Citrus Nutrition and Quality - ACS Publications - American Chemical

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12 Quality of Citrus Specialty Products Dried Pulp, Peel Oils, Pulp-Wash Solids, Dried Juice Sacs ROBERT J. BRADDOCK

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University of Florida, Institute of Food and Agricultural Sciences, Agricultural Research and Education Center, P.O. Box 1088, Lake Alfred, FL 33850 Expansion of processed citrus products into world markets has increased production and processing of citrus in those areas of the world where the climate is suitable for the growth of the crop. Large scale manufacturing of juices and concentrate creates waste and necessitates utilization of the remaining portions of the fruit as by-products or specialty products. Juice and concentrate quality is controlled by regulations, resulting in manufacture to uniform standards worldwide; however, less control is exercised over certain by-products and specialty products. Some of the factors important to quality of the specialty products, dried pulp, peel oils, pulp-wash solids, and dried juice sacs will be included in the following discussion. Dried Pulp and Pellets Data from a statistical report (1) indicated that over one million tons of dried citrus pulp and pellets were produced during a recent season from the Florida crop, which was about 70% of total U. S. citrus production. This by-product is important to the f u n c t i o n of the c i t r u s processing i n d u s t r y and to many l i v e s t o c k producers who use i t as a c a t t l e feed supplement. The p e e l , i n t e r n a l membranes, ruptured j u i c e v e s i c l e s and seed residue remaining a f t e r j u i c e e x t r a c t i o n represent the raw m a t e r i a l for production of d r i e d c i t r u s pulp. This r e s i d u e , i n i t s wet s t a t e , contains 75-85% water and ferments or sours r e a d i l y because of the presence of soluble sugars. The d i f f i c u l t y of handling t h i s wet m a t e r i a l n e c e s s i t a t e s dehydration to a moisture content i n the range of 107 water. Once d r i e d , i f proper precautions are taken to maintain dry c o n d i t i o n s , the product may be handled, stored, and shipped i n a manner s i m i l a r to other dry feed s t u f f s . o

0-8412-0595-7/80/47-143-273$05.00/0 © 1980 American Chemical Society In Citrus Nutrition and Quality; Nagy, S., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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Particle size. Uniform p a r t i c l e s i z e i s important during dehydration. I f large pieces are present, d r y i n g c o n d i t i o n s must be a l t e r e d to i n c l u d e longer d r y i n g times; s i n c e f i n e p a r t i c l e s and dust which dry r a p i d l y may burn and c o n t r i b u t e to product losses and a i r p o l l u t i o n problems. Figure 1 i l l u s t r a t e s a t y p i c a l p a r t i c l e s i z e d i s t r i b u t i o n of some feed m i l l pulp f r a c t i o n s . The d i s t r i b u t i o n of wet press cake and d r i e d pulp f r a c t i o n s were s i m i l a r i n that a f r a c t i o n of the p a r t i c l e s were about 1 mm w i t h another f r a c t i o n d i s t r i buted i n the 2 to 5 mm range (2). The major p a r t i c l e d i s t r i butions of the meal and dust p o r t i o n s of the f i n e s were below 1 mm. Moisture content. The importance of maintaining a low moisture content f o r e i t h e r d r i e d loose pulp or p e l l e t s has been documented (_3). F i r e or smouldering i s a d i s t i n c t danger i n feed m i l l operations or storage f a c i l i t i e s and u s u a l l y occurs when the moisture content of the d r i e d products exceeds the recommended 107 moisture l e v e l . Moisture e q u i l i b r i u m during storage of loose, d r i e d c i t r u s pulp at 607o r e l a t i v e humidity (RH) , 2 6 ° C , has been shown to occur at about 11 to 127 moisture ( 4 ) . Other researchers have shown t h i s e q u i l i b r i u m to take from 2 to 3 weeks ( 5 ) . For samples of loose commercial pulp, i t was shown that above 757 RH, at 25°C, moisture e q u i l i b r i u m occurred i n about 2 weeks (2^). However, less time was r e q u i r e d at lower r e l a t i v e h u m i d i t i e s (30 and 50J ) , with e q u i l i b r i u m moistures near the i n i t i a l moisture content of the sample ( 8 . 8 7 ) . Moisture e q u i l i b r i u m of d r i e d p e l l e t s takes longer to occur than f o r loose pulp. Results shown i n Figure 2 i n d i c a t e that above 757 RH at 25°C, e q u i l i b r i u m had not occurred w i t h i n 28 days. The samples at 31 and 527o RH reached e q u i l i b r i u m w i t h i n one week. Mold growth i n the p e l l e t s at 90 and 1007 RH atmospheres commenced a f t e r 28 and 25 days, r e s p e c t i v e l y . No mold growth occurred w i t h i n 28 days i n the other samples. In order to maint a i n the moisture content of d r i e d pulp or p e l l e t s i n the range of 10 to 127o, contact with a i r of g r e a t e r than 50 to 607 RH at 25°C should be minimized Other p r o p e r t i e s . Some p r o p e r t i e s of two common-sized comm e r c i a l p e l l e t s are i n c l u d e d i n Table I. The bulk d e n s i t y of p e l l e t s i s approximately twice the value f o r loose pulp. The 7o v o i d space r e f l e c t s the compaction e f f e c t o c c u r r i n g as a r e s u l t of p e l l e t i z i n g . Savings i n c o s t s f o r handling and s h i p p i n g occur as a r e s u l t of manufacturing p e l l e t s because of a large decrease i n volume. There i s a l s o some space advantage i n making smaller diameter p e l l e t s with g r e a t e r bulk d e n s i t y . N u t r i e n t composition. The n u t r i t i o n a l q u a l i t y of d r i e d c i t r u s pulp may be a f f e c t e d by p r o c e s s i n g c o n d i t i o n s , p a r t i c u l a r l y dehydration temperatures. Pulp d r i e d with dryer e x i t - s t a c k gas temperatures greater than 143°C shows c a r a m e l i z a t i o n or browning. Ammerman et a l . (6) and Chapman et a l . (]_) have shown that a o

0

0

o

0

Q

o

o

In Citrus Nutrition and Quality; Nagy, S., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

BRADDOCK

Citrus Specialty

Products

275

lu

-I Q_

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< co

Figure 1.

Particle size distribution of citrus press cake, dried pulp, meal, and dust (2)

0

2

4

6

β

10 12 14 16 18 20 2 2 24 26 26 3 0

TIME, DAYS Figure 2.

Moisture equilibrium of citrus pellets at 25°C and 31, 52, 75, 90, and 100% relative humidity atmospheres

In Citrus Nutrition and Quality; Nagy, S., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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276

CITRUS NUTRITION AND QUALITY

Table I.

Some P r o p e r t i e s of C i t r u s P e l l e t s R e l a t i n g Weight, Area, and Volume (2^)

Pellet Property Pellets/kg

diam.

0.64 cm

0.95 cm

1500

1400

4.5

4.6

7000

6500

1010

1070

625.8

577.6

63.3

60.4

2 Area (cm / p e l l e t ) 2 Area (cm /kg) 3 P e l l e t v o l (cm /kg) 3 Bulk d e n s i t y

(kg/m )

Void space (7o)

In Citrus Nutrition and Quality; Nagy, S., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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12.

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Citrus Specialty

Products

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d r i e d c i t r u s pulp, dark i n c o l o r , i s less p a l a t a b l e and has l e s s n u t r i t i o n a l value due to a reduced d i g e s t i b i l i t y of p r o t e i n and lower energy value. For comparison, the average n u t r i e n t compos i t i o n of a l a r g e number of samples of commercial c i t r u s pulp i s presented i n Table I I . When a study was made by P u l l e y and von Loesecke (8) of d r i e d g r a p e f r u i t pulp manufactured by three types of d r y e r s , they found no s i g n i f i c a n t n u t r i t i o n a l d i f f e r e n c e s between the products except where p r e s s i n g was avoided. However, carotene was almost completely destroyed by the d r y i n g process. I t has been demonstrated that the monohydroxy and dihydroxy-carotenoid f r a c t i o n s of orange and tangerine flavedo were e a s i l y destroyed during d r y i n g ( 9 ) . E l e v a t e d d r y i n g temperatures increased pigment l o s s e s . Samples d r i e d at e x i t - s t a c k gas temperatures of 99 and 110°C were l i g h t i n c o l o r and showed the l e a s t loss of pigment during d r y i n g . Extensive d e s t r u c t i o n of pigment occurred i n other samples d r i e d at an e x i t gas temperature of 143°C. Since 143°C i s widely used i n commercial feed m i l l s , a réévaluation of c i t r u s pulp d r y i n g temperatures i s suggested. Peel O i l s The economic importance of the various c i t r u s o i l s has r e s u l t e d i n i n t e n s i v e research d i r e c t e d toward processing methods, compositional analyses, q u a l i t y , and u t i l i z a t i o n . E a r l y work d e s c r i b e d recovery methods and some c h a r a c t e r i s t i c s r e l a t e d to q u a l i t y of c i t r u s peel o i l s i n the United States (10, 11). More r e c e n t l y , c i t r u s p e e l o i l y i e l d and q u a l i t y has been r e l a t e d to p r o c e s s i n g methods (12) and c u l t u r a l p r a c t i c e s (13). Chemical composition. D e t a i l e d compositional data conc e r n i n g the commercially important c i t r u s o i l s can be found i n s e v e r a l reviews. An extensive l i s t of various chemical compounds i d e n t i f i e d as components of orange, g r a p e f r u i t , tangerine, lemon, and lime o i l s has been compiled and d e s c r i b e d i n r e l a t i o n to c e r t a i n f l a v o r p r o p e r t i e s (14). Z i e g l e r (15) d e s c r i b e d some gas l i q u i d chromatography (GLC) techniques u s e f u l f o r analyses of e s s e n t i a l o i l components and reviewed c o n s i d e r a b l e research r e l a t i n g s p e c i f i c compounds to important f l a v o r c h a r a c t e r i s t i c s of o i l s from sweet and b i t t e r orange, bergamot, orange j u i c e , mandarin, g r a p e f r u i t , and limes. In a review of many e s s e n t i a l o i l s and important f l a v o r compounds, some d i s c u s s i o n was devoted to c i t r u s o i l composition and c e r t a i n a n a l y t i c a l methods u s e f u l i n comparing d i f f e r e n t o i l s (16). Use of GLC to determine q u a l i t a t i v e and q u a n t i t a t i v e comp o s i t i o n of v o l a t i l e compounds i n c i t r u s o i l s has become common. However, there are many d i s c r e p a n c i e s i n the l i t e r a t u r e conc e r n i n g the q u a n t i t a t i v e composition of c i t r u s o i l s . Analyses of v o l a t i l e aldehydes are of major importance, because compos i t i o n and q u a n t i t y of these compounds i n f l u e n c e the q u a l i t y and value of c i t r u s o i l s . Compositional d i f f e r e n c e s between

In Citrus Nutrition and Quality; Nagy, S., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

In Citrus Nutrition and Quality; Nagy, S., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Avg.

Range

Avg.

Range

basis

Dry

basis

0

0

2.0-18.4

8.48

Moisture

5.0-6.77

5.42

3.1-11.1

5.02

Ash

(%)

6.51-7.19

6.80

4.9-9.3

6.23

Protein

Nutrients

3.64-4.34

4.08

1.1-11.6

3.69

Ether Extract

12.44-13.94

13.32

6.4-17.8

12.12

Crude Fiber

13-year

69.56-71.48

70.38

54.2-72.3

64.46

N-free Extract

Average N u t r i e n t Composition of C i t r u s Pulp Samples C o l l e c t e d During a Period (6)

Air-dry

Samples (N = 3630)

Table I I .

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12.

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Citrus Specialty

Products

279

aldehydes i n C a l i f o r n i a , F l o r i d a , and I s r a e l i o i l s have been shown (17). Coleman et a l . (18) q u a n t i t a t i v e l y estimated orange essence o i l v o l a t i l e s by GLC and showed a p e c u l i a r absence of o c t a n a l and decanal. Another report estimated the t o t a l amount of o c t a n a l plus hexanal a t 1.297o i n a v o l a t i l e f a c t i o n of comm e r c i a l V a l e n c i a essence o i l , yet d i d not r e p o r t the presence of decanal, a major aldehyde of commercial orange essences and o i l s (19). Other q u a n t i t a t i v e GLC data a l s o shows c o n s i d e r a b l e v a r i a t i o n i n the amounts of s p e c i f i c aldehydes, o c t a n a l and decanal, i n V a l e n c i a orange o i l ( 1 5 , 17, 2 0 , 21). C e r t a i n values have been reported f o r the concentrations of oxygenated compounds i n c i t r u s o i l s using chemical methods, r a t h e r than GLC. Naves (22) reported 317o o c t a n a l , 277o decanal, 67o dodecanal, and 7.57« c i t r a l i n sweet orange o i l . More recentl y , the percentages of aldehydes, e s t e r s , a l c o h o l s , and acids present i n terpeneless c i t r u s o i l s (Table I I I ) have been determined ( 2 3 ) . Processing e f f e c t s . C i t r u s o i l q u a l i t y may be a f f e c t e d by c e r t a i n processing parameters. Some which have been s t u d i e d i n c l u d e e f f e c t s of y i e l d from the f r u i t , the amount of water used during recovery and e x t r a c t i o n , storage of f r u i t p r i o r to proc e s s i n g , blending of f r u i t v a r i e t i e s , and handling the emulsion or f i n i s h e d o i l s (12). The type or blend of f r u i t processed has a s i g n i f i c a n t e f f e c t on o i l q u a l i t y . An important aspect of t h i s v a r i a b l e which can be c o n t r o l l e d would be to avoid processing mandarin or other v a r i e t i e s i n with oranges. Subtle f l a v o r d i f f e r e n c e s , which can be detected by the f l a v o r i s t , may be imparted to orange o i l a d u l t e r a t e d with tangelos, murcotts, temples, or tangerines. A mixture of mandarin f r u i t s with oranges may be detected by u l t r a v i o l e t spectra and r e s u l t s i n i n c o n s i s t e n t f l a v o r q u a l i t y and lower aldehyde contents. The q u a n t i t y of water used to make the o i l - w a t e r emulsion a l s o a f f e c t s q u a l i t y . Aldehyde concentrations decrease with i n c r e a s i n g proportions of aqueous phase i n an emulsion. This decrease may be due to i n s o l u b l e s o l i d s which absorb aldehydes i n the emulsion. However, using large q u a n t i t i e s of water w i l l i n crease o i l y i e l d s . Therefore, a balance should be sought between aldehyde content, water usage, and o i l y i e l d . Current i n d u s t r y water usage f o r o i l recovery v a r i e s widely above and below 28 100 kg f r u i t depending on the type of recovery equipment ( 2 4 , 25). Data by Waters e t a l . (26) have demonstrated that the type of commercial e x t r a c t i o n had a s i g n i f i c a n t i n f l u e n c e on the tocopherol content and the evaporation residue of c i t r u s o i l s . The tocopherol content of midseason orange o i l s followed the order: Brown p e e l shaver (216 ppm), FMC i n - l i n e e x t r a c t o r (126 ppm) and screw press (104 ppm). The method of e x t r a c t i o n i n f l u enced both the evaporation residue and the tocopherol content of orange o i l , the higher the evaporation r e s i d u e , the higher the tocopherol content. Since tocopherol i s a good a n t i o x i d a n t ,

In Citrus Nutrition and Quality; Nagy, S., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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CITRUS NUTRITION AND QUALITY

Table I I I .

Concentrations of Classes of Oxygenated Compounds Present i n Various C i t r u s O i l s (23)

Citrus o i l

Aldehydes

% (wt/wt) of T o t a l O i l Alcohols Esters

Acids

Hamlin orange

1.48

0.35

0.55

0.13

Pineapple orange

1.20

0.26

0.40

0.11

V a l e n c i a orange

1.63

0.27

0.87

0.13

Temple orange

1.87

0.42

0.63

0.30

Dancy tangerine

1.10

0.25

0.47

0.24

Orlando

0.57

1.22

0.59

0.45

Duncan g r a p e f r u i t

1.80

3.26

1.06

0.39

V a l e n c i a essence o i l

1.38

0.91

0.84

0.04

tangelo

In Citrus Nutrition and Quality; Nagy, S., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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12.

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Citrus Specialty

281

Products

the i m p l i c a t i o n here i s that processes may be important to production of s t a b l e o i l s . Those o i l s with more tocopherol would tend to be s t a b l e f o r longer storage periods. Of c u l t u r a l e f f e c t s , f r u i t v a r i e t y probably has the most i n f l u e n c e on o i l q u a l i t y , p a r t i c u l a r l y aldehyde content (12). The aldehyde content of coldpressed o i l of oranges i s highest when made from V a l e n c i a oranges. Mixtures of pineapple and s e e d l i n g oranges y i e l d o i l s with lower aldehyde content; while mixtures of Hamlin and Parson Brown v a r i e t i e s give o i l s with the lowest aldehyde content. The e f f e c t of f r u i t maturity has a major i n f l u e n c e on the q u a l i t y of c i t r u s o i l s . For example, the aldehyde content of coldpressed V a l e n c i a orange o i l decreases by 0.3 to 0.5% i n a normal processing season, aldehyde content of the o i l i s lowest f o r immature and over mature oranges. Late bloom f r u i t w i l l a l s o give an o i l of low aldehyde content. I t i s understandable that f i r m , mature f r u i t of good q u a l i t y produces the best q u a l i t y o i l . Seasonal v a r i a t i o n , r a i n f a l l , f e r t i l i z a t i o n , i r r i g a t i o n , budwood, and r o o t s t o c k a l s o can a f f e c t q u a l i t y and y i e l d but w i l l not be d i s c u s s e d here. D i s t i l l e d and f o l d e d o i l s . Of the d i s t i l l e d o i l s , some mention should be made of q u a l i t y problems o c c u r r i n g during the production of d-limonene from p e e l press l i q u o r or o i l - w a t e r emulsions. These manufacturing processes are d e s c r i b e d i n d e t a i l elsewhere (_3). In p a r t i c u l a r , feed m i l l press l i q u o r or emulsion handling can a f f e c t the q u a l i t y and the y i e l d of d-limonene. At one time i n the i n d u s t r y , the press l i q u o r was p a s t e u r i z e d during o i l s t r i p p i n g p r i o r to h o l d i n g f o r feeding to molasses evaporators. Since the advent of waste heat recovery evaporators, press l i q u o r handling needs c o n s i d e r a b l e improvement in sanitation. For i n s t a n c e , the d i l u t e press l i q u o r i s pumped at ambient temperatures to large storage tanks which feed the evaporator. These tanks may be cleaned once per season or they may never be cleaned. The r e s u l t i s fermentation of the raw press l i q u o r which uses the most fermentable sugars, producing a l c o h o l which i s s t r i p p e d o f f i n t o the heat recovery evaporator condensate. Losses may be high i f limonene i s recovered from t h i s condensate since i t i s not uncommon f o r the condensate to c o n t a i n 10 to 20? a l c o h o l . This a l c o h o l may d i s s o l v e some of the limonene during the recovery process, r e s u l t i n g i n problems when the aqueous condensate ends up at the waste treatment p l a n t . A d d i t i o n a l l y , sour s m e l l i n g aromas may be produced by microorganisms during handling of emulsions or press l i q u o r . These components then may be present i n the f i n i s h e d product. o

In most i n s t a n c e s , storage and handling of f o l d e d o i l s are the same as f o r most s i n g l e - s t r e n g t h o i l s . The major s t a b i l i t y d i f f e r e n c e i s that the f l a v o r of f o l d e d o i l s p e r s i s t s i n products where high temperature i s a f a c t o r , i . e . , candy or baked products. The q u a l i t y of f o l d e d o i l s i s a f u n c t i o n of the f o l d i n g procedure. O i l s f o l d e d by washing with 607 a l c o h o l w i l l d i f f e r from those f o l d e d by d i s t i l l a t i o n under vacuum. For o

In Citrus Nutrition and Quality; Nagy, S., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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CITRUS NUTRITION AND QUALITY

d i s t i l l a t i o n , the time, temperature, and vacuum have major e f f e c t s on the q u a l i t y and y i e l d , as e s t e r i f i c a t i o n and dee s t e r i f i c a t i o n r e a c t i o n s can occur. Losses a l s o occur i n the aldehyde f l a v o r f r a c t i o n as the l e v e l of f o l d i n g i n c r e a s e s . This i s i l l u s t r a t e d i n Figure 3, wherein 40% loss of aldehydes has occurred at t h r e e f o l d c o n c e n t r a t i o n and over 50% loss at t e n f o l d (27). This loss i s q u i t e time-dependent i n a s t i l l under g i v e n temperature-vacuum c o n d i t i o n s ; thus, i t i s indust r i a l p r a c t i c e to perform the d i s t i l l a t i o n as r a p i d l y as p o s s i b l e to minimize losses and q u a l i t y changes.

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Pulp-Wash S o l i d s C i t r u s f r u i t i s processed i n t o s e v e r a l product streams at the time of j u i c e e x t r a c t i o n . The e x t r a c t e d j u i c e goes immediately to f i n i s h e r s where part of the ruptured j u i c e v e s i c l e s , or pulp, i s removed. Because there are s t i l l j u i c e and s o l u b l e s o l i d s remaining i n the f i n i s h e r pulp, f u r t h e r processing allows recovery of t h i s m a t e r i a l (28, 29). The general process c o n s i s t s of mixing water c o n t i n u o u s l y with the j u i c e pulp from the f i n i s h e r , a l l o w i n g j u i c e s o l u b l e s to be leached, or d i s t r i b u t e d i n t o the water, and f i n i s h i n g to separate the pulp and recovered s o l u b l e s . The wash l i q u i d so recovered may be c e n t r i f u g e d to remove p a r t i c u l a t e s and then concentrated by evaporation. This process i s known i n the c i t r u s i n d u s t r y as "pulp-washing" and the recovered s o l u t i o n as "pulp-wash". Pulp-wash concentrate i s an i n t e g r a l part of the c i t r u s by-products i n d u s t r y and i s s o l d world-wide f o r use as c l o u d , f l a v o r , or beverage base purposes. Composition. S c i e n t i f i c data concerning l i q u i d s washed with water from orange j u i c e f i n i s h e r pulp was f i r s t published by Olsen et a l . (30). They s t u d i e d B r i x / a c i d r a t i o s , sucrose, reducing sugars, pH, p e c t i c c o n s t i t u e n t s , t u r b i d i t y , pulp content, a s c o r b i c a c i d , v i s c o s i t y , and f l a v o n o i d content of experimental and commercial samples. C h a r a c t e r i z a t i o n of pulpwash continued with p u b l i c a t i o n of q u a l i t y data (31), examinat i o n of p e c t i c substances (32) , microbiology (33) , and comparison of pulp-wash with orange concentrate (34). G e n e r a l l y , pulp-wash concentrates are s i m i l a r i n composit i o n to orange j u i c e concentrates. In f a c t , i t i s not uncommon for j u i c e e x t r a c t i o n overages to end up i n pulp-wash during commercial o p e r a t i o n s . True pulp-washes i n general do not have the good f l a v o r or c o l o r of j u i c e concentrates. Color scores are s i g n i f i c a n t l y low enough t h a t , f o r the most p a r t , pulpwash c o l o r i s poor. Color measurements have been used e x p e r i mentally i n attempts to measure the amount of pulp-wash present i n true j u i c e concentrates (35). The composition of pulp-wash i s such t h a t , i f both pulpwash and j u i c e are from the same batch of f r u i t , i t may be i n c l u d e d as a component of the product c a l l e d concentrated orange

In Citrus Nutrition and Quality; Nagy, S., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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Figure 3.

Loss of aldehydes during folding of cold-pressed oil (21)

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j u i c e f o r manufacturing ( 3 6 ) . Under F e d e r a l law, the product, f r o z e n concentrated orange j u i c e , may c o n t a i n water e x t r a c t s of excess pulp ( 3 7 ) ; however, i n F l o r i d a , the a d d i t i o n of pulpwash s o l i d s to f r o z e n concentrated orange j u i c e i s p r o h i b i t e d . In a study of y i e l d and recovery of v a r i o u s c i t r u s byproducts, i t was reported that j u i c e f i n i s h e r pulp recovery was about 4 . 4 kg/100 kg of oranges and 2.7 kg/100 kg of g r a p e f r u i t . Commercial recovery of s o l u b l e s o l i d s (ss) as pulp-wash should y i e l d approximately 0.6 kg ss (oranges) and 0.2 kg ss (grapef r u i t ) from 100 kg f r u i t (38). Quality. F r u i t and pulp c o n d i t i o n s are major f a c t o r s a f f e c t i n g pulp-wash q u a l i t y . Handling d i f f i c u l t i e s are o f t e n experienced l a t e i n the season when very mature f r u i t are processed. I f the pulp c o n d i t i o n i s s o f t or f r a g i l e , c o n s i d e r able water s o l u b l e p e c t i n may be e x t r a c t e d during the counterc u r r e n t washing process. This p e c t i n causes l i q u i d s to be v i s c o u s , lowering e x t r a c t i o n e f f i c i e n c i e s i n subsequent washing stages. Viscous pulp-wash l i q u i d s a l s o present handling problems during c o n c e n t r a t i o n i n the evaporators. To a l l e v i a t e handling problems a s s o c i a t e d with h i g h v i s c o s i t i e s , processors now commonly add commercial p e c t o l y t i c enzymes to pulp-wash l i q u i d s p r i o r to c o n c e n t r a t i o n ( 3 £ , 4 0 , 4 1 ) . These enzymes degrade the p e c t i n , lower the v i s c o s i t y of the l i q u i d s , allow c o n c e n t r a t i o n to a uniformly high ss content ( 5 0 - 6 5 ° B ) , and have very l i t t l e e f f e c t on product q u a l i t y ( 4 2 ) . Q u a l i t y c o n t r o l of the process and of the f i n a l product i s d i f f i c u l t , and v a r i e s widely from p l a n t to p l a n t . G e n e r a l l y , f i n i s h e r pressures must be c a r e f u l l y c o n t r o l l e d to avoid e x t r a c t i n g u n d e s i r a b l e f l a v o r s and p e c t i c m a t e r i a l s i n t o the water phase. Process evaporation temperature should be cons i d e r e d an important parameter when good q u a l i t y products are required. I f l i q u i d s are too v i s c o u s , high temperatures may occur because of l o c a l overheating and poor heat t r a n s f e r , r e s u l t i n g i n a "cooked" f l a v o r and browning caused by c a r a m e l i zation. I f heat treatments are i n s u f f i c i e n t , n a t u r a l or added pectinases i n the l i q u i d s w i l l remain a c t i v e and products with poor c l o u d i n g p r o p e r t i e s (and/or g e l a t i o n problems) may be produced. Some q u a l i t y parameters, t y p i c a l of commercial pulp-wash concentrates and d i l u t e l i q u i d s , are i n c l u d e d i n the f o l l o w i n g statements : For 60°B pulp-wash concentrate, a v i s c o s i t y up to 1 0 , 0 0 0 cps ( B r o o k f i e l d with #4 s p i n d l e , 60 rpm, 2 6 . 7 ° C ) and a #2 g e l would be t y p i c a l . V i s c o s i t i e s above 15,000 cps would be cons i d e r e d high, but the range 2 , 0 0 0 to 5,000 cps would be good i f the l i q u i d s had been enzyme t r e a t e d . For a 10°Brix (°B) l i q u i d r e c o n s t i t u t e d from 60°B concent r a t e , c l o u d measured i n i t i a l l y on d i l u t i o n should read not more than 207o l i g h t t r a n s m i s s i o n (T) and more commonly i n the range of 107o T. A f t e r 24 hr at room temperature, cloud values should

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not be g r e a t e r than 35% T. Sinking pulp i n 10°B pulp-wash i s u s u a l l y l e s s than 107 and most o f t e n i s l e s s than 5%. Clarific a t i o n ( s e p a r a t i o n of serum from cloud c o n s t i t u e n t s ) of 10°B l i q u i d s i n a 100 ml graduate c y l i n d e r a f t e r standing 4 hr at room temperature w i l l normally r e s u l t i n a s e p a r a t i o n of from 5 to 20 ml with enzyme t r e a t e d l i q u i d s . At 10°B, serum v i s c o s i t y i s about 5 cps. A concentrate made from non-enzyme treated l i q u i d and then d i l u t e d to 10°B might have a serum v i s c o s i t y of 10 to 12 cps. Recoverable o i l (%> by volume) of 10°B l i q u i d r e c o n s t i t u t e d from concentrate i s u s u a l l y low (0.005 to 0.015%). Pulp-wash normally contains no f l o a t i n g pulp and should be reasonably free of h e s p e r i d i n c r y s t a l s and other d e f e c t s . P e c t i n e s t e r a s e a c t i v i t y should not exceed 5.0 P.E.U. (1 P.E.U. represents 1 meq. e s t e r hydrolyzed per min per ml per °B) (43). Pulp-wash concentrates are produced and handled i n much the same manner as concentrated orange j u i c e s , and commonly are conc e n t r a t e d to 50 to 65°B. The primary use of the concentrates are i n beverage base formulations as c l o u d i n g agents and j u i c e s o l i d s adjuncts. A major f a c t o r important to users of pulp-wash concentrates i s the ease of handling during mixing or blending i n t o the f i n a l beverage. Concentrates i n the lower range of v i s c o s i t i e s (2000 to 5000 cps) should meet t h i s h a n d l i n g requirement. F l a v o r s such as a s t r i n g e n c y or b i t t e r n e s s a s s o c i a ted with immature f r u i t or p e e l j u i c e s should be avoided.

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o

D r i e d J u i c e Sacs The j u i c e v e s i c l e s , or "sacs," remaining a f t e r j u i c e e x t r a c t i o n and pulp-washing may be i n c l u d e d i n the p o r t i o n of peel r e s i d u e d r i e d as c a t t l e feed. However, i t i s f e a s i b l e to recover and u t i l i z e t h i s m a t e r i a l as e i t h e r f r o z e n (_3) or drumd r i e d j u i c e sacs (44). D r i e d c i t r u s j u i c e sacs have e x c e l l e n t water and f a t a b s o r p t i o n c a p a b i l i t i e s , absorbing 10 to 12 times and 4 to 5 times t h e i r weight of water and f a t , r e s p e c t i v e l y . These a b s o r p t i v e p r o p e r t i e s make d r i e d j u i c e sacs v a l u a b l e as e m u l s i f i e r s or binders f o r comminuted meat products l i k e luncheon meats, bologna, sausages, and f r a n k f u r t e r s . I t has been proposed (44) that j u i c e sacs can be processed i n t o e x c e l l e n t t h i c k e n i n g or bodying agents which c o u l d be used by the baking or food processing i n d u s t r i e s . P o t e n t i a l uses f o r j u i c e sacs e x i s t i n the f o l l o w i n g s p e c i a l t y foods: canned or dehydrated g r a v i e s , sauces and puddings, preserves, cookie and pie f i l l i n g s , pet foods, breading mixes f o r f r i e d foods, and a v a r i e t y of other food products. Dehydrated beverage mixes, synthesized j u i c e products, and c e r t a i n i n s t a n t beverages a l s o o f f e r a p o t e n t i a l use f o r d r i e d j u i c e sacs s i n c e f r o z e n j u i c e sacs are c u r r e n t l y used i n c e r t a i n c i t r u s c o n t a i n i n g l i q u i d beverages. Drug formulations which u t i l i z e binders or water

In Citrus Nutrition and Quality; Nagy, S., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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absorbing m a t e r i a l s are a l s o envisioned as a p o s s i b l e market f o r d r i e d j u i c e sacs. Drum d r i e d - j u i c e sacs prepared from e i t h e r oranges or g r a p e f r u i t have a very m i l d , bland f l a v o r with an aroma that only f a i n t l y resembles the f r u i t from which they were prepared. The c o l o r of d r i e d g r a p e f r u i t j u i c e sacs i s white. Those p r e pared from oranges have a c h a r a c t e r i s t i c orange c o l o r which i s unstable i n the presence of l i g h t . C o l o r , however, i s not an important f a c t o r for most proposed uses of t h i s product. If d e s i r e d , the j u i c e sacs could be dyed with c e r t i f i e d food c o l o r s and used i n many food products (45). When stored i n opaque c o n t a i n e r s , the c o l o r w i l l disappear i n 3 to 4 months and become white making i t d i f f i c u l t to d i s t i n g u i s h between j u i c e sacs from e i t h e r oranges or g r a p e f r u i t . The chemical composition of d r i e d orange j u i c e sacs i s as follows (44): crude f i b e r (18.9%), p r o t e i n (9.0%), p e c t i n (20.6%), ash (3.1%), fat 2.0%), moisture (10%), and other mostly carbohydrate m a t e r i a l (36.4%). Another report (46), compared d r i e d j u i c e sac composition with whole peel and core m a t e r i a l and found the three to be s i m i l a r i n composition.

Literature Cited 1. Statistical Summary. Florida Citrus Processor's Assoc., Winter Haven, FL, 1976-77 Season. 2. Braddock, R. J . ; Miller, W. M. Proc. Fla. State Hortic. Soc. 1978, 91, 106. 3. Kesterson, J. W.; Braddock, R. J. "By-Products and Specialty Products of Florida Citrus", Univ. of Fla. Agric. Exp. Stn. Tech. Bull. 784: Gainesville, 1976; 122 pp. 4. Ross, I. J . ; Kiker, C. F. Trans. ASAE, 1967, p. 483. 5. Bissett, O. W.; Veldhuis, M. K. Feedstuffs, 1951, 23 (Sept. 8), 26. 6. Ammerman, C. B.; Hendrickson, R.; Hall, G. M.; Easley, J. F.; Loggins, P. E. Proc. Fla. State Hortic. Soc., 1965, 78, 307. 7. Chapman, H. L.; Ammerman, C. B.; Baker, F. S.; Hentges, J. F.; Hayes, B. W.; Cunha, T. J. "Citrus Feeds for Beef Cattle", Univ. of Fla. Agric. Exp. Stn. Bull. 751: Gainesville, 1972; 34 pp. 8. Pulley, G. N.; von Loesecke, H. W. Food Ind., 1940, 12(6), 621, 100. 9. Braddock, R. J . ; Kesterson, J. W. J. Food Sci., 1974, 39, 712. 10. Hood, S. C. U.S.D.A. Bull. 399, Washington, D. C., 1916; 19 pp. 11. Poore, H. D. USDA Tech. Bull. 241, Washington, D. C., 1932; 30 pp. 12. Kesterson, J. W.; Hendrickson, R.; Braddock, R. J. "Florida Citrus Oils", Univ. of Fla. Agric. Exp. Stn. Tech. Bull. 749: Gainesville, 1971; 180 pp.

In Citrus Nutrition and Quality; Nagy, S., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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13. Kesterson, J. W.; Braddock, R. J. Fruits, 1975, 30(2), 103. 14. Shaw, P. E. In "Citrus Science Technology"; Nagy, S.; Shaw, P. E.; Veldhuis, Μ. Κ., Eds.; AVI: Westport, Conn., 1977; Vol. 1, pp. 427-462. 15. Ziegler, E. Dtsch. Lebensm-Rundsch., 1970, 66(9), 290. 16. Guenther, E.; Gilbertson, G.; Koenig, R. T. Anal. Chem., 1973, 45, 45R. 17. Lifshitz, Α.; Stanley, W. L.; Stepak, Y. J. Food Sci., 1970, 35, 547. 18. Coleman, R. L.; Lund, E. D.; Moshonas, M. G. J. Food Sci., 1969, 34, 610. 19. Shaw, P. E.; Coleman, R. L. J. Agric. Food Chem., 1971, 19, 1276. 20. Shaw, P. E.; Coleman, R. L. J. Agric. Food Chem., 1974, 22, 785. 21. Stanley, W. L.; Ikeda, R. M.; Vannier, S.; Rolle, L. A. J. Food Sci., 1961, 26, 43. 22. Naves, Y-Rene. Perfum. Essent. Oil Rec., 1947, 38(7), 237. 23. Braddock, R. J . ; Kesterson, J. W. J. Food Sci., 1976, 41 1007. 24. Kesterson, J. W.; Braddock, R. J.; Crandall, P. G. Perfum. Flav., 1979, 4(4), 9. 25. Steger, E. S. Citrus Ind. Mag., 1979, 60(8), 25. 26. Waters, R. D.; Kesterson, J. W.; Braddock, R. J. J. Food Sci., 1976, 41, 370. 27. Kesterson, J. W. Unpublished data. 1980. 28. Belk, W. C. Trans. Citrus Eng. Conf., 1964, 10, 19. 29. McKinnis, R. B.; Andrews, R. Α.; Jones, H. L. Trans. Citrus Eng. Conf., 1964, 10, 1. 30. Olsen, R. W.; Wenzel, F. W.; Huggart, R. L. Proc. Fla. State Hortic. Soc., 1958, 71, 266. 31. Huggart, R. L.; Olsen, R. W.; Wenzel, F. W.; Barron, R. W.; Ezell, G. H. Proc. Fla. State Hortic. Soc., 1959, 72, 221. 32. Rouse, A. H.; Atkins, C. D.; Moore, E. L. Proc. Fla. State Hortic. Soc., 1959, 72, 227. 33. Hill, E. C.; Patrick, R. Proc. Fla. State Hortic. Soc., 1959, 72, 233. 34. Wenzel, F. W. Proc. Fla. State Hortic. Soc., 1959, 72, 235. 35. Petrus, D. R.; Dougherty, M. H. J. Food Sci., 1973, 38, 913. 36. State of Florida, Dept. of Citrus. "Official rules affecting the Florida citrus industry", 1975; Ch. 20-64.08. 37. USDA. Standards for Grades of Frozen Concentrated Orange Juice, 1968, 21 CFR 27.109. 38. Kesterson, J. W.; Braddock, R. J.; Crandall, P. G. Citrus Ind. Mag., 1978, 59(5), 17. 39. Braddock, R. J.; Kesterson, J. W. Proc. Fla. State Hortic. Soc., 1974, 87, 310. 40. Braddock, R. J.; Kesterson, J. W. J. Food Sci., 1976, 41, 82. 41. Braddock, R. J.; Kesterson, J. W. Food Technol., 1979, 33(11), 78.

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42· Braddock, R. J . ; Kesterson, J. W. Proc. Fla. State Hortic. Soc., 1975, 88, 292. 43. Praschan, V. C. "Quality Control Manual For Citrus Processing Plants"; Intercit, Inc.: Safety Harbor, FL, 1975; pp. 61-62. 44. Kesterson, J. W.; Braddock, R. J. Food Technol., 1973, 27(2), 50. 45. Braddock, R. J.; Kesterson, J. W. Proc. Fla. State Hortic. Soc., 1973, 86, 261. 46. Ferguson, R. R.; Fox, Κ. I. Trans. Citrus Eng. Conf., 1978, 24, 23. 25, 1980.

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