Refractometric Detection of Adulterated Milk Based on Multimode Interference Effects.

Area of Science:

• Optoelectronics
• Chemical Sensing
• Food Science

Background:

• Milk adulteration with water is a significant economic and safety concern.
• Accurate and rapid detection methods are crucial for quality control in the dairy industry.

Purpose of the Study:

• To develop and demonstrate a simple, highly sensitive optical fiber sensor for refractometric detection of water-adulterated milk.
• To investigate the sensor's performance, including sensitivity, repeatability, and thermal effects.

Main Methods:

• Utilized a multimode interference (MMI) optical fiber sensor constructed by splicing a coreless multimode fiber (NC-MMF) between two single-mode fibers (SMFs).
• The sensor's principle relies on the shift in transmission peak wavelength, which is dependent on the refractive index (RI) of the surrounding medium (milk-water mixtures).
• Tested the sensor with commercial milk samples at various dilution levels.

Main Results:

• The sensor successfully detected water adulteration in milk by observing shifts in the transmission peak wavelength.
• A linear response was observed in the 0-50% dilution range with sensitivities of -0.04251 nm/% and -0.03291 nm/% for two milk brands.
• The measurement protocol demonstrated good repeatability (<0.34 nm peak wavelength localization).

Conclusions:

• The developed optical fiber sensor provides a simple, sensitive, and effective method for detecting water adulteration in milk.
• The technology shows promise as a quality control tool for beverages, offering potential for real-time monitoring.
• Temperature control is recommended for accurate measurements due to observed thermal sensitivity (0.85 nm/°C).