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Making Use of

Tons of about 8 percent moisture, 6 percent ash, 6 percent crude protein based on total nitrogen, 6 percent crude fat, 14 percent crude fiber, and 66 percent Waste nitrogen-free extract. Although it must be supplemented with some other feed, Harry S. Owens, M. K. Veldhuis, it contains significant amounts of pro- W. Dayton Maclay tein, fats, and minerals. To make dried pulp, fresh is first ground in a hammer mill. One- half to 1 percent of is added to More than 2 million tons of pulp, the peel immediately after grinding; peel, and rag remain caeh year after the amount is carefully measured in citrus fruits are processed into juice, order to get the best pressing character- frozen concentrate, and sections. What istics. The lime neutralizes the to do with those mountains of waste? and catalyzes the de-esterification of When the industry was young, the the pectin in the peel to form only wastes were the culls and surplus pectate, which facilitates pressing and fruit, which were dumped on w^aste- drying. Formerly the peel was allow^ed lancl or used as soil conditioners on to stand in bins for about 45 minutes cultivated land. Solid wastes from early before pressing or drying to allow time canneries w^erc handled in the same for the lime to react. Now the time of way. The liquid wastes were ponded or reaction is shortened to 15 minutes or flushed into streams, lakes, or sewers. so by stirring the peel constantly as it All such makeshifts were unsatisfac- moves slowly through a pug mill. Con- tory and dangerous. A pile of rotting tinuous presses remove as much liquid peels soon begins to stink; as possible. In some processing plants underground water supplies are con- the pulp is heated by direct steam in- taminated ; and the increased biochem- jection to about 120° F. during this ical demand kills acjuatic life step to facilitate the pressing. The or exceeds the capacities of sewage- weight of liquor removed is about equal treating plants. to the w^eight of the pressed pulp. Industrial, State, and Federal re- Direct-fired or steam-heated rotary kiln search organizations investigated the driers are used to remove the moisture increasingly serious problem. From from the pulp. In some mills the pulp their efforts came several economically is given a preliminary drying in direct- valuable products. Now 80 to 90 per- fired units and finished in steam- cent of citrus wastes are converted into heated units. Careful control of the usable products, such as dried pulp, drying rates and temperatures is neces- molasses, pectin, essential oils, brined sary to produce the fluffy, light-colored peel, citric , , feed yeast, feeds that are considered desirable. and biologically active materials. About 1 ton of feed is obtained from 10 From the waste peel, marc, and seeds tons of cannery waste. In the past 10 that came from the processing lines, re- years, production of dried peel has in- search men developed dried pulp, creased to approximately 200,000 tons which is used extensively for feeding a year. dairy and beef cattle and is suitable Press or drain liquor from citrus peel for feeding other animals. It contains contains 5 to 7 percent sugar and a 268 MAKING USE OF TONS OF CITRUS WASTE 269 total of 10 to 12 percent soluble solids. show^ed an average of 71.4 percent It cannot be flushed into sewers or total solids, 42 percent sugars, 3.8 per- ponded unless care is taken to reduce cent crude protein, 1.1 percent pectin, the biochemical oxygen demand or to and 4.8 percent ash. The pH value prevent bad smells. Most of the press was 4.7. liquor is concentrated to produce mo- Citrus molasses is dark brown and lasses. Multiple-effect evaporation is bitter. It is used mainly in cattle feeds, commonly used. One plant in Texas in which it is usually mixed with other uses direct heating with a submerged materials, although it can be fed full- gas flame, followed by tw^o stages of strength. Som.e is mixed with wet citrus evaporation. pulp and then dried to make a feed. The first stage of a multiple-effect The amount of total digestible nutri- evaporator is operated under positive ents in the molasses is about 57 percent. pressure (up to 26 pounds) and the Some is used as a sub- last stage under negative pressure strate in the production of alcohol. (down to 26 inches of mercury). Inter- Production of citrus molasses in- mediate stages may be used to increase creased from none in 1940-41 to nearly the number of pounds of water evapo- 42,000 tons in the 1949-50 season. rated per pound of fuel consumed. Evaporators may be constructed of ANOTHER USE for press juice is in the mild steel. Corrosion is something of production of yeast, particularly Toril- a problem if not all of the acid is neu- lo psis utilis, which grows rapidly and tralized by the lime, A more serious is therefore less susceptible to contam- problem is scaling of the heat-ex- ination than other yeasts. It is rich in changer tubes in the evaporators, be- vitamins of the B complex and is a cause the scale builds up rapidly, inter- good supplement in feeds. About half feres with heat transfer and circula- the dried yeast is crude protein. It is tion, and must be removed about twice deficient in , one of the es- a week by boiling with lye. The exact sential amino acids, which, however, nature of the scale has not been deter- is present in cereal proteins. A ration mined, but it probably is composed containing this yeast with some cereal largely of , calcium pec- would provide all the essential amino tate, and fibrous material. Trouble is acids. encountered primarily in the first effect Research workers in the Southern of the evaporator. Some operators give Regional Research Laboratory, the the press juice a preliminary heating United States Citrus Products Labora- to 212° F. or higher in an auxiliary tory in Winter Haven, Fla., and a com- heat exchanger, which can be cleaned mercial cannery worked together to easily. The heating precipitates some develop a process for the production material, which is removed in a con- of feed yeast. Their experiments in- tinuous clarifier, and lengthens the cluded the operation of a 200-gallon- time the evaporators can be operated per-hour pilot plant. They developed between cleanings. a continuous method, which gives a In a recent installation, submerged good yield. The juice from the feed mill gas burners are used to give the press is first passed through an 80-mesh juice a preliminary heating and con- screen to remove particles of pulp. centration to about 22 percent solids. Then it is diluted with water to a sugar Carbonation by the products of com- concentration of about 2 percent, bustion forms a precipitate, which is heated to 200° F. to destroy micro-or- removed in continuous thickeners. ganisms, cooled, and pumped contin- Either method reduces the amount of uously into the yeast propagator. A suspended matter in the final product concentrated nutrient solution is me- and improves the quality. Analyses of tered into the propagator in proportion 13 samples of Florida citrus molasses to the feed rate. The propagator is 270 1950-1951 YEARBOOK OF AGRICULTURE kept thoroughly aerated by air intro- crude protein and 3.3 percent phos- duced through porous stone candles in phate (as the pentoxide). The product the bottom of the tank. The product is light in color, fluffy, and, though not from the propagator flows continuously w^ashed, only slightly bitter. into a collecting tank and thence to special centrifuges which separate the THE ISOLATION OF OIL from the rind yeast as a thick cream. The yeast cream of the is one of the earliest chem- is dried on a drum drier, pulverized, urgic applications of citrus fruit. Hand and packaged. pressing of the peel against sponges has As nutrients, phosphates and nitro- been practiced in Sicily since the 18th gen compounds must be added. Some ce:ntury; at one time the United States benefit can be obtained from the phos- im]:)orted nearly a half million pounds phorus in the juice, but it must be sup- of lemon oil annually. Machinery has plemented. AlDout 0.19 pound of am- made possible the production each year monium sulfate, 0.045 pound of of more than 1,500,000 pounds of oils anhydrous ammonia, and 0.045 pound from citrus peels. of 75 percent phos]Dhoric acid are re- The whole fruit, waste cannery peel, quired per pound of yeast. The acidity or flavedo, the colored part of the peel, in the propagator is easily controlled can be used. The material is ground within the range of pH 4 to 4.5 by and pressed in screw extractors or varying the ratio of ammonia to am- pressed between fluted rolls to yield an monium sulfate. With the method of oil emulsion. A recently developed aeration used, from 500 to 700 cubic juice extractor, which presses the feet of air w^as required per pound of whole fruit, delivers separately the yeast produced. Cooling coils w^ere in- edible juice and an oil emulsion. The stalled in the propagator to dissipate emulsion is screened and the oil sepa- the heat of fermentation and maintain rated by centrifuging. The centrifuged a constant temperature of 95° F. oil is placed in i:old storage, W'here A pure culture of Torulopsis utilis w'axes separate, the wax-free product is grown in the propagator. Continu- being known as cold-pressed oil. These ous feeding of the pasteurized ]>ress methods are used yjarticularly with juice and nutrients is started and main- , oranges, and . Less tained as soon as the actively growing than half the peel oil in the fruit is re- culture fills the propagator. No new covered from the fruit used. These oils culture is needed so long as the yeast are sometimes concentrated under vac- grows rapidly. The problem of foaming uum to produce concentrated oils in is controlled by closing the top of the which a major part of the limonene has propagator and providing a large over- been removed. flow tube to a collecting tank where the Distilled oils also are prepared from foam is broken. limes, oranges, and lemons. The whole Fermentation proceeds rapidly and fruit, peel, or liquid effluent from cold- the rate of feed an hour can equal one- pressed oil preparation is subjected to third the propagator volume. This . The oil separates means an average retention time of readily from the distillate. Distilled oils only 3 hours, w^hich is considered short are generally inferior to cold-pressed for . Yields of yeast are oils. A distilled oil of excellent quality progressively smaller with increasing is obtained in some juice canneries by sugar content of the feed. At a 2 per- flashing the juice under vacuum. Addi- cent concentration, the yield is 44 per- tional distilled oil is obtained during cent of the sugars consumed. Utiliza- the manufacture of molasses from the tions better than 95 percent of the first effect or during flashing of the sugars and tw^o-thirds of the total press juice, but it has little value for organic matter were obtained. The flavoring purposes. drum-dried yeast analyzed 47 percent Cold-pressed oils are used for - MAKING USE OF TONS OF CITRUS WASTE 271 ing, especially in bottled and fountain gether. The oil is used in cooking oils, beverages, cakes, candies, and pics. including a hydrogenated modifica- Some oils, particularly the distilled, are tion, and in detergents. The principal used to soaps. The amount constituents of the seed oils are glyceryl that can be used for these purposes is of oleic, palmitic, and linolcic limited and much less than the poten- acids, and smaller amounts of the tial supply. Scientists are trying to find esters of stearic, arachidic, and lino- other uses in plastics and as ; lenic acids. particularly arc they seeking further use for the distilled oil that is recov- JUICE FROM PROCESSED LEMONS is ered during other operations. Other used primarily to make . A outlets are needed; the potential sup- ton of lemons yields 15 to 50 pounds of ply from waste cannery peel is about citric acid. The whole fruit first is 20 million pounds annually. passed through presses and washed to The principal constituent in all the remove the juice. Then it is placed in citrus-peel oils is ¿f-limonene, which fermentation tanks to liquefy some con- constitutes 90 percent or more of the stituents, coagulate others, and ferment oil. It contributes little to the flavor of the sugars. It is then heated and fil- the oil, and its presence results in some- tered, and the citric acid is precipi- what less stability. Aldehydes (), tated with lime and . higher alcohols, higher acids, esters, Citric acid is released from the lime and compounds give by adding . Water is flavor and aroma to the oil. removed by evaporation, and crystal- Citrus seeds arc a source of food oils. lization proceeds in lead tanks. The Some seed oil was produced in Florida purification procedure is somewhat in the late 1930's, but operations were complicated. It involves decolorization suspended until 1946. During the and treatment with charcoal, sulfide, 1948-49 season the estimated oil re- and fcrrocyanide to prepare citric acid covery was between 300 and 400 tons of acceptable pharmaceutical qviality. in Florida. The potential supply from Eighty-five percent of the acid in the wastes from Florida citrus canneries is lemons is recovered. In this country, estimated at more than 5,000 tons. citric acid is used primarily as a food- Some varieties of citrus fruit, such as flavoring acid and in plasticizers. the navel orange and the Marsh seed- Citrus peel, left after the juicing or less grapefruit, have few seeds, but peel-oil operation, is a good source of others, the Seedling orange and Dun- pectin, which has been used in making can grapefruit, for example, contain jelly since the eighteenth centur^^ It many. was isolated and named in 1825. Work In the extraction of juice from fresh on it progressed sporadically until 1912, fruit, the seeds accompany the juice when patents on its production were and are removed by screening, along obtained. The patents stimulated fur- with some pulp. The adhering pulp is ther activity, particularly after 1930. removed by further screening, after New uses are being discovered con- which the seeds are dried in rotary stantly; if some of the promising ideas driers and sent to oil-e!xtraction plants, arc developed commercially, produc- where the oil is removed by screw tion should exceed the present 6 million presses or hydraulic presses. The yield pounds a year. of oil is about 600 pounds a ton of dried seeds. The fresh oil is pale amber MOST COMMERCIAL PECTIN in the and extremely bitter, but the bitterness United States is obtained from citrus can easily be removed and the oil re- peel, which is one of the richest sources ; fined by the methods commonly used about 2 million tons of the raw mate- with other seed oils. Seeds of grape- rial is available annually. Fresh peel fruit and oranges are processed to- contains 3 percent or more of pectin; 002722°—51- -19 272 195 0-1951 YEARBOOK OF AGRICULTURE washed, dried peel contains at least 30 tion of a precipitate with certain metal percent. Dried apple pomace, the only ions, which arc later removed by means other source of pectin that has been of acidified alcohol. Citrus pectin con- used on a commercial scale in this tains about 85 percent anhydrogalac- country, contains less than half that turonic acid, about 5 percent méthyl- much pectin. ène groups present as methyl , and When peel is used as a source of smaller amounts of sugars such as pectin it must receive more gentle treat- arabinose, galactose, and rhamnose. ment than that used in processing for Citrus pectin has a relatively high feed or soil conditioning. The proce- molecular weight, ranging from 60,000 dure developed at the Western Re- to 120,000, which partly accounts for gional Research Laboratory^ includes its ability to form jellies, films, and blanching and washing in a continuous fibers. jacketed washer that has a screw con- The use of pectin in jellies, marma- veyor. Blanching destroys an in lades, candies, and jams is generally the peel which changes the properties well known, as is its use in pharma- of pectin; washing removes sugar ceutical preparations for digestive dis- and colored and hitter constituents. turbances. The more recent develop- Leached peel can be used directly for ment of low-methoxyl pectin, which pectin extraction or stored dry to pro- increases the usefulness of pectic sub- vide for year-around operations. It can stances, is of special interest. be dried by artificial heat or in the sun. Pectin, when treated with alkali, Common commercial practice em- acid, or an enzyme called pectinester- ploys a hot-acid extraction of pectin ase, contains free acid groups that will from citrus peel in a batch process. react with small amounts of calcium Vigorous stirring during the 1-hour salts. No sugar or other solids are re- extraction period causes disintegration quired in order to make a gel with of the peel. The liquor then requires low-methoxyl pectin. screening or pressing and a filtration A procedure for making low-meth- for clarification. The high of oxyl pectin, worked out at the Western the dispersion must be reduced by Laboratory, comprises treatment of the maintenance of a fairly high tempera- cooled extraction liquor with ammonia ture, which causes some degradation to cause removal of part of the meth- of the pectin. Methods for extraction oxyl groups from the pectin, and then designed to simplify the process and precipitation of the altered pectin by maintain high quality of pectin are be- addition of acid. The washed low- ing investigated at the Western Labo- methoxyl pectin gel may then be partly ratory. neutralized, dried, and ground. The liquor can be concentrated and The uses of low-methoxyl pectin are sold as such, provided food-grade acids many and varied. The usual type of are used in the extraction, or it can be milk pudding can be prepared by add- treated with alcohol or with calcium or ing low-methoxyl pectin and sugar to aluminum salts to isolate the pectin. milk, heating, and stirring until the When precipitation is by a salt, the pectin has dissolved. Flavoring can be salt must be removed by washing with added and the whole allowed to cool. acidified alcohol. The pectin as finally This pudding is smooth and not pasty. obtained is dried and ground and sold The gelling agent in this case is the by its ability to form a jelly with 65 low-methoxyl pectin, which combines percent soluble solids. In 1950 no with the calcium ion in the milk. standard for that grade had been estab- A quick dessert for housewives, lished, but definite moves were under campers, and sportsmen can be pre- way to do so. pared with low-methoxyl pectin. Milk Pectin is purified by several precipi- powder, flavoring, and a combination tations in dilute alcohol or by forma- of sugar and pectin are mixed, then MAKING USE OF TONS OF CITRUS WASTE vigorously stirred into cold water. In Low-methoxyl pectin is now avail- 5 minutes a fluffy pudding is ready for able from commercial concerns. Fur- eating or for a pic filling. ther investigation of its properties Those who like a gelatin dessert, but probably will lead to other new uses. do not care to cat gelatin or much The conclusion might be reached sugar^ can make low-solids gels from that extraction of pectin destroys the low-methoxyl pectin and a calcium salt, feed value of the peel. The possibility like calcium raonohydrogen phosphate. exists, however, that the liquor from The flavor may come from fruit juices the blanching and washing operation or from synthetic . Color and can be concentrated to produce mo- sugar or saccharin are added as desired. lasses, the peel from the extractor can Low-methoxyl pectin lightens din- be dried, and the ammonium sulfate ner problems in another way. A fruit solution from the peeling operation can mix, like canned fruit cocktail, can be be concentrated. By suitable mixing of processed with this pectin and sugar to the three components, a feed or soil form a canned gelled salad or dessert. conditioner could be obtained. Thus The Army used nearly 30 milhon cans the peel would be utilized completely. of this dessert during the Second World Research has converted citrus waste War. Canned tomato aspic also is made into new, valuable products. Practi- possible by low-methoxyl pectin. cally all of it is used: hardly any goes Sparkling, clear, bright films can he down the sewer. Citrus molasses and prepared with low-methoxyl pectin. dried citrus peel go into feeds; citrus The ability of the calcium to hold to- essential oils and citric acid are used in gether the pectin molecules^ like rivets foods; citrus pectin makes a jelly fail- fastening steel beams, makes this pos- ure almost impossible, and has been sible. Spraying sticky stuff, such as can- altered for use in puddings and films. died fruit, with, or dipping it into, a Grower, processor, and consumer have solution of sodium pectinate and then benefited. Further work is needed on a solution of a calcium salt covers it uses of some of the byproducts, such as with a gel of sodium calcium pectinate. pectin and limonene, to develop new The gel is rapidly dried, after which it uses for citrus molasses or the press is impervious to sugar and is relatively liquor from which it is made, and to nonsticky. Candied fruit, when coated improve present processing methods. in this way, can be packaged mechani- cally instead of manually. HARRY S. OWENS is in charge of the Salted oily nuts have always been a carbohydrate section of the Western messy food item. Coating almonds or Regional Research Laboratory. He re- other nuts with pectinate containing a ceived degrees from the University of food dye and salt gives a clean, color- Idaho and Columbia University. From ful, and tasty product. Other food 1935 to 1942, when he joined the Lab- flavors, such as smoked salt, cloves, or oratory staff, he was engaged in re- chocolate, could be incorporated in the search on utilization of farm and forest film. Vitamins for health can be in- products and taught and cluded. The possibilities for use of the colloid chemistry in the University of film seem endless. Idaho. Fibers and films of certain salts of M. K. VELDHUIS has been a member low-methoxyl pectin are easily pre- of the Bureau of Agricultural and In- pared and are water-insoluble and fire- dustrial Chemistry since 1935. He has resistant. The cost of these materials been in charge of the United States may restrict their utilization to spe- Citrus Products Station in Winter cialty purposes, but the attractive pos- Haven, Fla., since 1944. sibilities of their use in open-weave W. DAYTON MAGLAY is head of the fabrics, decorative ribbons, and biochemical division of the Western casings have not been explored. Laboratory. He is a native of Nebraska, 274 1950-1951 YEARBOOK OF AGRICULTURE and holds degrees from the University Institute of Health in Washington. He of Nebraska. He taught chemistry Í7i joined the staff of the Laboratory in the Municipal University of Omaha 1940 and has been engaged in research and afterward conducted fundamental related to the utilization of fruit and carbohydrate research at the National vegetable byproducts.

PREPACKAGING fruits and vegetables at the farm shipping point offers obvious advantages in the reduction of shipping costs and in the utilization of-wastes on the farm, but it cannot be widely recommended until certain problems are solved. No package will improve the quality of its contents. All highly perishable com- modities decline in quality after harvest. The best handling methods only slow down the rate of decline. Studies made since 1948 by the Department of Agri- culture in cooperation with the Dickraan Farms. Ruskin, Fla.;, highlight the importance of adequate refrigeration at every step along the way from the time a product is harvested until it is sold to the consumer. For example, packaged broccoli retained a good green color for 15 to 20 days when held at 40° F. or below, but turned yellow in 2 or 3 days at 70°. Sweet corn lost sugar at the rates of 3.5 percent at 32°, 20.8 percent at 50°, and 59.4 percent at 86° during the first 24 hours after picking. Prepackaged sweet corn delivered in New York at temperatures in the 40's was graded as good to very good in quality but that delivered at temperatures above 50° was inferior. In tests so far, chemical treatments of various types appear to offer little benefit. Dips in ascorbic, citric, or did not prevent discol- oration in corn and cauliflower. Instead, these solutions accumulated great numbers of micro-organisms. Chlorine used in the hydrocooler water—where the vegetables were precooled immediately after harvest—did not completely sterilize the surfaces of the vege- tables. It reduced the micro-organism count, however, and held it to a reasonable minimum. Approximately 100 parts per million of chlorine gave as satisfactory results as higher concentrations. In general, the results show all packages should be perforated to allow for exchange of gas or air. Normal leaks through seams or poor seals do not provide sufficient ventilation to prevent fermentation. In turn^ off-flavors and off- soon develop when the packaged vegetables are held at high temperatures. Some products can be packaged more successfully near the terminal than at the distant farm market. For example, tomatoes need to be ripened to a market- able stage before they are packed. Otherwise they ripen unevenly and make an unattractive package. Also they may develop decay in the several days required to put them into retail ch?.nnels. For continuous growth of the prepackaging industry, marketing facilities must keep pace. At present, most wholesalers and retail stores lack refrigeration facility to handle adequately a line of prepackaged produce.—Harold A. Schomer, Bureau of Plant Industry, Soils, and Agricultural Engineering,