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Daniel, E. P., and Rutherford, M. B., Food Research, 1, 341-7 (1936). Eddy, C. W., IND. ENQ.CHEM.,28, 480-3 (1936). Ehrlich, F., and Schubert, F., Biochem. Z.,168, 13-66 (1926). Fabian. F. W., and Marshall, R. E., Mich. Agr. Expt. Sta., Circ. B u l l . 98 (revised) (1935). Hauok, H. M., J . Home Econ., 30, 183-7 (1938). Higby, R. H., J . Am. Chem. SOC.,60, 3013-18 (1938). Hucker, G. J., and Pederson, C. S., F a r m Research, 5 , 8-9 (1939). Jackson, J. M., and Olson, F. C. W., Food Research, 5, 409-21
,- a- -m- ,) .
(I
(16) Joslyn, M. A., and Marsh, G. L., IKD.ENG.CHEM.,24, 665-8 (1932); 27, 186-9 (1935). (17) Joslyn, M. A., and Sedky, A., Food Research, 5, 223-32 (1940). (18) Kertesz, Z. I., Ibid., 3, 481-7 (1938). (19) Ibid., 4, 113-16 (1939). (20) Kertesz, 8. I., J . Biol. Chem., 121, 589-97 (1937). (21) Loesecke. H. W. von, Mottern, H. H., and Pulley, G. N., IND. E N G CHEM.,26, 771-3 (1934). (22) Mottern, H. H., and Loesecke, H. W. Yon, Fruit Prod. J . , 12, 325-6 (1933). (23) Natl. Canners Assoc., Canned Food Pack Statistics, 1937, 1938, 1939. (24) Nelson, E. K., and Mottern, H. H., J . Am. Chem. Soc., 56, 1238-9 (1934); IND.ENG.CHEM.,26, 634-7 (1934).
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(25) Nolte, A. J., and Loesecke, H. W. von, Food Research, 5, 7381 (1940). (26) Olliver, M., J . SOC.Chem. Ind., 55, 153-631' (1936). (27) Olson, F. C. W., and Stevens, H. P., Food Research, 4, 1-20 (1939). (28) Parks, C. T., Canner, 90, No. 12, Part 2, 71-2 (1940). (20) Pilcher, R. W., Am. Can Co. Research Dept., Bull. 1 (1932). (30) Pulley, G. N., and Loesecke, H. W. yon, IKD.ENG.CHEM.,31, 1275-8 (1939). (31) Reynolds, H., Ark. Agr. Expt. Sta., Bull. 368, 67 (1938). (32) Sipple, H. L., McDonell, G. H., and Lueok, R. H., Canner, 90, No. 12, Part 2, 59-65 (1940). (33) Spiegelberg, C. H., Pineapple Quart., 4, No. 4, 231-6 (1934); 5, NO. 1, 1-17, NO. 2, 61-104 (1935). (34) Tanner, F. W., "Microbiology of Foods", p. 322, Champaign, Ill., Twin City Pub. Co., 1932. (35) Townsend, C. T., Food Research, 4, 231-7 (1939). (36) Tressler, D. K., and Curran, M., J . Home Econ., 30, 487-8 (1938). (37) Western Canner and Packer, 1940 Yearbook, p. 119. (38) Willaman, J. J., and Easter, S . S., ISD.ENG.CHEM.,21, 1138-46 (1929). (39) Winters, R. H., Food Industries, 3, 122-3 (1931). (40) Wood, J. F., and Reed, H. M., Texas Agr. Expt. Sta., Bull. 562 (1938). (41) Zoller, H. F., IND. EKQ.CHEM.,10, 364-73 (1918).
Olive Products W. V. CRUESS University of California, Berkeley, Calif.
A study of the changes in composition of ripe olives during pickling shows that little saponification occurs through action of the sodium hydroxide used t o destroy oleuropein, the bitter glucoside of the olive. However, most of the water solubles are nearly completely removed. In preparing fermented Spanish-type green olives, pH control has been found to be of great importance. At pH values above 4.2 zapatera spoilage is apt t o occur. The most practicable means of attaining and maintaining pH values below 4.2 is by
T
HE olive industry of California is based primarily upon the preparation and canning of ripe olives and the preparation of Spanish-style fermented green olives. While considerable olive oil is produced, i t is in the nature of a byproduct, since only surplus olives and those too ripe or too small for pickling are used for oil production. Other California olive products of lesser importance are canned greenripe olives, salt-cured Greek-style olives, dried olives, and pitted olives (also chopped olives, olive mince, etc.). Normally 600,000 to 800,000 cases of canned olives (24 quarts or 48 pints to the case) are packed annually, and 300,000 to 500,000 gallons of olive oil are produced annually. As the olive is a n alternate bearer (a heavy crop one year, a light one the next), the output of all products, but particularly of oil, varies from year to year. In years of short crops there is little fruit for oil; in years of heavy production there is much small and surplus fruit suitable only for oil.
judicious addition of commercial dextrose. Lactic organisms convert it into lactic acid and thus rapidly reduce the pH to below
4.0. Hydrogen swelling of canned ripe olives, darkening of canned green-ripe olives (green olives cured ripe style) by reaction of iron from the base plate of the can and olive tannin or other phenolic bodies, bacterial spoilage, effect of lime salts, and role of sodium chloride are other current problems of interest to food chemists and bacteriologists. Four varieties are grown commercially : the Mission, introduced by the Mission padres about 150 years ago; the Manzanillo, the medium size olive used in Spain for green pickling; the Sevillano or Queen olive, a fruit of very large size used in Spain for green pickling; and the Ascolano, a large olive from Italy. The Mission is the most important in respect to quantity and is the principal variety used for oil as well as for pickling. The Sevillano and Bscolano are used only for pickling; a few Manzanillos are used for oil, but their low oil content makes them rather unsatisfactory for that purpose. The Sevillano and hlanaanillo are the only varieties used for green pickling in California; this is true also in Spain. Procedure for Canning RIPE OLIVE. Olives on the tree are intensely bitter owing to their content of oleuropein, a bitter glucoside. One purpose
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of pickling is to destroy this bitter principle by hydrolysis with dilute sodium hydroxide. The sodium hydroxide, however, removes the natural color of the olive; hence it is necessary to darken the color by natural oxidation of orthodihydroxy compounds a t slight alkalinity. Two general procedures are used. In the less frequently used procedure, the olives are taken directly from the tree to the pickling vats, submitted to several (usually five or six) dilute sodium hydroxide treatments, exposed to air for 24 t o 48 hours between caustic treatments to permit oxidation of orthodihydroxy compounds to a black color, soaked in cold water changed three or four times daily to remove sodium hydroxide, cured in dilute brine 2 to 5 days, canned in dilute brine, and sterilized a t 240' F. for 60 minutes under State Board of Health inspection. In the more common procedure the olives are placed in a storage brine of 20-35' salometer (5 to 9 per cent salt) and held there for several months to undergo lactic fermentation and firming of the texture. They are then pickled as described above. I n both cases the product has a dark brown to black color and a nutlike flavor. GREEN-RIPBOLIVES. These are pickled directly from the tree by one or two lye treatments without exposure to the air. The aim is to destroy the bitterness and prevent darkening of the color. The finished product is canned as described for the canned ripe olives. The olives are greenish yellow to mottled gray in color and of a rich nutlike flavor. They are increasing rapidly in popularity. SPANISH-STYLE GREENOLIVES. These are of the Sevillano and Manzanillo varieties only. The olives are picked at full size but while still green. A dilute sodium hydroxide solution is applied to penetrate one fourth to two thirds of the way to the pit. The lye is leached out for 20-48 hours. The olives are barreled in heavy brine, which comes to equilibrium a t 28-30' salometer. They undergo lactic fermentation for 6 to 12 months. Dextrose sugar, 1-2 per cent, is often added to furnish fermentable carbohydrate if the fermentation ceases for lack of sugar. The olives are packed in glass in fresh brine, and may or may not be pasteurized in the container. These are the familiar green olives of commerce and are an important product in California. GREEK-STYLEOLIVES. Very ripe jet-black Mission or Manzanillo olives are stratified in bins with about 1 pound of quarter-ground or half-ground rock salt to each 2 pounds of olives, shoveled over once every 2 or 3 days, and separated from the salt by screening when the bitterness has nearly disappeared and the olive flesh has become sufficiently desiccated by plasmolysis from action of the salt. The olives are then coated with a thin layer of olive oil and barreled or boxed for sale to peoples of Mediterranean extraction in our eastern states. This is a salty, shriveled, oily, slightly bitter product, for which one must gradually acquire a taste. It is very nutritious and is the Greek equivalent of the German pretzel. SICILIAN-STYLEOLIVES. I n Mediterranean countries olives are pickled by storage in strong brine for 6 to 12 months, during which time enzyme action destroys most of the bitterness and bacterial fermentation improves the flavor. Before serving, the olives and brine are flavored with garlic, sliced sweet peppers, and sliced onion Fennel may also be added. In California a similar product is made under the name of Sicilian-style olives. Green Sevillano olives are used. They are pickled in 30-gallon barrels by storage in a brine of 28-30' salometer flavored with whole fennel weed, garlic, and sweet peppers. This product was formerly purchased only by peoples of Mediterranean origin; but it is now finding favor with other Americans. It resembles the Spanish green olive in appearance but has a much more pronounced flavor.
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Changes in Composition during Pickling In an investigation of the changes in composition of olives during ripe pickling, Cruess, El Saifi, and Develter (20)reported the following findings: The moisture content increased somewhat, usually 6 to 8 per cent, although the total weight of the olives chan ed very little The increase represents water alsorbed t o reduring picklin place the solufle solids leached from the fruit by the solutions used in picklin , Total solids Secreased, in most cases about 7 t o 8 per cent, OWin to loss in water-soluble solids, % he' decrease in water-soluble solids varied with the varietyfrom 4.2 per cent for a sample of Sevillano olives to 12.5 per cent for a sample of Mission olives. The average was about 7 per cent. Water-insoluble solids changed very little, which indicated only slight hydrolytic action of the hydroxide on such substances. Ether extract increased definitely, although not markedly. On the wet basis the increase was about 1 per cent; this increase occurred during preliminary storage for several months before pickling, and may represent actual increase in oil or merely formation of some other substance soluble in petroleum ether. Protein (N X 6.25) decreased slightly. Whether the decrease represented actual protein or only simpler nitrogen compounds was not determined. Olives are rich in mannitol, usually 2 t o 4 per cent. Most of this was lost during pickling, through bacterial fermentation duri n r l i m i n a r y storage and by leaching durin pickling. ost of the tannin and coloring matter disappeared during pickling, dropping to about 0.15 per cent in most cases. Total sugars practically disappeared. Most of the sugar was lost by fermentation during preliminary storage in brine before pickling. The percentage of oil of pickled olives expressed on the moisture-free basis was found, contrary to Pitman (do), not very useful in judging oil content of the original fruit; for the loss in dry matter due to extraction of water-soluble solids varied greatly from sample t o Sam le and resulted in an irregular and unpredictable variation in oifcontent on the dry basis.
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GREEK-STYLE OLIVES. Considerable spoilage of Greekstyle olives occurs through molding, and the quality is variable. Pomeroy and Cruess (81) obtained the following results, among others, in an investigation of factors affecting quality and resistance to molding: When the finished product contained about 25 per cent or less of moisture and 8 per cent or more of salt, it kept well. Above 25 per cent moisture, molding was frequent. Coating the finished product with olive oil retarded but did not prevent molding. Loss in weight during curing in coarse salt was in most cases 29 to 30 per cent. Temperature had a marked effect on the rate of curing. At 120' F. only 6 days were required; at 105' F., 11days; at YOOF., 19 days; at room temperature (65-70" F.), 30 days; and at 45" F about 60 days. At 120" and 105" F. the olives remained very Gtter; at other temperatures the flavor was satisfactory. On immersion of a sample of cured Greek-style olives in dilute hydrogen peroxide, oxygen bubbles form at points where molding has occurred. (This test was devised by Mrs. Tilden of the Federal Food and Drug Administration, San Francisco.) A new procedure was developed for pickling Greek-style olives. The fresh olives were stored in brine of 28-30" salometer for several weeks and were then dehydrated to about 25 per cent water content, This method permits of close control and gives a product more resistant to molding, but it is more costly. SPANISH-STYLE GREENOLIVES. Following a visit to the green olive pickling plants of the Seville district in Spain in 1923, the author spent several years in experimentation to determine the major factors involved in applying the Spanish procedure under California conditions (4). The most important observation was that the addition of a fermentable sugar such as commercially reiined dextrose during fermentation is desirable, in order to attain the final total acid content. In Spain the olives are taken directly from the lye treating vat into a brine of 11 per cent salt (11' Be.). This proved too drastic for most California Sevillano variety olives \
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,eft) PICKLING VATSFOR CALIFORNIA :PE OLIVES;(Lower Left) SPANISH-
IPE GREENOLIVES I N PROCESS I N ~ R R E L S ; (Below) GREEK-PROCESS
DRYSALTING
and generally resulted in shriveling by plasmolysis. It was found more satisfactory t o place the olives initially in a brine of 5" BB. and to build this up gradually to a permanent 7-7.5" BB. during the first few weeks of storage. Addition of dextrose during fermentation not only improved the quality but also greatly reduced losses by bacterial spoilage (4). Addition of acetic acid in the form of vinegar (4) to finished green olives of low acidity also prevented spoilage. Vaughn and Douglas (23) followed the microfloral and chemical changes occurring during normal fermentation of green olives and during spoilage; they have not yet reported fully upon their observations. They confirmed the observations of Ball ( 1 ) that the organisms responsible for zapatera spoilage (development of a pungent, penetrating, disagreeable odor) develop above pH 4.3, and that their growth can be prevented by maintaining the pH value below 4.3 through lactic fermentation of occasional additions of dextrose. BACTERIALSPOILAGE OF RIPE OLIVES. A number of years ago losses through bacterial spoilage of ripe olives during processing were excessive. Cruess and Guthier (11) found that this form of spoilage could be eliminated by pasteurization a t a temperature (160-180" F.) that would kill the bacteria but not injure the quality of the olives. Later Tracy (22) determined that the responsible organisms are members of the colon-aerogenes group; he found them present on the olives before pickling, in the water used in pickling, and in the pores of the m7alls of the pickling vats. During the past few years Vaughn, Douglas, and others of this laboratory have undertaken a comprehensive study of the colon-aerogenes bacteria, the aerobic spore bearers, and the anaerobic
spore bearers responsible for olive spoilage. They have made progress reports ($8) but have not yet published their findings in full. I n brief, they find that the colon-aerogenes organisms are not the only ones involved. Their data apply not only t o ripe olives but also to green and Sicilian-style olives. The author (6) found that mold and film yeasts are important in promoting spoilage of olives in storage before ripe pickling because they reduce the total acidity by oxidation and thereby render the olives susceptible to bacterial action. Work of National Canners' Research Laboratory For a number of years Esty (14) of the National Canners' Research Laboratory in San Francisco has examined many samples of canned olives taken from cannery warehouses and from the open market with respect t o quality, fill of can, salt content of brine and olives, vacuum, etc. From these data much information of use to the industry in improving quality has been secured. One of the most variable factors is salt content. Esty recommends more careful control of salt content. Kaufmann and Lamb of the same laboratory (16) carefully correlated the salt content of canned olive brines expressed from the olives, as determined by titration; total solids are considered to be sodium chloride determined by salometer hydrometer and by Abbe refractometer. They published a table (16) giving these relations. The brine expressed from a sample of olives naturally contains some water-soluble organic matter from the olives; therefore a correction is necessary in the indicated salt content by salometer and refractometer. Thus a t 8.29" salometer the indicated approximate per-
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INDUSTRIAL AND ENGINEERING CHEMISTRY
centage salt for a pure salt solution would be 2.29 by salometer; but by titration of an average brine from olives of that density, it was actually only 1.74per cent. Kaufmann (16) reported further data on these relations and devised a method of preparing the juice expressed from pickled ripe olives for direct titration of salt content. It d e pends on clarifying the sample with gelatin and tannin, filtering, and titrating with standard silver nitrate and chromate indicator. This procedure makes ashing unnecessary.
Color of Ripe Olives Cruess and Develter (9) found that the optimum pH range for maximum color formation during the ripe pickling of olives is within the approximate range of pH 7-8. By buffering the olives to within this pH range by soaking in suitable buffer solutions (sodium acetate, phosphate, citrate, or bicarbonate plus a weak organic or phosphoric acid, etc.), improved color was secured. It was also found (7) that the pH value of the olive flesh at the time of canning greatly affects the retention of color in the canned product. The pH a t time of canning should be below pH 7.8 but not below 7.0. The salts of magnesium and calcium in dilute solution were found (19) to fix the black color formed during pickling and to minimize greatly the loss of color by leaching during final soaking of the fruit in water. The Proceedings of the California Olive Association for the past nineteen years contain other reports on the effect of concentration of lye used in pickling, of preliminary storage in brine, and other factors as they affect color.
Composition of Fresh Olives Nichols (17)reported data on olive composition. Sugar (total) was found to increase in early and mid season and to decrease toward the end of the season. Pitman (19) made observations on the oil content of olives as affected by variety, maturity, and locality. The Mission was consistently highest in oil content, the Manzanillo second; kscolano third, and Sevillano fourth. He found some loss in oil during pickling and sterilization, presumably by saponification. Brandonisio (3) recently reported upon the oil content of several varieties of olives in Italy as affected by date of picking.
Olive Oil In Bari, Italy, in 1939 the author was interested (6) in observing that much oil extracted from olive pomace with carbon disulfide, trichloroethylene, or low-boiling gasoline is so highly refined by deodorization and removal of solvent with superheated steam in v m , treating with decolorizing carbon, and neutralization of free fatty acid, that the resulting oil is suitable for use as food. Most of this oil is now blended with natural virgin olive oil and consumed (presumably in Italy). There is need for a reliable test for the authenticity of socalled virgin olive oils (oils that have not been relined), since much inferior olive oil is refined abroad and sold in America as virgin oil. Cunningham and Saywell (13) found that the induction period required for 25 per cent reduction of the color of methylene blue of specified concentration, added to a sample of oil held under definite conditions of temperature and light, was greater for a virgin oil than for the same oil after r e h i n g in various ways. However, this induction period varied greatly with different virgin oils of known history; and it appears to have little practical use as a means of distinguishing between virgin and refined oils. In Italy considerable improvement has been made in
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extracting olive oil by pressure (8). Perforated rings of heavy sheet steel hold the crushed olives between single layers of heavy matting, and thus permit use of much heavier pressures than in the older procedure and omitting the folded press cloths and metal or wooden press racks. Labor costs are reduced and the oil yield is increased. Centrifugal separation of the oil and press liquor is now universal practice in modern European and California olive oil factories. The station a t Bari has experimented with centrifugal extraction of oil from the finely comminuted pulp mixed with water or brine; and with other methods of recovering the oil without use of hydraulic presses. Progress has been made, but full success has not yet been attained (18). Centrifugal separation was used fairly successfully on a mixture of warm brine and very finely ground olive pulp by the Burt Brothers’ plant in California several years ago. The method appears to be workable if certain difficulties, such as plugging of the centrifugal, are overcome. In America a t present there is considerable concern about the alleged adulteration of olive oil with tea-seed oil by wholesale dealers and adulteration with peanut oil and other low-priced oils by retailers.
The Bitter Glucoside Several years ago Cruess and Alsberg (8) reported briefly on oleuropein, the bitter glucoside of the olive. The purified product possessed a considerably higher specific rotation than had been reported previously by other investigators. It was readily hydrolyzed by emulsion, by an enzyme naturally occurring in olive leaves, and by Pectinol (a commercial enayme preparation) ; the rotation changing from a strong minus to a moderate plus rotation on hydrolysis. Acid hydrolysis liberated dextrose and a water-soluble, intensely bitter noncrystalline substance. Hydrolysis with sodium hydroxide destroyed the bitter taste and gave, among other products, caffeic acid [CSH,(OHz)&H=CHCOOH 1; the remaining residue was levorotatory. The oleuropein content of olives examined ranged from 0.59 to 2.28 per cent.
Literature Cited (1) Bdl, R. N.,Proc. Calif. Olive Assoc., 1938,30. (2) Brandonisio, V., “Oleifici moderni in Puglia”, Rome, Tipografia Ram0 Editoriale Agricoltori S.A., 1939. (3) Brandonisio, V., Staz. agrar. sper.,Bari, Italy, Mem. 29,Pub. 194, 1-64 (1938). (4) Cruess, W.V., Calif. Agr. Expt. Sta., Bull. 498, 3-42 (1930). (6) Cruess, W. V., Cunning Age, 9, 375-6 (1928). (6) Cruess, W.V., Fruit Products J . , 19 (I), 11-16, 25, 28 (1939). (7) Cruess, W.V., Proc. Calif.Olive Assoc., 1929,35-45. (8) Cruess, W.V., and Alsberg, C. L., J. Am. Chem. Soc., 56,211517 (1934). (9) Cruess, W.V.,and Develter, E., Fruit Products J., 14 (ll),346 (1935). (IO) Cruess, W.V., El Saifi, A., and Develter, E:, IND. EN*.CHEM., 31, 1012-14 (1939). (11) Cruess, W. V.,and Guthier, E. H., Calif. Agr. Expt. Sta., Bull. 368 (1923). (12) Cruess, W.V., West, N., and Beavers, D., Proc. Cutif. Olive ASSOC., 1940, 41-3. (13) Cunningham, B. B.,and Saywell, L. G., Food Research, 1, 45764 (1936). (14) Esty, J. R.,P ~ o cCalif. . Olive AssOC., 1932-1940. (16) Kaufmann, C. W., Ibid., 1939,30-2. (16) Kaufmann, C. W., and Lamb, F. C., Ibid., 1938,36-42. (17) Nichols, P.F., J. A g r . Research, 41,89-96 (1930). (IS) Pantanelli, E.,and Brandonisio, V., Staz. agrar. sper., Bari, Italy, Mem. 27, Pub. 188,1-40 (1937). (19) Pitman, G. A., J. Assoc. Oficial Agr. Chem., 18, 441-54 (1936). (20) Pitman, G. A,, Proc. C d i f . Olive Assoc., 1932,Sec. 2, 1-8. (21) Pomeroy, D., and Cruess, W. V., Fruit Products J., 16, No. 1, 11-13, 22,27, NO.2, 43-4, 69 (1936). (22) Tracy, R.L., Proc. Calij. Olive Assoc., 1932,supplement 26-31. (23) Vaughn, R. H.,and Douglas, H. C., Ibid., 1938, 26-30; 1939, 55-7.
