Smartphone-Assisted Paper-Based Analytical Device for Rapid Colorimetric Detection of Total Reducing Sugars in Honey

Determining reducing sugars in honey is key to ensuring its quality and authenticity. Honey mainly contains fructose and glucose, which represent around 90–95% of the total sugar content, and is one of the most adulterated foodstuffs worldwide. Fraudulent practices such as the addition of water, chemicals, or cheap sweeteners affect honey quality properties and pose health risks. This work presents a spot-test paper-based analytical device (PAD) for the colorimetric quantification of reducing sugars in honey, expressed as the sum of fructose and glucose, which was determined using Benedict’s reaction. Images of the spot-test PAD are captured with a smartphone camera under controlled light conditions and processed with the free web application Trigit. The increase in the color intensity in the blue channel gives a linear correlation with the concentration of reducing sugars in the range of 50–400 mg/L. The obtained limit of detection and quantification values were 11 mg/L and 37 mg/L, respectively. The proposed spot-test PAD offers a low-cost, biodegradable, and easily portable material for the rapid and simple quantification of reducing sugars in honey samples. Likewise, using the smartphone as a digitization system enables rapid data acquisition and analysis, making the method useful as a practical screening tool in food safety and quality control in small or non-centralized laboratories.