Synthetic Membranes: Volume II - American Chemical Society

1 Development of a Tomato Juice Concentration System by Reverse Osmosis

Downloaded by UNIV OF CALIFORNIA SAN DIEGO on June 2, 2015 | http://pubs.acs.org Publication Date: May 27, 1981 | doi: 10.1021/bk-1981-0154.ch001

K. ISHII, S. KONOMI, K. KOJIMA, and M. KAI Daicel Chemical Industries, Ltd., 1 Teppo-cho, Sakai-shi, 590, Japan N. UKAI and N. UNO Kagome Co., Ltd., 3-14-15, Nishiki, Naka-ku, Nagoya-shi, 460, Japan

There have been many s t u d i e s on the a p p l i c a t i o n of membrane technology to food i n d u s t r i e s . Few have, however, reached a comm e r c i a l success except those of d a i r y processes ( 1 ) . DAICEL has been studying s i n c e 1971 the a p p l i c a t i o n of its cellulose a c e t a t e RO membranes and polyacrylonitrile UF membranes to food, pharmaceutical, m e d i c a l , paper and other i n d u s t r i e s . As t o the use o f membranes in food i n d u s t r i e s other than d a i r y processes, o n l y two cases were developed to a semicommercial s c a l e , that is, grape juice c o n c e n t r a t i o n f o r wine must and tomato juice c o n c e n t r a t i o n f o r p r o c e s s i n g and storage of the j u i c e till next h a r v e s t . The RO c o n c e n t r a t i o n of f r e s h fruit j u i c e has two diffculties. The one is that the h i g h osmotic pressure of fruit juice prevents c o n c e n t r a t i n g the j u i c e to the r e q u i r e d c o n c e n t r a t i o n , and the other is the l o s s of light f l a v o r . In case o f tomato j u i c e c o n c e n t r a t i o n , the r e q u i r e d product sugar content is ca. 20%, which i s e x c e p t i o n a l l y low enough to be a t t a i n e d by RO process. In a d d i t i o n , the l o s s of l i g h t f l a v o r does not s i g n i f i c a n t l y s p o i l the commercial v a l u e . The expected advantages of membrane process over c o n v e n t i o n a l evaporation process was the improvement of the product q u a l i t y e s p e c i a l l y i n t a s t e and c o l o r . The major problem was to develop a system which produces h i g h q u a l i t y condensed j u i c e without adding t o the cost over that of the c o n v e n t i o n a l process. A j o i n t study s t a r t e d i n 1971 at DAICEL s l a b o r a t o r y , and a f t e r three seasons' f i e l d t e s t s a t Kozakai, F u j i m i and I b a r a g i p l a n t s of Kagome Co., L t d . , a semicommercial equipment was b u i l t a t I b a r a g i p l a n t i n 1975. Since then i t has been producing ca. 1 m /hr of concentrated f r e s h t o mato j u i c e . 1

3

Experimental Tomato j u i c e . D i l u t e d canned tomato paste was used f o r l a b o r a t o r y experiments w i t h 28 cm f l a t membrane c e l l s . For f i e l d t e s t s w i t h t u b u l a r membranes, s t e r i l i z e d f r e s h j u i c e was used. 2

0097-6156/81/0154-0001$05.00/0 © 1981 American Chemical Society In Synthetic Membranes: Volume II; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

2

SYNTHETIC MEMBRANES:

HF

AND

UF

USES

.Membranes. Three d i f f e r e n t grades of.DAICEL's c e l l u l o s e acetate RO membranes, DRS-97, DRS-95 and DRS-90 were used both i n f l a t sheets and tubes. T h e i r NaCl r e j e c t i o n v a l u e s were 97%, 95% and 90%, r e s p e c t i v e l y . Apparatus and equipment. For l a b o r a t o r y experiments, two to s i x f l a t membrane c e l l s of 28 cm e f f e c t i v e area and 0.3 mm chann e l t h i c k n e s s were used i n s e r i e s w i t h a plunger pump of v a r i a b l e output up to 50 1/hr under the pressure of up to 100 Kg/cm . For f i e l d t e s t s , 12 to 192 membrane tubes (1.4 cm i n n e r diameter and 4.5 m by l e n g t h each) were used both i n s e r i e s and p a r a l l e l w i t h one or two plunger pumps of v a r i a b l e output up to 2 m /hr under the pressure of up to 70 Kg/cm . Both a s i n g l e - and a two-stage system were examined. 2


2

3

2

Measurement and a n a l y s i s . The v i s c o s i t y of tomato j u i c e was measured using Tokyokeiki BH type d i s c r o t a t i n g v i s c o s i m e t e r . Sodium c h l o r i d e c o n c e n t r a t i o n was measured u s i n g TOA HA5a e l e c t r i c c o n d u c t i v i t y meter. Sugar c o n c e n t r a t i o n was determined by reversed phase l i q u i d chromatograph w i t h a 4.6 mm99 .9 >99 .9 99 .8 >99 .9 >99 .9

.47 .37 .38 .36 .40 .49

DRS--90 FLUX REJ. m/d %

DRS--95 REJ FLUX m/d % 1.31 1.31 1.24 1.13 1.33 1.34

90.0 97.3 96.7 91.8 99.3 99.6

1 .71 1 .67 1 .64 1 .43 1 .64 1 .73

95 .4 99 .3 99 .2 96 .8 >99 .9 >99 .9

CONDITIONS: MEMBRANE AREA: 28 cm CONCENTRATIONS: 0.35% (NaCl) & 2% (SUGARS) PRESSURE: 40 Kg/cm TEMPERATURE: 25°C 2

2

The sugar content of raw tomato j u i c e i s about 4.5% R e f r a c t i v e Index ( R I ) . The sugar l o s s d u r i n g the c o n c e n t r a t i o n up t o 20% RI must not exceed 5% of the t o t a l sugar contained i n raw j u i c e . From the r e l a t i o n s h i p between c o n c e n t r a t i o n r a t i o and s o l u t e r e t e n t i o n shown i n F i g u r e 1, the sugar r e j e c t i o n o f the membrane to be employed must be over 97%. As l i s t e d i n Table 1, a l l the membranes t e s t e d has r e j e c t i o n v a l u e s higher than ca. 97% f o r glucose, f r u c t o s e and sucrose. The curves i l l u s t r a t e d i n F i g u r e 1 were c a l c u l a t e d from the equation 3 d e r i v e d from mass balance equation 1 and the r e l a t i o n s h i p between v o l u m e t r i c and c o c e n t r a t i o n a l condensation r a t i o s 2 assuming that the membrane r e j e c t i o n i s uniform throughout the whole membrane a r e a . C

V x R e t e n t i o n (%)/100 = CV

0

(1)

0

(C/C ) = ( V / V ) 0

R

(2)

0

R e t e n t i o n (%) = 1 0 0 ( V o / V )

R_1

Loss (%) = 100-Retention (%) where V V Co C R 0

= = = = =

1

= 100(C/C ) " 0

1 / R

(3) (4)

i n i t i a l volume f i n a l volume i n i t i a l concentration f i n a l concentration r e j e c t i o n of the membrane

Table I I demonstrates a l l the membranes t e s t e d have amino a c i d r e j e c t i o n v a l u e s over ca. 97%.

In Synthetic Membranes: Volume II; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

4

SYNTHETIC MEMBRANES: H F AND U F

USES

Table I I MEMBRANE PERFORMANCE ON AMINOACID AQ. SOLN.


SOLUTE

CONTENT (mg%)

SERINE VALINE ARGININE ASPARAGINE GLUT AMINE GLYCINE GLUTAMIC ACID PHENYLALANINE LEUCINE LYSINE

DRS-97

/PRETENTION DRS-95

DRS-90

99.6 99.4 99.7

99.1 99.0 99.2

97.6 97.7 97.6

99.9 99.7

99.6 98.6

98.8 96.5

99.8 99.8 99.6

98.9 99.3 99.2

96.7 97.7 98.1

10.1 9.2 6.8 6.6 6.6 4.8 4.0 2.4 2.1 1.9 z

MEMBRANE AREA: 28 cm CONCENTRATION: 10-20 mg% pH: 4.2 (ADJUSTED BY ADDING CITRIC ACID) PRESSURE: 40 Kg/cm TEMPERATURE: 25°C 2

As f o r sour t a s t i n g o r g a n i c a c i d s , p e r m i s s i b l e l o s s up t o 10% corresponds t o the membrane r e j e c t i o n of no l e s s than 93% which w i l l be a l s o f u l f i l l e d by a l l the membranes t e s t e d as shown i n Table I I I , as more than 90% of the organic a c i d i n tomato j u i c e i s c i t r i c acid. Table I I I MEMBRANE PERFORMANCE ON ACID AQ. SOLUTION

SOLUTE CITRIC ACID LACTIC ACID

DRS--97 FLUX REJ. (m/d) (%) .54 .52

98.0 84.3

DRS--95 REJ. FLUX (m/d) (%) ' 1.50 1.46

97.1 70.0

DRS--90 REJ. FLUX (m/d) (%) 1.93 1.89

94.5 64.0

2

MEMBRANE AREA: 28 cm CONCENTRATION: 0.1 wt% PRESSURE: 40 Kg/cm TEMPERATURE: 25°C CIRCULATION RATE: 8 ml/min CHANNEL THICKNESS: 0.3 mm 2

As t o water f l u x , DRS-90 membrane showed the h i g h e s t value i n a l l cases; we concluded that DRS-90 i s best s u i t e d f o r m i n i mizing the membrane a r e a . By the way, r e l a t i v e l y low f l u x and r e j e c t i o n v a l u e s f o r D-ribose represented i n Table I suggest that D-ribose might have a s p e c i f i c a l l y strong i n t e r a c t i o n w i t h c e l l u l o s e a c e t a t e RO membranes.


Tomato Juice Concentration System


ISHII E T A L .

Figure 2. Osmotic pressure of tomato juice


5

6


HF

AND

UF

USES

Water f l u x . Secondly, the e f f e c t s of f a c t o r s which were ant i c i p a t e d to i n f l u e n c e the membrane performance and the system e f f i c i e n c y were evaluated. They were the osmotic pressure and the v i s c o s i t y of tomato j u i c e as the f u n c t i o n of j u i c e concentrat i o n and feed v e l o c i t y , and o p e r a t i n g pressure. I t was observed that the r i s e i n temperature i n c r e a s e s water f l u x . F i g u r e 2 shows that the osmotic pressure of tomato j u i c e i n creases w i t h c o n c e n t r a t i o n . The osmotic pressure of 20%RI tomato j u i c e was about 20 Kg/cm . F i g u r e 3 i l l u s t r a t e s t h a t water f l u x decreases i n p r o p o r t i o n to the l o g a r i t h m of j u i c e c o n c e n t r a t i o n . This r e l a t i o n s h i p suggests that tomato j u i c e forms a g e l l a y e r which c o n t r o l s the wat e r f l u x . In order to e l i m i n a t e the i n f l u e n c e of osmotic p r e s sure which e x p o n e n t i a l l y r i s e s w i t h j u i c e c o n c e n t r a t i o n , a s e r i e s of experiments was c a r r i e d out, u s i n g a f l a t UF membrane which permeates sugars and s a l t s completely. As i l l u s t r a t e d i n F i g u r e 4, water f l u x i s not s i g n i f i c a n t l y dependent on pressure. Cons i d e r i n g that t h i s UF membrane permeates water i n p r o p o r t i o n to pressure up to 3 Kg/cm when pure water i s f e d , i t can be supposed that water f l u x of tomato j u i c e i s governed by a g e l l a y e r . The e f f e c t of j u i c e v e l o c i t y on water f l u x i s demonstrated i n F i g u r e 5. This e f f e c t i s smaller than a n t i c i p a t e d from the data shown i n F i g u r e 4. One reason of t h i s discrepancy might be the d i f f e r e n c e of the tomato j u i c e used. Fresh j u i c e was used to o b t a i n the r e l a t i o n s h i p summarized i n F i g u r e 5, w h i l e canned t o mato paste was used i n d i l u t e d form f o r the experiments shown i n Figure 4. Another reason might be the d i f f e r e n c e i n flow chann e l s , 1.4 cm i n n e r diameter tube and t h i n f l a t channel of 0.040.06 cm t h i c k n e s s . Although the exact reason i s not c l e a r , the r e s u l t s i l l u s t r a t e d i n F i g u r e 5 suggest that i t i s not necessary to feed f r e s h tomato j u i c e at high v e l o c i t y to get h i g h water flux. F i g u r e 6 represents the r e l a t i o n s h i p between tomato j u i c e v i s c o s i t y and f l o w v e l o c i t y . The measurement was done w i t h the j u i c e prepared from canned paste, u s i n g a d i s c r o t a t i n g v i s c o s i meter. The v a l u e , v i s c o s i t y m u l t i p l i e d by v e l o c i t y was n e a r l y independent of the v e l o c i t y . This suggests that the e f f e c t of f l o w v e l o c i t y on the pressure drop would be s m a l l . This a l l o w s the v a r i a t i o n of j u i c e feed v e l o c i t y i n a wide range without s i g n i f i c a n t change i n pressure drop. In F i g u r e 7, the v i s c o s i t y of tomato j u i c e i n c r e a s e s n e a r l y e x p o n e n t i a l l y w i t h j u i c e c o n c e n t r a t i o n . As a n t i c i p a t e d from the r e s u l t s shown i n Figure 7, pressure drop r i s e s almost exponent i a l l y w i t h i n c r e a s e i n c o n c e n t r a t i o n when f r e s h tomato j u i c e was fed i n a t h i n tube of 0.4 cm inner diameter (Figure 8 ) .


2

2

System

design

I f there were not a pressure drop along w i t h feed f l o w ! I f so, i t would be easy to concentrate any s o l u t i o n up to the con-




ISHII E T A L .

7

JUICE CONCENTRATION (REFRACTIVE INDEX)

Figure 3. Water flux as a function of tomato juice concentration observed by using 12 membrane tubes. Circulating the juice and discarding the permeate.

KEY VELOCITY(cm/s) THICKNESS(cm) 37.8 0.04 • 13.9 0.04 A 0.062 2U.U • 8.97 0.062

•

i

3

2 2

PRESSURE(Kg/cm )

Figure 4. Water flux as a function of pressure. A UF membrane (DUY-L) dcut-off molecular weight was 5 X 10 daltons.

w

a

s

use

T

n

e



8


H F AND U F

USES

R1--9.0

5

-3

.2

L

20

Figure 5.

30 AO 50 60 80 100 120 JUICE FLOW VELOCITY ( cm/sec )

Effect of tomato juiceflowvelocity on waterfluxobserved by using 12 membrane tubes

KEY

•

A •

£

o 8 S

RI 24.8 13.5 4.5

6

4

2

3 4 VELOCITY(cm/sec)

Figure 6. The viscosity of tomato juice decreases in proportion to the reciprocal of juice velocity. Measured at 20°C by using a disc-rotating viscosimeter.



ISHII E T A L .

Figure 7.


The effect of tomato juice concentration on the viscosity observed at 20°C by using a disc-rotating viscosimeter

Figure 8. The effect of tomato juice concentration on the pressure drop of the juiceflowingthrough 4 mm X 4 mL tube at a velocity of 110 cm/s. Temperature: 24°-30°C.



10


H F AND U F

USES

c e n t r a t i o n l i m i t e d by the osmotic pressure of the feed s o l u t i o n , u s i n g a one-through s i n g l e - s t a g e system by simply extending the feed f l o w l e n g t h . P r a c t i c a l l y , however, e f f e c t i v e pressure goes down so much that the membrane performance and/or system e f f i c i e n c y a r e g r e a t l y decreased, and i t i s necessary to i n s e r t a second pump i n the long f l o w l i n e and add pressure and v e l o c i t y to the flow. Some devices t o match the d i v i d e d flows i s necessary. The l o s s of s o l u t e s can be decreased by r e p l a c i n g the second stage membrane w i t h that of higher r e j e c t i o n . I n a s o p h i s t i c a t e d scheme shown i n F i g u r e 9 ( 2 ) , the water f l u x or the o u t l e t conc e n t r a t i o n can be r a i s e d by employing a c o n s i d e r a b l y low r e j e c t i o n membrane a t the o u t l e t stage, w h i l e the use of a high r e j e c t i o n membrane i s r e q u i r e d a t the permeate d i s c a r d i n g stage i n o r der t o minimize the s o l u t e l o s s to the permeate. From the s a n i t a r y p o i n t of view, i t i s necessary to minimize the number of a r t i c l e s , such as r e s e r v o i r s , pumps, v a l v e s , gages e t c . , which may cause contamination and s t a g n a t i o n of f l o w , even i f these a r t i c l e s are s a n i t a r y grade. C i r c u l a t i n g the j u i c e i s a l s o u n d e s i r a b l e f o r s a n i t a r y reason s i n c e i t y i e l d s the everstaying-in-the-system p o r t i o n of the feed j u i c e . A c i r c u l a t i n g system g e n e r a l l y r e q u i r e s more frequent c l e a n i n g and s t e r i l i z a t i o n than a one-through system. As a l r e a d y been discussed i n the preceeding p a r t of t h i s paper, the water f l u x and the pressure drop are both s t r o n g l y a f f e c t e d by the j u i c e c o n c e n t r a t i o n , w h i l e they a r e i n s e n s i t i v e to the feed f l o w r a t e . The l a t t e r c h a r a c t e r i s t i c a l l o w s to i n c r e a s e or decrease the feed f l o w v e l o c i t y a t w i l l w i t h s l i g h t change of water f l u x and pressure drop. This makes i t p o s s i b l e to a t t a i n the r e q u i r e d o u t l e t c o n c e n t r a t i o n w i t h one-through s i n g l e - s t a g e system by simply decreasing the feed r a t e . The decrease i n feed r a t e enhances the r a t i o , water f l u x to feed r a t e , hence r a i s e s the v o l u m e t r i c c o n c e n t r a t i o n r a t i o as e l u c i d a t e d by equation 5: s

(V /V) = V / ( V 0

0

0

- F) = 1/[1-(F/V )]

(5)

0

3

where Vo = feed r a t e (m /hr) = feed v e l o c i t y (m/hr) x cross s e c t i o n (m ) V = o u t l e t r a t e (m ) = o u t l e t v e l o c i t y x cross s e c t i o n F = water removal r a t e (m /m hr) = water f l u x (m /m hr) x membrane area (m ) 2

3

3

2

3

2

2

The o n l y p o s s i b l e problem of decreasing the feed r a t e was whether the t h i c k e n i n g of g e l l a y e r and c o n c e n t r a t i o n p o l a r i z a t i o n due to the slow j u i c e speed would r a i s e the osmotic pressure on the membrane surface as h i g h as the o p e r a t i n g pressure before the bulk c o n c e n t r a t i o n reaches the r e q u i r e d v a l u e . A f t e r the o p e r a t i n g c o n d i t i o n s f o r producing 20% RI concent r a t e d j u i c e had been mastered by u s i n g a 12 to 96 tube s i n g l e pass equipment ( 3 ) , i t was decided to b u i l d a semicommercial system c o n s i s t e d of 1440 tubes. The flow diagram of the semicommer-


1.

ISHII E T A L .


SINGLE-STAGE

-KE>-

CIRCULATING


ONE-THROUGH

-(EH if

TWO-STAGE

Journal of Applied Polymer Symposia

Figure 9.

Four types of concentration systems (2)

i

STERILIZED FRESH JUICE

A

A

A

A

A

A

A

1 -1.2 mHEAT EX. RESERVOIR

UP TO 92(Ucm0xA.5mL)TUBES/LINE 72 TUBES(K.Am2) 20 LINES = 288m 2

x

3

5m/h 3

~T~3£~4 m /h

Figure 10.

Flow diagram of the semicommercial equipment built at Ibaragi Plant, Kagome Co., Ltd


12


H F AND U F

USES

3

c i a l system i s shown i n F i g u r e 10. Approximately 5 m /hr s t e r i l i z e d f r e s h j u i c e i s f i r s t cooled to 30°C. R e s e r v o i r i s s e t i n order to absorb the temporary unbalance of f l o w r a t e s . The j u i c e i s then d i s t r i b u t e d to 20 l i n e s , each equipped w i t h 72 tubes. T o t a l membrane area i s 288 m . About 4 m /hr o f permeate and c a , 1 m /hr of product were expected. I t i s necessary to r i n s e the outer surface of membrane tubes i n order t o prevent m i c r o b i a l growth on i t . 2

3

3


Performance of the semicommercial equipment In order to see how the j u i c e c o n c e n t r a t i o n goes up and how the pressure and the f l o w v e l o c i t y go down as the j u i c e courses the 72 tubes, gages and sampling p o r t s were b u i l t i n 2 l i n e s . T y p i c a l observations are shown i n F i g u r e 11 and 12. Figure 11 demonstrates that the product c o n c e n t r a t i o n r i s e s t o 20% RI by decreasing the feed v e l o c i t y below 50 cm/sec (ca. 290 1/hr. tube) under the i n l e t pressure not more than 65 Kg/cm. I n case the j u i c e was f e d a t 45 cm/sec, the l a s t s e v e r a l tubes h a r d l y cont r i b u t e d t o c o n c e n t r a t i o n , perhaps due to both low pressure caused by pressure drop and h i g h osmotic pressure on the membrane surface as the r e s u l t of the higher c o n c e n t r a t i o n and lower v e locity. As i l l u s t r a t e d i n F i g u r e 12, the slower the feed v e l o c i t y , the more r a p i d l y diminishes the o p e r a t i n g pressure along w i t h the j u i c e f l o w . This behavior corresponds to the experimental observ a t i o n that the v i s c o s i t y of the j u i c e goes up n e a r l y exponent i a l l y w i t h i n c r e a s e i n c o n c e n t r a t i o n and i t goes down almost i n p r o p o r t i o n to the r e c i p r o c a l of feed v e l o c i t y . Considering t h a t the c o n c e n t r a t i o n of the j u i c e s u p p l i e d a t 45 cm/sec h a r d l y r i s e s i n the l a s t s e v e r a l tubes, the osmotic pressure on the membrane surface can be estimated to be 30 t o 35. Kg/cm . While the osmom e t r i c r e s u l t s shown i n F i g u r e 2 suggests that the osmotic p r e s sure of the bulk f l o w j u i c e must be about 20 Kg/cm. The r e l a t i o n s h i p between water f l u x and j u i c e c o n c e n t r a t i o n (Figure 13) observed by the semicommercial equipment i s n e a r l y the same to that observed i n f i e l d t e s t s summarized i n F i g u r e 3. F i g u r e 14 shows that the j u i c e v e l o c i t y dependance of water f l u x i s s i m i l a r to that observed by the f i e l d t e s t s . As i s seen i n Figure 15, the pressure drop rose e x p o n e n t i a l l y w i t h i n c r e a s e i n j u i c e c o n c e n t r a t i o n as had been observed i n the model experiments i l l u s t r a t e d i n F i g u r e 8. The q u a l i t y of the product i s s u p e r i o r to that of the conv e n t i o n a l i n c o l o r and t a s t e as shown i n Table IV. The r e t e n t i o n of s o l u t e s i s more than r e q u i r e d as l i s t e d i n Table V. 2



ISHII E T A L .

JUICE VELOCITY • • 4 5 - 1 0 cm/sec O 52-* 1 2 • 59-15 O 89*26

20


15

- 20

15

10

-

5

—' 0 10

Figure 11.

20 30 AO 50 60 NUMBER OF MEMBRANE TUBES

70

Tomato juice concentration observed along the juice flow through 72 membrane tubes at various feed velocities

70

70

60

50

AO

UJ

30

£ 20

30

JUICE VELOCITY • • A5*10 cm/sec O 52*12 • 59*15 O 89*26

20

10 -

- 10

10

Figure 12.

20 30 AO 50 60 NUMBER OF MEMBRANE TUBES

70

Tomato juice pressure observed along the juice flow through 72 membrane tubes at various feed velocities



14


H F AND U F

USES

Figure 13.

Water flux as the junction of tomato juice concentration. Semicommercial plant (72 membrane tubes X 20 lines).

Figure 14.

Effect of tomato juice flow velocity on water flux. Semicommercial plant (72 membrane tubes X 20 lines).



1.

ISHII E T A L .


15

VELOCITY (cm/sec) ® 300

Synthetic Membranes: Volume II - American Chemical Society

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