March, 1941
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
should be stated that while the pressure in the deaerating chamber was only 0.7 inch of mercury, the juice was subsequently exposed to room conditions that permitted some surface aeration. The juice in the sealed containers showed 72 to 80 per cent total gas removal. Furthermore, the containers were type L tin-plate cans lined with a special juice enamel coating. On the basis of these tests we do not feel that deaeration is so essential in the handling and processing of apple juice. Modern apple juice processing is entering its third or fourth season. All processors operating in 1939 in Michigan will process on much larger scales in 1940, and several new plants are now being installed. It is possible that the value of the pack in Michigan may reach a million dollars during the coming year. Packers and prospective packers in other states may equal or surpass the Michigan pack.
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Literature Cited Carpenter, D. C., Pederson, C. S., and Walsh, W. F., IND. ENG. CHEM.,24, 1218-23 (1932). Carpenter, D. C., and Walsh, W. F., N. Y. State Agr. Expt. Sta., Tech. BUZZ.202 (1932). Fabian, F. W., and Marshall, R. E., Mich. Agr. Expt. Sts., Circ. Bull. 98 (1935). Xertesz, 2. I., N. Y. State Agr. Expt. Sta., Bull. 589 (1930). Marshall, R. E., Fruit Products J., 16, No.11, 328-9,331 (1937). Marshall, R. E., Mich. Agr. Expt. Sta. Quart. Bull., 14, No. 3, 208-14 (1932). Marshall, R. E., and Kremer, J. C., Ibid., 20, No. 1, 28-34 (1937). Ibid., 21, No. 1, 12-17 (1938). Mottern, H. H., and Loesecke, H. W. von, Fruit Products J . , 12, NO.6, 325-6 (1933). Pederson, C. S., and Tressler, D. K., IND. ENQ.CHBM.,30, 954-9 (1938). Sipple, H.L.,et al., Fruit Products J . , 19, No. 6, 167-87 (1940).
Citrus Pectates
PROPERTIES, MANUFACTURE, AND USES
W. E. BAIER AND C. W. WILSON California Fruit Growers Exchange, Ontario, Calif.
Pectates result from the saponifkation of pectins. Treatment of commercial pectin with an alkali will form a type of pectate that has been known since 1790. Treatment of protopectin under proper conditions gives a different type of pectate, characterized by more viscosity in aqueous sols, and an alcohol precipitate which is stringy and fibrous rather than amorphous as is the case for ordinary types of pectate. The viscous type may be irreversibly transformed into the less viscous or ordinary type by acid treatment. Chemical relation of the two types is discussed. Both types of pectates form gelatinous salts with alkaline earth or heavy metals. Sodium pectate is a typical hydrophilic colloid, which forms gels a t low concentrations and hence very cheaply. Sols tend to remain on the surface of paper, and
ECTIC substances are widely distributed in plants, being present a t some stage in the growth of practically all vegetable materials. Pectin (the jelly-making substance in fruits) is the only pectic substance so far commercialized. Another, pectic acid, has been widely investigated both chemically and as regards its functions in the plant. Exploration of possible industrial applications of this and related pectic substances is a practically untouched field, Upon treatment with cold dilute alkali (sodium hydroxide), pectin hydrolyzes and depolymerizes to yield moderately viscous, soluble pectates or salts of pectic acid. The corresponding alkaline earth salts are insoluble. The soluble pectates form alcohol precipitates which are granular gels. To obtain pectates, the sols of which are very viscous and which yield precipitates with alcohol that are in the form of visible fibers, it is necessary to start from the plant material in an earlier stage, protopectin. If this protopectin is treated with alkali, 8, pectate results whose alkaline earth salts are likewise insoluble but whose alkali salt solutions are highly viscous and form fibrous precipitates with alcohol.
P
hence pectates are poor adhesives but may be used to prevent substances from sticking to paper, etc. This property may also be used in coating building board to retard penetration of paint. If continuous, pectate films are generally impervious to oils and this property has suggested their use in treatment of paper, the air permeability also being reduced. A crude material is suggested for this work and for such other uses as thickening or concentrating rubber latex or for modifying the rate a t which water quenches heated steel. A wide range of severity of quench may be obtained by varying the concentration. Certain heavy metal pectates are water repellent, and this property suggests a preparation of nonhygroscopic fillers for plastics. Other uses are discussed.
Both types of pectates will withstand boiling in neutral or mildly alkaline solutions without appreciable change, whereas if pectin is boiled with alkali, it is converted largely to nonviscous materials no longer capable of yielding calcium precipitates (6). When acidified, pectates give pectic acid from which only the nonfibrous pectate may be regenerated upon neutralization. Figure 1 shows this relation. Acid P r o t o p e c t i n w P e o t i n
I
I
Cold Alkali
Fibrous Peotat-Pectic
Hot Alkali
Cold Alkali
-4
Nonfibrous Peotate Acid
Acidi
Low-Viscosity Degradation Products (Calcium Salts Soluble)
p a l i Acid
FIGURE 1. RELATION OB'PECTIC SUBSTANCES
I N D U S T R I A L AND E N G I N E E R I N G CHEMISTRY
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The pectates are salts of solid, nonhygroscopic, and nearly insoluble acids. These acids are polymers of galacturonic acid of varying complexity and in addition may contain sugars. The manner of polymerization is such as t o block the aldehyde groups of the galacturonic acid and sugars, and as a consequence the pectates are not readily oxidized. The structural formula of d-galacturonic acid follows; its similarity to the sugars is obvious, and the manner of polymerization t o form pectates is thought t o be like that in which dextrose is linked to form starch and cellulose:
0
p=
OH H OH C-C-C-C-C-CHOH
bases. Pectates of the alkali metals and organic bases are water soluble, while salts of metals of higher valence and of the heavy metals are insoluble.
Fibrous Viscous Pectate As previously mentioned, a pectate may be formed by treatment of protopectin with an alkali. Under controlled conditions of temperature and alkalinity, the pectate may be left in an insoluble form which is readily washed, pressed, and dried. A scheme for producing this insoluble cellulosecontaining intermediate product is outlined in Figure 3.
OH H CITRUB PULP 1000 lb.
PL:3
Pectic Acid Production
'
The nonfibrous pectate may be prepared by the scheme shown in Figure 2. This process may advantageously utilize pectin solution extracted from fruit pulp with hot dilute acid, and is an extension to factory scale of the analytical procedure described by several authors, particularly Carre and Haynes (8) and Wichmann (8).
Grind
I
Soda Ash 20-30 l b
