Quality Analysis Migrates From Lab To Line

March 28, 2003
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New sensors measure product quality on-line and at-line to reduce lab-analysis time, speed process adjustments, minimize downtime and boost productivity.

The InfraLab measures moisture and fat in hard and semi-hard cheese samples at-line in 30-45 seconds, enabling cheesemakers to optimize yields. (Source: NDC Infrared Engineering)
Over the past 15 to 20 years, many tests for analyzing product quality have been moving out of the lab toward the production line as instrumentation based on infrared spectroscopy, optical and laser technologies combines with advancing computer technologies for application on-line and at-line. Armed with real-time or near real-time quality information, operators can quickly adjust the process without waiting for laboratory analysis, thus boosting productivity while minimizing downtime and wasted product. Many sensors can be integrated with process-control systems to automatically adjust process conditions to meet product specifications.

The MM55plus NIR analyzer continuosly measures moisture and fat on-line in a wide range of food applications, including snack foods, where the sensor can integrate with process controls to adjust fryer or oven conditions to maintain specified product moisture content. (Source: NDC Infrared Engineering)

Wide NIR applications

One example of an on-line Near Infrared (NIR) analyzer with wide food applications is the MM55plus, developed by NDC Infrared Engineering (Irwindale, Calif.) for noncontact on-line measurement of any two of three product characteristics: moisture, fat and protein. Applications include snack foods, chocolate, coffee, tea, potato powders, flour, starch, crystalline sugar, breakfast cereals, nuts, soy, sugar-beet pulp and animal feeds. The MM55plus is precalibrated to the generic application, then adjusted on-line to match the appropriate laboratory reference method. This allows quick installation and operation in just a few hours, says NDC. A stainless-steel scanning head resists CIP routines, while a sapphire optical window eliminates the risk of accidental glass contamination. An optional aircooler ensures reliable operation near ovens, fryers and dryers.

MM55plus controls incorporate automated referencing, sampling, batch-averaging and communications functions. As many as 80 different recipes can be stored in the system's memory and recalled at the touch of a button or automatically via the plant's process-control system.

The MM55plus integrates with PLCs, PCs and SCADA systems, enabling closed-loop control of process equipment. On potato chip lines, for example, the unit monitors oil and moisture content of product emerging from the fryers or ovens and regulates time/temperature to optimize moisture content and minimize waste. On-line oil measurement is essential to maintaining flavor and labeling requirements.

The Kraft Maxwell House coffee plant at Jacksonville, Fla., installed an MM55plus about 1½ years ago for at-line sampling and measurement of moisture content of coffee emerging from the roaster before grinding. The optimum moisture content of coffee going into the grinder is 5.4 percent for best yield, says Process Engineer Steve Desauer. If the moisture content is incorrect, the coffee tends to plug-up the grinder, adversely affecting process efficiency and productivity, he adds. Should the instrument indicate that moisture is going out of spec, roaster conditions are adjusted to maintain the optimum.

The major advantage of the MM55plus is its self-calibration function, says Desauer. Moisture measurements are accurate to within 0.5 percent, and QC lab validation "is always right on," he adds. The unit is housed in a NEMA 4X enclosure to resist washdown .

NDC Infrared recently introduced to U.S. markets the InfraLab system for at-line measurements of moisture, fat and protein across a wide range of applications. One major application is for measuring moisture and fat content in hard and semi-hard cheese, where it has enabled New Zealand cheesemakers to manage their processes for optimum yields, product consistency and shelf life while saving analysis time. The InfraLab combines NIR measurement technology with Windows NT software to provide quick test results and integration with Laboratory Information Management Systems (LIMS).

One of the first U.S. InfraLab installations is at the Krohn Dairy Products plant in Luxemburg, Wis., a producer of pasta-filada style mozzarella and provolone cheese. Krohn's InfraLab is in the plant's laboratory rather than directly at-line. According to President Roger Krohn, InfraLab is used to measure moisture and fat both in curd and finished cheese from every vat of every day's production. "We can take curd right off of our finishing tables or off the cooker, get an idea of where we stand, and make (process) changes on the fly to optimize yields," says Krohn. The major advantage of InfraLab is speed of analysis, he continues. Sample preparation requires merely shredding a piece of cheese or curd into the pan "and you have results within 30 seconds" as compared to about 3½ minutes for microwave-oven analysis. InfraLab moisture-test results are typically within 0.2 percent of microwave results, he adds, and fat results are within 0.3 to 0.5 percent of Babcock-test results.

Milk & meat standardization

More than 90 percent of all milk analysis worldwide is performed on Foss instruments such as MilkoScan systems, which measure fat, protein, lactose and solids in both raw milk (for producer payment) and in finished products. The Foss ProcessScan FT analyzer applies the same Fournier Transform InfraRed technology to measure fat, protein, lactose and solids in milk on-line in real time for milk standardization.

Last year, Foss North America (Eden Prarie, Minn.) introduced ProcessTouch software to integrate ProcessScan with plant process-control systems (such as PLCs) to automate milk standardization. ProcessTouch applies the analytical input from ProcessScan to control the blending process, standardizing milk either on-line or in tanks. According to Chuck Lowden, business unit manager for the food group at Foss, standardizing milk in-tank has been accomplished with an accuracy of 0.013 percent of reference test.

About a year ago, Foss established a joint venture with Wolfking Inc. (Columbus, Ohio) to market the CFA continuous fat analyzer to control fat content in ground-meat products on-line in real time. The CFA samples meat directly from the blender every three seconds, measures the sample for fat, moisture and protein, and returns the sample to the blender. It combines NIR analysis with neural-network technology to standardize lean-to-fat ratios, and incorporates a feedback loop to control the weight of trimmings conveyed into the blender, thus maintaining desired fat content. Foss markets, calibrates and commissions CFA systems retrofitted to existing Wolfking blenders, and also calibrates and commissions CFA units sold by Wolfking with its blenders.

At-line Aw

At the annual meeting of the American Society of Baking March 6 in Chicago, CCFRA Technology (a unit of the Campden & Chorleywood Food Research Association Group in the U.K.) showcased ERH CALC software, which calculates water activity (Aw) and predicts mold-free shelf life of bakery products. Although originated for product development, the software has been combined with infrared technology for an on-line/at-line system in a commercial plant: The infrared sensor periodically measures product moisture content on-line, then the ERH CALC software calculates water activity and predicts mold-free shelf life at-line. This information is then used to adjust moisture content if needed in the batter. "It's a specialized application -- it only works with thin products that have a minimal moisture differential" between crust and center crumb and very short residence time in the oven, says Stanley P. Cauvain, director of the cereals and cereal processing division at C&C. Although adjustments to batter viscosity will be minimal, a one-half percent difference in desired moisture content can vary the 28-day mold-free shelf of certain products marketed in the U.K. by five or six days, Cauvain pointed out. Batter viscosity adjustments are made by the operator, but ideally could be done automatically with a feedback loop, he added.

The ProcessScan system measures fat, protein, lactose and solids in milk on-line in real time as inputs to ProcessTouch software, which automates milk standardization on-line or in-tank. (Source: Foss North America)

Milk, meat and edible oils

ABB Bomem (Quebec City, Que.) recently developed several NIR systems for on-line analysis of milk, process cheese, ground meats and edible oils.

Bomem's new Food Networkir is a multiconstituent, multisampling-point milk-standardization system that measures fat and protein in milk and standardizes milk on-line. Constituents measured include moisture, fat, total solids, casein and lactose, says Douglas Brown, food business unit manager at ABB Bomem. The first two units, installed in Quebec dairy plants, are currently being validated (i.e., calibrated to standard analytical reference methods); a third system will soon be installed in a Norwegian dairy plant. The first installation in Quebec has one measurement point for on-line standardization of milk off a pasteurizer, a second measurement point for on-line standardization of butter off a churn "for two completely different applications in the same unit."

Bomem's meat analyzer continuously measures four constituents -- fat, protein, moisture and collagen -- in ground or comminuted beef, pork and poultry products as they are blended in mixers or moving in screw conveyors. Four sy stems are currently installed (three validated) in Scandinavia, with two more slated soon for North American meat plants. Another Bomem system, currently being validated at a Wisconsin cheese plant, continuously measures moisture and fat content in process cheese and cream cheese on-line as it flows from the cooker, enabling the operator to optimize moisture content.

Measurement of iodine value (IV) is critical to determining the degree of saturation in edible oils. An ABB Bomem FT-NIR system currently measures IV of 27 different edible oils on-line in 50 refineries in 35 countries, Brown reports. One system, recently installed in a Memphis refinery, measures IV with a probe inserted directly into a hot, catalytic hydrogenation tank to determine when the desired degree of hydrogenation has been reached.

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