New Generation of Instruments Deliver Reliable Process Feedback

July 3, 2013
Technical advances and manufacturer comfort with process instrumentation are dispensing with the need for laboratory tests in favor of in-line and at-line monitoring systems.

Replacing human muscle with machine power is the main point of automation, but it isn't enough. Replication of human senses also is needed, and process analytics are the eyes, ears, nose and (light) touch of automation.

Food and beverage processors usually are dependent on laboratory tests to alert them when work in progress or finished goods are out of spec. As machine speed increases and automation advances, however, the time delay in learning about a quality issue magnifies the waste. Higher throughput means more waste with each minute of delay. Increasingly, manufacturers require real-time process feedback. Fortunately, a new generation of industrially hardened instruments that deliver reliable process feedback are answering the need.

Although nuclear magnetic resonance spectroscopy and other analytical technologies have been used in industry for decades, in-line quality measures are a relatively new phenomenon in food and beverage.

"Twelve years ago, there were near-infrared products that put gauges in line with a filter wheel and a hole for a quartz window, then placed a lab instrument next to it," recalls Rick Cash, marketing technology manager with Thermo Fisher Scientific Inc., Minneapolis. Those crude systems have given way to solutions that are better integrated into a line and are specifically designed to function in the production environment.

"The instrumentation and sensing technology today has been ruggedized and made more factory-floor usable," seconds Derek Deubel, vice president at Techniblend Inc., Waukesha, Wis. It also is simpler to maintain and use without highly skilled technicians. The next step in in-line testing's evolution is the multifunction sensor, preferably functioning without a dedicated controller, with feedback sent directly to a plant-floor controller for extrapolation.

Precise standardization of cheese milk can be done inline with Thermo Scientific's E scan analyzer, an instrument based on guided microwave spectroscopy. The analyzer has produced readings within 0.05 percent of actual milk fat.

Reflection and refraction of light, amplitude and frequency of waves, absorption of energy -- the core technologies of in-line sensors vary, but relating the measurements they provide to the product characteristics of interest to the processor is the key to their utility. Sometimes, end-users and system integrators discover new applications for the technology.

An instrument based on visible near-infrared (NIR) spectroscopy that is primarily used in mining operations is being tested for pork grading, leading the device's supplier to suggest NIR could be suitable for grading sides of beef. (That's a stretch: NIR light only penetrates a few millimeters, so unless it is measuring a homogenous mass, readings won't be representative.) A recent buyer of the SM-35000 spectrometer from Spectral Evolution, Lawrence, Mass., hopes to develop a model that relates the readings to the characteristics of tender ham.

"They're trying to generate markers to guide the selection of which hams will make the best product," explains Maurice Kashdam, the firm's marketing & sales director. "Every time I think the technology is mature, I get a call from someone looking at a new application."

King of probes

High-volume breweries long have led the industry in their use of in-line sensors, and the King of Beers is acknowledged as the segment's pacesetter. "Anheuser-Busch is the leader in in-line measurement," proclaims Mettler Toledo's Brian Vaillancourt, a judgment echoed by others.

Soft drink bottlers also have production volumes that are high enough to justify the investment, and "we're seeing more and more measurement in dairy, particularly those selling product to pharmaceutical and neutriceutical firms," adds Vaillancourt, aftermarket services and key accounts manager in the firm's process analytics division in Bedford, Mass.

In years past, craft brewers never considered in-line instrumentation until they reached the 75,000 barrel threshold in annual production; today, even small-scale producers are installing in-line sensors to ensure consistent outcomes.

Turbidity, pH, color and dissolved carbon dioxide are some of the variables beer makers monitor. Trace amounts of oxygen can greatly reduce shelf life and produce off-flavors, and segment leaders have intensified efforts to control oxygen levels in recent years. "Twenty years ago, 300 ppb of oxygen was OK," says Vaillancourt. "Now, brewers want less than 10 ppb."

To satisfy those demands, Mettler replaced its polarographic oxygen sensors with optical sensors that measure both dissolved oxygen and CO2 levels. Digital signal accuracy, ease of use and solid-state electronics are additional enhancements.

Multifunction sensors have obvious appeal to industry, and mid-infrared instruments are the most likely to deliver it. Considerable interest surrounds VitalSensors Technologies, a Hudson, Mass., venture powered by MIT scientists working toward IP-ready units that don't require a dedicated controller, which can account for half a system's cost.

Mettler Toledo's Dennis Steeves demonstrates FreeWeigh.Net, a system that provides on-line monitoring of instruments for fill-level checks and other quality parameters. The system also helps document processing performance.

In theory, infrared devices can deliver hundreds of readings, though "the practical limitation for most of these instruments is three, and it's usually two," notes Thermo Fisher's Cash. Nonetheless, quantifying fat and protein levels in milk or solids and oils in peanut butter with a single device is appealing.

"The simplicity of infrared and its ability to measure several things gives end users more bang for the buck," says Techniblend's Deubel. The newer devices also are less obtrusive than instruments that rely on a slip stream of product to conduct evaluations. Pump failure and vibration-distortion problems are eliminated, and newer devices feature solid state construction and probes that barely dip into the product stream.

Deubel's firm is working with one infrared supplier on development of an infrared sensor that could be used with diet soft drinks. Instruments that measure brix are of little use in the absence of sugar, so developers are focusing on the titratable acidity of diet beverages. Currently, that is done off line. "We're still involved in mapping the signature of a diet cola and making sure the results are repeatable and it doesn't take a Ph.D. to set up the instrument," he says.

Quantifying complex streams

While most sensor technology is best suited for a fluid stream, guided microwave spectroscopy (GMS) is finding a niche with ground beef. The technology excels at moisture analysis and first was applied 20 years ago at a grain milling operation. But it also can accurately measure both fat and lean constituents, based on the amplitude and frequency of the waves transmitted between two points.

Thermo Fisher introduced its GMS solution nine years ago, though extensive refinements are reflected in the E scan analyzer. The instrument often is mounted at the end of grinder to ensure lean content is in spec. "If you can save 1 percent giveaway on a grinder, it's worth a couple hundred dollars an hour, and the instrument provides a payback pretty quickly," Cash points out. The unit also has been used to measure fat in milk, with results close to the Mojonnier lab method. Mojonnier calculates fat by weight to within 0.03 percent; the GMS analyzer has been demonstrated at 0.05 percent.

Recalibration is the limiting factor with all these devices and helps explain why in-line sensors are more common in other industries. Raw material variability is a fact of life in food production. "Unlike the ingredients in shampoo, food is not a chemical, and it's not going to be the same every day," says Cash. If an ingredient's signature falls outside the fingerprint calibrated for the device, feedback data will not be reliable without recalibration.

Most lab technicians are unfamiliar with GMS, but the same can't be said of infrared. Cognizant of that, PerkinElmer Inc. recently commercialized a mid-infrared at-line instrument for trans-fat analysis. Until now, gas chromatographic methods requiring transesterfication in sample preparation were necessary.

Those lab analyses produce more comprehensive results on the types of fat in a product, allows Robert Packer, food solutions development leader in PerkinElmer's Shelton, Conn., office, but partially hydrogenated fats are the focus of public health concerns. The new instrument -- about the size of a laptop and "field deployable" -- generates results in less than a minute, he says.

"It gives us the ability to put the instrument in the hands of nonscientists and get reliable results," Packer adds. "Trans-fat is an issue everywhere, and just because your plant is in North America doesn't mean your fats and oils aren't coming from India or other markets where trans-fat levels are very high."

This article originally appeared in our July issue of Food Processing magazine.

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