Improving Consumer Lexicon to Describe Aesthetic Issues in Water Quality

By Katherine Phetxumphou, Ph.D. candidate of Civil Environmental Engineering and Water IGEP, presented at 11th IWA Symposium on Tastes, Odours & Algal Toxins in Water in Sydney Australia on February 2017 

Introduction: Published food and beverage Taste-and-Odour (T&O) Wheels, and associated lexicons, were developed to summarize sensory qualities and organoleptic characteristics unique to foods and beverages (Drake and Civille 2003; Lawless and Civille 2013), including beer, scotch whiskey, wine, and drinking water. The drinking water industry’s attention focuses on characterizing eight major general categories of aesthetic issues: earthy-musty, chlorinous, grassy, sulfurous/septic, fragrant/vegetable, fishy/rancid, medicinal, and chemical (Mallevialle & Suffet 1987;  Khiari et al. 2002; Standard Method 2170, APHA 2012). The inner drinking water T&O Wheel has eight general categories of odours, four tastes, and mouth feel. The middle ring indicates specific descriptors for each of the general categories of odours and taste. There is a third outer ring with chemical names and reference standards. This tool is available to water personnel, but most consumers do not know that it exists.

Globally, consumers are first responders and experts at detecting changes in aesthetic water quality, but are often challenged to provide accurate descriptions due to unfamiliar lexicons and unexpected odours in their drinking water. Consumers sometimes can provide valuable feedback on water off-flavors and odours (Burlingame & Mackey 2007; Yu et al. 2014; Dietrich and Burlingame 2015; Piriou et al. 2015; Phetxumphou et al. 2016), and other times, consumers find it difficult to effectively describe off-flavors and odours in drinking water (Burlingame 2015; Gallagher and Dietrich 2014; Dietrich et al. 2014; Burlingame 2015; Webber et al. 2015). Average drinking water consumers are naïve as they lack the experience and the vocabulary to accurately describe odours, especially when unexpected odours are present (Köster et al. 2002; Köster 2005). Thus, this research focuses on improvements to methods and tools that can help water personnel and consumers describe odourants in drinking water.

Methods and Materials: The odourants investigated are common odours detected in drinking water and present on the T&O wheel (Khiari et al. 2002; APHA 2012).  2-MIB is a musty odourant (APHA 2012); geosmin is an earthy odourant (APHA 2012); orange extract with limonene is a citrus-orange-lemon odourant (Dravnieks 1992); and dimethyltrisulfide (DMTS) has unpleasant onion, garlic, sulfur, septic, rotten egg descriptors (Dravnieks 1992; Dietrich et al. 2014; Watson and Jüttner 2015). In the first odour sensory study, fifty naïve consumers sniffed vials with common odour standards and responded to a “pre-training” response form that asked for demographic information and odourant descriptors. Forty milliliter amber volatile organic analysis vials were prepared a day before the sensory test. Each odour vial contained a cotton ball absorbing each odourant. Subjects sniffed the odour vials in random order at room temperature. They waited at least 2 minutes between sniffing of odourants. After several months, in a second odour sensory test, the same group was trained to use the Drinking Water Taste and Odour (T&O) Wheel and asked again to sniff and describe the same odourants.  Subjects also completed a “post-training” questionnaire that included questions for them to rate the helpfulness of the T&O Wheel in describing the odourants.

Correct responses to odourant descriptors were based on words on the T&O Wheel and from the Atlas of Odours Character Profiles (Dravnieks 1992), which is a compilation of odour descriptors for common reference standards in the food and beverage industry developed by a panel of trained sensory experts and contained more detailed descriptors than the T&O Wheel. Statistical analysis used McNemar’s test to determine if the T&O Wheel was an effective tool in aiding consumers in describing the odourants. Consumer responses were compared to two lists and measured for correctness: 1) “pre-training” responses with “post-training” responses using correct words from only the T&O Wheel; 2) “pretraining” responses using only T&O Wheel words with “post-training” responses using T&O Wheel descriptors and descriptors from the Atlas of Odours.

Results: Results revealed that consumers were equal at describing orange with or without the T&O Wheel as citrus, orange-like. McNemar’s test showed that the T&O Wheel did improve consumers’ descriptors of orange, but with additional descriptors present in the Odour Atlas over the T&O Wheel, the addition of Odour Atlas words can improve consumer description. Descriptors for geosmin (Figure 1a) and 2-MIB (Figure 1b) initially varied from “official” earthy/musty to medicinal, camphor, chlorine, but were more consistent after applying the T&O Wheel. McNemar’s test confirmed that the T&O improved consumers’ descriptors of geosmin and 2-MIB, and the addition of the Odour Atlas made no difference since same correct descriptors were present in both. Dimethyltrisulfide has “official” septic-swampy descriptors and varied with sewage to propane and chemical, but consumer descriptors were not more consistent after using the T&O Wheel as seen by the McNemar’s test. Including additional DMTS descriptors from the Odour Atlas does show a slight improvement to consumer descriptions of DMTS.

Conclusions: Majority of subjects stated that the Drinking Water T&O Wheel would be helpful for describing one of the eight general categories of the odourants, and they believed that having a copy of the T&O Wheel present will improve their ability in identifying odours. With a few improvements to the T&O Wheel, that includes additional descriptors from the Odour Atlas, the T&O can serve as a valuable tool for consumers to use in describing nuisances in their drinking water. This study demonstrated that if proactive activities are introduced, like providing the T&O Wheel or training consumers with a lexicon of common descriptors for odours in drinking water, then consumers can provide more accurate and less variable descriptors for T&O problems in their drinking water.

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