Performance Evaluation of Refractometer Devices for Brix Determination in Rock Melons

Abstract

Rock melon (Cucumis melo Linn), one of the most popular and delicious fruits of Malaysia has great potential for commercial development. This study aimed to determine the performance evaluation of refractometer devices for brix determination in rock melons in a greenhouse. A Brix meter, also referred to as a refractometer, is an essential instrument used for measuring the sugar content, or Brix level. One of the main reasons for growing rock melons in greenhouses is to mitigate pest and disease attacks. The experiment comprised the following soilless media: T1 = 100% Coconut Peat, T2 = 100% Burnt Rice Husk, T3 = 50% Coconut Peat + 50 % Burnt Rice Husk, T4 = 70 % Coconut Peat + 30 % Burnt Rice Husk, T5 = 30% Coconut Peat + 70% Burnt Rice Husk. This experiment was conducted at the Institute of Sustainable Agrotechnology (INSAT), the University of Malaysia Perlis (UniMAP) at Sungai Chuchuh, Padang Besar, Perlis, Malaysia. This study evaluated the accuracy and precision of three refractometer types, which are Reichert TS Meter‑D (benchtop standard), Atago PR‑201α (digital handheld), and a Extech RF15 Portable Brix Refractometer, to measure Brix in rock‑melon juice. The Reichert TS Meter-D demonstrated laboratory‐grade precision (refractive index accuracy ±0.0001 nD, ~±0.10 °Bx). Compared to this reference, the Atago PR-201α had minimal mean bias (–0.02 °Bx) and narrow 95% limits of agreement (LoA: –0.26 to +0.23 °Bx), meeting practical interchangeability thresholds (±0.30 °Bx). The manual model showed similar average bias (–0.03 °Bx) but wider variability (LoA: –0.49 to +0.43 °Bx), exceeding acceptable error margins. Paired t-tests confirmed biases were not statistically significant (p > 0.75). These findings indicate that the Atago PR-201α offers a reliable, high-throughput alternative to lab equipment for Brix grading whilst the Extech RF15 Portable Brix Refractometer remains useful for everyday field checks where rapid portability is essential.