Agriculture Reference
In-Depth Information
Excessive bitterness is undesirable in orange juice and is
usually due to flavonoid and limonoid compounds, which
are found in varying concentrations in the various fruit com-
ponents including the juice. Bitter components can also par-
tition into the juice if the fruit undergoes excessive process-
ing, as defined by high extractor and/or finisher pressures
that maximize yield but result in diminished quality. Sweet
oranges, those classified as Citrus sinensis, do not contain
the highly bitter glucoside naringin, which is found in other
citrus such as grapefruit. Navel oranges, although classified
as sweet oranges and excellent as a fresh fruit variety, are
not suitable for juice processing due to the development of
an intense bitterness that renders the juice unpalatable. This
is due to the acid hydrolysis of a nonbitter limonoid precur-
sor into the very bitter limonin after the juice is extracted.
The common oranges used in processing (e.g., 'Hamlin,' a
midseason variety, and 'Valencia') generally contain levels
of limonoids below the flavor threshold. Other potentially
bitter compounds found in oranges, such as hesperidin, do
not generally occur in the juice at levels which adversely
affect taste.
Orange flavor is strongly dependent on the volatile com-
pounds found primarily in the essential oil of the peel, and
recovered as described in “Orange By-products.” There are
numerous reviews describing the volatile composition of
orange aroma due to the commercial importance of orange
flavors (Maarse and Visscher, 1989). The volatile com-
pound d-limonene is present in orange oil in concentra-
tions greater than 95% (v/v), although this citrus terpene
does not contribute to orange aroma. Compounds responsi-
ble for characteristic orange aroma include other terpenes,
which are prevalent in plant essential oils and are hydro-
carbons arranged in isoprene units. The level of aldehydes
in an essential oil is an indicator of relative quality, with
higher levels more desirable.
Numerous studies have attempted to quantify individual
chemical components in orange oil and assess their con-
tribution to orange flavor. The sesquiterpene valencene is
thought to be present in large amounts in cold press citrus
oil. It is found in typical orange oils at levels ranging from
400-4,000 ppm and is thought to possess the characteristic
“fresh orange” note that is so highly desirable However,
more recent studies have suggested that valencene, while
present in relatively large quantities, may not have sig-
nificant aroma impact (Elston et al., 2005). Decanal and
octanal comprise major parts of the aldehyde content that
is commonly determined in citrus oils and are associated
with “green” and “fresh fruity” characteristics. Figure 21.4
summarizes key volatile compounds found in orange juice
that are thought to contribute to orange juice aroma.
QUALITY STANDARDS
Although broad regulations for fruit nectars and juices exist,
there are very specific quality standards for orange juice. In
each country or world region, standards are driven by con-
sumer preference, market pricing, and safety regulations.
In the United States, the US Department of Agriculture
(USDA) established the “grades” for fruit and fruit juices
in terms of quality. The FDA regulates the standards of iden-
tity (Title 21, Part 146 of the Code of Federal Regulations).
Furthermore, individual states also have the authority to
regulate their juices. Chapter 601 of the Florida Code, titled
“Florida Citrus Code,” empowers the Florida Department
of Citrus to modify rules for grading, processing, packag-
ing, and so on, provided that they do not contradict federal
law. In the European Union, the European Commission
implemented directive 2001/112/EC that covers all fruit
juices and similar products. Based on current per capita
consumption of processed orange juice, the United States
and the European Union are the two most relevant regions
of the world. Hence most processors attempt to meet these
countries standards. However, other regions such as Latin
America, Australia, New Zealand, the Middle East, and
some Asian countries have their own standards and regu-
lations. Mandatory and voluntary regulations are followed
by processors. Efforts to harmonize the major quality stan-
dards are being made, but the process is slow. The Codex
Alimentarius, which was created in 1962 as a joint effort
of the Food and Agriculture Organization (FAO) and the
World Health Organization (WHO), achieves some harmo-
nization as it is used by some countries that do not have
standard regulations. The Codex Alimentarius has served
as the basis for some countries that have recently devel-
oped regulations. The Codex Alimentarius's standards for
orange fruit and fruit juices that now include and supersede
the 1981 standards for orange juice and concentrate became
effective in 2004 and 2005, respectively. All standards es-
sentially dictate the composition of the juice, mostly in
terms of SSC and titratable acidity (TA), the method and
extent of processing, and the addition of any material of
origin other than citrus. Table 21.4 summarizes some of
the main standards for orange juice and orange juice con-
centrate. One must bear in mind that quality standards of
bulk and packaged (canned) commercial juice are different
and that actually packaged juice typically exceed regula-
tory standards (set in the United States by the FDA). In
the United States, also the Department of Agriculture de-
fines three different grades of orange juice as “A,” “B,”
and “Substandard” (Anon, 1983). For example, the stan-
dards of identity for pasteurized juice mandate a minimum
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