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Vitamin C retention in orange juice production

Maria Norlin

Getting past the myths and doing more with less

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The truth about orange juiceProcessing experiments expose the myths

• Pasteurization does NOT adversely affect vitamin C retention

• Strong deaeration is NOT necessary to retain vitamin C levels

• There are similar findings for other quality indicators such as aroma, taste, or colour

• These findings have practical consequences for beverage applications

…but let’s start the story at the beginning

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How is orange juice quality defined and measured?Key components: vitamin C content, flavour and colour

Vitamin C content decreases over storage time, due to oxidation and non-oxidative reactions.

Colour is normally analysedusing a colorimeter (L*a*b*-system), digital image colouranalysis, or simply by visual inspection.

Orange juice colourbecomes darker over time – oxidation and non-oxidative reactions.

Flavour and taste are not significantly affected by processing

Measurements are based on reflectometers or titration, in everyday process control.

High-pressure liquid chromography (HPLC), is normally performed by external labs.

Flavour and taste are normally tested by a taste panel.

Aromas can be quantified with gas chromatography.

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Thermal processing, such as pasteurization, can remove 30% or more of vitamin C content.

MYTH 1: Thermal effects

Truth: The short time at elevated temperature during continuous processing actually has little effect.

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MYTH 2: Strong deaeration

Orange juice requires strong deaeration in order to avoid vitamin C degradation of the juice during storage.

Truth: The difference between strong deaeration and moderate deaeration in terms of vitamin C degradation is very small.

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MYTH 3: Aroma loss

A significant aroma loss takes place during deaeration.

Truth: This may have been believed because of the aromas people sensed around the deaerator. However, gas chromatography analysis showed already in 1999 that these losses are only minor.

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Busting myths with large-scale field tests

• Data collection over several years from internal pilot plant tests as well as full-scale operations together with customers

• Measured orange juice quality after processing and after packaging, focussing on the levels of vitamin C

• Results were analysed internally at Tetra Pak laboratory facilities in Sweden, Brazil, and Germany

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Vitamin C levels before and after pasteurizationExpressed as mg/l, showing very small percentage losses

No significant effect of the pasteurization process on vitamin C loss, when the level of vitamin C is measured directly before packaging.

Past. Temp./timeBefore pasteurization

After pasteurization

Loss (%)Vitamin C test method

95°C/15s OJ FC 450 445 1.1 Reflective method

80°C/15s OJ FC 450 442 1.7 Reflective method

95°C/17s NFC OJ 348 348 0.0 Titration

95°C/17s NFC OJ 333 323 3.0 Titration

95°C/17s NFC OJ 360 342 5.0 Titration

95°C/17s OJ FC 425 422 0.7 Titration

95°C/17s OJ FC 413 404 2.2 Titration

85°C/30s OJ FC 435 431 0.9 HPLC

95C°C/30 OJ FC 435 425 2.2 HPLC

105°C/30s OJ FC 435 425 2.3 HPLC

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If the vitamin C analysis is not done immediately after juice production, a low vitamin C measurement might be misinterpreted as a loss due to juice pasteurization, rather than the effects of oxidation.

Effects of deaeration on vitamin C retentionOxygen quickly degrades the product

0

1

2

3

4

5

6

7

50 100 150 2000

O2 ppm as function of storage time in 1 L orange juice

Hours

Most oxygen is used up within the first 24 hours

Dissolved O2 ppm

pp

m

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How much deaeration is needed?Tests run with three different levels of deaeration

No deaeration >8ppm (O2) in the package (0 D in the graph)

Moderate deaeration 2.4ppm (O2) in the package (+D in the graph)

Strong deaeration 0.8ppm (O2) in the package (++D in the graph)

Samples were stored

at either 23°C or 35°C for 20 weeks

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Deaeration resultsMaximum deaeration creates no advantage

• Warmer storage (35°C) yielded a stronger degradation

• Almost no difference between moderate deaeration (2.4 ppm O2) and strong deaeration (0.8 ppm O2)

• In other words, strong deaeration will not provide any additional benefit

7 +D 35°C8 ++D 35°C9 0 D 35°C

10 +D 23°C11 ++D 23°C12 0 D 23 °C

450

400

350

Vit

amin

C (

mg/

l)

150

200

250

300

100

50

0

Storage time (weeks)

0 2 4 6 8 10 12 14 16 18 20 22 24

Theoretically 1 mg O2 consumes 11 mg vitamin-C per liter

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Effects on colour Colour is affected by heat, not by deaeration

• Samples showed a clear browning over time, but not dependent on degree of deaeration

• The non-deaerated juice was only slightly darker than the deaerated juices

• Warmer storage temperature (35°C) produced darker colours than lower temperature (23°C)

0 4 8 12 16 20 24

56

60

64

52

48

44

L*-

valu

e (

white

-bla

ck)

Storage time (weeks)

7 +D 35°C8 ++D 35°C9 0 D 35°C

10 +D 23°C11 ++D 23°C12 0 D 23 °C

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Effects on sensory properties

Different levels of deaeration did not have any impact on the sensory properties of the juice, neither immediately after processing, nor during storage

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ConclusionsExperiments debunked the myths surrounding vitamin C degradation

• Vitamin C degradation is due to dissolved oxygen or level of deaeration, not thermal treatment

• There is an optimal level of deaeration

– Not necessarily all oxygen must be removed to obtain a product with good quality

• Thermal treatment and deaeration have no significant negative effects on the other key quality characteristics of taste and colour(Earlier tests had indicated no effects on aromas)

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The role of field tests in processing knowledgeWe should assess “industry know-how” more often

• To maintain quality and safety of the beverages we produce, we need more information about the processing parameters of individual beverages

• Beverage processing can be a highly variable area where optimizing processing can come down to individual beverages and the characteristics of their raw materials

• Tetra Pak stands ready to help you determine what that optimal process is, based on practical field trials, our calculation tools, and our years of expertise

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