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Sensory Quality Measurements

Florence ZakharovDepartment of Plant Sciences

fnegre@ucdavis.edu

Evaluating Fruit Flavor Quality

• Appearance• Taste, Aroma

• Texture/mouthfeel

Instrumental evaluation / Sensory evaluation

Qualityaspectsforfreshproduce

• Color• Shape• Blemishes• Decay• Affectsinitialdecisionto

purchase• Generallylongershelflife

• Taste/aroma• Texture• Nutrition• Affectsdecisionforrepeat

purchase• Generallyshortershelflife

External characteristics Internal characteristics

Mary Lu Arpaia

Appearance• Shape, size

• Color (uniformity, intensity)

• Gloss (wax)

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Quality Class of compound Examples

Sweet Sugars Sucrose, fructose, glucose

Sour Acids Citric acid, malic acid, tartaric acid

Bitter Alkaloids, Phenolics, Terpenoids, some proteins

Naringin, cucurbitacins, limonoids

Salty Ions Sodium, calcium

Umami Amino acids Glutamate, aspartate

Fruit Composition and Taste Sweet Taste – Rapid Methods

TOTAL Soluble Solids = sugars, organic acids, soluble pectins, anthocyanins, phenolic compounds, ascorbic acid…

Socrative poll– roomnumber:FRUITRIPENING

Sweet Taste – Rapid MethodsEnzyme-based sugar quantification

Fructose

Glucose

Sucrose

Glucose-6-P 6-P-gluconate

NAD+ NADH

Ø More accurate measurement of sweetness-related solutes

Sour Taste – Rapid Methods

• pH

• Titratable acidity

• Enzyme-based acid quantification

• SSC/Acidity meter from ATAGO (citrus, grape, tomato)

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Electronic Tongues

Alpha MOS ASTREE e-tongue St Petersburg Univ. e-tongue

Beullens et al., 2008

Texture

• Penetrometer

• Texture Analyzer

• Aroma (or smell or odor) is the sensation perceived when volatile compounds are drawn into the nose.

n Ripe fruits generally produce tens to hundreds of volatiles. This mixture of volatiles is what we perceive as “aroma”.

Aroma VolatilesWhat is a volatile compound?

• A small molecule which has a high tendency to evaporate.

• Volatiles are naturally produced by plants (from almost all plant organs) and animals.

• Fruit aromas are made up of complex mixtures of volatile compounds (recall strawberry – over 200!).

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What does a volatile compound smell like?

• Each single volatile compound has a distinct smell/odor.

Floral, woody, sweet, fruity, berry, green

Sulfurous, vegetable,

cabbage, onion

b-ionone Dimethyl disulfide Myrcene

Peppery, spicy

Volatile Analysis by GC-MS: the “gold standard”

GCMS

Electronic NosesiSense Colorimetric Sensor Array Airsense Portable Electronic Nose

Gómez et al., 2008Suslick et al., 2010; Askim et al., 2013

Odor Thresholds

• Our olfactory system has different sensitivity levels for different volatiles.

• Some volatiles, like furaneol, we can detect at extremely low levels; while others, like acetic acid (vinegar!), we can detect only at higher levels.

• Even though acetic acid is much more abundant than furaneol in strawberries, it is furaneol that is most important for determining the characteristic aroma of the strawberry (because of its low odor threshold value).

O

OHO

O

OH

OT≈10ppb

OT≈60ppm

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Sensory Attributes and Fruit Composition

• All fruit components (sugars, acids, volatiles, etc…) combine to generate a unique sensory experience for the consumer.

• Physical methods give accurate measurements of fruit composition but it is difficult to relate these measurements to fruit quality without information about sensory perception.

Whatissensoryevaluation?

• ASCIENCE thatmeasures,analyzes,andinterpretsthereactionsofthesensesofsight,smell,sound,tasteandtexturetoproducts

• ItisaPEOPLE science,i.e.peopleareessentialtoobtaininformationaboutproducts

H. Stone, 1999, Food Technology, 53(10):124.

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Sensory Evaluation

• Cantelldifferencesb/wproducts

• Cantellwhyandhowmuch

• DoNOTaskpreference• 10-12panelists• Hoursoftraining

• Cantelldifferencesb/wproducts

• Cannottellwhy• Cantellpreferencesbetweenproduct

• 50-100panelists• Logistics

Trained panel (objective)

Consumer panel (subjective)

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Your Tools: Panelists• Consumerpanels(notraining)indicatehowmuchaproductisliked

• Donotindicatewhichcomponentoftheproductisthedriverforliking

• Descriptiveanalysis(trainedpanels)todefinedescriptors,traits

• RelateconsumerwithdescriptivePreferencemapping

Mary Lu Arpaia

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Sensory evaluation is no trivial matter!

Beforeyoustart• Knowwhatquestionyouwanttoaskandhowyouaregoingtogettheanswer!

• Makesureyoumakeadjustmentstocommodityneedsforexperiment

• RecognizethatthisisaTIMEintensiveactivity• Workwithsomeonewhohastraininginthisarea

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Variability – within tree

Characteristics of the distribution of SSC/TA of

Valencia orange fruit in 5 light Classes Light Class SSC/TA Range Outside 12.56 8.54 – 21.00 Canopy 10.99 4.80 – 16.50 Inside 10.14 5.71 – 14.17 Top outside 12.78 9.69 – 18.47 Top inside 11.50 8.92 – 10.41 All fruit 11.56 4.80 – 21.00

• Outside– fruitonouteredge,max.light• Canopy– fruitembeddedinleafcanopy;partiallyshadedatalltimes• Inside– continuousshade• TopOutside– fulllightallthetime• TopInside– topoftree,embeddedinfoliage;partiallightSitesandReitz,Proc.Amer.Soc.HortSci.,1950

SSC varies in treeLess variation in TA

SSC/TA variation due to SSC

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Variability within the fruitSSC (%) Titratable Acidity (%)

SSC Lowest in inner middle of fruit

TA Highest in inner middle of fruit

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Does citrus postharvest handling influence eating quality of navel oranges?

M. L. Arpaia and D. Obenland

Mary Lu Arpaia

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Field Bin Washer Waxer Packed Box

1 2 34

Packing House Fruit Sampling Scheme

Does the packing line affect fruit flavor?

6.4 a 6.1 a 6.1 a 6.0 bAverage Acceptability (Hedonic Score)

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Fruit stored at 41F for 0, 3, 6 weeks followed by 4 days at 68 F and 3 days at 54 F

Does time in storage affect fruit flavor?

6.4 a 6.2 a 5.7 b

Average Hedonic Score

0 wk 3 wk 6 wk

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10 compounds changed significantly due to storage duration

5 compounds changed due to handling

Differences in aroma active compounds and internal ethanol were detected due to

storage and handling

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Conclusions• Onegrowerlotoutof3wasdistinctlydifferent• Commercialpacklinehandlinghadaninfluenceoneatingquality

• Eatingqualitydeteriorateswithstorage• Thesedifferencesappeartobeprimarilyrelatedtothefinalstepsoffruithandlingsincewedetecteddifferencesduetoplacementonpackline

• ThealterationineatingqualityisduetochangesinvolatilecharacteristicsratherthanchangesinSSCorTA

Mary Lu Arpaia

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Althoughtherearechallengesweareonlylimitedbyourimaginationonhowtoapplythistooltoourprograms

Thequestionswewillaskneedtobefocusedandspecific

Understandingthatsensoryevaluationisanothertooltobeusedinenhancingourknowledgeofproductquality

Concluding remarks

Mary Lu Arpaia

Questions?Many thanks to Mary Lu Arpaia for sharing her slides on sensory evaluation