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Proc. Fla. State HorL Soc. 107: 248-253. 1994.
ST. AUGUSTINE SWEET ONIONS
Reginald L. Brown
Florida Fruit and Vegetable Association
4401 East Colonial Drive
Orlando, Florida 32814-0155
James D. Dilbeck
St. Johns County Cooperative Extension Office
2125 Agricultural Center Drive
St. Augustine, Florida 32092-0572
Dale R. Hensel
Hastings Research and Education Center
Institute of Food and Agricultural Sciences
University of Florida
P.O. Box 728
Hastings, Florida 32145-0728
Michael T. Talbot *
Agricultural and Biological Engineering Department
Institute of Food and Agricultural Sciences
University of Florida
Gainesville, Florida 32611-0570
Abstract. "St. Augustine Sweet" trademarked onions were suc
cessfully marketed in the Spring of 1994. This important event
was the result of much work, cooperation, and coordination
between the growers, the FFVA, the Florida Department of Ag
riculture, the buyers, and University of Florida faculty at coun
ty, research and education center, and campus departments.
The onion variety selection, growing conditions, and cultural
practices developed over several years are discussed. The
harvest and postharvest procedures and equipment which are
so important for maintaining top quality are presented. The
growing area and growers, their background and number, are
detailed from a county perspective related to production, orga
nization, meetings, and development of a cooperative market
ing goal. The formal establishment of the St. Augustine Onion
Growers Exchange, Inc., bylaws, incorporation, trademark de
velopment, and other organization information are outlined.
Marketing window opportunity, publicity efforts, and coordina
tion with buyers are discussed because producing an excel
lent crop must be accompanied by equally excellent
marketing.
"St. Augustine Sweet" trademarked onions were success
fully marketed in the Spring of 1994. This important event
was the result of much work, cooperation, and coordination
between the growers, the Florida Fruit and Vegetable Associ
ation (FFVA), the Florida Department of Agriculture and
Consumer Affairs (DACS), the buyers, and the county, re
search and education center (REC), and state faculty of the
University of Florida Institute of Food and Agricultural Sci
ences (IFAS).
After thirty years of sweet onion variety selection and de
velopment of cultural practices for Florida growing condi
tions by IFAS personnel, nine visionary growers initiated the
first commercial marketing of sweet onions that have the tex
ture and flavor of the popular Vidalia onions grown in Geor-
Florida Agricultural Experiment Station Journal Series No. N-01029.
gia. The growers believe the St. Augustine Sweets are
comparable to, if not better, than the Vidalias. Georgia grow
ers have long dominated the sweet onion market because of
a good sweet onion, but also as a result of an excellent job of
marketing and promoting the Vidalia onions. Florida's earli
er planting and harvesting cycle allows the St. Augustine
Sweets to reach market two to three weeks before the Vidalia,
a key advantage in both introducing the onions and in gain
ing a market share. This relatively small venture was an at
tempt to establish identity with consumers and demonstrate
that Florida can produce a quality sweet onion.
The objective of this paper is to present the background
information concerning the people, effort, equipment, and
procedures which were necessary for the successful initial
marketing of St. Augustine Sweet Onions.
In view of the success of the Georgia Vidalia onions, many
believe that Florida can produce high quality sweet onions.
Florida's winter climate and soil conditions are favorable and
the earlier crop could yield premium market prices. The ma
jor factors preventing commercial scale onion production in
Florida appeared to be the prevailing high humidity and high
probability of rainfall at harvest time, which would make field
drying infeasible. These climatic conditions at harvest favor
growth of decay organisms necessitating the use of artificial
drying. The poor quality often associated with inadequate
postharvest curing and handling diminished the market ap
peal and potential.
In July 1990, IFAS established a multi-disciplinary Sweet
Onion Working Group to study opportunities associated with
making the Florida sweet onion into a viable agricultural in
dustry. This group included faculty from Hastings-REC,
North Florida REC-Quincy, Gulf Coast REC-Bradenton,
Southwest Florida REC-Immokalee, Horticultural Sciences,
Food and Resource Economics, Agricultural and Biological
Engineering, Food Science and Human Nutrition Depart
ments, and IFAS research and extension administrators. Top
ics covered by IFAS research projects included onion cultivar
selection, transplant versus direct seeding, mulching materi
als, planting and harvest dates, physiological maturity, popu
lation densities, fertilization requirements, bulb size, total
yield, and quality.
Hastings-REC has been involved with sweet onion re
search for nearly 30 years and has demonstrated sweet onions
can be grown successfully. In 1990, small scale plantings pro
duced yields as high as 56 metric tons/ha (25 tons per acre)
US No. 1 onions over 76mm (3 inch). Several local growers
demonstrated continued interest in sweet onion production.
Although plantings by these growers, in conjunction with the
Hasting-REC programs, produced excellent sweet onions,
there was a significant problem in marketing these onions
due to low price.
Cultural Practices. The standard 1 m (40 inch) ridged row
has been used on the low flatwood soils in the Hastings area
for several decades. This provides sufficient drainage during
wet weather. Recent research showed that by adopting 2 m
(80 inch) beds, nearly a two fold increase in onion produc
tion can be attained (Hensel and Shumaker, 1992). The
raised wider beds provide an effective 1.5 m (60 inch) plant
ing surface. Research also showed that plant population
248 Proc. Fla. State Hort. Soc. 107: 1994.
Figure 1. Sweet onions planted on wide beds ready for harvest.
around 198,000 plants/ha (80,000 plants per acre) is near the
optimum for early yield of large onions. Higher populations
tend to reduce earliness as the competition increases. Six
rows of onions (approximately 25 cm (10 inches)) on the
wide beds with slightly less than 15 cm (6 inch) spacing (Fig.
1) provides the optimum plant population (Unpublished da
ta). Yields of over 103 metric tons/ha (46 tons per acre) of
large onions (greater than 76 mm (3 inches)) have been at
tained using this system.
Onions are susceptible to disease and a timely spray pro
gram must be incorporated into the production system. Ro
tating iprodione (Rovral®) with either chlorothalonil
(Bravo®), or Maneb fungicides on a 7 to 10 day schedule has
been satisfactory. Weed control can be accomplished by using
DCPA (Dacthal® W-75) and oxyfluorfen (Goal® 1.6E). This can give weed free beds for 150 days after transplanting.
Presently, 56-112 kg N/ha (50-100 lb N/acre) is recom
mended for sweet onions. No response to extra nitrogen was
found over the 3 year period 1989-91 (Hensel and Shumaker,
1990,1992). Potassium and phosphorus should be applied ac
cording to soil test levels. Sulfur is not presently a limiting nu
trient factor in the Hastings area. Excess sulfur is generally
associated with high levels of pungency in onions. Therefore,
sulfur free fertilizer is recommended.
Planting Dates. The date of planting is a very important
consideration for earliness. For the 1993-94 season there was
Table 1. Effect of planting date for four cultivars on yield of onions. 1993-94.
Planting dates
12/1/93 12/16/93 1/3/94
Cultivar' 2-3 in >3 in 2-3 in >3in 2-3 in >3 in
Sweet Dixie
Rio Bravo
Mr. Max
Granex 33
3.2X
5.0
6.9
5.3
30.3
21.5
20.1
19.4
---YieldT/A
6.0
8.1
9.1
6.4
20.6
15.3
14.2
15.4
8.6
12.0
11.9
10.6
10.0
6.8
7.1
8.3
'Seed for Sweet Dixie, Rio Bravo, and Mr. Max supplied by Rio Colorado
Seed Company and Granex 33 by Asgrow Seed Company.
"Significance: 2-3 in >3 in
Cultivars *** ***
Planting date *** ***
V X PD NS **
Significance denoted by F test values: ** at 1 % level, *** 0.1 % level, and NS
as not significant.
a significant effect of planting date for all varieties and a sig nificant interaction between varieties and planting dates for
size fraction greater than 76 mm (3 inches) (Table 1). For
Sweet Dixie, a delay in planting beyond December 1, resulted
in about 1.5 metric tons/ha/day (0.67 ton per acre per day)
less yield of large onions. The harvest date for this test was
April 7, 1994, which was considered early in the season.
Growers and Growing Area. The Hastings Tri-County area in
North East Florida has long been a major vegetable produc
tion region with significant acreages of potatoes and cabbage,
and this is the area where the St. Augustine Sweet Onions are
grown. The successful sweet onion work at Hastings-REC, in
cooperation with area growers, led to a February, 1991 meet
ing concerning options available for curing of sweet onions.
Arrangements were coordinated by the Agricultural and Bio
logical Engineering Department which allowed several grow
ers to rent drying equipment from a Levy County peanut
shelter in April, 1991.
Curing and marketing of sweet onions that season and the
following by a few growers were marginal. The growers real
ized that to be successful they would need to organize and
work together closely with IFAS, DACS, and FFVA.
In the summer of 1993, IFAS county extension agents in
the Hastings area notified all vegetable growers (mailing to
100 growers) of a meeting to discuss the potential of sweet on
ion production in the area. This meeting led to the formation
of the St. Augustine Onion Growers Exchange in the fall of
1993. The exchange is composed of nine growers: Tommy
and Jerry Beach; Charles and Mike Burrell; David and Rich
ard Jones; Wallace Inman; Frank Robinson; Gregg Barnard;
Frank Johns; Danny Johns; and John Howie. All are potato
growers, except Gregg Barnard, who also grows watermelons
and bell peppers. The locations where these nine growers
grow sweet onions are indicated in Fig. 2.
Following the organization of the Exchange a top priority
was the promotion of the onions in order to create consumer
awareness of this new product and its availability. The St. Au
gustine Sweet Onions received extensive local, state and na
tional coverage through magazines, newspapers, radio, and
television. The Exchange also made presentations before the
St. Augustine City Commission and the St. Johns County
Commission to promote their onions. The St. Augustine City
Commission adopted a resolution congratulating the Ex
change for using the name St. Augustine Sweets and the logo
design.
Harvest and Postharvest Methods. Although premium early
crop prices often motivate growers to dig early (i.e. short mar
ket window prior to Vidalia harvest season), the condition of
the crop, the weather, and the grower's knowledge and expe
rience with the crop should be the factors determining in
when to harvest. In general, the crop is ready to harvest when
10 to 20 percent of the plant tops have fallen over (Maw et al.,
1993). The crop should be harvested at the optimum crop
maturity and when good harvest weather condition is avail
able. The quality of the crop at harvest determines the quality
at packing. Quality was of utmost importance during this first
year of commercial marketing to insure a future position in
the marketplace.
When the decision to harvest was made, the onion tops
were rolled down with a tractor-towed drum roller. Then the
onions were undercut with a tractor-mounted cutter bar. Af
ter the initial machinery operations, the harvest became labor
intensive.
Proc. Fla. State Hort. Soc. 107: 1994. 249
st. Augustine
Figure 2. Location of the nine members of the St. Augustine Onion Grow
ers Exchange, Inc.
The onions were pulled from the ground by hand and the
roots and tops were clipped with hand clippers (Fig. 3). The
harvest worker served a very important role in the initial grad
ing and sizing, which ultimately determined the success of the
final pack out. The length of the roots and tops, the size, and
shape of the onions had to meet established standards
(Chance et al., 1993). Undesirable onions were left in the
field. Onions selected for harvest were placed in 19 liter (5
gal) plastic buckets. Some growers chose to transfer the on
ions from the buckets to burlap bags. If the weather permit-
Figure 3. Hand harvest of onions in field near Hastings, FL.
ted, onions were allowed to air dry for a period of time in
these burlap bags.
In Florida and other Southeastern States field curing, is
not feasible, but there are several potential artificial curing
methods (Buffingtonetal., 1981). Curing with forced, heated
air at 35°C (95°F) for up to 48 hours is effective. Curing is a
treatment to dry the outer surfaces and neck of an onion and
results in surface layers of onion tissue becoming less perme
able to moisture loss and more resistant to entry of disease or
ganisms. Curing recommendations provided by USDA Ag.
Handbook 66 (Hardenburg et al., 1986) suggest the best skin
color develops with curing between 24°C (75°F) and 35°C
(95°F). Onions are considered cured when the neck is tight
and the outer scales are dry and will rustle when touched.
This condition is reached when onions have lost 3 to 5 per
cent of their weight.
Forced, heated air was provided by drying fan/heater
units connected to drying wagons (Fig. 3). Two types of dry
ing wagons were used, although both perform similar func
tions. A few growers purchased onion drying wagons, which
have a heavier suspension system, hydraulic dump cylinder,
and wooden dumping gate. Others leased peanut drying wag
ons and heater/fan units from the Levy County peanut
sheller and the equipment was transported to Hastings. This
arrangement allowed the onion growers the ability to cure on
ions this first year without a major capital investment and pro
vided the peanut sheller a positive cash flow with otherwise
idle equipment prior to the peanut harvest season.
Both type wagons have false floors which are perforated.
Air enters beneath the false floor from a flexible canvas duct
that connects the wagon to the drying fan/heater unit. The
propane-heated air passes upward through the layer of bulk
onions and exists the open trailer top.
After the buckets or burlap bags of onions were emptied
into drying wagons, it was important to connect the wagon to
the dryer fans immediately and initiate the airflow. Leaving
the onions in a wagon without airflow and initiation of curing
greatly increased the opportunity for respiration heating, dis
ease development, and sprouting.
The management of the curing process was very impor
tant. The curing time, amount of airflow, temperature, and
relative humidity of the curing air are critical elements that
were controlled. The outside air conditions dictate the re
quired air temperature rise, as well as the time required for
complete curing. The heater/fan units provided a fan capac
ity of 15 to 24 cubic meters per minute of air flow per square
meter of drying floor (50 to 80 cubic feet per minute per
square foot) while operating against static pressure of 186 to
311 pascals (0.75 to 1.25 inches water). The manufacturing
literature on the drying systems indicated a curing time of 12-
25 hours, at a cost of approximately $5.52 per metric ton
($0.25 per 1001b onions).
The optimum air temperature for curing is between 24°C
(75°F) and 35°C (95°F) with a relative humidity between 55
and 80%. The growers were cautioned to never attempt to in
crease the temperature above 35°C (95°F) in order to speed
the curing process. To prevent over-drying early in the har
vest season when the outside air temperature was often cool,
the growers were advised to limit maximum temperature rise
of curing air (produced by the heater) to 5°C (10°F) to 8°C
(15°F) above the outside temperature. This advice was neces
sary to prevent the relative humidity of the curing air from
falling below the lower limit. As rule of thumb, a 8°C (15°F)
250 Proc. Fla. State Hort. Soc. 107: 1994.
Table 2. Desired Curing Temperature, °F
Outside Temperature, °F
40
50
60
70
80
90
Outside
90%
Relative Humidity
60%
Desired Curing Temperature7,
65
70
75
80
85
95
60
65
70
75
80y
90y
30% ;
op ||
55 I 60 I 65 1 70> 1 80y I 90y 1
The amount of added heat needed is based on outside temperature and
outside relative humidity. For example, if the outside temperature is 60°F
and the outside relative humidity is 60%, the desired temperature is 70°F
This means that 10°F of added heat is needed.
'"No additional heat is needed, for example, once the outside temperature
reaches 70°F and the outside relative humidity drops to 30%.
rise in temperature will lower the relative humidity by 40%.
Table 2 was designed to assist growers in the selection of the
maximum curing temperature rise above the ambient tem
perature depending on the relative humidity of the ambient
air. The required overnight thermostat temperature setting
was normally lower than the daytime temperature setting.
In addition to the curing temperature management, con
trol of the maximum depth of onions was important to insure
neither the available fan capacity nor the structural strength
of the drying wagon were exceeded. As the depth increases,
the airflow decreases because there are more onions per
square foot of curing floor. The increased depth raises the
static pressure, causing the fan to deliver less air. The static
pressure could be measured to determine if high static pres
sure was reducing the air flow. If so, then the depth of onions
was reduced. More uniform drying results when onions are
distributed evenly over the entire drying trailer. Mounding or
heaping the onions to increase trailer capacity results in non-
uniform curing. When peanut drying wagons were used, the
manufacturer's recommended drying depth for grain was
used so as not to exceed load capacity of the wagon.
To avoid over-drying, frequent quality control checks
were required to determine when the onions had lost be
tween 3 to 5% of their weight. The curing process was stopped
when the neck was tight and the outer scales were dry and rus
tled when touched. The onions near the bottom of the wag
on, where the drying air entered, dried first and reached the
highest temperature. Therefore, when sampling a batch to
determine if curing was complete, onions near or next to the
Figure 5. Unloading of onion wagon after completion of curing.
perforated floor at the bottom of the wagon were sampled us
ing the dump door in addition to samples from the top layer
of onions.
Handling and Packing. After curing, the bulk-loaded on
ions were unloaded from the wagons onto a packing line (Fig.
5). The onion wagons provided an advantage because of the
hydraulic dump cylinder. To unload the peanut wagons a
forklift was used to elevate one end which permitted the on
ions to flow out onto the pickup conveyor of the packing line.
The Exchange made arrangements for the purchase and
construction of a packing line suitable for onions. The line
was located in a warehouse at an Exchange member's farm
near Hastings. The packing line consisted of a pickup convey
or, initial manual grading conveyor, roller brushes and ex
haust fans to remove scales, debris and for cleaning, a belt
sizer, manual grading conveyor (with manually applied dis
tinctive logo stickers, Fig. 6), mechanical weight sizers for 23
kg (50 lb) boxes of onions over 76 mm (3 inch), and take off
conveyors for culls. In addition, a bagger unit was provided to
Figure 4. Drying wagon and drying fan/heater used for curing onions.
Proc. Fla. State Hort. Soc. 107: 1994.
line.
Figure 6. Product identification logos attached to onions leaving packing
251
Figure 7. Dr. Hensel holding St. Augustine Sweet Onions above shipping
containers.
place medium size onions between 51-76 mm (2-3 inch) in
bags. These bags were not sold as St. Augustine Sweets.
Surface injuries made in the field by cuts, punctures, and
wounds from snippers and fingernails were eliminated dur
ing grading. Bruising injuries are made by impact shocks or
vibration damage in the field or on the packing line. Bruising
causes superficial cracks in the outer scales of the onions, al
lowing bacteria and mold organisms to penetrate and break
down the internal tissues and results in decayed onions. Bruis
ing may not show up before the onion is shipped but can sig
nificantly reduce the onion quality and shelf life. Efforts to
reduce bruising included careful management of harvest and
postharvest operations and education of the workers on the
proper handling and fragile nature of onions. Every effort was
made to reduce drop heights and to pad surfaces on the pack
ing line. Onions can be damaged during harvest, handling,
curing, and grading.
The exchange designed and purchased an excellent ship
ping container (Fig. 7). This container provided beautiful St.
Augustine Sweet Onion artwork as well as structural integrity
and proper venting of adequate ventilation. These 22.68 kg
(50 lb), 40 x 50 x 30 cm (15.5 x 19.5 x 12 inch) containers
were hand-stacked on pallets with six cartons per layer, three
layers high. After packing, the pallets were transported to the
buyer's warehouse in refrigerated produce trailers. The
USDA Ag. Handbook 66 (Hardenburg et al., 1986) recom
mended storage conditions (after curing) are temperature,
0°C (32°F) and relative humidity, 65 to 70 percent.
Grower Organization and Marketing. Efforts to provide assis
tance to sweet onion growers were first initiated with those in
terested individuals at an extension team meeting in the late
summer of 1993. At this first meeting growers expressed a
general desire to find an organizational structure that would
enable them to collectively develop a sweet onion production
and marketing program. FFVA staff member Reggie Brown
attended the early meetings and presented the opportunities
for the group within an agricultural marketing cooperative
act. The cooperative corporate approach was endorsed by
those present and FFVA staff were asked to develop incorpo
ration documents and bylaws for the group to review as the St.
Augustine Onion Growers Exchange, Inc. This organization
was duly incorporated in the State of Florida and its board of
directors and officers were elected on October 12, 1993.
Figure 8. Registered trademark and identifying logo of the St. Augustine
Onion Growers Exchange, Inc.
The immediate concern after organizing was to collective
ly develop a functional business plan and marketing program
for the sweet onion crop. Extensive discussion was held on the
key issues to develop these and subcommittees of the board
were appointed to refine and present these to the Exchange.
The business plan included the purchase and refurbishing of
a packing line and the proposals to fund such operation by
the group. The marketing effort included the initial contact
with the Marketing Division, DACS, and the development of
a series of potential identity logos and names for the onions.
Extensive discussion was held to formulate an agreement on
the marketing program. The key issues considered were qual
ity standards, policies in regard to brand name use, and a mar
keting program for the 1994 crop.
The marketing program primary mission was to develop a
strategy to build identity for a premium sweet onion. A logo
using the traditional symbol of St. Augustine, the Conquista
dor, was chosen to identify the St. Augustine Sweet Onion
(Fig. 8). The mark was incorporated into packaging, promo
tional materials and media efforts to establish consumer and
buyer recognition of the onion. The mark has been trade-
marked and will be strongly protected by the Exchange to in
sure that only premium onions grown by Exchange members
are marketed under the mark.
Efforts to develop a market were initially concentrated in
Northeast Florida. Two major supermarket chains were po
tential marketers of the product. Discussion began with the
regional produce merchandising team for Publix in Jackson
ville. They were open to developing a regional item provided
it would not conflict with their traditional merchandising of
Vidalia onions.
The St. Augustine Sweet Onion production program en
abled the Exchange to precede the Vidalia deal by approxi-
252 Proc. Fla. State Hort. Soc. 107: 1994.
mately 3-4 weeks, thus providing a narrow window of
opportunity for sales. In the interest of providing incentives
for Publix to promote the St. Augustine Sweet onion, the Ex
change agreed to give Publix an exclusive on the branded
product. Extension Agents in the area played a key role in
supporting the Exchange through their network of media
contacts.
Initial harvest and packing of the onions were extremely
well covered by regional television and newspapers, providing
consumers awareness of the product and its availability
through the local Publix supermarkets.
Publix supermarket's regional merchandisers provided
additional support for the program by encouraging the Lake
land Produce Division Distribution Center to handle the
product. All premium branded onions were successfully mar
keted through Publix and efforts are currently under way to
expand production by over 300% in 1995. The ongoing rela
tionship with Publix will continue with additional regional
warehouses to be included.
Conclusion
This paper presented the background information con
cerning the people, effort, equipment, and procedures that
were necessary for the successful initial marketing of St. Au
gustine Sweet Onions by the St. Augustine Onion Growers Ex
change, Inc. This relatively small venture established a
distinctive product with consumers and demonstrated that
Florida can indeed produce a quality sweet onion. The ex
change members realized success would require, in addition
to hard work, organization and cooperation with each other
and with IFAS, DACS, and FFVA. The ultimate goal of the ex
change is the long-term viability of growing and marketing
high quality sweet onions. The exchange plans to improve
upon the initial success through expansion of acreage, in
creased product promotion, expanded market opportunities,
and improvements in harvest and postharvest operations to
insure the highest quality product. The success of the St. Au
gustine Sweet Onion provides a new component to Florida's
agriculture industry and provides the consumers with an ex
cellent, nutritional product.
Literature Cited
Buffington, D. E., S. K. SastryJ. C. Gustashaw,Jr. and D. S. Burgis. 1981. Ar
tificial Curing and Storage of Florida Onions. Transaction of the Am. Soc.
of Agric. Eng. Vol. 24. No. 3, pp. 782-788.
Chance, W. O., D. M. Granberry and W. J. McLaurin. 1993. Dry Bulb Onions-
Commercial Vegetable Production. U. of GA, Coop. Ext. Service. Horti
cultural Cir. C-801.
Hardenburg, R. E., A. E. Watada and C. Y. Wang. 1986. The commercial stor
age of fruits, vegetables, and florist and nursery stocks. Agricultural Hand
book No. 66. U.S. Department of Agriculture. Washington, D.C.
Hensel, D. R. andj. R. Shumaker. 1990. Plant bed configuration, fertilization
rate and application method, and cultivar effects on sweet onion produc
tion. Proc. Fla. State Hort. Soc. 103:105-107.
Hensel, D. R. andj. R. Shumaker. 1992. Evaluation of cultural practices, ni
trogen rates, and cultivar selection for sweet onion production in north
east Florida. Proc. Fla. State Hort. Soc. 105:338-340.
Maw, B. W., E. W. Tollner, D. A. Smittle and Y. C. Hung. 1993. Curing Vidalia
Onions. Am. Soc. of Agric. Eng. Paper No. 93-1043. Spokane, WA.
Proc. Fla. State Hort. Soc. 107: 253-256. 1994.
CHANGES IN THE SACCHARIDE COMPOSITION OF CITRUS JUICE AND ANATOMICAL
FRACTIONS DURING FRUIT MATURATION
Paul F. Cancalon
Florida Department of Citrus
Scientific Research Department
Citrus Research and Education Center
700 Experiment Station Road
Lake Alfred, Florida 33850
Abstract. To understand variations in juice composition, the
sugars and organic acids of several orange subfractions were
examined during the development and maturation of the fruit.
The fractions included: flavedo, albedo, segment wall mem
branes and juice. Saccharides were analyzed by HPLC and or
ganic acids by capillary electrophoresis. The increase in
sugar concentrations occurred mainly during the first part of
the season, and was very significant since in most fractions
they tripled or quadrupled. During the winter, the sugar con
centrations plateaued reflecting the formation of sucrose from
preexisting glucose and fructose. Degree Brix values did not
increase to the same extent due to the sharp decrease in citric
acid concentration. In immature fruits, this acid is the main de
terminant of the °Brix. It is only at later times that sugars
played a major role in setting the °Brix.
Orange juice composition can vary considerably. The rea
sons for those changes include: the plant cultivar, the maturi
ty of the fruit, the type of extractor used or the quality of
extraction and finishing (Attaway and Carter, 1975; Carter et
al. 1975; Rebeck, 1990). Albrigo and Carter (1977) examined
in details the influence of the structure of citrus fruits on pro
cessing and juice production. Different chemicals are present
in each subfraction (Waterman and Grundon, 1983)and un
der certain circumstances may be found in the juice in various
amounts. The flavedo is rich in colored carotenoids (Ting
and Hendrickson, 1968; 1969) and oils (Schneider, 1968).
The albedo contains the pectic material (Rouse et al., 1962 a;
b). Segment walls accumulate limonin (Scott, 1970). The
juice vesicles themselves contain most of the sugars and ami-
no acids as well as almost all of the organic acids. We have
seen previously that most of the "non-juice" chemicals of pulp
wash (PW) are extracted from the segment walls (Cancalon
and Attaway, 1993). Sugars represent the most valuable com
pounds in oranges. As early as 1948, Curl and Veldhuis
showed the presence of glucose, fructose, sucrose in Valencia
orange juice in the 1/1/2 ratios, if expressed in grams or 1/
1/1 if expressed in moles. However, as pointed out by Mc-
Cready (1977), the juice contains less than 50% of the total
sugars. The peel contains as much as 20%, the membrane
10% and juice sacs 20%. The proportions vary considerably
during the growth and maturation period. Seasonal changes
Proc. Fla. State Hort. Soc. 107: 1994. 253