Maximising the benefits of NIR rapid analysis for sugarcane mill laboratories

Abstract

Obtaining, training and retaining laboratory personnel for Australian sugarcane mills is a growing concern within the industry. The test duration for some primary laboratory methods is often too long to make the required process adjustments in time, such as altering the high-grade centrifugal settings. Once established, near-infrared (NIR) laboratory instruments using mature calibrations provide many advantages that address both issues, such as ease of use, speed of analysis, multiple constituent results generated in one scan for multiple mill products, and precision and accuracy of results. However, an initial “development” procedure is required to achieve mature calibrations, followed by an ongoing “operation” procedure. This paper demonstrates how the “development” and “operation” procedures were successfully applied to two sugarcane mills. A previously generated globalised calibration, created from various mill instruments and sample populations, was used to develop a mature localised calibration specific to the mill sample sets and their respective laboratory instruments. Stored raw sugar (pol. sugar, water), fresh raw sugar (pol. sugar, water), and molasses (dry substance, sucrose, and final molasses sucrose) were the targeted products considered for the two mills. The “development” methodology used as much data as was practical to rapidly represent the mill sample populations until the equation achieved stability, i.e. the standard error of prediction (SEP) was less than the error control limit (ECL) for each product’s constituent equations. Once matured, the “operation” methodology was implemented, where only 10% of the total sample population scanned by the NIR instrument was required for validation to monitor and maintain prediction performance. Novel software tools were implemented to improve the efficiency of the validation process. Both mill instruments underwent the “development” procedure during the 2019 season. Multiple NIR calibration updates were applied to achieve SEPs that were within or converging to their respective ECLs. The “operation” procedure was implemented during the 2020 and 2021 seasons, where only a single-seasonal NIR calibration update was required for each mill for all product constituent equations to meet the required prediction performance criteria. Providing reliable NIR test results within such short time frames allowed near real-time decisions to be made by process operators with minimal training requirements. The two-stage NIR development/operation methodology can be employed with the appropriate data for similar products.