| The
pectin factory receives apple residue (pomace) or citrus
peel from a number of juice producers. In most cases this
material has been washed and dried so it can be transported
and stored without spoilage. |
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|
If the raw material is dry, it can be assessed and selected from
store as required for different purposes. If wet citrus peel is
used, it has to be used as received, as it deteriorates very rapidly. |
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| The
raw material is added to hot water containing a processing
aid (usually a mineral acid, although others such as enzymes
could be used). |
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Water alone will only extract a very limited amount of pectin. |
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|
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| After
time to extract the pectin, the remaining solids are separated,
and the solution clarified and concentrated by removing
some of the water. |
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The
solids can be separated by filter, centrifuge, or other means.
The solution is then filtered again to clarify it if necessary. |
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|
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| Either
directly, or after some further holding time to modify the
pectin, the concentrated liquid is mixed with an alcohol
to precipitate the pectin. |
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The
pectin can be partly de-esterified at this stage, or earlier or
later in the process.. |
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The
precipitate is separated, washed with more alcohol to remove
impurities, and dried.
The alcohol wash may contain salts or alkalis to convert
the pectin to a partial salt form (sodium, potassium, calcium,
ammonium) |
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|
The
alcohol (usually isopropanol) is recovered very efficiently, and
reused to precipitate further pectin. |
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| Before
or after drying, the pectin may be treated with ammonia
to produce an amidated pectin if required. |
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Amidated
pectins are preferred for some applications. |
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| The
dry solid is ground to a powder, tested, and blended with
sugar or dextrose to a standard gelling power like 150° Sag using the IPPA-Sag-method or other functional
property such as viscosity or stabilising power. |
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|
Pectins
are also sold blended with other approved food additives for use
in specific products. |
