The Best of the Best: A Critical Look at Basic Inspection Tools
By Robert W. Powitz, Ph.D., MPH
It was about a decade ago that Jim Balsamo, director of Environmental Health and Safety at Tulane University and I started a column in the Journal of Environmental Health in which we evaluated the field instruments used during our inspections and audits. Although the column ended after five years, we have neither lost our penchant nor predilection to play with our professional sanitarian’s toys. We still try to acquire the latest portable instruments and use them (as well as abuse them) during our consulting field work. We still try to find the ones that are the most rugged, have the best accuracy and greatest utility.
At almost every meeting we attend, someone asks us about this or that thermometer, how best to take a pH of sushi rice, better conduct a field evaluation of water activity or characterize air movement in kitchens, or to identify the brightest flashlights or the least-hassle chemical test strips, just to give a few examples. We’re always happy to oblige, and I still conduct instrumentation workshops at the National Environmental Health Association’s (NEHA) Annual Educational Conferences. So, I thought that it would be a good idea to share some of this information with you, particularly those field instruments we use in evaluating retail food establishments using the U.S. Food and Drug Administration (FDA) Food Code.
A Bit of Background
Jim and I tried to pattern our articles similar to Consumer Reports, where we would write about the good, bad and the ugly—without incurring the wrath of those we panned. Interestingly, as a result of our evaluations, several companies incorporated the changes we’ve suggested over the years into their instruments’ designs. To assuage any doubt, please be assured that the field equipment presented in this column are the ones we regularly use on the job. We buy most of our instruments through manufacturers, dealers and distributors; those that are donated to us for evaluation are done so with no strings attached. If any instrument does not pass muster, so be it. Our motto remains: There is no special dispensation for largesse.
But first, a bit of background on how we evaluate the equipment we write about. We are both professional sanitarians with active forensic and institutional practices, focusing primarily in food safety. We regularly do our work in a variety of settings, from small franchise restaurants, to huge correctional foodservice operations, to food processors and manufacturers. Most of these are a considerable distance from our home base and there is little opportunity to retrieve a specialized instrument from our office to help us measure a problematic environmental parameter. Therefore, our instrument kit is designed to help us measure most, if not all, criteria listed in the Food Code.
To do this successfully, we have adopted certain expectations of the instruments that we take into the field. We expect our field instruments to be:
• Portable, preferably small and lightweight, non-reactive, rugged and safe to use.
• Disposable or easily cleaned and decontaminated or easily protected from contamination. All of our field equipment must be as clean or cleaner than any utensil we inspect.
• Relatively inexpensive (there are exceptions).
• If powered, we favor those that run on “standard” batteries. It’s easy to replace any battery readily available from most convenience stores.
• Expendable materials used with any instrument should be non-proprietary; although we recognize that this is often a tough one to achieve.
• Simple and easy to operate with one hand because our other hand is generally holding a notebook, pen and flashlight.
• Accurate and easy to read, even in poor lighting conditions.
• Easy to calibrate or validate in the field.
• Capable of maintaining accuracy during hard use.
• Not subjected to interference or damage by adverse environmental conditions or during transportation (think of the trunk of a car in the summer or the belly of a plane in the winter).
• Direct read or requiring only minimal interpretation of results.
• Conforms to standards or standard protocols whenever possible or practical.
• If any part of the instrument comes into contact with food, it should be non-toxic (preferably NSF listed).
• Importantly, we expect our field instruments to be versatile, so that we are able to take accurate and numerous measurements in myriad different settings.
When we conduct the initial evaluation of any instrument, we use an evaluation form on which we list those attributes that are applicable (although much expanded) and grade each one from A to F, based upon our perception of the unit’s performance in the field. Generally, only those with a “B” grade or better in all our expectations will make it to the “Best of the Best” final list. There are a few exceptions made for some instruments due to their uniqueness and/or particular usefulness. Needless to say, since we started these evaluations, we have become a trifle more discriminating and far more objective in our selection of tools that accompany us to our job sites.
Because we use our instruments in support of our forensic work, we often have had to defend our choices in court. We are pleased to say that our recommendations have held up under rather intense scrutiny in both testimony and deposition, and we were probably the first to introduce the infrared thermometer as a screening tool into court records.
The Best of the Best Unveiled
Our “Best of the Best” are presented in four categories; the first three have specific criteria listed in the Food Code. Because it is so critical to food safety and basic to all inspections and audits, we place temperature-measuring instruments in their own category, “Thermometry.” And, since form follows function, the next category, “Other PHF Tools,” lists the other instruments we use to measure some parameter that is part of the definition of potentially hazardous foods (PHFs). Next is a category we affectionately call “Food Code Necessities,” which contains those field instruments for which the Food Code has a specific value. Finally, the “Other Essentials” category contains tools that help us measure some of the operating conditions detailed in consensus standards or helps us evaluate the very subjective measurement of “how clean is clean?”
We have purposely not included prices, since these will vary depending upon the vendor. However, suffice it to say that the instruments we have listed here, which make up our basic inspection kit, collectively cost about $4,000, give or take.
Thermometry is the backbone of our practice. The more we use the different temperature-measuring devices available to us, the more proficient we become. Consequently, with proficiency comes preference in our choice of instrument. In conducting a Food Code compliance inspection, we rely on every type of thermometer; there is no such thing as “one size fits all.” I find myself using at least five different temperature-measuring devices to evaluate the potential for temperature abuse in even the smallest retail food establishment. For obvious reasons, my selection of thermometric field instruments increases (almost) exponentially when I’m evaluating a food processor or conducting a complex Hazard Analysis and Critical Control Points (HACCP) audit. Therefore, the following thermometers are listed in no particular order of preference; each plays a separate yet necessary part in a thorough food safety evaluation.
Bimetal Thermometer. The 0F to 212F range, 1” dial, 5” stem bimetal dial thermometer remains the handiest and probably our most versatile inspection tool. We use it for almost all noncritical temperature measurements, particularly in those areas where we can place a thermometer, go about our business and retrieve it later when it has had time to equilibrate. To do justice in most establishments, I carry at least a dozen bimetal thermometers in my kit, so that I may place one in each piece of refrigeration equipment, as well as measure the ambient temperatures or the temperature of anything questionable other than food.
Because it is so handy and versatile, we have refined our requirements of the pocket bimetal dial thermometer to meet the following criteria:
• The dial should be is easy to read, even under poor lighting conditions. The numerals on the dials should be crisply printed and the indicator hand works best if it is of a contrasting color, such as red. Given a preference, the lens should have some magnification.
• The distance from stem tip to the dimple should not exceed 2”; the shorter, the better.
• It must be NSF listed.
• For ruggedness and non-toxic properties, the dial case and bezel, as well as the stem, should be made of 304 stainless steel or equivalent.
• For utility, we found that the carrying case should hold the thermometer securely anywhere along the stem. Therefore, the traditional plastic case with a metal clip is much preferred to the newer molded all-plastic cases, which simply do not hold the thermometer securely, other than when it is fully depressed in the case.
The pocket bimetal thermometer that best meets our criteria (including price) is the Pocket Test Thermometer, B1098M82C-5.0 by Miljoco Corp.
Thermocouple Thermometer. For critical temperature measurements, the needle-probe thermocouple thermometer is our mainstay in conducting foodservice inspections, and for good reason: it is convenient, fast and accurate. While all thermocouple thermometers demonstrate about the same performance, there are distinct differences between brands. Over the past few years, we’ve evaluated more than a dozen of the more commonly encountered units used by our profession. The ones we favor have a few characteristics in common:
• If we are only to use a needle probe, we have come to appreciate having the K-type connector integral to the unit. This ensures a good connection and does not serve as a catch area for food, nor are there any sharp edges where the male plug is connected to the cord.
• We have also come to appreciate having our thermocouple thermometer powered by the less expensive AA size battery, which is held in the unit with a threaded waterproof closure, rather than a 9-volt battery. I use a fresh battery daily.
• Any thermocouple used in food safety applications should be NSF listed.
• Because the thermocouple thermometer is the most frequently used during an inspection, the display should be easy to read.
• The case should be rugged and cleanable. We shy away from units that have a rubber sleeve because these tend to become quite septic and food particles tend to accumulate between the sleeve and the unit.
However, we also learned that accuracy and utility come at a price and that the best thermocouple thermometer units are not the least expensive. For these reasons, we are quite partial to either the Atkins model number 34040 or model number 33032. Both units come with a needle probe.
In conducting HACCP audits, the thermocouple thermometer has to accept a variety of probes. Almost any unit that meets our original criteria will be suitable; although we still favor those powered by AA batteries such as the Atkins model number 386 or Comark C28 K type. The Comark unit is nicely designed. The case is comfortable in the hand and easily cleanable, and features a clock, timer and hold function.
I use about nine different K-type probes for most comprehensive audits. The probes are purchased from several different vendors based on my preferences of their geometry and convenience of use. I also found it quite handy to have a coiled retractable extension cable in my HACCP kit to access those hard-to-reach places.
Manufacturers of thermocouple units will tell you that mixing and matching the thermometer and probes from various sources may not be a good idea. So, to overcome any problems with accuracy, we use the Dwyer model CA10 digital thermocouple calibrator to validate our base unit and each probe prior to an audit. Because the CA10 calibrator is just slightly larger than most thermocouple units, it is also ideal to take along for field validation.
Thermister Thermometer. The pen-type thermister thermometer is ideal when we need a waterproof electronic minimum/maximum-registering thermometer, and we have only one free hand and no chance of seeing the LCD readout due to the inaccessible location of the sample. Because of their diminutive size, the LCD readout is not always easy to see, even under the best lighting conditions. However, the min/max feature and “hold” button allows you to take a temperature and read the display when a more suitable ergonomic opportunity presents itself.
There are so many manufacturers and distributors of these little units, it’s a matter of color and price and whether we prefer the more traditional pen type unit or the “lollipop” style with a perpendicular readout. The only requirement I believe important when selecting a thermister thermometer is that the control buttons are easy to operate by touch (trust me on this one). I also favor those thermister thermometers that operate with an easy-to-replace single button battery. There are some units out there that can be field calibrated, though I’ve found that simple validation is sufficient for most units we have used.
Infrared Thermometer. We were first introduced to the affordable infrared (IR) thermometer in 1996. Since then, we have had considerable practice in its use and found new environmental health applications for it, when used in conjunction with other equipment. We participated on the Unerwriters’ Laboratories (UL) 2333 Standard Committee that set out to codify performance and instructional manual language for the infrared thermometers primarily used in food safety. For most of the early years, our preferences were rather catholic; it seemed like every month a new and improved unit was introduced to our profession. However, over the past few years, the IR’s have become refined in size and operation. For our purposes, the IR units’ emissivity (preset at 0.97) and aspect ratios are no longer left to guesswork. Just a reminder: it doesn’t matter how sophisticated these units are, or how ideally they are designed for food safety application, they are still a screening tool and can only measure surface temperature.
The Fluke Company, which manufactures the trademarked Raytek infrared thermometers, have designed three relatively inexpensive units, specifically for use in our industry: the new NSF listed FoodPro Series, which consists of two hand-washable models, the FoodPro and the FoodPro Plus. Both units have a 2.5:1 aspect ratio with a target illuminating system, and red/green go/no-go lights, which immediately show if temperatures are within HACCP guidelines. This is a great feature. In addition, the FoodPro Plus has a probe and timer that makes it ideal for production line work. The MiniTemp FS is a single-point, laser-sighted, back-lit, trigger-operated, lightweight unit that fits nicely in a holster and is one of the most ergonomically-friendly field tools in our arsenal. I regularly find use for all three models during food safety audits.
Other PHF Tools
The Food Code also defines potentially hazardous foods in terms of water activity (AW) and pH, and the interaction of the two under certain conditions. Therefore, any comprehensive food safety evaluation of retail food establishments must include the monitoring of these two parameters.
Water Activity. There are a few very good portable water activity monitors offered in the marketplace. They are similar to the pen-type hygrometer and not really easy to operate. About five years ago, Decagon Devices, Inc. introduced the easy-to-use and compact Pawkit. The Pawkit is a small, lightweight, albeit rather pricey, field kit for measuring water activity in foods. We find it most useful in separating foods requiring refrigeration from those that do not. We also use the Pawkit for measuring ambient relative humidity, if conditions call for it.
Measuring water activity with the Pawkit is relatively simple: just open the bottom of the instrument, insert your sample and press a button. In 5 minutes, the water activity measurement will appear along with the temperature. Calibration is also easy to check and adjust whenever necessary. The kit contains everything needed for field work including the instrument, sample cups and verification standards.
Measuring pH. For some inexplicable reason, we have never had much luck with pH pens in the field. The pH pens do well back in the lab but whether it is the jarring or temperature extremes from transporting them to the job site, it seems that we always have to rely on some other method for pH screening. I can honestly say that I’ve probably spent more time, effort and money on finding reliable pH field monitoring equipment and techniques than any other instrumentation. So, for the past several years, we left the pH pens in the shop and have settled on two methods of measuring pH in the field. While they are not as accurate, both are excellent for screening. If we need more accurate readings, a sample is taken back to the lab.
The first method is a bit traditional. We take along a small Nalgene plastic dropper bottle filled with buffered deionized water and Whatman Type CF, 0–14 pH indicator papers. The sample is mixed with the buffered water and the indicator paper inserted into the liquid. Surprisingly, even colored liquids do not mask the endpoint of the Whatman indicators. Both the dropper bottle and indicator papers are available through most scientific supply retailers.
For measuring sushi rice or any other lower moisture food, we found that the LaMotte soil pH kit that uses duplex indicator yields absolutely the most striking endpoint with the least effort. Place a small sample in the white porcelain well and drop the indicator on the food. Simply compare the color of the liquid in the collector well to the comparator chart.
Refractometers. There is always another way to characterize potentially hazardous foods from those that are not potentially hazardous: refractometry. Consider purchasing inexpensive hand-held sugar/Brix and salinity refractometers to measure syrups and brines. Refractometers are available through most scientific suppliers. At the least, and as a courtesy, I use a Brix meter to monitor my clients’ post mix drink dispensers. It’s a nice way to soften the anxiety auditees may feel in my presence.
Food Code Necessities
As noted earlier, the Food Code guidelines necessitate the use of several types of food safety inspection instruments, including light meters, single-use paper thermometers, and sanitizer indicator papers.
Light Meter. We are partial to the General Electric (GE) Type 217 light meter available through most scientific catalogs. It is the ideal portable instrument: smaller than the typical size of a digital unit, rugged, versatile and lightweight—and it uses the light it measures as its energy source—therefore, no batteries. Its only drawback is that it cannot measure illumination below 10’ candles, a capacity needed when you are evaluating a facility for compliance with the NFPA Life Safety Code. However, since the lowest light reading permitted by the Food Code is 10’ candles, this little meter works quite well.
Single-Use Paper Thermometer. In evaluating a warewasher, our first choice is a thermocouple thermometer with an Atkins 50415 dishwasher probe. However, for routine inspections and day-to-day quality assurance we have found the paper thermometer to be convenient and quite accurate. For the past several years, we have come to rely exclusively on the self-adhering Thermolabel Dishwasher Labels, manufactured by the Paper Thermometer Co. Our reasons for this selection are the following: First, the self-adhering label works on any clean porcelain or metal surface. Second, the Thermolabel measures the temperature on a heat-sink (which implies a dwell time). Third, the label is accurate to within 1% of the calibrated temperature. The label is removable and can be repasted on the inspection report and serve as a permanent record.
Sanitizer Indicator Papers. The reaction on most chlorine indicating papers is a change in the intensity of blue color. We use Code 4250-BJ, acid-free LaMotte Chlorine Test Papers, whose end-point color is probably the easiest to interpret. Quaternary ammonium chloride sanitizers, however, are measured in the same manner as pH. The pHydrion QT-40 test papers, manufactured by Micro Essential Laboratory, relies on color change. The comparator with each roll pack is already given in parts per million (ppm). Micro Essential Laboratory has a wide variety of sanitizer test kits available for applications beyond that of the Food Code.
Flashlights. For years we have used the basic AA-cell type halogen flashlight featuring one-handed operation. Now, however, we ratcheted it up a notch with new technology. Our latest constant companion is the Streamlight 4AA ProPolymer LED flashlight. This flashlight uses four AA batteries and features seven LED bulbs that produce an extremely intense white light. While this flashlight cannot be adjusted to produce a spot, its light provides startling visual contrast, thereby making it easier to spot insect and rodent damage, water leaks and chronic wetness, and general soiling. The flashlight is ruggedly built and features a protected on/off switch. The battery life far exceeds that of the halogen lights.
If you want an LED flashlight that yields an extremely bright, undistorted beam of light, I highly recommend the Lightwave Infinition C3 or D3 flashlight. A bit larger and heavier than the LED flashlight listed above, the 80 lumen directed light beam of the Infinition shows everything and is indeed the best tool for any inspection.
UV Light. We were always reluctant to carry an ultraviolet (UV) light to a food safety audit because of its size and weight. However, in the past year the Emissive Energy Corp. introduced the Inova X5 UV flashlight. The Inova X5 is a small (4.75”), hand-held LED powerhouse that uses five super-bright UV LEDs to produce a broad smooth pattern of light. For the first time, we now have a flashlight bright enough to detect rodent urine and mold. We also find it quite handy to qualify the level of cleanliness in restrooms. The Inova X5 uses two 3V lithium batteries and comes with an open-top nylon belt holster.
Electrical Safety. We continue to rely on two small instruments to ensure our safety (and that of the employees), and to detect most electrical problems. The A/C Sensor, which is slightly larger than a pen, simply indicates the presence of electrical current when held close to a live source or piece of equipment. A ground fault circuit interrupter/receptacle tester is also needed to check the wiring configuration of outlets, as well as the GFI. Both are available in most hardware stores. Make sure the unit is UL listed before you buy.
As a further commitment to safety and as a service in older and institutional kitchens, we also use a Daniel Woodhead Co. 1760 Receptacle Tension Tester to check the spring contact tension of standard straight blade receptacles, as well as the ground pin receptacle.
Ventilation. In an effort to characterize ventilation, particularly direction and flow, we rely on the Flowchecker. a small squeeze bottlethat contains amorphous silicon dioxide powder available from Lab Safety Supply. For something a bit less expensive, try a zinc stearate powder in a small, empty nasal spray bottle. To complement this low-tech “if and where” tool, we also take along an inexpensive and compact Dwyer 460 Air Meter, just in case we need a velocity or static pressure measurement.
ADA Compliance. We have always contended that any retail food establishment that meets Americans with Disabilities Act (ADA) requirements is also safe for the general public. Therefore, we always include an 8’ tape measure in our inspection kit. It has universal application, both for ADA and for measuring other critical areas such as aisle space. In addition, we include a pen-sized door pressure gauge and a 1:20/1:12 ramp-slope bubble measuring device in our kit. The pressure gauge and ramp-slope bubble measuring device are manufactured by HMC International of Littleton, CO.
What’s Your Best?
So there you have it: the “Best of the Best” tools for the food safety inspection toolkit. I am confident that foodservice establishments, food manufacturing operations, and instituitional facilities that perform in-house inspections (or pre-inspections prior to third-party auditors or regulatory public health inspectors arriving on the premises) will benefit from the use of these instruments in maintaining food safety best practices and compliance aims. With your help and encouragement, I hope to make this a biennial feature. If I have left anything out, or if you have any ideas for other field instruments or peripheral supplies that should be included, please send me your thoughts. I welcome your input and promise that I will present all recommendations, ideas and suggestions in future articles.
Forensic sanitarian Robert W. Powitz, Ph.D., MPH, RS, CFSP, is principal consultant and technical director of Old Saybrook, CT-based R.W. Powitz & Associates, a professional corporation of forensic sanitarians who specialize in environmental and public health litigation support services to law firms, insurance companies, governmental agencies and industry. In 2006, he was awarded the New Jersey Environmental Health Association’s 2006 Harry R.H. Nicholas Award, which recognizes Dr. Powitz’s outstanding and dedicated service to the advancement of public and environmental health. Reader suggestions and comments for The Sanitarian’s File can be sent to Dr. Powitz directly at firstname.lastname@example.org or through his website at www.sanitarian.com.