Hot air drying of red beet: Process and product quality monitoring by digital images and near infrared spectroscopy

Abstract

The use of nondestructive techniques that can guarantee in situ monitoring of the quality of food products during drying processes can promote improvements in industrial processes. In this context, digital imaging and near infrared spectroscopy can play an important role. Red beet moisture content, betalain content, shrinkage, and color were measured during drying. The digital images showed changes in color, which intensified with increasing temperature and correlated with betalain content through multivariate linear regression (R² of 0.90). In addition, sample shrinkage was identified by digital images. The volumetric shrinkage increased proportionally to the drying air temperature, with a shrinkage of 85.4 ± 0.3% at 70 °C. Spectral data were obtained by a low-cost portable near infrared spectrometer. Partial least square regression was used to predict the product moisture content ($R_P^2=0.89;\mathit{RMSEP}=0.79\%$) and total betalain content ($R_P^2=0.79;\mathit{RMSEP}=0.30\frac{mg}{g}d.b.$) during drying. These tools can be used for the in situ control of red beet drying.

Keywords:

• PAT
• NIR portable spectrometer
• chemometrics
• betalains
• digital image
• shrinkage

Acknowledgments

We are also grateful to our academic colleagues for their contributions.

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Data availability

Data will be made available on reasonable request.

Authors’ contributions

Pedro Renann Lopes de França: Validation; Data curation; Formal analysis; Investigation, Writing - original draft. Jam Pier Cruz-Tirado: Validation, Formal analysis, Investigation, Writing - original draft. Douglas Fernandes Barbin: Writing - review & editing, Resources. Louise Emy Kurozawa: Writing - review & editing, Resources, Supervision, Project administration, Funding acquisition.

Additional information

Funding

J. P Cruz-Tirado acknowledges scholarship funding from FAPESP, grant numbers 2020/09198–1 and 2018/02500–4. Louise Kurozawa and Douglas Barbin are CNPq Research Fellows. Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); S?o Paulo Research Foundation (FAPESP).This work was supported by Coordination for the Improvement of Higher Education Personnel – Brasil (CAPES) – Finance Code 001; National Council for Scientific and Technological Development (CNPq) – process n° 130384/2019-4; and The São Paulo Research Foundation (FAPESP) – process n° 2019/23032-1.