Kelly Phang, Rebecca Johnson, Alyson Mitchell PhD

1 Shields Avenue, University of California, Davis.

Acknowledgements

Alyson Mitchell, PhD. Rebecca Johnson. Food safety

and Measurement Facility. Micheal Clegg. Musco

Family Olive Co.

Conclusions

• Of the polyphenolics measured, only tyrosol

demonstrated a trend between phenolic content and

color measurements.

• Tyrosol concentration was found to be positively

correlated with the a* color value [degree of red (+) vs

green(-)] and b* color value [degree of yellow (+) vs

blue (-)] on the insides of CBROs.

• Color values do not have linear trends for a* or b* color

value over time, but group similarly due to processing

and/or storage.

• In comparison, the two other prominent polyphenols

tyrosol and hydroxytyrosol 4-O glucoside are much

higher in concentration in CBROs and do not correlate

to any linear model to colorimetry measurements.

Abstract

Consumers expect a particular shade of black in

California-style black ripe olives [CBROs] indicative of

olive quality. During prolonged storage, the color of

CBROs may degrade and lead to consumer rejection of

the product. Herein, the color of canned CBROs over

27 months was quantified using a Hunter Lab

colorimeter. The levels of twelve polyphenols

associated with olive bitterness and/or health (i.e.

tyrosol, hydroxytyrosol, and hydroxytyrosol 4-O

glucoside [HT4-O]) were quantified using ultra high

performance liquid chromatography (UHPLC)

electrospray mass spectrometry (ESI/MS). Preliminary

data indicate that olives are initially darker with shades

of red and yellow which diminish in intensity during

prolonged storage time. Hunter L*a*b color values were

correlated with polyphenolic levels. Colorimetry data

indicates a non-linear trend of L*a*b color values over

time. A linear trend between tyrosol and a* and b* color

values was observed. Tyrosol was the only polyphenol

with a linear correlation to L*a*b* color value. Levels of

tyrosol were lowest (< 20 mg/kg) relative to

hydroxytyrosol (20-102 mg/kg) and HT4-O glucoside

(3-260 mg/kg).

Introduction

L*a*b Color Space

Andy Williams. Newspaper Color Quality Club 2002-2004.

L* values on the z-axis, and represent lightness.

a* values on the x-axis, representing green (-a) to red (+a).

b* values on the y-axis, and represent blue (-b) to yellow (+b).

–

–

Results Correlation of a* color values on the

inside of olives to tyrosol levels

The above diagram shows the formation of phenolic compounds hydroxytyrosol from oleuropein, and tyrosol from ligstroside. Herein we measured the three chemicals highlighted in red.

Color Trends in California-Style Black Ripe

Olives in Correlation to Polyphenolic Content

y = 3.2963x + 3.5965R² = 0.9499

0

5

10

15

20

25

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

Tyro

solm

g/k

g

a inside

Tyrosol

Plotting phenolic concentration against a* color value

demonstrates that there is a correlation between tyrosol

levels and a* values.

The b* values have a similar linear correlation to tyrosol

concentration.

This model may be potentially be used to link a* values

and b* values of the inside of olives, to their tyrosol

levels.

0

50

100

150

200

250

300

0 5 10 15 20 25 30

mg

/ k

g o

live

Months

Hydroxytyrosol 4-O Glucoside

0

2

4

6

8

10

12

0 1 2 3 4 5

b in

sid

e

a inside

a* and b* inside value

3 Months

9 Months

15 Months

27 Months

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 5 10 15 20 25 30

a in

sid

e

Months

a value of olive inside value vs month

0

5

10

15

20

25

30

35

0 5 10 15 20 25 30

L v

alu

e (

L:i

gh

tne

ss

)

Months

L value of olive inside vs month

Hydroxytyrosol content ranges

from 20-102 mg/kg olive.

Tyrosol content was in a range

of <20 mg/kg olive.

*Tyrosol’s values correlate with

a* values and b* values in

colorimetry measurements,

show in the box to the right.

Hydroxytyrosol 4-O glucoside

levels were at 3-260 mg/kg

olive.

Colorimetry

a* values and b* values of the

inside the olive have similar

values per month, with clear

separation between time points.

The a* inside values do not have

a linear trend, but are

comparable to tyrosol levels.

Therefore a model was created,

linking tyrosol levels to a values

of the insides of olives.

a* values refer to red (+a) vs

green (-a).

L values did not vary much over

time.

L values refer to lightness

values. A higher value

corresponds to a lighter color.

MethodCanned olives were processed on a single date and canned olives

were stored for 27 months. Olives were sampled at 3, 9, 15, 27

months. Three cans were measured, with three composites per

can, and with ten olives in each composite.

L*a*b values measured

using a Hunter

Colorimeter inside and

outside each olive.

Homogenized using a

professional spice grinder.

Olives were defatted using

a hexane removal of 40mL.

Olives were dehydrated for 48 hours

and homogenized every 24 hours.

0.1g of sample

was sieved and

weighed out.

Sample extraction

with 4mL of 60%

methanol solution

in water.

Filtered with

a nylon 0.22

micron filter.

920uL injected with 80uL O-

coumeric acid internal standard

0

20

40

60

80

100

120

140

0 5 10 15 20 25 30

mg

/ k

g O

live

Months

Hydroxytyrosol

0

5

10

15

20

25

0 5 10 15 20 25 30

mg

/kg

Oli

ve

Months

Tyrosol