Understanding Sensory Analysis of Drinking Water

Understanding Sensory Analysis of Drinking Water:

Challenges for Describing Taste and Odor

Andrea M. DietrichProfessor, Civil and Environmental Engineering

OUTLINE

•T+O in Drinking Water

•Human Senses of Taste and Smell

•Communicating T&O

•Moving forward

• Sensory Monitoring and Analysis of Taste, Odor, Color, and Turbidity for aesthetic and algal/cyanobacteria problems.

HUMAN sense of odor, taste, and sight are essential!

• Chemical Analysis to determine the identity of and measure the concentration of the problem compound

• Treat and Remove Once the cause of the taste/odor/color is known

Burlingame, GA. Solving Customers’ Taste and Odor Complaints –Opflow, 1999. Dietrich, Aesthetic Issues in Drinking Water, JW&H, 2006.Burlingame. Diagnosing Taste and Odor Problems Field Guide, AWWA, 2011.Lauer. Water Quality Complaint Investigator’s Field Guide, AWWA, 2011.Dietrich, Phetxumphou, and Gallagher. Water Research, 2014.

3

Keys to Solving Aesthetic Issuesin Drinking Water

Data customers provide

1. Description of problem2. Location of problem3. Number people/type of

residence affected

1. Is this routine or serious?2.GIS‐ spatial cluster3. Prevalence of problem

How Water Industry can use

TEAMWORK to identify and resolve Water Quality Issues/Concerns

REMINDER‐Water Industry depends on consumers to report for water main breaks and low pressure.

Environmental and Water ResourcesCivil and Environmental Engineering

Humans are GREAT at detecting odors and tastes Can be better than instrumentation Temperature impacts Varying sensitivities Expect 100‐, even 1000‐, fold difference between

individuals ppt detection common for air and water Genetics, exposure, culture, age Time of day, recent meal, health

Humans as Sensory Instruments


CONSISTENCY!

What do humans want in water, foods, beverages?

Human Chemical Senses

Tasteof select tastants in water

Taste, a “Chemical” Sense5 tastes are straight forward to recognize and describe

Different receptors in mouth for each taste

About 100‐fold difference in sensitivity between least and most sensitive humans for sweet (sucrose), salty (sodium chloride) and sour (citric acid)

•Sweet•Salty•Sour•Bitter•UmamiHöchenberger, Ohla, Nutrients (2020) 1‐19.

Descriptors for the Taste of Sodium as NaCl

Literature demonstrates consensus in descriptors

Sodium has a salty taste, especially in presence of chloride. Less so with sulfate and carbonate.

Dietrich & Burlingame. 2020 Science of the Total EnvironmentPlatikanov et al. 2013. Water Research

Descriptors for of AntifreezeEthylene Glycol (OH groups)

Literature demonstrates consensus in descriptorsHydroxyl groups cause sweet taste.

Dietrich & Burlingame. 2020 Science of the Total Environment

The intriguing and variable human chemical sense of

Odorof select odorants in water

• Million+ odors – a lot to smell and name!

• Challenging for humans to recognize and describe because highly depends on memory and vocabulary

• Literature demonstrates diversity for descriptors, sometimes without consensus

Odor

Complex Human Olfactory SystemBC open textbookHumans have ~350

different types and >1,000,000 odorreceptors.

An odor receptor recognizes multiple odorants.A single odorant interacts strongly/weakly with multiple receptors.Combinations of receptors produce million recognizable smells.

Nobel Prize, 2004, https://www.nobelprize.org/prizes/medicine/2004/buck/symposia/

• Odor Threshold Concentration (OTC) is the concentration at which 50% of the population can detect an odor; which means 50 % cannot.

• An OTC range, but not often reported

• 100‐1000 fold difference in sensitivity common

• Specific anosmia common – inability to smell specific odors

Odor

Those trained in odor identification do not experience the “Natural Emotional Impact”

• Naïve subjects descriptions were individual dependent and difficult to materialize; subjective

• Trained perfumers used more objective descriptions and formal terminology; objective

Degel & Köster, 1999 Rouby et al., 2002 Chastrette, 2002

Trained vs. Naïve subjects

1.People readily Detect an odor1. “it’s different”2. “it smells”

2.More difficult to Recognize the odor

3.Even more difficult to Describe the odor

Jonsson & Olsson, 2003 Köster, 2005Dietrich, Phetxumphou, Gallagher, 2014

Linguistics of Odors

Taste and Odor Wheel

Standard Method 2170

Global Water Odors

18

Global Taste and Odor Survey of Water Utilities, P. Ömür-Özbek, 2012

2012

Khiari et al., WRF 2002

More than Geosmin and 2‐MIB….

Algae and Cyanobacteria BloomsGeosmin (earthy)

2‐Methylisoborneol (musty)

Geosmin and 2‐MIB

• Both have odor threshold concentrations of 1‐10 ng/L(Rashash et al. JAWWA, 1997; Piriou et al. 2009)

• 12 ng/L is median concentration for consumer complaints (Graham et al., WRF 2000)

• Estimates are that about 15 % of the population have specific anosmias to either geosmin or 2‐MIB

2-MIBLiterature descriptors

Descriptors given by50 naïve consumers

Dietrich, Burlingame. Science of the Total Environment, 2020

Phetxumpou et al., JAWWA 2017


Lab staff

Operators

Consumers

2‐MIB ‐MUSTY, earthy, moldy

earthy

musty

dirty

medicinal

mothballsammonia

camphorcloves

grassy

leather

moldy-bread

old-lady-perfume

restroom

smokey

weak-pinesol

earth

y

musty

dirty

grassy

flow

ers

mild

ew

pinesol ammonia

cave fu

ngal

gras

s

hunt

ing-

cove

r

medicinal

mol

d

moldy

mus

hroo

ms

old-dudes

piney

shoe-polish

soil

wax

wet

dirt

medicine

mustysoil

camphor

chlorine

cleaner

drug

earthy

male-musk

medicinalmib

mold

moldy-breadmoth

mothballs

no-idea

not-good

pillsstagnant-pond

wet-wood

Dietrich, Phetxumphou, Gallagher; Water Research, 66:63‐74, 2014.

LAB = Operators > Consumers

Odor threshold 1‐10 ng/L around world Customer complain at ~12 ng/LUtilities 10 ng/L guideline

Geosmin

Phetxumpou et al. JAWWA 2017


Summary: Geosmin and 2‐MIB

•Experience with these odors matters

•Water utility personnel are better at describing as “earthy, musty” than typical customer smelling their tap water

HALOANISOLESEarthy, Musty, Moldy

INCREASING Odor Episodes by these Compounds

• 0.01‐100 ng/L haloanisoles in tap water from 22 cities

• 2,4,6‐trichloroanisole most odor, some 2,4,6‐tribromoanisole

• 2,3,4 and 2,3,5 –trichloroanisole frequently present below OTC

• Positively correlated with drinking water chlorination

• Greater concentrations in summer than winter

N. Zhang et al., Water Research, 2016

Haloanisoles

Malleret and Bruchet, JAWWA 2002; Díaz et al. JAFC 2005

K. Zhang et al. Envir Poll. 2016; N. Zhang et al. Water Res. 2016

45° GC-O

Earthy, Musty, Moldy Haloanisoles

•Focus 2,4,6‐trichloroanisole from 2,4,6‐TCP•Biomethylation: O‐methyltransferases in bacteria, actinomycetes, fungi, CYANOBACTERIA and ALGAE

•Rates of biomethylation affected by water quality and temperature

K. Zhang et al. Envir Poll. 2016

Haloanisolesvariable descriptors

2,4,6-Tribromoanisole 2,4,6-Chloroanisole


Pyrazines•Produced from cooking – pyrazines are the reaction product of a simple sugar and an amino acid

• “Roasted” flavor is desirable in many foods, but not water•Meat•Coffee•Nuts

Baneras et al. Food Chem, 2013Wang et al. Water Research 2020

31

mustysweet

pungent

grassy

earthyirritatingfloral

personal-care-products

metallic

chemical

unpleasantgreen

burnt

nutty

plastic

woody

solventmustysweet

chocolate

earthynutty

grassy solventcoffeeburnt

candyirritating

rubber-smellpungent

medicinal

greenmetallic

plant-smell

almond-like

fragrantroasted

unpleasant

woody

cheese

copper

licorice

cleaningagent

food-smell

chemicalsmoky

green

plastic

chlorox

benzenes

medicine

orange

vinegar

sharpodor

lemon

muddy

mustychocolate

sweet

earthy

grassyirritatingnutty

pungentsolvent

coffee

rubber-smell

medicinal

green

chemicalcandy

foul

almond-like

copper

licoricesweat-smell

organic

spicy

sharp

cheeseroasted-hazelnut-like

dirt

chlorox

plant-smell

burnt-plasticsoap-laundry-products

baking

floral

sea-weed-smell

rancid

bitter

dusty-smell

metallic

sweetirritating

mustyfloralpungent

grassyunpleasant

fired-corn

rice-boiling-smell


smoke

roastedsweat-smell

cheese

rubber-smell

sweetsolvent

pungent

musty

sulphurous

pine-tree-smellmedicinal

burnt

organic

plastic

fruity

candybenzene-smell

soap-laundry-products

floral

irritating

eggshell-like

acid

rubber-smell

salty-mixed-smell

woodydeodorant

personnel-care-products

rancidchocolate

chemicalalcohol

spicy

earthy

vinegar


glue-like

sour

bad-odor

metallic

pyrazine 2,6-dimethyl-pyrazine 2,3,5-trimethyl-pyrazine

3,5-dimethyl-2-methoxypyrazine 2,3,5,6-tertramethyl-pyrazine

Wang et al., Water Research, 2020

Naming the Odor, so that everyone understands the problem, is key to solving an odor problem. So

many earthy, musty, moldy odorants and descriptors increases challenge to implement.

Sensory Monitoring

Chemical Analysis

Treat and Remove

Other Common Odorants and Their Descriptors

Odor of Hydrogen sulfide, H2S

Dietrich and Burlingame, Sci. Total. Envir. 2019Carneiro et al. Sci. Total. Envir. 2020

Literature demonstrates consensus in descriptors

• Sometimes, lack of consensus for descriptors

•N‐Heptanal(lipid oxidation product of cell walls, especially algae)

Odor, a “challenging” Sense

Dietrich and Burlingame, Sci. Total. Envir. 2020Carneiro et al. Sci. Total. Envir. 2021

Do Chlorinated Water Drinkers Like Chlorine?

• A study of French consumers…

•No significant difference in chlorine flavor threshold between chlorinated tap water and non‐chlorinated water consumers

• Chlorinated tap water consumers gave a higher liking score for chlorinated solutions and were more inclined to accept these solutions as drinking water.

•Hedonics/Preference vs. Detection/ThresholdPuget et al, Water Research 2010


CONSISTENCY!Provide “language” tools

HOW TO ASSIST CONSUMERS with DESCRIPTORS

_____ Astringent/Aftertaste_____ Bitter_____ Cardboard_____ Chemical/Solvent_____ Chlorine/Swimming _____ Citrus/Orange/Lemon_____ Earthy/Dirt_____ Flat/Stale_____ Fishy_____ Gasoline_____ Grassy_____ Metallic_____ Mineral‐like_____ Muddy_____ Musty/Moldy/Damp _____ Plastic_____ Salty_____ Shoe‐Polish_____ Sulfurous/Rotten Egg/Sewage _____ Sweet_____ Other

Assessing Consumers’ Ability to Describe Odors

1. Naïve, Untrained Consumers asked to describe single odorant in vials.

2. 2 months later, same subjects given 5‐10 min of instruction about wheel.

3. After instruction, asked to again describe the odorants.

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General categoriesInner wheel

Specific categoriesOuter wheel

Phetxumphou, et al. 2017. Implementing the drinking water taste-and-odor wheel to improve consumer lexicon. JAWWA, 109(11)

McNemar’s Test: p‐value

3.8x10‐4

InterpretationT&O Wheel significantlyimproved consumer

descriptionPhetxumphou et al. JAWWA 2017

Pre‐wheel2‐mos later with wheel

Naïve Consumers Describing 2‐MIB

Untrained Consumers Describing Odors with

T&O WheelQuestions to Consumers Response

Would you prefer to have a copy of the T&O Wheel to identify aesthetic problems? 92 % yes

How helpful would theT&O wheel be for describing the general category of the odor? 94 % helpful

How helpful was having a copy of the T&O Wheel in improving your ability to identify specific odors? 78% helpful

Phetxumphou, Raghuraman, Dietrich. 2017. Implementing the drinking water taste-and-odor wheel to improve consumer lexicon. JAWWA, 109(11)

T&O Check-If-Apply List

Another approach is to use check lists, which are common in the food and beverage industry.

Both consumers and water industry personnel can use.

_____ Astringent/Aftertaste_____ Bitter_____ Cardboard_____ Chemical/Solvent_____ Chlorine/Swimming Pool/Bleachy_____ Citrus/Orange/Lemon_____ Earthy/Dirt_____ Flat/Stale_____ Fishy_____ Gasoline_____ Grassy_____ Metallic_____ Mineral‐like_____ Muddy_____ Musty/Moldy/Damp Basement_____ Plastic_____ Salty_____ Shoe‐Polish_____ Sulfurous/Rotten Egg/Sewage _____ Sweet_____ Other

Carneiro et al. Science of the Total Environment, 2021Dietrich, A.M., Burlingame, JAWWA, 113(3) 33-42, 2021

Consumer Testing of Check‐If‐Apply:It works!

Check‐If ApplyDESCRIPTORS

Water Samples

Intense

Not selected

Salty

MetallicAstring.

EarthyMusty

Carneiro et al.; Sci. Total. Envir, 2020

Summary

• Customers and utility staff work collaboratively on aesthetic issues

• The common language provided by the Wheel or Check‐If‐Apply T&O List improves:

• dialogue

• consistency of descriptors

• easy of electronic data tracking

AcknowledgementsAesthetic Quality and Perception Committee

Djanette Khiari

Gary Burlingame

Anastasia Nicoloudakis

Rita Kopansky

Dennis O’Connor

… and all the human subjects who provided taste and odor data.

Colleagues, students

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Understanding Sensory Analysis of Drinking Water