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