Comparative Evaluation of Near-Infrared Spectroscopy and Classical Reference Methods for Nutritional Analysis of Fast-Food Products

Nutritional profiling of fast-food products is essential for both consumer transparency and industrial quality control, yet conventional methods such as Kjeldahl, Soxhlet, and gravimetric assays are time consuming and require specialized laboratories. Near-infrared (NIR) spectroscopy offers a rapid and non-destructive alternative, but its reliability in complex food matrices such as burgers and pizzas remains underexplored. In this study, four types of burgers (10 samples each, three replicates) and thirteen types of pizzas (three replicates each) were analyzed using both reference methods and a Tango FT-NIR spectrometer to determine protein, fat, carbohydrates, sugars, ash, dietary fiber, and dry matter. Results indicated excellent agreement between NIR and classical methods for major components, including protein, fat, carbohydrates, and dry matter, with no statistically significant differences (p > 0.05). However, sugars showed systematic deviations, with overestimation in burgers (p < 0.05) and underestimation in pizzas (p < 0.01). Ash content also differed significantly in pizzas (p < 0.05), while dietary fiber showed the largest discrepancy, with NIR consistently underestimating values (p < 0.05). Despite these limitations, NIR displayed high repeatability, with standard deviations below 0.2% for most parameters. These findings confirm NIR as a robust and efficient tool for routine nutritional screening in fast food, though reference methods remain indispensable for sugars and dietary fiber.