ATP-Bioluminescence as a method to evaluated microbiological quality of UHT milk

A.F Cunha,K Davenport,C.F Abreu,M.M.O.P Cerqueira,M.A Ferraz,A.D Lage,A.R Tassinari,M.M Pereira E Araújo

doi:10.1590/1678-7396

Abstract

New approaches are needed to quickly indicate possible contamination of UHT milk, among them the technique of ATP-Bioluminescence. Therefore, the aim of this study was to compare the results of culture methods with the results of ATP-Bioluminescence technique of 102 UHT whole milk samples incubated at 48, 72, and 168 hours. UHT milk samples were analyzed for the presence of mesophilic and psychrotrophic aerobic microorganisms using Plate Count Agar (PCA), Brain-Heart Infusion (BHI) media and PetrifilmTM Aerobic Count (AC) plates. The ATP-Bioluminescence technique was applied through the Microbial Luminescent Screening (MLS) system. Significant correlations were found between counts of aerobic mesophilic microorganisms on PCA, PetrifilmTM AC, BHI and results of ATP bioluminescence technique (P≤0.05). The ATP-Bioluminescence technique had higher correlation with counting method in PCA than BHI media. At lower pass/fail limits of Relative Light Units (60, 50, 45 and 40 RLU), the number of samples identified as positive increased and statistically agreed with aerobic mesophilic microorganism counts (P>0.05). For the dairy industry, the ATP-Bioluminescence technique may become an important tool that assists the official methods to quickly monitor the microbiological quality of UHT milk though this will likely require a threshold below 150 RLU.

Highlights

Despite the growth in the dairy sector in Brazil, the quality of the Ultra High Temperature (UHT) milk commercialized is one of the factors that put a limit on the continued expansion of internal and external markets
Given the importance of establishing new quality indicators and fast detection methodologies for microorganism in UHT milk, this paper describes the evaluation of UHT milk microbial quality according to Brazilian law using a variety of different culture media and incubation times, and to compare the culture methods with the ATP-Bioluminescence technique
The samples, collected in the original package were quickly transported to the food microbiology laboratory of the veterinary school at the Universidade Federal de Minas Gerais (UFMG), where they were prepared for the tests

Summary

Introduction

Despite the growth in the dairy sector in Brazil, the quality of the Ultra High Temperature (UHT) milk commercialized is one of the factors that put a limit on the continued expansion of internal and external markets. After the UHT process, spores of some heat resistant microorganisms and microbes introduced to the milk during packaging can be present in the product, making it legally unfit for use (Simmonds et al, 2003; Rezende-Lago et al, 2007) These microorganisms can modify the characteristics of the product, decreasing its shelf-life and potentially compromising the consumer’s health (Hassan et al, 2009). Some of them are routinely used in laboratories and referenced by research institutions and by the company inspection group These traditional methodologies require extensive amounts of time to obtain the results, making the fast implementation of corrective actions impossible. These failures occasionally culminate in important economic losses for the entire milk industry (Park et al, 2001; Vilar et al, 2008; Freitas et al, 2009)

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Conclusion