131
(Fishman et al. 2000). But these methods are associated with the drawbacks like the
direct boiling takes about 2 h to extract pectin which can degrade the molecular
structure of pectins. Pectin can also be extracted by using different solvents like
water, buffers, chelating agents, acids, and/or bases in a sequence mentioned. This
not only isolates pectin selectively but also the extracted pectin may have different
properties like solubility, gel forming ability and strength etc. It must be noted that
the sequence in which the solvents are used affects the purity and the solubility of
the pectin. For instance if the solvents used follow the order from water to bases as
mentioned above, the extraction of pectin will be selective and the solubility will
also be different from the source material. However when the acid is used first, the
selective extraction of pectin is not so effective. Similarly if we use the other solvents individually, it not only affects the yield but the properties of pectin as well
even if the starting material remains same. The stepwise industrial extraction of
pectin is given in (Fig. 3).
Broadly speaking, conventional pectin extraction involves the following steps:
1. Pre-treatment stage.
2. Extraction operation.
3. Post-extraction stage.
Conventional Acid Extraction
Acids are generally cheaper and give the highest yield of pectin among the commercially mineral acids are employed to extract pectin and these include hydrochloric acid, nitric acid and sulphuric acid (Iglesias and Lozano 2004; Mesbahi et al.
2005).The extraction method involving acids yield pectin that is rich in GalA units.
The process involves pre-treatments such as washing of the parent material to
remove off the dirt and ensure stability during transportation, storage and blanching
or drying to inactivate enzymes such as pectin methyl-esterase (PME) and bacteria
which can be detrimental in degrading pectin. Following the pretreatments, the
peels can be dried to a moisture content of 10–12% to prevent fermentation. The
most commonly used sources of pectin include citrus peels, apple pomace, and
sugar beet pulp. Currently food and agricultural wastes from industries are also
being harnessed for obtaining pectin. This enables us to combat the waste management problems and also widen the availability of the cheap materials for commercial use. Fruit wastes such as banana peels (Emaga et al. 2008), kiwifruit pomace
(Yuliarti et al. 2015) papaya peels (Koubala et al. 2014) grapefruit peel (Xu et al.
2014) sugar beet (Maxwell et al. 2016) and many other sources have been exploited
as sources of pectin. The pretreated or fresh parent material is then subjected to
extraction in demineralized water whose acidity is maintained to pH 1.5–3.0 at
50–100 °C for approximately 3 h (Nussinovitch and Hirashima 2013). The next step
involves separation of extracted pectin from the raw materials by filtration or centrifugation. Pectin can also be precipitated by using polyvalent cations such as aluminum or copper salts. Here in this case the cations can be removed by first washing
Pectin
(Fishman et al. 2000). But these methods are associated with the drawbacks like the
direct boiling takes about 2 h to extract pectin which can degrade the molecular
structure of pectins. Pectin can also be extracted by using different solvents like
water, buffers, chelating agents, acids, and/or bases in a sequence mentioned. This
not only isolates pectin selectively but also the extracted pectin may have different
properties like solubility, gel forming ability and strength etc. It must be noted that
the sequence in which the solvents are used affects the purity and the solubility of
the pectin. For instance if the solvents used follow the order from water to bases as
mentioned above, the extraction of pectin will be selective and the solubility will
also be different from the source material. However when the acid is used first, the
selective extraction of pectin is not so effective. Similarly if we use the other solvents individually, it not only affects the yield but the properties of pectin as well
even if the starting material remains same. The stepwise industrial extraction of
pectin is given in (Fig. 3).
Broadly speaking, conventional pectin extraction involves the following steps:
1. Pre-treatment stage.
2. Extraction operation.
3. Post-extraction stage.
Conventional Acid Extraction
Acids are generally cheaper and give the highest yield of pectin among the commercially mineral acids are employed to extract pectin and these include hydrochloric acid, nitric acid and sulphuric acid (Iglesias and Lozano 2004; Mesbahi et al.
2005).The extraction method involving acids yield pectin that is rich in GalA units.
The process involves pre-treatments such as washing of the parent material to
remove off the dirt and ensure stability during transportation, storage and blanching
or drying to inactivate enzymes such as pectin methyl-esterase (PME) and bacteria
which can be detrimental in degrading pectin. Following the pretreatments, the
peels can be dried to a moisture content of 10–12% to prevent fermentation. The
most commonly used sources of pectin include citrus peels, apple pomace, and
sugar beet pulp. Currently food and agricultural wastes from industries are also
being harnessed for obtaining pectin. This enables us to combat the waste management problems and also widen the availability of the cheap materials for commercial use. Fruit wastes such as banana peels (Emaga et al. 2008), kiwifruit pomace
(Yuliarti et al. 2015) papaya peels (Koubala et al. 2014) grapefruit peel (Xu et al.
2014) sugar beet (Maxwell et al. 2016) and many other sources have been exploited
as sources of pectin. The pretreated or fresh parent material is then subjected to
extraction in demineralized water whose acidity is maintained to pH 1.5–3.0 at
50–100 °C for approximately 3 h (Nussinovitch and Hirashima 2013). The next step
involves separation of extracted pectin from the raw materials by filtration or centrifugation. Pectin can also be precipitated by using polyvalent cations such as aluminum or copper salts. Here in this case the cations can be removed by first washing
Pectin