Caseinomacropeptide index in UHT whole milk stored under different conditions of temperature and time

Abstract

Caseinomacropeptide (CMP) index is a method used to detect adulteration of milk by addition of cheese whey, since CMP is a glycopeptide characteristic produced during cheesemaking, and soluble in the whey phase. The objective of this work was to evaluate the caseinomacropeptide index of UHT milk stored under different temperatures. Six batches of recently processed UHT milk were collected and stored under three temperatures (21°C, 6°C, and -12°C) and analyzed by HPLC in the day of the milk collection (day 0) and at 30, 60, 90, and 120 days of storage. The experiment was run as a randomized block design with a 3x5 factorial arrangement, and the Student-Newman-Keuls (SNK) method was used as the posthoc test (p = 0.05). There was a progressive increase of the CMP index during the storage period of 120 days, and this indicates the possibility of false positive results if the CMP index is used as an adulteration test for long term stored UHT milk. The validity of the CMP index as an adulteration indicator is only possible soon after packaging, and sample freezing is the only alternative when immediate analysis is not possible. The method was found to be precise, with robust CV of 1.9% even with high CMP levels.Keywords: UHT whole milk, caseinomacropeptide, HPLC 0, 30, 60, 90 RESUMO O objetivo deste trabalho foi avaliar a influência da temperatura e do tempo de armazenamento de amostras de leite UAT, em relação ao índice de caseinomacropeptídeo, por cromatografia líquida de alta eficiência, e a precisão do método de detecção. Seis lotes foram coletados e armazenados em três temperaturas (21°C, 6°C e -12°C ± 1°C) e analisadas durante o armazenamento nos dias

Loss of UHT milk quality: changes in compositional and physicochemical parameters triggered by different storage conditions

“…Increases in MUN concentration might be the result of non-protein nitrogen formed due to milk proteolysis (Milaneze et al, 2018;Santos et al, 2018) and this finding is corroborated with the increased CMP index, which is used as an indicator of illegal cheese whey addition to milk, and may be an indicator of milk proteolysis (Ferron-Baumy et al, 1992;Milaneze et al, 2018;Recio et al, 2000;Villanoeva et al, 2014).…”

“…At 30 days of storage, CMP index was greater than 30 mg L -1 in 87.5% of the samples, and above 75mg in 37.5% of the samples (Table 2). In poor quality raw milk, microbial contaminants, particularly the psychrotrophic microorganisms, produce proteases that cleavage the κ-casein close to the hydrolysis site of chymosin (rennet), producing the pseudo CMP, which is detected together with the CMP using the HPLC method (Olieman & Riel, 1989;Recio et al, 1996;Villanoeva et al, 2014). Although this index was devised to detect cheese whey addition to freshly processed milk samples, it proved to be an optional parameter of milk quality, since it is able to detect extensive proteolysis in milk, which can be an indicator of raw milk quality.…”