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Factors influencing mandarin fruit quality

David Obenland, USDA-ARS, Parlier, CAMary Lu Arpaia, UCR

OutlineWhat drives the eating experience in mandarins?

Exterior appearance is important for the initial purchase and can have some impact on the perception of taste

Flavor quality is even more critical. Consumer acceptance……and whether they will buy again….is strongly linked with flavor quality

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Outline of talk

Impact of sugar and acid balance

Influence of aroma compounds

Off-flavor formation during storage

Sensory properties of food related to flavor

Odor/smell/aroma

Taste

Texture/mouthfeel

Temperature

Irritation/pain

Flavor

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TasteTaste is a sensation that is perceived inthe mouth by the tongue

• Sweet

• Salty

• Bitter

• Sour (acidic)

• Umami (protein – savory)

Very important in mandarins

Outline

Analysis: Mark LoeffenDelytics Ltd, New Zealand

CA Standard = (SSC – (TA * 4)) * 16.5

California Standard

In navel oranges sweetness and acidity are described by the California standard

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California Standard

California Standard

Data from Australia suggests that if a California standard for mandarins is developed the value may need to be higher than that currently set for navels

Navels – California data

Mandarins – Australian data

Analysis: Mark LoeffenDelytics Ltd, New Zealand

50% liking

35% liking

1

2

3

4

5

6

7

8

9

0 2 4 6 8 10 12 14

Brim A

He

do

nic

Sc

ale

2003-2004

2004-2005

2005-2006

Dislike Extremely

Like Extremely

The scatter in the individual points (fruit)below indicates that sugar and acid doesnot entirely determine flavor

Navel orange data

SSC-(4*TA)

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Flavor is not just Sugar:Acid….aromacompounds are very important

80-90% of taste isaroma 2% of the human genome is involved in olfactory perception

Elizabeth BaldwinUSDA/ARS

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

These compounds are also perceived by the brain when

they travel up the back of the

throat.

Aroma compounds (Volatiles)

Florence Negre-Zakharov, UC Davis

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GCMS for aroma volatile analysisRobotic solid phase microextraction system

Aroma Analysis and Product Quality

• Odor thresholds (minimum concentration of a substance at which a majority of test subjects can detect and identify the substance characteristic odor) Florence Negre-Zakharov, UC Davis

• Odor descriptors

Hexyl acetate apple, cherry,

floral, pear, wine

2-Ethyl hexanolcitrus, fresh, floral,

oily, sweet2-Methyl

butyl acetate banana, candy,

citrus5 ppb

270,000 ppb

2 ppb

?…

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Many aroma volatiles are present in mandarins and help determine flavor. These below were found to change as a result of storage.

Sweet, fruity

Storage time (wks)

Compound (µg/L) Gold Nugget (low) Pixie (high)

Alcohols 0 3 0 3

Ethanol (mg/L) 359 554* 930 3445*

3‐Methylbutanol tr tr tr 75*

2‐Methyl‐1‐butanol tr tr tr 44*

Linalool 254 34* 122 60*4‐Terpineol 104 22* 41 24*Esters

Ethyl acetate 1753 2922* 487 5812*

Ethyl propanoate 92 201* 36 320*

Ethyl isobutyrate tr 8* tr 73*

Ethyl butanoate 18 37* tr 466*

Ethyl 2‐methylbutanoate tr 6* tr 209*

3‐Methylbutyl acetate tr tr tr 9*

2‐Methylbutyl acetate tr tr tr 8*

Octyl acetate 256 60* 185 106

Decyl acetate 102 19* 64 34

Ketones

1‐Penten‐3‐one 7 7 6 8*

Carvone tr 12* 15 8

Aldehydes

Pentanal 9 11* 9 15*

Hexanal 20 24 28 19

E‐2‐Hexenal 27 21 18 47*

Heptanal 17 16 15 19

Octanal 179 48* 386 66*

E‐2‐Octenal tr tr 8 6

Nonanal 83 44* 106 47

E‐2‐Nonenal tr tr tr tr

Decanal 529 38* 223 54*

Malty, woody, earthy

Spearmint, caraway

Fatty, grassy, green

Mandarins often develop off-flavorduring storage

SpoiledSpoiled Really oldReally oldStrange aftertasteStrange aftertaste

Over ripeOver ripeNot freshNot fresh

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Weeks

0 1 4 7

Acc

epta

bili

ty

5.0

5.5

6.0

6.5

7.0

Off

-fla

vor/

Tar

tnes

s

40

45

50

55

60

65

70

Likeability Off-flavor Tartness

Typical mandarin response to cold storage + 1 week at 68F

W. Murcott

Some factors influencing off-flavorin mandarins

0

1

2

3

4

5

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8

0 1 2 3 4 5 6

He

do

nic

sc

ore

Weeks after packing

41F 0 weeks 2 weeks 4 weeks

Warm temps enhance

Time in cold storageinfluences response

Some varieties moreproblematic than others

68 F storage

W. Murcott

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Warm temperature response of other mandarin types

4.04.55.05.56.06.57.0

0 1 3 @ 5 °C + 1

Hed

onic S

core

Weeks following packing

China S-9

5 °C

20 °C

4.04.55.05.56.06.57.0

0 1 3 @ 5 °C + 1

Hed

onic S

core

Weeks following packing

Okitsu Wasi

5 °C

20 °C

4.04.55.05.56.06.57.0

0 1 3 @ 5 °C + 1

Hed

onic S

core

Weeks following packing

Fairchild

5 °C

20 °C

4.04.55.05.56.06.57.0

0 1 3 @ 5 °C + 1Hed

onic S

core

Weeks following packing

Nova

5 °C

20 °C

Harvest date can affect the negative impact of storage on mandarin flavor

OjaiLindcove

Early in the seasonthere was less of aflavor difference

When the flavor lossoccurred it was mainlydue to off-flavor

Data from Owari satsumas

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Coatings provide a formidable barrier to gas exchange

Waxed Unwaxed

Bailey-Serres et al., 2012

O2ethanol

We assayed for ethanol asan attempt to screen foroff-flavor susceptibility

• Ethanol easy to measure

• Substrate for volatile synthesis

• Major product of low oxygen and fermentation

Is there variability out there?

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Large varietal differences exist in the amount ofethanol accumulated after waxing and storage

Harvest Coating + 68F 1 week

Pix

ie

Gol

d N

ugg

et

0.00

5.00

10.00

15.00

20.00

25.00

0 50 100

Time after waxing (h)

GN

P

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2000

0 50 100

EtO

H (

mg

/L)

Time after waxing (h)

GN

P

Response of a high ethanol producer (Pixie) vs. a low ethanol producer

(Gold Nugget)to waxing

After waxing Gold Nugget maintains a higher internal oxygen level and produces less ethanol than does Pixie

% I

nte

rna

l O2

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EthanolCO2 O2

Passage of gases through the peel occurs more slowly in Pixie than Gold Nugget

0.00

5.00

10.00

15.00

20.00

25.00

0 50 100

% I

nte

rnal

O2

Time (h)

GN

P

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200

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1000

1200

1400

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2000

0 20 40 60 80 100 120

Eth

ano

l (m

g/L

)

Time (h)

GN

P

Ethanol production similar forboth varieties in nitrogen gas and suggests an important role for the peel

Lowering internal oxygen in the fruit with nitrogen gas leads to a very similar ethanol response for Pixie and Gold Nugget

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ConclusionsThe sugar:acid balance is a very important

component of mandarin taste

Aroma compounds also play a critical role in determining mandarin flavor

Loss in flavor quality as a result of storage is common

• Waxing• Temperatures following waxing• Time of season• Variety

Our joint lab groupUC and USDA-ARS

Our research has been funded by the California

Citrus Research Board and the US-IS BARD Program

Our research has been funded by the California

Citrus Research Board and the US-IS BARD Program

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Questions?