Sensors and Instruments for Brix Measurement: A Review

Abstract

Quality assessment of fruits, vegetables, or beverages involves classifying the products according to the quality traits such as, appearance, texture, flavor, sugar content. The measurement of sugar content, or Brix, as it is commonly known, is an essential part of the quality analysis of the agricultural products and alcoholic beverages. The Brix monitoring of fruit and vegetables by destructive methods includes sensory assessment involving sensory panels, instruments such as refractometer, hydrometer, and liquid chromatography. However, these techniques are manual, time-consuming, and most importantly, the fruits or vegetables are damaged during testing. On the other hand, the traditional sample-based methods involve manual sample collection of the liquid from the tank in fruit/vegetable juice making and in wineries or breweries. Labour ineffectiveness can be a significant drawback of such methods. This review presents recent developments in different destructive and nondestructive Brix measurement techniques focused on fruits, vegetables, and beverages. It is concluded that while there exist a variety of methods and instruments for Brix measurement, traits such as promptness and low cost of analysis, minimal sample preparation, and environmental friendliness are still among the prime requirements of the industry.

Low-Cost Sensor for Continuous Measurement of Brix in Liquids

“…Brix can be measured using sample-based measurement or in-line measurement. There is a linear relationship between SG and density, hence Brix measurement can be done through one of these two quantities [ 4 ]. SG or density can be measured using various methods, such as hydrometer principle [ 5 ], optical methods based on refractive index [ 1 ] or infrared absorbance, near-infrared spectroscopy, X-ray absorption, ultrasonic method [ 6 ], fibre Bragg grating [ 7 ], mass flow of liquid based on Coriolis principle [ 8 ], differential pressure measurement [ 9 ], or biosensing [ 10 ].…”

“…Both analogue and digital versions of refractometer are available but analogue type is generally a cost-effective option. Since analogue refractometers are not very accurate due to subjective reading, digital and benchtop refractometers are the preferred versions in the industry despite being expensive compared to their analogue counterparts [ 4 ]. Electronic tongue is another modern portable and cost-effective solution that provides a quick Brix measurement; however, its low selectivity is a major issue [ 14 , 15 , 16 ].…”

“…Surface plasmon resonance (SPR)-based sensors and chromatography are also among the sample-based methods used for Brix measurement. In summary, sample-based methods are manual, time-consuming, and most importantly cannot be the solution of choice for continuous monitoring [ 4 ].…”

“…Tilt hydrometer is an economical free-floating digital hydrometer. However, it is specifically designed for home brewing and is not suitable for large industries [ 4 ].…”

A Smart Alcoholmeter Sensor Based on Deep Learning Visual Perception

“…The low technology readiness level (TRL) of this novel sensor prevents widespread use for now. Other techniques [ 16 , 17 , 18 , 19 ] for ethanol detection and concentration measurement are also the focus of many researchers.…”