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Transcript of Zahra Mohammed
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8/13/2019 Zahra Mohammed
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Olive oil volatile compounds, flavor developments and quality
Zahra Mohammad
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8/13/2019 Zahra Mohammed
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Overview
1. Introduction
2. Olive oil quality
3. Volatile compounds
4. Formation of volatile compounds5. Enzyme action in volatile compounds
6. Processing condition and volatile compounds
7. Volatile compounds and olive oil flavor
8. Oxidation of volatile compounds
9. Conclusion
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Introduction
Olive oil is known to possess a highly distinctive taste and
flavor. The quality and flavor of olive oil is attributed to the
formation of volatile compounds that are formed as a result of
oxidation of fatty acids. A number of factors influence the
formation of these compounds and the quality of olive oil.
Thus, an understanding of the formation stages of volatile
compounds can be used to control the volatile composition and
enhance the quality of olive oil.
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Olive oil quality
The International Olive Oil Council(IOOC) have defined
the quality of olive oil based on the free fatty acid which is
an important factor for classifying olive oil into
commercial grades. The olive oil with high quality is
called extra- virgin. The quality of olive oil is affected by
many parameters such as cultivar, climatic conditions
,agronomic practices and presence or absence of certain
volatile compounds.
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Olive oil quality
The stability and sensory characteristics of olive oil
also can be affected by phenolic content and may
serve as a good indicator of olive oil. Olive oil is
susceptible to both hydrolytic and oxidative reactionsthat can change the quality of olive oil.
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What is Volatile Compounds
Volatile compounds are low molecular weights which vaporize at
room temperature, it is formed during and after olive oil extraction
due to the oxidation of fatty acids (triglycerides), and it is responsible
for Olive oil aroma and quality . Reported that the major volatilecompounds that responsible for positive aroma are the aldehydes,
alcohols, esters, hydrocarbons, ketones, and furans that are involved
C6 and the C5 volatile compounds .
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What is Volatile Compounds
The Volatile compounds are influenced by a number of factors such
as cultivar, geographic region, fruit maturity, processing methods and
parameters.
- Fruit from different cultivars grown under the same environmental
conditions produce oils with different volatile compounds.
- fruit of the same cultivar grown in different geographic regions alsoproduce oils with different volatile compounds.
- Different volatile compounds and different aroma are produced with
different degree of olive fruit maturity.
-Different volatile compounds are produced with different with
different Extraction methods and condition , and processingtemperature and time.
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Formation of Volatile Compounds
Volatile compounds formed as a result of oxidation of olive fatty acid.
During the climacteric phase (earlier) fruits produce ethylene, oil from
this phase has a high quality and rich in aromatic volatile
compounds. The formation of volatile compounds include different
pathways , these pathways involve chemical and enzymatic
oxidation. However, the volatile compounds from chemical pathways
are responsible for the off- flavor due to the oxidative rancidity. And
the volatile compounds that give a high oil quality and aroma are
those formed through enzymatic pathways especially through the
lipoxygenase pathway.
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Lipoxygenase pathway include two pathways, one pathway is
enzymatic cleavage of linoleic and linolenic acid into C6 and C9
aldeydes and C9 and C12 oxo acids. Another pathway is through
fatty acid metabolism, producing acids, alcohols, esters and ketones.
Volatile compounds can be formed by other enzymatic pathways,such as amino acids, but this pathway has been paid less attention.
However, an understanding of the various pathways can improve the
production and storage of premium quality olive oil.
Formation of Volatile Compounds
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Formation of Volatile Compounds
Lipoxygenase
Olive Lipids
Linoleic
acid
Linolenic acid
9-
hydroperoxide
13- hydroperoxide 13-
hydroperoxide9-
hydroperoxide
Hexanal Cis-3-hexenal
Trans-2-
hexenal
Hexanol Cis-3-hexenol
trans-2-
hexenol
Hexyl
acetate
Cis-3- hexenyl
acetate
Trans-2-hexenyl
acetate
Hydroperoxide lyase
Alcohol dehydrogenase
Alcohol acetyl transferase
Acyl hydrolase
Cis-3: trans-2-enal isomerase
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Enzyme action in volatile compounds
The formation of volatile compounds throughlipoxygenase pathway involves a series of enzymes.
The volatile compounds start with enzyme acyl hydrolase(AH) and
hydrolyses triglycerides and phospholipids to release free fatty acids.
Then fatty acids are oxidized by the action of enzyme
lipoxygenase(LOX) to produce hydroperoxides , this enzyme is moreactive with linolenic acid than linoleic acid and produce more C6
unsaturated volatile compounds that is contributed to virgin olive oil
aroma. And it is more active with alkaline range than acidic
conditions.
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Enzyme action in volatile compounds Fatty acid hydroperoxides are cleavage by enzyme hydroperoxide
lyase (HPL) to produce volatile C6 aldehydes and C12 oxoacids
from 13-hydroperoxides of linolenic or linoleic acid which are
responsible for olive aroma or produce C9 aldehyde and C9
oxoacids from 9- hydroperoxide which are responsible for cucumber
like odour. Then, aliphatic aldehydes catalyses to alcohols by
enzyme alcohol dehydrogenase (ADH) which is abundant in the
plant kingdom and is responsible for the formation of volatile
compounds that responsible for the aroma of vegetable products.
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Enzyme action in volatile compounds The activity of enzyme ADH decreases when the olive fruit color
changes to purple during the ripening process which leads to
decrease of C6 alcohols in the aroma of olive oils. Then, from
alcohols that are produced by ADH, volatile esters and acetate esters
such as (hexyl acetate) which are important compounds of sweet,
fruity note produced by the action of enzyme Alcohol acetyl
transferase (AAT). This enzyme is more active with long chains.
Thus, increasing the AAT activity can increase the production of
volatile esters responsible for the fruity and sweet aroma in olive oil.
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Processing conditions and volatile formation
Processing conditions of olive fruit can affect both quality and
quantity of olive oil because the formation of volatile compounds is
dependent on the action of enzymes, which have different optimum
temperature for activity. Thus, Malaxation temperature and time canbe controlled to produce high quality and quantity of olive oil.
However, different processing parameters may be required in
different geographic growth regions to produce high quality olive oil.
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Volatile compounds and olive oil flavor
More than 120 volatile compounds that contribute both positive and
negative flavor and sensory of olive oil has been identified. The
evaluation of the flavor and quality of olive oil depend on the volatile
compounds that are formed during the processing of olive fruit. The
IOOC provides some standards flavor to evaluate virgin olive oil
sensory quality.
The positive attribute
Fruity: the flavor of the oil from unripe olives, and it is grassy or leafy
attributes. Whereas, ripe olives has aromatic flavor.
Bitter: it is characteristic taste of olive oil from green or turning colorolive.
Pungent: it is characteristic taste of olives that are unripe
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Volatile compounds and olive oil flavor The negative attribute of olive oil
Fusty: a characteristic flavor of oil from olives stored in piles of
notable thickness or in jute sacks for long time before extraction due
to anaerobic.
Musty- humid: a characteristic flavor of oil from fruit infested withfungi and yeast that stored in low temperature and high humidity.
Muddy sediment: a characteristic flavor of oil that has been left in
contact with the sediment for a long time.
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Volatile compounds and olive oil flavor Winey-vinegary: a flavor due to the fermentation that lead to the
formation of acetic acid, ethyl acetate and ethanol that has a flavor
reminiscent of wine or vinegar.
Metallic: a flavor, reminiscent of metals due to the long contact with
metallic surfaces during process or storage. Rancid: a flavor of oils that have undergone oxidation of unsaturated
aldhydes.
The flavor sensory is due to the interaction of several volatile
compounds, but not single volatile. The positive aroma have been
associated with volatile C6 aldehyde , alcohols, and C5 aldehydes ,alcoholes and esters.
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Oxidation of volatile compounds
Oxidization of the triglycerides of virgin olive oil causes significant
changes in the chemical, sensory and nutritional properties of oil thataffect the quality. The oxidation is influenced by external factors,
such as storage condition like temperature, light and oxygen
concentration. At low temperature ketones and aldehydes dominate
the volatile compounds in oil, whereas oil stored at high oxygen
concentration carboxylic acids dominate the volatile compounds inoil, and at high temperature the polymeric volatile compounds are
produced.
It has been reported that the absence of C6 aldehyde, C6 alcoholes
and esters from the lipoxtgenase pathway and presence of many
C7-C12 aldehydes and other volatile cause off-flavors of olive oil. Nonanal and the ratio of hexanal/nonanal used as indicator of
oxidation. However, most studies have been used nonanal as a
primary indicator of rancidity that has focused on the volatile
compound that causes the rancid off-flavor.
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Conclusion
It is important to understand the formation of volatile compounds and
their pathways in order to be able to enhance the desirable flavor
and the quality of olive oil. However, producing the high quality of
olive oil remains challenge since the quality of olive oil depends on
the rate of volatile compounds in oil. Volatile compounds and the
quality of olive oil are influenced by a number of factors such ascultivars, agronomic practices, geographic region, fruit maturity,
processing condition, and storage condition of fruits. However,producing olive fruit with high properties and positive attributes with
controlling the processing parameters are essential to produce high
quality olive oil. More studies should be done in post harvest fruithandling technologies that enhance production of positive volatile
compounds.
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Questions ?