UV-Vis Spectroscopy: Application In Food Products Characterization

Food quality is an important factor in food manufacturing. It is a great concern to produce quality food products to avoid contamination and to produce healthy foods during the manufacturing process. It is a must to ensure the ingredient quality and the environment of the food processing is clean to produce safe food for the consumers. 

Food comprises water, fat, proteins, carbohydrates, and other minor components. The molecular and intermolecular interactions in the food system define the functional properties of these components. 

The amount present in the food system defines the characteristics of food products. The food products should meet the minimum standards to fit human consumption. Recent developments and increased industries in food production have increased demand for high standard quality and safe food production. 

This in turn demands appropriate analytical tools to test the quality standards of food products. Two important techniques used in food analysis are atomic absorption and molecular spectroscopy.

UV/Vis Spectroscopy is the most important analytical technique used for food and beverages testing. This UV/Vis spectroscopy technique does not disturb the sample compounds and does not produce any byproducts as residue.

What is UV/VIS spectroscopy?

UV Visible spectroscopy is optical spectroscopy that is based on the interaction of light with samples. Light is an electromagnetic wave, the light energy periodically oscillates like a wave between maximum and minimum as a function of time. The distance between the one maxima or minima to the other is termed as wavelength and is measured in nanometer (nm).

UV Visible spectroscopy technique is based on the absorption of light by the sample substance. Depending on the nature of the substance the light is absorbed partially and other transmitted is measured as a function of wavelength with a suitable detector. 

This provides the UV/Vis spectrum of the sample. Each substance has a unique nature absorption of light and hence specific relationship exists between the  UV/VIS spectrum and the nature of the substance. This helps to quantify the substance.

UV Visible spectroscopy is usually used in the analysis of solid materials such as films or glass, organic molecules,  inorganic ions, and complex solutions. The UV/VIS spectrum obtained from the UV/VIS spectroscopy is useful for quantitative and qualitative measurements of specific compounds. 

The concentration of the sample can be determined by the absorbance at specific wavelengths. There are different types of UV/Visible spectrophotometers available in the market. 

• UV/Vis Single beam spectrophotometer
• UV/VIs Double beam spectrophotometer
• Split beam spectrophotometer
• UV/Vis-NIR spectrophotometer
• Microvolume or Nanodrop spectrophotometer

Depending on the applications and accuracy requirement spectrophotometers are chosen.

Measurement Principle

The UV Visible light is passed through the sample in a cuvette. Depending on the nature of the sample the light is either absorbed, transmitted, or reflected. 

The absorbed light is measured with UV/VIS spectrophotometer. UV/Vis spectrophotometer is composed of a light source, a sample holder, a monochromator to separate the white light into the different wavelengths of a light source, and the detector to measure the light after absorbance.

Lambert-Beer law

According to Lambert-Beer law, when the light is passed through the cuvette filled with the sample solution, the intensity of the light is attenuated proportional to the sample concentration i.e., the absorbance of light is more in the higher concentrated sample solution. 

The light absorption is also proportional to the length of the cuvette. The longer length of the cuvette leads to higher absorption of light.

A = ?.c.d

Where A is the absorbance of light, ? is the extinction coefficient, c is the concentration of the sample solution, and d is the path length of the cuvette. 

UV/Vis spectrophotometer is widely in various industries such as,

• Cosmetic industry
• Petrochemistry
• Pharmaceutical research
• Optical components
• Food and agriculture
• Life sciences
• Traditional chemistry
• Microbiology
• Material Science
• Analytical Chemistry
• Chemical and Biotech industry

Here in particular we are going to discuss UV/VIS spectrophotometry application in the food and beverage industry to improve product quality and consistency. 

UV/VIS  spectrophotometry, the analytical technique has become important in various scientific researches in biotechnology, analytical chemistry, etc., due to its availability, flexibility, and simplicity. 

Recently, the requirement of reduced samples volumes and reagent quantity to develop analytical measurement led to the development of UV/ VIS microvolume spectrophotometric instrumentation.

Based on the above relationship between concentration and absorbance, The UV/Vis spectrum enables you to determine the different components present in the sample and the absorbance peaks allow defining to what extent the components are present, organic compounds or solvent purity can be easily checked with UV/VIS spectrophotometer. 

This UV-Vis spectrophotometer helps in quantitative analytical techniques such as food and beverages, biotechnology, chemical industries, pharmaceuticals, and water testing, etc. 

In addition to the product quality, the chemical deterioration and degradation process of packaging material, stabilizers are observed with UV/VIS spectrophotometer.

One of the important applications of UV/Vis spectroscopy in the food and beverage segment is the enzymatic determination of carbohydrates like starch, glucose, sucrose, fructose, and total dietary fiber. Enzymes are specific for particular molecule and hence it is suitable for quantitative analysis without sample preparation.

UV/Vis spectrophotometer is widely used to determine the purity of different types of olive oil such as extra virgin, virgin, olive oil, and others. Olive oil is rich in Vitamin E, antioxidants, and monosaturated fatty acids and so it is considered healthy to consume with food.  

Monosaturated fatty acids are essentially long-chain fatty acids that lower cholesterol and prevent heart diseases. The oxidation process that involves lipids plays important role in oil quality. 

Unsaturated lipids that undergo the oxidation process leads to allylic hydroperoxides. The diene and triene double bonds present in the hydroperoxides show strong absorption between 200nm to 300nm. 

Low absorption in this wavelength range represents the high quality of olive oil. UV/Vis spectrophotometer helps in the determination absorption of the olive oil sample and hence enables to differentiate the different quality of olive oil samples.

It is important to estimate the nitrate content in processed food products, especially meat products. Inorganic nitrites naturally present in plant food and vegetables, but these nitrates are also used as additives in the industrially processed food as meat. 

When the nitrogen content is increased in the food it will result in significant health hazard for the consumers. As these nitrogen is converted into nitrosamines which causes thyroid disorders, carcinogenesis, and more. For the safety of food consumers it is important to estimate the amount of nitrate present in the meat products

Conclusion

The UV/Vis spectrophotometer and sample preparation have got their importance in several industry types of research. One of the industries where UV/Vis spectrophotometer got its importance is the food industry. 

Food is the most essential and basic need for humans. Food eating behavior has changed in large in this modern world. It is the vital responsibility of the food manufacturers to produce quality and safe food for the consumers. 

UV/Vis spectrophotometer is the essential analytical tool that helps to test the food quality without disturbing the nature of the food materials.