Food Analytical Methods

, Volume 11, Issue 7, pp 2022–2028 | Cite as

A New Tool for Interpretation of Thermal Stability of Raw Milk by Means of the Alizarol Test Using a PLS Model on a Mobile Device

  • Gilson Augusto Helfer
  • Bruna Tischer
  • Paula Freitas Filoda
  • Alessandra Betina Parckert
  • Ronaldo Bastos dos Santos
  • Layane Lenardon Vinciguerra
  • Marco Flôres Ferrão
  • Juliano Smanioto Barin
  • Adilson Ben da Costa


This article describes the development of a new tool for interpreting the thermal stability of raw milk by means of the alizarol test, using a multivariate calibration model on a mobile device. The alizarol test is a semiquantitative test that uses an alcoholic solution containing a pH indicator (alizarin). Color judgment and correlation with pH are done visually and may involve several errors and differences between one analyst and another. Therefore, a pH scale (3 to 12) was constructed with raw milk for the alizarol test using a mobile device for image acquisition for each pH point (in triplicate). For quantitative pH determination, a new version of the PhotoMetrix® app was developed (named PhotoMetrix Pro®), including partial least square (PLS) regression tools, choosing RGB histograms and mean center preprocessing. The alizarol stability test was performed using 2 mL of sample and 2 mL of alizarol. To verify the performance of the PLS model, seven samples from different milk producers were analyzed. The results indicate that the root mean square error of calibration (RMSEC) was 0.25, and the root mean square error of prediction (RMSEP) was 0.30, very satisfactory. The results obtained by the proposed method were compared to those obtained using the potentiometric method (reference method); agreement between 95.0 and 100.9% was obtained, without statistical difference (p > 0.05). This application using PhotoMetrix Pro® could be an alternative for fast and reliable interpretation of the alizarol test.


Raw milk Smartphone Digital image analysis pH Alizarol test 



The authors would like to thank Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul (FAPERGS), and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES).

Compliance with Ethical Standards

Conflict of Interest

Gilson Augusto Helfer declares that he has no conflict of interest. Bruna Tischer declares that she has no conflict of interest. Paula Freitas Filoda declares that she has no conflict of interest. Alessandra Betina Parckert declares that she has no conflict of interest. Ronaldo Bastos dos Santos declares that he has no conflict of interest. Layane Lenardon Vinciguerra declares that she has no conflict of interest. Marco Flôres Ferrão declares that he has no conflict of interest. Juliano Smanioto Barin declares that he has no conflict of interest. Adilson Ben da Costa declares that he has no conflict of interest.

Ethical Approval

This article does not contain any studies with human participants or animals performed by any of the authors.

Informed Consent

Not applicable.


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Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  • Gilson Augusto Helfer
    • 1
  • Bruna Tischer
    • 2
  • Paula Freitas Filoda
    • 2
  • Alessandra Betina Parckert
    • 3
  • Ronaldo Bastos dos Santos
    • 3
  • Layane Lenardon Vinciguerra
    • 4
  • Marco Flôres Ferrão
    • 4
  • Juliano Smanioto Barin
    • 5
  • Adilson Ben da Costa
    • 2
    • 6
  1. 1.Departamento de ComputaçãoUniversidade de Santa Cruz do SulSanta Cruz do SulBrazil
  2. 2.Programa de Pós-Graduação em Sistema e Processos IndustriaisUniversidade de Santa Cruz do SulSanta Cruz do SulBrazil
  3. 3.Departamento de QuímicaUniversidade de Santa Cruz do SulSanta Cruz do SulBrazil
  4. 4.Instituto de QuímicaUniversidade Federal do Rio Grande do SulPorto AlegreBrazil
  5. 5.Departamento de Tecnologia e Ciência dos AlimentosUniversidade Federal de Santa MariaSanta MariaBrazil
  6. 6.Programa de Pós-Graduação em Tecnologia AmbientalUniversidade de Santa Cruz do SulSanta Cruz do SulBrazil

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