Agriculture Reference
In-Depth Information
and during transportation were some risk factors identified
by the outbreak investigators as contributing to the juice
contamination.
Flavedo & Oil Sacs
Albe
Juice Sacs
Segment Membrane
Spoilage micro-organisms
Several acid-producing bacteria have been isolated from
citrus juices. However, only lactic acid bacteria such as Lac-
tobacillus and Leuconostoc and the spore-forming Alicy-
clobacillus spp. have been reported to significantly impact
juice quality. Alicyclobacillus spp. produce the compound
guaiacol that has a strong medicinal off-flavor at very low
concentration. Most of the time, under refrigerated con-
ditions, Alicyclobacillus does not affect pasteurized juice.
However, in shelf-stable juice stored at ambient tempera-
tures, spores that were not destroyed during pasteurization
can germinate and spoil the juice.
Yeast species typically found in orange juice include
Saccharomyces cerevisiae, Candida parapsilosis, Candida
stellata, Torulaspora delbrueckii, and Zygosaccharomyces
rouxii. Hanseniaspora, Pichia, Rhodotorula, Debary-
omyces, Leucosporidium, Schizosaccharomices, and
Metxchnikowia geni are also found (Arias et al., 2002).
Fermentative yeasts such as Saccharomyces cerevisiae pro-
duce ethanol and carbon dioxide from simple sugars such
as fructose, glucose, and sucrose, which constitute most of
the soluble solids present in orange juice. Fresh (unpasteur-
ized) orange juice is particularly susceptible to spoilage
by yeasts, as they are capable of growth at refrigerated
conditions.
Heat-resistant molds (HRMs) are another type of
spoilage organism that can adversely affect orange juice
quality. These fungal contaminants, mostly from the genera
Byssochlamys, Eurotium, Neosartorya, and Talaromyces
(Worobo and Splittstoesser, 2005) can form unattractive
fungal masses in shelf-stable juices, including orange.
HRMs are resistant to typical juice pasteurization regimes
and, even in hot-filled product, can produce cloud loss in
orange juice due to the production of pectolytic and other
enzymes.
Core
Seeds
Figure 21.3. Orange fruit components.
called flavedo. The flavedo is comprised of a waxy layer that
protects the fruit from the environment and oil glands where
terpenes and essential oils accumulate. The albedo, the in-
ner spongy white portion of the peel, contains large amounts
of pectin, other sugar polymers, and flavanone glycosides.
Figure 21.3 shows orange major components. About 85%
of the fruit is water and only about 50% (wet basis) of the
fruit is juice, hence the utilization of by-products, in partic-
ular the peel which accounts for approximately 21% of the
fruit, is important (Braddock 1999a).
Flavor chemistry and aroma
active compounds
Orange juice flavor is dependent on volatile and non-
volatile components, as well as on physical characteristics
such as viscosity and pulp levels in the juice. Orange fla-
vor varies with fruit maturity and variety, pre- and posthar-
vest handling, juice processing conditions, storage, product
packaging, and shelf life conditions.
The basic tastes of sweetness, sourness, and bitterness
are important components of the taste profile of the juice.
Sweetness is directly related to the soluble solids content
(SSC) measured in Brix and often referred as “Brix.” Most
of those solids are sugars, with sucrose comprising about
50% of the total sugar content and glucose and fructose
making up the other half. The other major soluble compo-
nent responsible for juice flavor is citric acid, a triprotic
organic acid associated with the characteristic sourness of
citrus juices. A certain level of sourness is desirable in high
quality orange juice, as long as it is not excessive. The
Brix/acid ratio (BAR) is a quality control parameter that
is widely used in discussing juice flavor, and is an indicator
of the sweet/tart balance of the juice.
ORANGE COMPONENTS, FLAVOR CHEMISTRY,
AND TECHNOLOGY
Components
Oranges are composed mainly of peel, juice vesicles con-
tained in segments, carpellary membranes that separate the
segments, core, and seeds. Segment membrane and core are
typically referred as rag. The membrane of juice vesicles
is referred as pulp. The outer colored portion of the peel is
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