Application note · Food & Beverage

Using UV-Vis for Color and Routine Quantitation

A method-first guide to fixed-wavelength color tests and routine absorbance work in food QC, including when a colorimeter is enough and when a spectrophotometer earns its place.

Laboratory bench with a spectrophotometer, cuvette racks and a microscope in soft daylight

Yoke Application Team · Reviewed by Yoke Application Team · Updated October 22, 2026 · 3 min read

The short answer

Color is a perception, so a number that stands for it has to name the scale: fixed-wavelength transmittance, platinum-cobalt, or tristimulus values.
A colorimeter is built for one job at production frequency; a spectrophotometer adds the ability to find a wavelength and run a second method.
Color standards fade quietly — give them their own check and replacement interval.

Color and concentration are two different questions asked of the same platform. Color asks whether the sample matches a reference; concentration asks how much of a substance is present. Both can be answered by absorbance, and confusing the two is where routine food QC goes wrong.

Color is not a wavelength

Color is a perception, and a number that stands for it has to be defined: transmittance at a fixed wavelength, a platinum-cobalt value, or a set of tristimulus values. Each is valid and each answers a different question. A specification that says “color within limit” without naming the scale is not measurable.

Fixed-wavelength quantitation

For a single known analyte, a fixed wavelength and a calibration curve are enough. The discipline sits in the details: blank measured in the same cell, wavelength verified, curve bracketing the samples, and every dilution recorded with the result.

Two tasks, one platform

Task	Measurement approach	Common error
Color against a reference	Transmittance at a fixed wavelength, or a color scale	Comparing values produced at a different path length
Color of a turbid sample	Filter or centrifuge, then measure	Reading the sample with particles in suspension
Single analyte, routine	Calibration curve at a fixed wavelength	Sample outside the calibrated range
Scanning for a maximum	Spectral scan before fixing the wavelength	Choosing a wavelength from a published method without checking it on this matrix

Colorimeter or spectrophotometer

A colorimeter is built for one job and does it quickly with a fixed optical geometry — appropriate when the measurement is a color scale at production frequency. A spectrophotometer covers the same measurement and adds the ability to locate a wavelength, scan a spectrum and run a second method. Choose by the number of methods, not by the number of samples.

Calibration for color

Color standards drift and fade. A reference material that has aged quietly shifts every result that depends on it, so the standards need their own check and their own replacement interval. Write both down, and record the standard’s identifier with the result.

Cell handling

In color work the cell is part of the method. Path length, cleanliness, filling height and orientation all change the reading. Keep one cell per product where possible, check it against a blank at the start of the shift, and handle it by the frosted faces only.

Where color results go wrong in practice

Four failures recur. A sample read without filtration, so particles add apparent absorbance. A cell used in a different orientation from the one it was filled in. A reference standard that has aged past its own validity. And a result compared with a value produced on a different instrument type, where the optical geometry differs enough to change the number.

All four are cheap to prevent and hard to detect afterwards, because each produces a plausible value rather than an error message.

The brief

Send the color scale required, the sample form and path length, the number of methods the laboratory runs, the sample frequency and the record format. Those five decide the platform.

Instruments used in this note

The configuration described above, with the full specification of each model.

Colorimeter Series

Colorimeter BC-2000H

Colorimeter with a 7-inch high-resolution touchscreen and a user-friendly graphical interface.

Measurement Method: Platinum-Cobalt Colorimetry
Measuring Range: 0-500PCU
Abs Range: —0.3~3A

View specifications

N Series Color Screen Spectrophotometer

7-inch color screen and Windows graphic interface.

Wavelength Range: 190-1100 nm
Wavelength Accuracy: ±0.1 nm @ 656.1 nm, ±0.3 nm @ all
Wavelength Repeatability: ≤0.1nm

View specifications

1000 Series Basic Spectrophotometer

Five basic single-beam spectrophotometers from V1000 to UV1100N, with a 1200 lines/mm grating, for routine visible and UV-Vis measurement.

Optical System: Single Beam, Grating 1200 lines/mm
Wavelength Repeatability: 1nm
Photometric Range: 0-200%T, -0.3-3.0A

View specifications

Questions about this method

Can a spectrophotometer replace a colorimeter for color grading?

It can produce the same measurement and more, at a lower throughput per sample and a higher cost. Where the only task is a color scale at production frequency, a dedicated colorimeter is the more practical instrument.

Why does the same sample give different color values on two instruments?

Different optical geometry, different cell path, or a different scale. Color numbers are only comparable when the instrument type, the path length and the scale are the same — which is why the specification has to name all three.

Does turbidity affect a color reading?

Yes. Particles scatter light and add apparent absorbance, so a turbid sample reads darker than it is. Filter or centrifuge before measurement, and state which in the method.