Color Classification of Foods: Differentiating Opaque, Translucent, and Transparent Samples

Color measurement is a common practice in the food industry and provides a consistent and quantitative analysis of color. True color is often misrepresented by a variety of factors such as human color perception differences, variations in lighting conditions, and the angle of observation. Since various foods respond differently to these numerous elements, a color classification system has been developed to help food manufacturers make the best decisions in color measurement instrumentation based on food appearances and consistencies.

biscuits color classification
Foods vary in color, texture, and consistency. Developing a color classification system ensures that the right methods and instrumentation are used to generate the most accurate color data.
Image Source: Flickr user Pen Waggener

Developing a color classification system

Color classification is based on how light reacts to a food product. Spectrophotometric analyses of opaque food samples rely solely on reflectance light value to quantify color. These foods vary from liquids to solids as well as texture and uniformity. Translucent food samples are typically liquid or semi-solid. The path of light that travels through translucent samples has the tendency to shift or change directions and can alter the color data. The third color classification type is transparent samples that are usually liquid and require a sample holder with a fixed light source.

Many foods can vary in visual quality and consistency. Texture and viscosity both play a significant role in color measurement and can create challenges in sample preparation. Having the right tools and knowing the best methods for spectral analysis are an important reason for developing a color classification system.

Opaque color measurement

Opaque foods can vary greatly in texture, color, and consistency. Liquids such as orange or tomato juice, or soft food products such as cheeses and meats, and even highly textured and non-uniform food samples such as fruits, cereal, and nuts all exhibit opaque color qualities. Color measurement of these foods is based completely on light reflectance value and most accurately measured with a geometric sphere based technology. This technology observes light reflectance from various angles and provides a more uniform color reading of samples with opaque color classification properties.

Opaque samples are often highly textured and non-uniform and require color sample averages to obtain accurate readings. Using non-contact spectrophotometric instrumentation allows for consistent measurements without jeopardizing the structure or consistency of opaque food samples. This is especially important in baked and fried foods, where the integrity of the product is best preserved to provide an accurate representation of consumer perception.

potato chips color classification
Baked and fried foods often present a challenge in color measurement due to their highly textured and non-uniform consistency. Using the best color measurement instrumentation for these sample types will ensure accurate color quantification.
Image Source: Flickr user Procsilas Moscas

Translucent color measurement

Translucent foods can vary in levels of transparency, which alters the amount of light that passes through the sample and may change the direction and angle of reflection. It is important that the sample holder is correctly placed for color measurement and that the background is a solid white so that the path of light remains fixed and the reflectance values accurately represent the true color of the sample.

Foods such as syrups and gelatin-like products are often hard to measure due to their consistency and the way they adhere to the sample holder surface can cause difficulty in cleaning. Sample holders for these color classification types of foods should be easy to use and clean. Durability is also an important factor for repeated use of similar sample materials and excess washing.

Transparent color measurement

Transparent foods are often liquefied and must be placed in a transmission cell for optimum viewing. These color classifications rely on light transmission to accurately quantify color data. Clear juices, soft drinks, spirits, and oils typically fall into this category and these solid or semi-solid foods are measured best with a 0/45 degree fixed angle with a horizontal viewing port. This geometry most accurately represents the true color of the sample and allows for the highest level of consistency among these types of food products.

soybean oils color classification
Translucent and transparent samples can range in levels of light transmission and must be handled and measured according to these color classification attributes.
Image Source: Flickr user United Soybean Board

Leading technology and instrumentation

Spectrophotometric technology has become a highly developed science. Instrumentation features of these tools have been specifically design to match the color classification of foods. From sphere technology to non-contact sample measurements, new technology continues to make this process easier and more effective for food manufacturers.

Changes to design features, more portable instrumentation, and higher durability have made the spectrophotometer a common tool in food manufacturing and preparation. Studies have shown that having consistent product color increases consumer approval. At HunterLab we are innovators of spectrophotometric technology and color measurement tools. For more information on how HunterLab is changing the way the world sees color, contact us today.

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