Lemon and Lime - Tropical and Subtropical Fruits: Postharvest Physiology, Processing and Packaging - page 378

to (Brown system) or during (FMC system) extraction, the
lemon oil in the peel is recovered by washing with water to
form an emulsion that is used to produce cold-pressed (CP)
lemon oil (Goodrich, 2003). After extraction, the juice is
separated from the rag, seeds, and ruptured juice sacs in a
process known as finishing. The juice sacs, along with a
small amount of juice, may be stabilized and packaged to
produce a product termed pulpy juice, which can be added
to juices, beverages, and other food products. Juice that
requires even more depulping can be centrifuged to reduce
the insoluble solids level even further.
Most lemon and lime juices are heat stabilized and con-
centrated in special evaporators developed for the citrus
industry. These evaporators operate under a moderate vac-
uum and thus lower temperatures to minimize undesirable
thermal effects. While all citrus juices are particularly sus-
ceptible to thermal abuse during processing, lemon juices
are especially prone to reactions such as browning and acid
hydrolysis, which are accelerated by the very high TA of
the juice. Most fruit and vegetable juices are concentrated
to a standard soluble solids ( ◦ Brix) level. Since the major
soluble solid in high-acid fruit (lemons and limes) is citric
acid, not sugar, lemon and lime concentrates are produced
and sold on the basis of grams of equivalent citric acid per
liter of solution (GPL). Lemon concentrates of 400 GPL
(Goodrich, 2003) and lime 400-500 GPL (Berry, 2003) are
most commonly produced. The concentrate is then either
stored at low temperature in large stainless steel tanks or
packed in drums or pails and frozen.
Single-strength lemon and lime juice can be bottled or
otherwise packaged for consumer, food service, or indus-
trial use. Most often, the juice is reconstituted to a stan-
dardized GPL from lemon or lime concentrate and purified
water. Approved preservatives, such as sodium benzoate
at very specific levels, are often added. Some not-from-
concentrate (NFC) lemon juice is produced and packaged,
but its initially higher quality suffers unless the product is
quickly pasteurized, packaged, and then frozen (

Regulations and must have the requisite GPL of citric acid
from the lemon juice (not added) to be marketed under that
name. Elsewhere, standards may differ, although almost
all lemonade is composed of lemon concentrate, water,
and sweetener(s), and possibly added flavors and colors, in
slightly differing proportions.

By-product utilization
Lemon and lime oil
Lemon oil is a valuable by-product and, along with lime
oil, has the greatest economic value of all of the citrus oils.
Expressed lemon and lime oil may be produced by press-
ing the outer rind of the fruits by sponge-press (by hand) or
machines (Poucher, 1991). In commercial lemon process-
ing facilities, as the water-oil emulsion is produced just
before or during the juice extraction step, when it enters the
oil recovery process (Goodrich, 2003). The emulsion may
contain small particles of peel and other insoluble solids
and may be sent to a finisher for their removal. In both
the Brown and FMC systems, the emulsion, containing
about 0.5-3.0% oil, goes through a two-step centrifugation
process. The first centrifuge, known as the desludger, con-
centrates the mixture to about 50-60% oil, removing water
and insoluble solids. The second step, known as polishing,
removes the remaining water, along with any remaining
solids. Depending on the specifications of the oil that is
being produced, the lemon oil may be dewaxed. This pro-
cess is known as winterization and refers to the removal
of natural waxes from the peel, by exposing the oil to low
temperatures and letting the wax solidify and settle out. The
oil is then packaged in containers that are inert and that ex-
clude air (Goodrich, 2003; Kimball et al., 2005). Table 20.9
details the physical and chemical properties of lemon and
lime oil.
Lemon and lime oil are also produced by distillation
of expressed oils or direct distillation of fruit (Swaine
and Swaine, 1988; Burdock, 1995). Distillation removes
terpenes thereby improving solubility, which makes it
amenable for flavoring carbonated beverages (Burdock,
1995).
The typical yield of oil from lemon peel is somewhat less
than the total amount available (60-70%) and is dependent
on the efficiencies of the operations, fruit condition, and
even economic incentives. Lemon oil recovery processes
usually try to recover as much oil as possible due to the
value of CP lemon oil. Recovery of lemon oil from some
lemons range from about 4 to 10 kg of oil per ton of fruit
(Goodrich, 2003) and somewhat less for limes, based on
the weight of whole fruit (Burdock, 1995).

10 ◦ − to

20 ◦ C) throughout warehousing, distribution, and market-
ing. Like most citrus drinks, lemon and lime in one form
or the other find use in juices, sweeteners, acids, colorants,
flavors, texturizers, clouding agents, nutrients, and preser-
vatives.
Lemon and lime juice and concentrate are most often
used throughout the world not as pure juice but as an ingre-
dient in juice beverages. In many parts of the world, a sweet-
ened, diluted lemon drink, known as lemonade/limeade, is
the most popular citrus drink, with a significant role in the
citrus drink industry (Kimball et al., 2005). Lemonade is
specifically defined in the USA under the Code of Federal

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