragon et al, 2002;Ritota et al, 2017) while the ultra-high temperature technique (UHT) applies high temperatures (135-150°C) during a short time (1-10 s). Hence, food products subjected to one of these two treatments can be stored at room temperature during several weeks or months, while pasteurization extends the shelf life of the products for a few weeks or days.…”

“…In milk, many fluorophores (e.g., aromatic amino acids, vitamin A, riboflavin, NADH, oxidation products, and Maillard reaction products) have been used. They allow (i) detection of changes induced in milk following the application of thermal treatments, (ii) classification of milk samples according to their thermal treatments, or (iii) prediction of changes in concentrations of certain constituents in milk during the application of thermal treatments (Andersen and Mortensen, 2008;Ritota et al, 2017;Shaikh and O'Donnell, 2017;Sikorska et al, 2019).…”

Application of qualitative tests for detection of adulterants in sterilized milk and during its subsequent storage

“…Lactulose has been proposed by the International Dairy Federation and by the European Commission as an analytical index to distinguish UHT milk from sterilized milk (Amine et al, 2000). Lactulose is hydrolyzed into glucose and fructose by enzyme β-D-galactosidase (Ritota, Costanzo, Mattera, & Manzi, 2017). The lactulose concentration of heat-treated milk noticeably increased during storage at 30°C (Cho, Hong, & Kim, 2012).…”

Radio Frequency Heating of Milk–Effects on Quality, Safety, and Shelf Life Assessed Using Artificial Senses and Chemometric Tools

“…ALP and LPO are two milk' native enzymes which are often used as retrospective indexes for the degree of heating applied during the process of pasteurization, and to discriminate between well-pasteurized and raw or insufficient heat-treated products [41]. ALP is inactivated during the process of pasteurization, while LPO is more heat-stable, and it is inactivated if the milk has been exposed to higher temperatures [42]. Hence, it is expected that a successful treatment will lead to milk where at least ALP is absent.…”