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FOOD & BEVERAGE


Keijo Pyörälä, from Vaisala, explains how in-line refractometers, located strategically at every stage of the brewing process, save energy, reduce waste, lower costs and help deliver top quality beer


The Vaisala


refractometers do not require any routine recalibration or maintenance


developed and branded, it’s all about consistency. Process monitoring therefore has a key role to play. Some breweries rely on


manual sampling and laboratory analysis, but the disadvantages of this approach means there is an inevitable trend toward in-line monitoring and increased automation. Laboratory analysis is obviously an


essential component of research and development; providing an insight into the effects of different raw materials or processes on characteristics such as flavour and aroma. Laboratory analysis also plays an important role in investigatory work; helping to understand the chemistry. However, from a production perspective, sampling and analysis can be of limited value because of the cost and the delay incurred – by the time a lab result uncovers a problem; a significant volume of product may have already passed through the brewery. Similarly, samples represent a ‘snapshot’ of the process at one moment in time, and are therefore unable to support feedback control or provide timely alarms, and are less able to uncover trends. Vaisala’s K-PATENTS sanitary refractometers


can be calibrated in Plato, Brix, Balling, gravity, or density, depending on the preference of the brewery. They are available with 3-A Sanitary and EHEDG certifications and are designed to withstand CIP/SIP cleaning and rinsing procedures. A number of different technologies have


been employed to monitor various aspects of the brewing process, but some methods such as turbidity and density can experience measurement errors from fouling and interference by the larger suspended particles


BETTER DATA FOR BETTER BEER B


rewers will often attribute their success to passion, determination and innovation, but once a beer has been


(especially in mashing and the lauter tun) and by the bubbles and foam that are present in most stages. Refractive Index monitoring is therefore preferred, and the Vaisala refractometers provide accurate measurements at every stage of the brewing process without suffering from these interferences. A further advantage of


refractometers is their speed of response, which is a particular


advantage in the packing/filling line and CIP process – to be discussed later. Refractive Index (RI) measurements are


based on the angle of refraction of light in the process medium, using an LED light source. A sensor continually detects the critical angle at which the total reflection of light commences, and the concentration of dissolved solids is calculated taking pre-defined process conditions into account. Vaisala’s sanitary refractometers are therefore supplied factory calibrated to meet the requirements of the specific brewery and are deployed at most stages of the brewing process, some of which are described below. Mashing – Typically, mashing takes place in


a tun, which is an insulated brewing vessel with a false bottom. Malt is steeped in hot water which activates enzymes that cause starch in the malt to break down and release simple sugars, producing wort. It is important to maintain a consistent wort


output, so the refractometer is used to measure the concentration of the mash in water at the outlet pipe. Lautering – Sparge water rinses the grains


inside the lauter tun to complete the extraction of sugars, producing a clear wort with a concentration that gradually decreases during the rinsing. The refractometer continuously measures this concentration, allowing the detection of the appropriate shut-off point for rinsing, which prevents the


34 DECEMBER 2021/JANUARY 2022 | PROCESS & CONTROL


excessive use of water and saves energy. Wort boiling –Once the sweet wort has


been separated, it is pasteurised in a wort boiler or brew kettle, and hops and flavourings may be added. Wort boiling terminates enzymatic activity, preserves foam-positive proteins, evaporates unwanted flavour volatiles, and helps to form desirable taste and aroma compounds. It also brings the brew to the appropriate strength or gravity. The refractometer is installed directly in the


wort boiler, providing continuous measurements of wort strength/gravity so that the brewer can determine exactly when the wort has reached the required strength. This improves beer quality and consistency, while helping to optimise brewing time and energy consumption. Whirlpooling – After boiling, the wort is


transferred to a whirlpool, where solid particles (hop rests and coagulated proteins) are separated from the bitter wort. The whirlpool causes residual particles to coagulate and settle out of the liquid as a sludge known as trub, which is partially removed from the bottom of the kettle. It is important that the solids are removed quickly and effectively to produce a clear, bitter wort for transfer to the next stage, so a refractometer may be installed before and/or after the whirlpool. Cooling –Once boiling is complete, the wort


is cooled by a heat exchanger which recovers some of the energy used to boil the wort. Refractometers can be installed in the outlet of the cooler as a quality control measure; ensuring that the bitter wort contains the correct level of dissolved solids before fermentation. Alternatively, or additionally, a measurement can be made after the boiler and prior to the whirlpool, to avoid the possibility of processing bitter wort that does not meet the required specification. Fermentation – During the fermentation process, yeast converts sugars and amino


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