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

C.N.B.C Villanoeva,L.M Fonseca,J.C Baffa Junior,E.H.P Andrade,M.M.O.P Cerqueira,M.R Souza,C.F.A.M Penna,M.O Leite

doi:10.1590/s0102-09352014000100039

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 (21ºC, 6ºC, and -12ºC) 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 post-hoc 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.

Highlights

Ultra High Temperature (UHT) milk is processed by homogenization and heating at a temperature range of 130oC to 150oC during two to four seconds, followed by cooling to 32oC, and aseptic packaging (Brazil, 1997)
The resultant products are the insoluble para-κ-caseín (105 amino acids) which will be retained in the cheese and the soluble glycomacropeptide called caseinomacropeptide (CMP) which will be found in the whey
The samples were transported to the Chromatograph Laboratory of the School of Veterinary Medicine, Universidade Federal de Minas Gerais (UFMG), were they were stored under different conditions, i.e., 21°C, 6°C, and 12°C, and analyzed on the sampling day, and after 30, 60, 90, and 120 days of storage

Summary

Introduction

Ultra High Temperature (UHT) milk is processed by homogenization and heating at a temperature range of 130oC to 150oC during two to four seconds, followed by cooling to 32oC, and aseptic packaging (Brazil, 1997). UHT milk physical-chemical characteristics and sensorial properties are influenced by several reactions that may occur during and after heating. Among other changes, these reactions can result in cooked or stale flavors, protein gelation, and proteolysis. The proteolysis may occur due to the action of endogenous enzymes such as plasmin or leukocyte proteases present in the milk, enzymes that are added during the cheese making process and / or psychrotrophic microorganisms, which produce extracellular proteases that are heat resistant and contribute significantly to protein degradation. The resultant products are the insoluble para-κ-caseín (105 amino acids) which will be retained in the cheese and the soluble glycomacropeptide called caseinomacropeptide (CMP) (polypeptide amino acids 106-169) which will be found in the whey

Objectives

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Results

Conclusion