Using Your Senses to Find Microbial Niches
By Virginia Deibel, Ph.D., and Kara Baldus, M.B.A.
Sensory analysis examines ingredients and products using sight, touch, hearing, smell and taste. Analysis is conducted during ingredient procurement, product development or re-development to assess the end product’s appeal and acceptability to consumer senses.
Sensory analysis should not be restricted to product development laboratories. Combined with microbiological testing, quality control personnel and sanitarians can and should use their senses of sight, touch, hearing and smell to assess cleaning and sanitation effectiveness on a daily basis and during unique times where microbial harborage point investigations are required.
Sight: During daily sanitation inspections, the visual appraisals of cleaned equipment and areas uncover a range of problem types, see Table 1.
Touch: After cleaning and prior to sanitation, surfaces should not feel slippery, indicating residual fats/oils. Sticky or tacky feelings indicate residues of sugar-type substances. See Table 2 for chemical detergents that will eliminate specific types of soils. With large pieces of equipment, especially those that are jacketed, such as vats, step inside and feel whether the baseboards give or are soft in any way. This may give an indication of leaks that have caused rotting. In a similar fashion, press against boards, walls, welds and caulking to assess firmness. Equipment in good repair is typically solid and will offer resistance when pressed.
Hearing: Rotate utensils, especially those that contain welds and are hollow, product transport racks, end to end. Listen for liquids or movement to give an indication if the welds are discontinuous (cracks, weakening) and liquids have permeated the interior. Small drips from the interior to exterior of hollow equipment/utensils will cause intermittent cross-contamination. The liquid, however, can be highly concentrated with bacteria, yeast and/or mold. Solutions: Create an inventory for all equipment containing hollow parts. Place on sanitation check-list for examination of water accumulation. On preventative maintenance check-lists for each piece of equipment, add a section for weld quality. Having defined criteria for weld evaluations including the size of the weld and the presence of discontinuities are components of successful outcomes. Weld size often correlates directly to strength and performance. Undersized welds may not withstand stresses applied during equipment activity, and oversized welds can produce stress or distortions.
Weld integrity evaluations, conducted by a trained individual, include but are not limited to non-destructive radiographic or ultrasonic methods. Radiographic testing uses x-rays wherein radiation is passed through the weld and the image is captured on film. The amount of energy absorbed by the weld depends on thickness and density. Areas of the weld where the thickness has been changed by pores or cracks will appear as dark outlines on the film. Ultrasonic testing makes use of vibrations similar to sound waves but of higher frequency. A beam of ultrasonic energy is directed into the weld and as the beam travels through the weld there is insignificant energy loss, except when there is a discontinuity. A further type of evaluation, an ultrasonic contact pulse reflection technique, is used that employs a transducer that changes electrical energy into mechanical energy and serves as a receiver of reflected energy. The transducer is excited by a high-frequency voltage that causes a crystal probe to vibrate mechanically. These vibrations are transmitted into the test piece through a coupling fluid, usually a film of oil, called a couplant. When the pulse of ultrasonic waves strikes a discontinuity in the test piece, it is reflected back to the transducer. The signals of the test piece are displayed on a screen of a cathode-ray oscilloscope.
Smell: Microbial growth results in by-products that will emit off odors. For example, lactic acid bacteria (LAB) or acetobacteria, commonly found in meat products, will produce a sour, sharp odor associated with lactic or acetic acid, the by-product of fermentation. Bacillus spp., found in dairy, meat and agricultural products, are highly proteolytic (able to cleave proteins into smaller protein fragments-peptides). Peptides have a distinctive "locker room" type of odor. E coli or coliforms will produce a fecal or barnyard smell. Additionally, depending on the type of organic material that is present, decomposition of food residues will cause a "rancid" smell stemming from oxidation of fats or oils.
While the senses of sight, touch, hearing and smell are not the only tools used to eliminate contamination, they are not used as often or as thoroughly as possible. Considering that they are relatively "free of charge," it is financially worthwhile to develop these investigative tools among those involved in the fight against pathogen and spoilage contamination in all types of products.
Dr. Virginia Deibel, Ph.D., is the CEO of TRAC Microbiology, Inc., a microbiology and chemistry contract laboratory conducting routine product and environmental testing, research, auditing and consulting. She opened TRAC in 2001, while completing her Ph.D. dissertation, a practice not recommended. At TRAC, she conducts third-party audits, performs specialized consulting including problem solving, recalls, investigations and expert witness work. Dr. Deibel earned undergraduate and graduate degrees in Bacteriology and Microbiology from the University of Wisconsin-Madison. She served as the Chair of the Wisconsin Association of Food Protection, and is member of IAFP, IFT American Society of Microbiology, AOAC and is on the editorial board of Food Safety Magazine.
Kara Baldus joined TRAC Microbiology, Inc. in August of 2005. She is involved in HACCP Plan Development, Research Experimental Design and Data Analysis. Kara graduated from the University of Wisconsin-Madison in December of 1995 with a double major in Bacteriology and Genetics. She has worked in the food industry as a microbiologist for almost 10 years. During that time, she also earned her Master’s of Business Administration and Total Quality Graduate Certificate from Edgewood College.