Novel beer bitterness measurement instrument using optical fiber sensor

Abstract

This paper presents a novel optical fiber sensor for measuring the bitterness of beer samples. The sensor is based on a Mach–Zehnder interferometer (MZI) composed of two long-period fiber gratings (LPFGs). The sensor exploits the sensitivity of the LPFGs to the refractive index of the surrounding medium, which varies according to the concentration of iso-α-acids that cause bitterness in beer. The sensor uses a two-point on-line self-calibrating procedure to estimate the bitterness of unknown samples by comparison with reference samples of known bitterness. The sensor performance was evaluated in both laboratory and factory settings, showing good repeatability, reproducibility, and low bias. The proposed sensor offers a fast, simple, and low-cost alternative to the conventional method of measuring beer bitterness based on UV spectroscopy. The sensor can be integrated into the Industry 4.0 framework to improve the quality and consistency of beer production.