G-WON GMK-835N Fruit Acidity Meter

Overview

The G-WON GMK-835N Fruit Acidity Meter is a dedicated electrochemical instrument engineered for rapid, field-deployable assessment of titratable acidity (TA) in fresh fruits. Unlike general-purpose pH or conductivity meters, the GMK-835N implements a calibrated conductometric titration principle—measuring changes in solution conductivity during controlled acid–base reaction—to infer organic acid concentration (expressed as citric, malic, or tartaric acid equivalents). This method eliminates reliance on subjective endpoint detection and provides repeatable results across variable fruit matrices without sample dilution or reagent titration. Designed specifically for post-harvest quality control labs, orchard-side grading stations, and food processing QA/QC teams, the GMK-835N delivers consistent readings under ambient conditions, supporting objective maturity indexing, harvest timing decisions, and compliance with internal specification limits aligned with ISO 750:2021 (fruit juice acidity determination) and Codex Alimentarius standards for fruit-based products.

Key Features

• Conductometric measurement principle optimized for intact fruit juice extracts—no manual titration or indicator dyes required
• Pre-programmed calibration curves for 12 fruit types including citrus (orange, tangerine), pome (apple, pear), stone fruit (peach, plum), berry (strawberry, blueberry), and tropical (pineapple, kiwifruit)
• Platinum-coated electrode with integrated Pt1000 temperature sensor enabling automatic temperature compensation (ATC) across 5–40 °C
• Onboard statistical processing: stores up to 99 measurements per session and calculates mean, SD, and CV% automatically
• Self-diagnostic battery monitoring with low-power warning and auto-shutdown after 10 minutes of inactivity
• One-button operation: single press initiates full measurement cycle—including electrode rinse, sample aspiration, conductivity scan, and result display
• IP65-rated enclosure with rubberized grip for resistance to juice splashes, dust, and incidental impact in packinghouse environments

Sample Compatibility & Compliance

The GMK-835N accepts homogenized juice extracts obtained via standard fruit press or centrifugal extraction (e.g., AOAC 974.02 or ISO 2173 procedures). It is validated for use with pulp-free filtrates from apples, pears, grapes, citrus, berries, and melons—excluding highly fibrous or viscous samples (e.g., banana, mango puree) without pre-filtration. Instrument firmware complies with IEC 61000-4 electromagnetic immunity requirements and meets RoHS Directive 2011/65/EU for hazardous substance restrictions. While not FDA 21 CFR Part 11–certified out-of-the-box, audit-ready data export (via optional USB-C adapter) supports GLP-aligned recordkeeping when paired with validated SOPs and instrument logbooks.

Software & Data Management

Data output is accessible via LCD display (dual-line, 128 × 64 pixel) showing acidity value (g/L as citric acid), temperature (°C), and measurement status. Optional PC connectivity enables CSV export of timestamped datasets—including sample ID, operator code, fruit type selection, raw conductivity delta, and calculated TA—for integration into LIMS or Excel-based QC dashboards. Firmware supports user-defined calibration offset adjustment within ±0.2 g/L—traceable to NIST-traceable citric acid reference solutions (1.000 ± 0.005 g/L)—and retains calibration history for internal audit review.

Applications

• Harvest readiness evaluation in commercial orchards and vineyards
• In-line sorting of fruit lots by acidity grade prior to cold storage or processing
• Batch release testing for juice concentrate, jam, and puree manufacturing
• Research applications in horticultural physiology (e.g., acid degradation kinetics during ripening)
• Training and extension services for cooperative grower associations requiring standardized TA benchmarks

FAQ

Does the GMK-835N require daily recalibration?
No—its factory-loaded fruit-specific algorithms and ATC eliminate routine recalibration. Verification against a certified citric acid standard is recommended weekly or before critical batches.
Can it measure acidity in frozen or dried fruit samples?
Only after rehydration to original juice-equivalent concentration and filtration to remove particulates; validation per AOAC 974.02 is required for non-fresh matrices.
Is electrode cleaning required between samples?
Yes—a brief rinse with deionized water followed by gentle blotting is necessary to prevent cross-contamination; no enzymatic or acidic cleaning agents are needed.
What is the measurement repeatability (RSD) for apple juice at 5.2 g/L TA?
Typical intra-instrument RSD is ≤1.8% (n=6, same operator, same extract batch) under controlled lab conditions (25 ± 1 °C).
Does the device store calibration coefficients per fruit type?
Yes—each of the 12 selectable fruit modes retains its own slope/intercept parameters, updated only during manual calibration mode—not during routine measurement.