The effect of storage on olive oil quality Jamie Ayton, Rod Mailer - - PowerPoint PPT Presentation

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The effect of storage on olive oil quality Jamie Ayton, Rod Mailer - - PowerPoint PPT Presentation

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The effect of storage on olive oil quality Jamie Ayton, Rod Mailer and Kerrie Graham Wagga Wagga Agriculture Institute 2012 AOA National Olive Industry Conference 31 st October/1 st November 2012 Adelaide Introduction Considerable

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The effect of storage on olive oil quality

Jamie Ayton, Rod Mailer and Kerrie Graham Wagga Wagga Agriculture Institute

2012 AOA National Olive Industry Conference – 31st October/1st November 2012 – Adelaide

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Introduction

  • Considerable time, effort and money is required to produce

high quality extra virgin olive oil (EVOO).

  • EVOO quality deteriorates over time, however the rate of

deterioration depends on: – Composition of the oil – Storage conditions

  • Research to determine the rate of deterioration based on

initial oil composition and storage conditions (temperature,

  • xygen, light exposure and storage container type).
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Introduction – RIRDC projects

Project 1 – Effect of storage conditions on

  • live oil quality.

– Investigation of a number of different types of olive oil stored in bottles under variable conditions. » Temperature » Oxygen » Light

Project 2 – Effect of storage in bulk containers on olive oil quality.

» One oil stored in different container types

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Project 1– Effect of storage conditions

LOW OXIDATIVE STABILITY

Low polyphenols High linolenic acid Low PP Mid C18:2 Low PP Low C18:2 Mid PP High C18:2

MEDIUM OXIDATIVE STABILITY

Mid polyphenols Mid linolenic acid Mid PP Low C18:2 High PP High C18:2 High PP Mid C18:2

HIGH OXIDATIVE STABILITY

High polyphenols Low linolenic acid

Least stable Most stable

Typical Australian olive oil types

PP = total polyphenols C18:2 = linoleic acid

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Initial oil composition

Least stable Most stable

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Storage conditions

  • Nine oils stored for 3 years – analysed at regular intervals
  • Temperature (stored in dark, closed)
  • 15°C
  • 22°C
  • 37°C
  • Oxygen (stored at room temp, in the dark)
  • Open
  • Closed
  • Light (stored at room temp, closed)
  • Clear bottle, exposed to light
  • Dark bottle, stored in darkness
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Temperature

Factory Warehouse Supermarket Home

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Temperature - Peroxide value

Least stable (LP,HL) Most stable (HP,LL)

AS-5264-2011 – <20 mEq O2/kg oil

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Temperature - Free fatty acids

AS-5264-2011 – < 0.8%

Least stable (LP,HL) Most stable (HP,LL)

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Temperature - DAGs

AS-5264-2011 – >35%

Least stable (LP,HL) Most stable (HP,LL)

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Temperature - Pyropheophytin a

AS-5264-2011 – < 17%

Least stable (LP,HL) Most stable (HP,LL)

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Temperature Sensory analysis – low stability oil

15°C, dark, closed 22°C, dark, closed 37°C, dark, closed

  • Results shown are for low stability oil (LP,HL)
  • Similar results for other oils
  • High stability oils – less likely to be rancid at low temperature
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Oxygen

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Oxygen - Peroxide value

AS-5264-2011 – <20 mEq O2/kg oil

Least stable (LP,HL) Most stable (HP,LL)

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Oxygen - UV absorbance - K232

AS-5264-2011 – < 2.50

Least stable (LP,HL) Most stable (HP,LL) Least stable (LP,HL) Most stable (HP,LL)

  • Similar results for K268
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Oxygen - Polyphenols

Least stable (LP,HL) Most stable (HP,LL)

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Oxygen - α-tocopherol

Least stable Most stable Least stable (LP,HL) Most stable (HP,LL)

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Oxygen - Sensory analysis

Closed Open Least stable Most stable

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Not affected by oxygen

FFA PPP DAGs

  • FFA slight increase
  • PPP - increase 8-10% per year
  • DAGs decrease – 25-35% per year then reaches equilibrium
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Light

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Light - α-tocopherol

Least stable Most stable Least stable (LP,HL) Most stable (HP,LL)

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Light - Chlorophyll

  • Significant decrease in oils exposed to light
  • Same response in all oils
  • Antioxidant in dark, pro-oxidant in light

Green Brown/golden

  • Pyropheophytin a – breakdown product of chlorophyll
  • No chlorophyll = no PPP. Undetectable after initial analysis
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Light – Sensory analysis

Dark Light Least stable Most stable

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Compliance with AS5264-2011

PV FFA Pyro DAG Sensory K232 K268 15°C 12 18 22°C 24 18 6 12 37°C 6 3 3 6 Closed 24 18 6 12 Open 6 6 24 24 18 6 3 Dark 24 18 6 12 Exposed 24 18 *ND 6 12 UV Absorbance Storage Temperature Oxygen Light

Least stable

*ND: Not detected after 3 months storage

Within AS5264-2011 limit after 36 months Exceeds AS5264-2011 limit Number = months before exceeding limit

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Compliance with AS5264-2011

PV FFA Pyro DAG Sensory K232 K268 15°C 22°C 18 18 37°C 36 30 3 3 6 Closed 18 18 Open 18 12 24 18 18 18 Dark 18 18 Exposed 6 *ND 18 18 UV Absorbance Storage Temperature Oxygen Light

Most stable

*ND: Not detected after 3 months storage

Within AS5264-2011 limit after 36 months Exceeds AS5264-2011 limit Number = months before exceeding limit

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Project 2 - Bulk storage

  • One oil stored for 1 year
  • Bulk storage containers

» Polyethylene » Nylon » Metallised polyester » Silver foil » HDPE

  • Storage conditions

» 22°C » closed » dark

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Bulk storage - Peroxide value

  • Container type had significant effect
  • Oxygen permeability
  • Oil in polyethylene container

increased significantly – outside limit after 12 months storage.

AS-5264-2011 – <20 mEq O2/kg oil

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Bulk storage - UV absorbance - K232

  • Container type had significant effect
  • UV absorbance of oil in PE container

increased significantly – outside limit after approx 6 months storage.

AS-5264-2011 – < 2.50

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Bulk storage - Total polyphenols

  • Container type had significant effect
  • Oxygen permeability of PE –

polyphenols consumed in oxidation process

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Bulk storage - DAGs

  • Same as results from previous project

eg presence of oxygen had no effect, identical for all containers

  • 30% decrease in DAGS over 12 months

AS-5264-2011 – >35%

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Conclusions – storage conditions

  • Storage conditions - significant influence on the quality of olive oil.

– Higher storage temperature – More rapid increase %FFA and PPP, decrease in DAGs and sensory quality – Oxygen exposure – More rapid increase PV and UV absorbance, decrease in antioxidants and sensory quality – Light exposure – More rapid decrease in tocopherols, chlorophyll, sensory quality

  • PPPs and DAGs

– Good indicators of freshness of oil – initial quality and storage conditions important

  • Keep olive oil in dark, cool areas and ensure exposure to oxygen is kept minimal to

maintain EVOO quality

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Conclusions - Bulk storage

  • Bulk storage containers can have a significant effect on
  • live oil quality

– be aware of the type of material used – oxygen permeability – ensure storage temperature is kept as low as possible and exposure to light is limited.

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Acknowledgements

NSW DPI Staff

  • Veronica Woodbury
  • Francisca Boshuizen
  • Donna Seberry
  • Chris Wallace
  • Helen Taylor
  • Janelle Rowland

Special thanks to all members

  • f the Wagga Wagga Olive

Oil Sensory Panel (WWOOSP)