Development of a Portable LED-Based Photometer for Quality Assessment of Red Palm Oil in SMEs

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Generally a worthy project. Some areas of sharpening to make the paper better.

The device is described as using 269 nm/446 nm channels in the abstract yet the measured LED peaks are ≈277 nm and ≈449 nm. This discrepancy needs to be specifically mentioned with implication for the ISO DOBI definition (A446/A269). There should be a rigorous equivalence mapping to the bench spectrophotometer (e.g., regression + Bland–Altman/Deming). 

Claims of “<5% deviation” lack replicates, error bars, confidence intervals, and method‑comparison statistics in Figs. 17–19. Please report n, mean ± SD (or 95% CI), R², and limits of agreement; add error bars to all plots.  

Calibration and equations use hexane, while application refers to isooctane or 95% hexane; ensure a single solvent system or show transferability. Also, correct Eq. (2): the factor 383 is the specific extinction coefficient, not a “diffusion coefficient,” and its applicability depends on solvent/path length.  

Reconcile inconsistent power‑rail descriptions, specify LED drive currents during measurements, and correct the software step that says the system “stores the absorbance values of the blank” (it should store blank voltages V₀).  

Fix duplicated/incorrect captions (e.g., Fig. 18 labeled “UV… λ = 269 nm” though it appears to be the visible/446 nm channel), ensure axes have units, and avoid reusing identical caption text for different workflows (Figs. 13–14).  

The first‑page header shows “Audiol. Res.”; please correct to AgriEngineering. Cite the ISO standard at first mention (currently ISO 17932:2011 is [72] but the text cites [71]); review the reference list for accuracy/typos and add DOIs where available.  

Provide raw calibration/validation data, the correction‑factor formula, and essential build files. Substantiate “low‑cost” with a component‑level BOM. Also add a brief note on UV‑C safety in the enclosure.  

 

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Two LEDs and two PDs sharing the same chamber maximize the chance of overlap or that of stray light. No consideration of the way optical isolation or interference is managed. LED and PD can shift with temperature. A fan cooling system by itself is detailed, but performance tests under variable ambient situations were not included.

The paper lacks the critical analysis of the limitations, i.e.,

• Sensitivity to solvent purity.
• Necessity for frequent calibration.
• Fitness for turbid or unrefined samples.

The device is promising and well designed, but the paper is too small in scope and doesn't have adequate critical statistical rigor and performance characterization. To be published in AgriEngineering journal, the following are the absolute necessities:

• Include error analysis, statistical validation, and replicates.
• Expand calibration results with LOD, LOQ, linearity range.
• Find the long-term stability, cross-talk, and the.
• Compare DOBI and carotenoid values with industry standards.
• Strengthen the arguments for limitations and practical fielding concerns.

 

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Generally fine, just some issues that need some correction, that are quick writing additions. 

Explicitly state that only one LED is on while its corresponding PD is read, and quantify residual optical/electrical crosstalk (measure PD269 with LED446 on and vice versa, for blank and sample).

Report numerical irradiance (µW·cm⁻²) using a calibrated UV radiometer or fiber spectrometer at defined locations, and compare with ICNIRP/ACGIH exposure limits (replace the qualitative “ambient-level” claim). If this can't be done, then mention it as a limitation. 

Specify the exact PC10‑2‑TO5 window type used (UV‑transmitting glass vs fused silica) with vendor part number; confirm responsivity at ~269 nm for the installed part.

Replace the fixed “0.0078125 mV resolution” statement with the selected PGA full‑scale range and resulting effective LSB used during measurements.

Document that the slope‑correction/transfer function remains valid across diverse RPO matrices (different producers, storage/oxidation levels), or clearly state this as a limitation if only validated on the microwave‑treated series.

 

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This version is technically strong but still has some minor issues where it can be improved before final submission. Though the DOBI meter developed is highly precise and reproducible, several areas can be improved further to maximize its performance and versatility. System operation currently assumes steady laboratory conditions that are not always achievable in field or industrial uses. This can be enhanced by introducing temperature and humidity compensation circuits to minimize environmental effects on LED brightness and detector sensitivity. Another aspect to improve long-term stability and minimize user dependence is by introducing an automatic self-calibration routine by internal optical references. Also by making the replacement units for LEDs and photodiodes modular would allow the range of measurements to be extended to other wavelengths and thus make the device capable of measuring various chemical components within various edible oils. Such refinements would further improve the ruggedness, versatility, and reliability of the DOBI meter to small- and medium-scale production uses.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf