UNIVERSITY OF CALIFORNIA PUBLICATIONS COLLEGE OF AGRICULTURE AGRICULTURAL EXPERIMENT STATION BERKELEY, CALIFORNIA STORAGE OF PERISHABLE FRUITS AT FREEZING TEMPERATURES PRELIMINARY REPORT BY W. V. CRUESS, E. L. OVERHOLSER and S. A. BJARNASON BULLETIN No. 324 August. 1920 UNIVERSITY OF CALIFORNIA PRESS BERKELEY 1920 David P. Barrows, President of the University. EXPERIMENT STATION STAFF HEADS OF DIVISIONS Thomas Forsyth Hunt, Dean. Edward J. Wickson, Horticulture (Emeritus). Walter Mulford, Forestry, Director of Resident Instruction. C. M. Haring, Veterinary Science, Director Agricultural Experiment Station. B. H. Crocheron, Director of Agricultural Extension. Hubert E. Van Norman, Vice-Director; Dairy Management. James T. Barrett, Acting Director of Citrus Experiment Station; Plant Pathology William A. Setchell, Botany. Myer E. Jaffa Nutrition. Charles W. Woodworth, Entomology. Ralph E. Smith, Plant Pathology. J. Eliot Coit, Citriculture. John W. Gilmore, Agronomy. Charles F. Shaw, Soil Technology. John W. Gregg, Landscape Gardening and Floriculture. Frederic T. Bioletti, Viticulture and Fruit Products. Warren T. Clarke, Agricultural Extension. John S. Burd, Agricultural Chemistry. Charles B. Lipman, Soil Chemistry and Bacteriology. Ernest B. Babcock, Genetics. Gordon H. True, Animal Husbandry. Fritz W. Woll, Animal Nutrition. W. P. Kelley, Agricultural Chemistry. H. J. Quayle, Entomology. Elwood Mead, Rural Institutions. H. S. Reed, Plant Physiology. L. D. Batchelor, Orchard Management. J. C. Whitten, Pomology, f Frank Adams, Irrigation Investigations. C. L. Roadhouse, Dairy Industry. R. L. Adams, Farm Management. F. L. Griffin, Agricultural Education. John E. Dougherty, Poultry Husbandry. L. J. Fletcher, Agricultural Engineering. Edwin C. Voorhies, Assistant to the Dean. fin co-operation with office of Public Roads and Rural Engineering, U. S. Department of Agriculture. STORAGE OF PERISHABLE FRUITS AT FREEZING TEMPERATURES Preliminary Eeport by W. V. GRUESS, E. L. OVERHOLSER, and S. A. BJARNASON INTRODUCTION Many quickly perishable fruits such as berries, apricots, cherries and others can not be held successfully for very long periods at the usual cold storage temperatures for fruit, of 32° F. to 35° F. because of rapid softening and decay. If held without preliminary treatment at a temperature of 10° F., low enough to freeze the fruit, there is a tendency in certain fruits for the color to become brown and the flavor seriously impaired. It, therefore, seemed desirable to make a pre- liminary experimental study of methods of treating the above fruits before storage, at 10° F. to prevent or minimize undesirable changes in color and flavor. At these low temperatures molding or fermenta- tion does not occur and ripening processes are effectively arrested. Therefore, if the problems of retention of color and retention of flavor could be satisfactorily solved, this method of storage should have wide application. The investigations have included not only experiments upon the storage of various quickly perishable fruits, but also upon the utiliza- tion of such fruit in canning, preserving, confections, etc., after six to ten months storage. The data of the first year's experiments have been so promising that it is believed the results will be of considerable immediate value to cold storage establishments, ice cream manufacturers, fruit pre- serving factories, and others. Former breweries are equipped with large refrigerating plants, very large glass lined or wooden tank cold storage capacity, and other facilities which could be used for the receiving, preparation and storage of the types of fruits used in the tests. It is probable that a very extensive market could be quickly developed for such fruits during the winter and early spring months and it is believed that the development of such an industry offers a very attractive field. REVIEW OF PREVIOUS WORK The extensive keeping of such quickly perishable fruits under refrigeration is a comparatively new undertaking. A few storage houses have adopted certain methods for particular fruits which enable them to keep the product for a considerable period of time 26 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION by employing freezing temperatures. Usually different methods are employed by the different houses. As a rule, they have simply found satisfactory methods and have not definitely determined that these are the best. Fulton 1 in 1907 mentioned that in certain of the larger cities the practice of freezing small fruits for the purpose of holding them indefinitely in a frozen condition to be used in making ice cream and pastries had come into use to a limited extent among confectioners, bakers and restauranteurs. He pointed out that much of the fruit used for this purpose was bought when the market price was low, such as on Saturday evenings or when the market was glutted. The fruit was hurried into cold storage and frozen at a temperature ranging from about 5° F. to 12° F. Previously some restauranteurs had packed berries in dry granulated sugar and held them at a tempera- ture of 31° F. to 32° F., but this practice has been discarded and the freezing method adopted. Fulton gives further information based primarily upon observa- tions, stating that frozen strawberries for ice cream have been used in a limited way by confectioners, while frozen blackberries, currants, blackcap raspberries, huckleberries, and other small fruits were being used successfully for pies and other pastries by a few restauranteurs and bakers. He cites the hearsay that when made into pies the flavor of the product was said to be practically equal to that made of fresh fruit. Considerable quantities of cherries and damson plums were also frozen by one company for use in pies. Usually these latter fruits were put into the pies whole without seeding. Sometimes, however, they were dipped into cold water to take out the frost and then pitted. The fact was noted that frozen cherries and plums shriveled somewhat in baking, and were therefore not used so suc- cessfully as some of the berries. Fulton also mentions two tests made by the Bureau of Plant Industry. In one test Gandy strawberries were frozen and held at a temperature of 10° F. to 14° F. for ten months in tight paper wrapped cartons of paraffined cardboard, with very little change in color and practically no shrinkage. Berries frozen in open crates at the same time evaporated and shrunk away fully one-half within a few months. Fulton's advice was that if the fruit was intended for long preservation, it should be placed in loosely covered tin cans to prevent evaporation, but if it was to be kept only a short time, it could be stored in the ordinary crates in which it was conveyed to market. i S. H. Fulton, The Cold Storage of Small Fruits, Bur. Plant Ind., Bull. No. 108, U. S. D. A., 1907. Bulletin 324 STORAGE OF PERISHABLE FRUITS 27 In the other test Gandy and Tennessee varieties of strawberries and Miller and Kansas raspberries were frozen and stored in different styles of packages at a temperature of 12° F. in a general freezing room containing meats, poultry, and game. The packages used were (1) paper-wrapped paraffined cardboard carton; (2) the same carton with an additional heavy paraffined paper wrap over the cardboard, which with the outside paper jacket constituted a triple thick carton; and (3) the common open slat crate generally used. After approximate^ seven months, the fruit was still normal in appearance except for a slight fading in the color of the strawberries and a slight shrinkage of both strawberries and raspberries in the open crates. The fruit in the closed packages was plump and attractive in appearance. The flavor of the fruit of both strawberries and raspberries in the open crates was objectionable since apparently the fruit had absorbed odors from other commodities in the storage room. The flavor of the fruit in the triple box was a little better, but Fulton believed it had been "tainted" through the effect of the carbon-dioxide gas exhaled by the fruit before it was solidified in freezing. The flavor of the fruit in the double carton which was not so impervious to the air, was not contaminated, and it retained much of the sprightliness and flavor of the fresh fruit. In Fulton's judgment this test seemed to indicate that for frozen fruit, the best results can be obtained by the use of^a closed package provided the package is not so tight as to prevent the escape of the gases given off by the fruit after it is packed and before it is frozen. Darrow 2 writes of two methods of preserving strawberries in cold storage which seem to be practices followed by a few cold storage houses. The first method is suggested as being adapted for packing- small quantities of strawberries for use when not in season, with the preservation of the fresh-fruit flavor. Sound, ripe berries are selected, washed and hulled. A tin of convenient size to which a tight cover can be fitted is used. To each ten pounds of fruit one cup of sugar is added. The cans are filled with sugar and berries, the tops are fitted on and their edges covered with the adhesive tape used in sealing packages. The containers of fruit are then put in freezing cold storage and kept frozen until wanted. Darrow describes this product as being satisfactory when used for short-cakes, by restau- rants and hotels, and as crushed fruit at soda fountains, and by ice cream manufacturers. The second method outlined is referred to as being the one employed by the large manufacturers of the crushed fruits and syrups 2 George W. Darrow, Strawberry Culture, Western United States Farmers ' Bulletin 1027, U. S. D. A., 1919. 26 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION by employing freezing temperatures. Usually different methods are employed by the different houses. As a rule, they have simply found satisfactory methods and have not definitely determined that these are the best. Fulton 1 in 1907 mentioned that in certain of the larger cities the practice of freezing small fruits for the purpose of holding them indefinitely in a frozen condition to be used in making ice cream and pastries had come into use to a limited extent among confectioners, bakers and restauranteurs. He pointed out that much of the fruit used for this purpose was bought when the market price was low, such as on Saturday evenings or when the market was glutted. The fruit was hurried into cold storage and frozen at a temperature ranging from about 5° F. to 12° F. Previously some restauranteurs had packed berries in dry granulated sugar and held them at a tempera- ture of 31° F. to 32° F., but this practice has been discarded and the freezing method adopted. Fulton gives further information based primarily upon observa- tions, stating that frozen strawberries for ice cream have been used in a limited way by confectioners, while frozen blackberries, currants, blackcap raspberries, huckleberries, and other small fruits were being used successfully for pies and other pastries by a few restauranteurs and bakers. He cites the hearsay that when made into pies the flavor of the product was said to be practically equal to that made of fresh fruit. Considerable quantities of cherries and damson plums were also frozen by one company for use in pies. Usually these latter fruits were put into the pies whole without seeding. Sometimes, however, they were dipped into cold water to take out the frost and then pitted. The fact was noted that frozen cherries and plums shriveled somewhat in baking, and were therefore not used so suc- cessfully as some of the berries. Fulton also mentions two tests made by the Bureau of Plant Industry. In one test Gandy strawberries were frozen and held at a temperature of 10° F. to 14° F. for ten months in tight paper wrapped cartons of paraffined cardboard, with very little change in color and practically no shrinkage. Berries frozen in open crates at the same time evaporated and shrunk away fully one-half within a few months. Fulton's advice was that if the fruit was intended for long preservation, it should be placed in loosely covered tin cans to prevent evaporation, but if it was to be kept only a short time, it could be stored in the ordinary crates in which it was conveyed to market. i S. H. Fulton, The Cold Storage of Small Fruits, Bur. Plant Ind., Bull. No. 108, U. S. D. A., 1907. Bulletin 324 STORAGE OF PERISHABLE FRUITS 27 In the other test Gandy and Tennessee varieties of strawberries and Miller and Kansas raspberries were frozen and stored in different styles of packages at a temperature of 12° F. in a general freezing room containing meats, poultry, and game. The packages used were (1) paper-wrapped paraffined cardboard carton; (2) the same carton with an additional heavy paraffined paper wrap over the cardboard, which with the outside paper jacket constituted a triple thick carton; and (3) the common open slat crate generally used. After approximately seven months, the fruit was still normal in appearance except for a slight fading in the color of the strawberries and a slight shrinkage of both strawberries and raspberries in the open crates. The fruit in the closed packages was plump and attractive in appearance. The flavor of the fruit of both strawberries and raspberries in the open crates was objectionable since apparently the fruit had absorbed odors from other commodities in the storage room. The flavor of the fruit in the triple box was a little better, but Fulton believed it had been "tainted" through the effect of the carbon-dioxide gas exhaled by the fruit before it was solidified in freezing. The flavor of the fruit in the double carton which was not so impervious to the air, was not contaminated, and it retained much of the sprightliness and flavor of the fresh fruit. In Fulton's judgment this test seemed to indicate that for frozen fruit, the best results can be obtained by the use of # a closed package provided the package is not so tight as to prevent the escape of the gases given off by the fruit after it is packed and before it is frozen. Darrow 2 writes of two methods of preserving strawberries in cold storage which seem to be practices followed by a few cold storage houses. The first method is suggested as being adapted for packing small quantities of strawberries for use when not in season, with the preservation of the fresh-fruit flavor. Sound, ripe berries are selected, washed and hulled. A tin of convenient size to which a tight cover can be fitted is used. To each ten pounds of fruit one cup of sugar is added. The cans are filled with sugar and berries, the tops are fitted on and their edges covered with the adhesive tape used in sealing packages. The containers of fruit are then put in freezing cold storage and kept frozen until wanted. Darrow describes this product as being satisfactory when used for short-cakes, by restau- rants and hotels, and as crushed fruit at soda fountains, and by ice cream manufacturers. The second method outlined is referred to as being the one employed by the large manufacturers of the crushed fruits and syrups 2 George W. Darrow, Strawberry Culture, Western United States Farmers ' Bulletin 1027, U. S. D. A., 1919. 28 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION used by the soda fountain and ice cream trade in the preparation of their product. The uncooked berries are kept in barrels in cold storage, preserved in the following manner: the strawberries are hulled, sorted and then washed. The washing is done by running the berries on a belt through a tank of water. They are then conveyed over another belt, where they are slowly turned and sprayed with water. After the washing, the berries drop into pans and are weighed. From one-half to one pound of sugar is added to each pound of berries, proportions used depending upon the variety, the ripeness of the fruit, the moisture conditions, and the way in which the product is to be used. The proportions most commonly used are one-half pound of sugar to one pound of fruit. Heavy water-tight barrels holding about 375 pounds of the mixture of berries and sugar are used. Before use they are carefully cleaned and coated on the inside with parafine, which is applied hot with a paint-brush. The sugar and berries are put in alternate layers and mixed by a machine or by hand. As soon as the barrels are headed they are shipped in a refrigerator car to a cold storage warehouse, where they are held at a temperature of 30° F. or lower. Several thousand barrels of strawberries are put up in this manner each year. Darrow writes that if equal weights of sugar and berries are used, tlje barrels of fruit may be stored at a temperature of 34° F. to 36° F., but if the fruit is to be held for long periods the flavor is best pre- served at a lower temperature. EFFECT OF PRELIMINARY TREATMENT3 The experiments reported in 'this publication have been divided into two groups, namely "Effect of Preliminary Treatment" and "Utilization of Fruits from Freezing Storage." During the summer of 1919, strawberries, loganberries and red raspberries, currants, Royal Anne cherries and Royal Apricots were received at the University. With the exception of the apricots, which came from the University Farm at Davis, the fruits were purchased from local commission houses. The cherries were grown in Oregon; the other fruits were California-grown products. The fruits were prepared in the Fruit Products Laboratory for storage. In most cases stoneware crocks were used as containers. The fruit was then placed in rooms of the cold storage plant of the Division of Pomology. Temperatures of 32° F. and 10° F. were compared and small lots of the fresh fruits were made into preserves and stored in glass jars 3 The authors wish to thank Mr. A. W. Christie, Instructor in Fruit Products, for suggestions and assistance given during preparation of the fruit for storage. Bulletin 324 STORAGE OF PERISHABLE FRUITS 29 at room temperature to serve as checks for the various lots held in cold storage. The following tables and observations summarize the results obtained. Table 1. — Cherries Stored at 8° F. to 12° F Date stored, June 23, 191.9. Expt. No. Treatment before storing Notes on August 2, 1919 Samples taken out and thawed on January 23, 1920 Date spoiled Color Flavor Texture at room temperature 15 Whole cherries, no treatment Brown color Dark brown Good to fair Medium January 27th. 5 Pitted cherries Brown color Dark brown Good to fair Medium January 27th. 1 Pitted, frozen in water Color not chang- ed Very good, natural Excellent Good January 29th. 2 Pitted, frozen in 10% sugar solution Color not chang- ed Very- good, natural Excellent Good January 29th. 3 Pitted, frozen in 20% sugar solution Color not chang- ed Very good, natural Excellent Good January 29th 4 Pitted, frozen in 40% sugar solution Color not chang- ed Very good, natural Excellent Good January 29th. 7 Same as No. 1 but heated to 175° F. before storage Color pinkish Bleached to grey- ish pink Very good Medium to poor January 27th. 8 Same as No. 2, but heated to 175° F. before storage Color pinkish, color and flavor gone into juice to some extent Bleached to grey- ish pink Very good Medium to poor January 27th. 9 Same as No. 3, but heated to 175° F. before storage Color pinkish, color and flavor gone into juice to some extent Bleached to grey- ish pink Very good Medium to poor January 27th. 10 Same as No. 4, but heated to 175° F. before storage Color pinkish, color and flavor gone into juice to some extent Bleached to grey- ish pink Very good Medium to poor January 28th. 11 Same as No. 1, but heated to 212° F. before storage Color bleached Bleached to grey- ish pink or light gray Good Poor January 27th. 12 Same as No. 2, but heated to 212° F. before storage Color bleached Bleached to grey- ish pink or light gray Good Poor January 27th. 30 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION Table 1 — Cherries — {Continued) Expt. Treatment before storing Notes on August 2, 1919 Samples taken out and thawed on January 23, 1920 Date spoiled No. Color Flavor Texture at room temperature 13 Same as No. 3, but heated to 212° F. before storage Color bleached Bleached to grey- ish pink or light gray Good Poor January 27th. 14 Same as No. 4, but heated to 212° F. before storage Color bleached Good Poor January 29th. 18 Same as No. 11, but heated to 212° F. 20min. before storage At Room Tem- ^[perature: Color bleached Bleached Good Flavor of cherry in juice 6 Cherries in water with sulfurous acid At 32 F.: Bleached white Flavor- less Tough 16 Whole cherries Spoiled before August 2d. Bulletin 324 STORAGE OF PERISHABLE FRUITS 31 Table 2. — Apricots Stored at 8° F. to 12° F Date stored, July 31, 1919 Expt. No. Treatment before storage Observations, December 5, 1919 Observations, February-March, 1920 After 15 days at room Color Flavor Texture temperature 1 Whole fruit Color of skin dark, flavor good Flesh light, skin dark Disagree- able cold storage flavor Very soft Spoiled 2 Halved and pitted Browned badly, flavor good Browned Disagree- able flavor Very soft Spoiled 2a Halved and pitted in water Very bright color, flavor good Bright Good, fresh Rather soggy 3 Halved and pitt- ed in 30% sugar syrup Color good; taste somewhat too sweet Good Excellent Better than in water Sour 4 Same as No. 3, but 50% syrup used Color good, sweet, not frozen Good Very good Better than in water Poor flavor 5 Crushed Frozen solid, flavor good, brown only on top Good Good, fresh Spoiled 6 Crushed + equal sugar Not frozen, good flavor and color Good Very good No change 7 Halved, 50% sugar syrup, heated to 165° F. Good color, tastes sweeter than No. 4 Good Preserve- like flavor but good Very soft Fermented 8 Same as No. 7, but heated to 212° F. Good color, tastes sweeter than No. 4 Good Not so good as No. 7, more pre- served flavor Very soft Sour, moldy 13 Crushed 44 sugar and boiled Stored at 32 F. : Good color and flavor Good Not so good as No. 7, more pre- served flavor No change 9 Same as No. 5 Moldy by Aug. 15, 1919 10 Same as No. 6 As good as No. 6 Good Good No 11 Whole fruit (as No. 1) Moldy by Aug. 20, 1919 change 12 Crushed + equal sugar, heated to 212° F. Coating of sugar on top, good color and flavor As on Dec. 5 As on Dec. 5, preserve- like flavor 32 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION Table 3.' — Loganberries Stored at 8° F. to 12° F. Date stored, July 3, 1919. Expt. Treatment before storing Notes on August 14, 1919 Samples taken from storage on January 20, 1920 Date spoiled No. Color Flavor Texture at room temperature 1 None Color and flavor good, probably not quite so good as No. 2 Natural, a trifle bleached Aroma not so good as No. 3, fresh good flavor Fair January 23d. 2 Crushed Frozen, solid mass, color and flavor good Natural or a trifle lighter Aroma not so good as No. 3, fresh good flavor January 24th. 3 Crushed + equal sugar Not frozen, flavor excellent Natural Rich aroma, flavor very sweet, excellent Some berries hard; in general good February 28th dis- continued, very slight deteriora- tion 4 Crushed + equal sugar, heated to 165° F. Not quite so good as No. 2, slight preserved flavor Natural Same as No. 3, but slight preserved flavor Soft February 28th dis- continued, very slight deteriora- tion 5 Crushed + equal sugar, heated to 212° F. Not quite so good as No 2, slight preserve flavor Natural Same as No. 3, but pre- served flavor somewhat more pro- nounced Soft February 28th dis- continued, very slight deteriora- tion 6 Crushed, heated to 212° F. Stored at 32° F. Color and flavor good, but slight preserve flavor Natural Similar to No. 2 but not so fresh in flavor Soft January 25th. 7 Drawer of fruit Molded by July 27th. Bulletin 324 STORAGE OF PERISHABLE FRUITS Table 4. — Strawberries 33 Stored at 32° F. Date stored, July 3, 1919. Expt. Treatment before storing Observations on August 14, 1919 Samples removed from storage January 28, 1920 Date of spoiling No. Color Flavor Texture at room temperature 1 No treatment (2 baskets) Spoiled 2 Stemmed (2 baskets) Spoiled 16 Crushed 4- equal sugar Flavor and color good Very good Good (very sweet) Color faded but flavor fair on March 6, 1920 when dis- carded 21 Crushed + equal sugar and heated to 212° F. Slight preserve flavor, color good Good, very slightly faded and somewhat brownish Slight preserve flavor; too sweet Color faded but flavor fair on March 6, 1920 when dis- carded 22 Crushed +1§ wt. sugar, heated to 212° F. Stored at 8° F. to 12° F.: Slight preserve flavor, color good Good, but very slightly faded Preserve flavor Color faded but flavor fair on March 6, 1920 when dis- carded 8 Stemmed (4 baskets) Frozen solid, color and flavor good Good, slightly bleached Fresh Soft 3 Stemmed, stored in water Flavor very good, some color in the water Natural, good Fresh, very good Soft January 31st. 4 Stemmed, stored in 10% sugar syrup Better than No. 3 for flavor, some color in syrup Natural, good Fresh, excellent Soft February 2d. (sour) 5 Stemmed, stored in 20% sugar syrup Better than No. 3 for flavor, some color in syrup Natural, good Good excellent Soft February 2d. (sour) 6 Stemmed, stored in 40% sugar syrup Better than No. 3 for flavor Natural, good Good (sweet) Soft February 4th. 34 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION Table 4.- — Strawberries — {Continued) Stored at 8° F. to 12° F Date stored, July 3, 1919. Samples removed from storage January 28, 1920 Date Expt. Treatment Observations on of spoiling No. before storing August 14, 1919 at room Color Flavor Texture temperature 7 Stemmed, stored Better than Natural, Good, Soft February in 60% sugar No. 3 for flavor, good but some 6th. syrup some color in syrup what too sweet 9 Crushed berries, Flavor and color Natural, Good, February no sugar good good fresh 2d. (sour) 10 Crushed berries Flavor and color Natural, Very February +-J wt. of better than good good 6th. sugar No. 9 (sweet taste) 11 Crushed berries Flavor and color Natural, Very February +| wt. of better than good good 16th. sugar No. 9, plastic (sweet taste) 12 Crushed berries Nearly unfrozen, Natural, Very Color im- + M wt. of color good good good paired but sugar (quite sweet) flavor fair ; discon- tinued on March 6th 13 Crushed berries Unfrozen, Natural, Very Color im- + equal wt. of color good good good paired but sugar (very sweet) flavor fair; discon- tinued on March 6th 14 Crushed berries Unfrozen, too Natural, Very Color im- + Hwt. of syrupy, color good good paired but sugar good, berries tend to float (too sweet) flavor fair; discon- tinued on March 6th 15 Crushed berries Unfrozen, too Natural, Very Color im- + U wt. of syrupy, color good good paired but sugar good, berries tend to float (too sweet) flavor fair; discon- tinued on March 6th 17 Same as No. 11, Flavor scarcely Slight Sweet, February but heated to as fresh as No. darken- slight 20th. 165° F. 11, some pre- serve flavor ing preserve flavor ( Very 18 Same as No. 13, Syrupy, color Good, March 6th but heated to good but sweet, color im- 165° F. slight darkening some preserve flavor paired, flavor fair ; discon- tinued Bulletin 324 STORAGE OF PERISHABLE FRUITS 35 Table 4. — Strawberries — {Continued) Stored at 8° F. to 12° F. Date stored, July 3, 1919. Expt. Treatment before storing Observations on August 14, 1919 Samples removed from storage January 28, 1920 Date spoiling No. Color Flavor Texture at room temperature 19 Same as No. 15, but heated to 165° F. Syrupy, color good Good, but slight darkening Too sweet, some preserve flavor March 6th color im- paired, flavor fair; discon- tinued 20 Same as No. 13, but heated to 212° F. Preserve flavor, color deeper red than No. 13 Darken- ing of natural color Very sweet, more preserve flavor than No. 18 23 Whole berries, stemmed + equal sugar and heat to 212° F. for 4 minutes Preserve flavor marked, color decidedly darker Dark red not natural red Very sweet, more preserve flavor than No. 18 Fair, as in preserves Color nearly unchang- ed, flavor same 24 Same as No. 23, but l\ sugar by weight added at room temperature Preserve flavor marked, color decidedly darker Dark red not natural red Too sweet Fair, as in pre- serves Color nearly unchang- ed, flavor same 25 Strawberries + equal weight of sugar heat- ed to boiling and sealed hot in jars, stored at room tem- perature Quality and color fair Bleached to light brown Poor Soft 36 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION Table 5. — Red Raspberries and Currants Stored July 3, 1919 Observations, January 20, 1920, on Date Expt. Treatment Observations, thawed samples from storage of spoiling No. before storing August 14, 1919 at room temperature Color Flavor Texture Raspberry* 1 No treatment Solid, color good Very Very Fair to January flavor good good good soft 23d. Raspberry* 2 Crushed +f Plastic, color Very- Very Seeds February wt. of sugar and flavor good good sweet, excellent con- spicuous 12th. Raspberry* 3 Same as No 2 Plastic, color Good Very Seeds February but heated to good, flavor not sweet, con- 16th. 165° F. quite as good as No. 2 excellent spicuous Raspberry* 4 Same as No. 2 Plastic, color Good Very Seeds February but heated to good, flavor not sweet, con- 16th. 212° F. quite as good as No. 2 excellent spicuous Raspberry* 5 Crushed, heated Solid, color and Good Very Seeds January to 212° F. flavor good sweet, excellent con- spicuous 23d. Raspberry! 6 Untreated Date of mould- ing earlier than August 14th. , 7 Raspberry! Made into jam Color and flavor Brown Poor Poor and stored at good room temper- ature Currants (red) * 1 No treatment Solid, color and flavor good Good Good Soft January 23d. 2 Currants (red)* Crushed+equal Unfrozen, fresh Good Excellent Test dis- sugar color and taste very sweet continued on Feb- ruary 28th flavor slightly stale Currants (red)* 3 Crush + equal Darker than Good Not as Test dis- sugar, heat to No. 2, unfrozen fresh as continued 212° F. No. 2, more preserved taste on Feb- ruary 28th flavor slightly stale ''Stored at 8° F.-12 F. tutored at 82° F. Bulletin 324 STORAGE OF PERISHABLE FRUITS 37 Table 6.— Grape Juice at 8° F. to 12° F. On September 20th, 1919, several lots of ripe grapes of the varieties indicated in the following table were received from the University Farm. The red varieties were crushed; heated to 150° F., and pressed to extract the color. White varieties were crushed and pressed only. The juices were strained and placed in cold storage at 8° F. to 12° F. in open stoneware crocks. Check lots of the same juice were pasteurized at 165° F. in glass bottles and stored at room temperature for future comparison with the lots from cold storage. Lot Variety Treatment Observations, May 11, 1920 1 Alicante Bouschet Stored at 8° F. to 12° F. Color deep purplish red, flavor good, rich and fresh. No cooked taste. Superior to No. 2 2 Alicante Bouschet Pasteurized at 165° F., stored at room temper- ature Inferior to No. 1 in color, flavor, and aroma; noticeable cooked taste; color brownish red 3 Muscat Stored at 8° F. to 12° F. Flavor and aroma equal to those of fresh grapes although not so intense. Pro- bably some flavor and aroma have evaporated. Much superior to No. 4 4 Muscat Pasteurized at 165° F., stored at room temper- ature Inferior to No. 3; "raisin pie" flavor 5 Muscat + Alicante Bouschet Stored at 8° F. to 12° F. Rich Muscat flavor; color purplish red; much superior to No. 6 6 Muscat + Alicante Bouschet Pasteurized. Stored at room temperature Inferior to No. 5. Color brownish red. Flavor cooked. Aroma poor. Juice is better than average commercial juice 7 Isabella Stored at 8° F. to 12° F. Very rich Isabella flavor and aroma. Color deep purplish red 8 Isabella Pasteurized, stored at room temperature Inferior to No. 7. Color brownish red. Flavor noticeably cooked 9 Petite Sirah Stored at 8° F. to 12° F. Flavor about same as fresh juice. Color deep purplish red. No noticeable cook- ed taste 10 Petite Sirah Pasteurized, stored at room temperature Inferior to juice No. 9. Color brownish red. Flavor cooked 38 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION DISCUSSION OF TABLES From the results given in the foregoing tables certain conclusions may be drawn. The discussion of the results of the various tables will be taken up according to the individual fruits. Cherries. — Untreated cherries in open containers stored at 8°-12° F. soon became brown in color throughout by oxidation. This held true for both the pitted and unpitted fruit. Freezing the untreated cherries in water prevented darkening of the color during storage probably as a result of the exclusion of air. The natural light pink color of the Royal Anne was well preserved by this method. The substitution of syrups varying from 10-40% cane sugar content seemed to be no improvement over water as a storage medium, in so far as retention of color, quality and texture of the fresh fruit was concerned, although these syrups added some- thing to the flavor. Heating the fruit to 175° F. in water or dilute syrups before storage resulted in bleaching of the color of the cherries and in the imparting of a noticeable cooked taste. Heating to 212° F. intensified these defects giving a product very similar to ordinary canned cherries. Therefore, heating the fruit before storage seems inadvisable and an unnecessary expense. Untreated cherries stored at 32° F. soon became moldy. No storage tests of this fruit in syrups at 32° F. were made. Cherries stored in sulfurous acid by the usual commercial methods were inferior in flavor to those stored by the various freezing methods noted above. Apricots. — This fruit gave excellent results in several methods of storage at 8°-12° F. because of its stable color and rich flavor. The skin of whole untreated fruit stored at 8°-12° F. became brown; both the skin and flesh of the halved untreated fruit became brown at 8°-12° F. The fruit in both cases after several months' storage developed a very disagreeable ' ' cold storage ' ' flavor rendering the products made from them almost inedible. The halved fruit stored at 8°-12° F. in water or in syrups of 30% and 50% cane sugar, retained a remarkably fresh flavor and color, although the fruit softened noticeably on thawing. It appeared equal in all other respects to the fresh fruit. The crushed fruit with an equal weight of sugar added and stored at 8°-12° F. retained its fresh flavor and color in an excellent manner. It was found very suitable for ice cream, short cake, etc. Very ripe fruit required only about one-half its weight of sugar to give good Bulletin 324 STORAGE OF PERISHABLE FRUITS 39 results. Fruit crushed and with no sugar added, became brown at the surface, but the remainder of the lot to which air had no access was of excellent fresh color and flavor, indicating' that sugar is not necessary for the retention of flavor and color of the crushed fruit. Crushed fruit at 32° F. spoiled in about two weeks. Crushed fruit plus an equal weight of sugar stored at 32° kept perfectly. This same mixture heated to 212° F. and stored at 32° F. kept well, but possessed an tl apricot preserve" flavor. The unheated fruit was preferable to the cooked article and much superior in flavor to the ordinary canned apricot of commerce. Logwmberries. — Fewer tests were made upon this fruit than upon strawberries. Because of its extremely rich and permanent flavor as well as its deep color, the loganberry is a very satisfactory fruit for freezing storage. The fruit kept fairly well without treatment at 8°-12° F. There was, however, considerable shriveling and some loss of color and flavor. Untreated crushed fruit kept perfectly and seemed equal to the fresh fruit in every way. Sugar added to the crushed fruit reduced its tart flavor and made the fruit richer than the unsweetened article. Heating the crushed and sweetened fruit to 165° F. and 212° F. imparted a noticeable "jam "-like flavor. Heating is not recom- mended although it does deepen the color of the juice and softens the fruit. Unheated sweetened fruit if not thoroughly crushed tended to become hard through the effect of the sugar's removing moisture from the berries. . Untreated fruit at 32° F. became moldy in less than three weeks time. No tests of sweetened fruit were made at this temperature. Bed Raspberries. — This fruit required less sugar than loganberries for the imparting of a rich flavor. The untreated fruit at 8° F. to 12° F. shriveled slightly but retained its color and flavor well. The crushed fruit plus two-thirds its weight of sugar retained more of the fresh fruit aroma and flavor than did the unsweetened fruit. This amount of sugar rendered the fruit very sweet in flavor; a slightly smaller proportion would have been sufficient. The seeds of the crushed berries were quite conspicuous. Heating the fruit to 212° F. before storage imparted a cooked flavor. The unheated fruit was preferable to the heated product. Currants. — Untreated currants at 8°-12° F. retained their color and flavor remarkably well and were as suitable for jelly and jam as the fresh fruit. The crushed fruit to which was added an equal weight of sugar retained its fresh flavor to a greater degree than did 40 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION the untreated fruit. Heating- the crushed fruit to boiling before storage injured the quality slightly and is not recommended. Strawberries. — Strawberries held untreated at 32° F. spoiled in less than six weeks. The same fruit after crushing and mixing with an equal weight of sugar retained very well its flavor, color and aroma without molding or fermenting at 32° F. Heating the crushed fruit and sugar before storage injured the color and flavor. The use of one and one-half times as much sugar as fruit was tested, but this amount of sugar is not necessary and rendered the fruit too sweet. Berries frozen in water or dilute syrups and stored at 8°-12°F. were superior to the same fruits stored untreated at this same tem- perature. The berries tended to float in very heavy syrups. The flavor and color of the fruit stored in water was as good as those of the lots stored in syrups. Untreated berries in open containers shriveled slightly and lost some of their color. Crushed unsweetened berries retained their flavor and color very well at 8°-12° F. The addition of sugar to the crushed berries before storage made the flavor richer but this addition is not necessary. With more than an equal weight of sugar the crushed fruit tended to float. Heating the crushed fruit impaired the color and quality. Strawberries preserved by the usual household method by cooking with an equal weight of sugar and storing in sealed containers were much inferior to fruit preserved at 8°-12° F. after similar prelim- inary treatment; and very much inferior to the sweetened unheated fruit stored at 8°-12° F. Grape Juice. — All grape juices stored 8°-12° F. were very much superior in every respect to the same juices preserved by pasteurizing at 165° F. The bright fresh color of the juices from cold storage was in great contrast to the brownish red color of the pasteurized juices. Pasteurized Muscat juice possesses a strong characteristic "raisin" flavor; the juice held at 8°-12° F. resembles the fresh juice in flavor and aroma. The juices in cold storage were held in open containers, a con- dition which resulted in considerable volatilization of flavor and aroma. Doubtless sealed containers would greatly reduce this loss. In general, the quality of the cold stored juices was so much superior to that of the pasteurized juices that freezing as a means of preserving fruit juices should in time compete with pasteurization. Preliminary tests with apple juice indicate that it also retains its flavor and aroma very well at 8°-12° F. BULLETIN 324 STORAGE OF PERISHABLE FRUITS 41 UTILIZATION OF FRUITS FROM FREEZING STORAGE The fruit from the more important experiments described else- where in this report were made into various products such as jellies, jams, canned fruits, preserves, candied fruits and ice cream. Cherries held in freezing storage in water or syrup gave excellent results for candying, for preserves, for cooking purposes and for can- ning. Those stored untreated in open containers were brown in color and inferior in flavor for the above purposes, to fruit stored in water or syrup. The texture of the products was in all cases good. Storage of pitted cherries in water at 8°-12° F. should prove a satis- factory method of storing the fruit for use in the preparation of Maraschino and candied cherries. This product is certainly more wholesome and more attractive in flavor than is the same fruit held in sulfurous acid solution. Cherries stored without treatment were not so satisfactory for pies as were those stored under water. Apricots stored untreated in open containers became brown in color and developed a very disagreeable flavor which precluded their satisfactory use in preserves, etc. The fruit held at 8°-12° F. under water or syrup was excellent for jams and marmalades, although some- what soft for canning. The flavor of jams made from this fruit was equal to that of the same products made from the fresh fruit. Crushed apricots preserved at 8°-12° F. with an equal weight of sugar produced an ice cream of very rich fresh fruit flavor and of excellent color. No additional sugar was necessary in preparing the ice cream. The crushed unsweetened apricots made an excellent ice cream after sweetening with sufficient sugar. The heated fruit produced an ice cream of very pleasing flavor, but slightly darker in color with more of a cooked flavor than did the other two lots. As a check ice cream was made from home preserved apricots. Although of good quality, this ice cream was not equal in flavor to that prepared from the unheated crushed fruit. The tests clearly demonstrated the superiority of the crushed unheated fruit from cold storage for use in ice cream and other frozen dishes where the fresh rather than the "preserved" flavor of the fruit is desired. Strawberries yielded results in the preparation of various products similar to those obtained with apricots. The unsweetened crushed fruit, the crushed unheated sweetened fruit and the crushed sweetened fruit heated to 165° F. before storage were used in ice cream making. Of these the unheated, unsweetened crushed fruit gave the best flavor. The fruit heated to 165° F. gave a slightly darker ice cream of less 42 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION fresh fruit flavor than did the other two lots, but was still of very pleasing quality. The crushed sweetened berries were used successfully without further sweetening in short cakes. The flavor and color of this fruit for this purpose were equal to those of the fresh fruit. Using the fruit from cold storage, a comparison was made of the quality of strawberry jams and preserves made by the usual open kettle process and by cooking under a vacuum. The latter process gave products of remarkably fresh fruit flavor and color; superior in every way to the usual kettle-cooked article. The same results were obtained with loganberries, red raspberries and apricots. This method deserves attention from preserve manufacturers. Loganberries from the cold storage tests previously described were tested for ice cream and for pies. The results were similar to those obtained with strawberries. The crushed fruit was very satisfactory when used on ice cream "sundaes" and should be excellent for ice cream sodas and similar fountain specials. The unsweetened fruit was satisfactory for jelly making, giving a jelly of good color, flavor and texture, but for some reason not yet clearly understood, the sweetened fruit failed to give a firm jelly. This same trouble was also encountered with sweetened currants from freezing storage. Raspberries crushed, sweetened with two-thirds of their weight of sugar and held at 8°-12° F. gave excellent ice cream. This crushed fruit was also very satisfactory for use as a jam or spread for bread or as a dressing for ice cream sundaes, etc. The heated fruit was satisfactory, but not of quite such fresh flavor as the unheated. Currants stored without sugar gave good results in jelly making. The product was equal in every way to that made from the fresh fruit. i : i; I: , IHJ I In general, fruits of the varieties used in the tests were after six to ten months at 8°-12° F. equal to the fresh fruits for most purposes. SUMMARY 1. Soft fruits such as apricots, cherries and berries can be pre- served at cold storage temperatures of 32° F. for not more than a week to three weeks. Present commercial methods of storing these fruits at temperatures lower than 32° F. are not standardized and are in many cases unsatisfactory. 2. These fruits if held in water or syrup at 8°-12° F. retain their flavor and color very well for at least a year. Lots of certain of these BULLETIN 324 STORAGE OF PERISHABLE FRUITS 43 same fruits held at 8°-12° F. in open containers without liquid, in time lose color and flavor. This is especially true of cherries, which become brown, and of apricots which in time develop a disagreeable "cold storage" flavor and a brown color. Berries in open baskets retain their color and flavor very well. 3. The crushed fruits with or without sugar retained their color and flavor almost perfectly at 8°-12° F. for almost a year; the dura- tion of these tests. This fruit was excellent for ice cream, for pies, for use as a jam on bread, for shortcakes and general soda fountain use. 4. Grape juice stored at 8°-12° F. was very much superior to the juice preserved by pasteurization. 5. Former brewing plants are well equipped for undertaking the storage of soft fruits and fruit juices by the methods discussed and recommended in this report. The storage of these fruits should form a profitable method of utilizing such otherwise idle equipment. 6. The storage of these fruits will be studied further during the present fruit season. STATION PUBLICATIONS AVAILABLE FOR FREE DISTRIBUTION BULLETINS No. 168. Observations on Some Vine Diseases in Sonoma County. 169. Tolerance of the Sugar Beet for Alkali. 185. Report of Progress in Cereal Investiga- tions. 208. The Late Blight of Celery. 250. The Loquat. 251. Utilization of the Nitrogen and Organic Matter in Septic and Imhoff Tank Sludges. 252. Deterioration of Lumber. 253. Irrigation and Soil Conditions in the Sierra Nevada Foothills, California. 257. New Dosage Tables. 261. Melaxuma of the Walnut, " Juglans regia." 262. Citrus Diseases of Florida and Cuba Compared with Those of California. 263. Size Grades for Ripe Olives. 266. A Spotting of Citrus Fruits Due to the Action of Oil Liberated from the Rind. 267. Experiments with Stocks for Citrus. 268. Growing and Grafting Olive Seedlings. 270. A Comparison of Annual Cropping, Bi- ennial Cropping, and Green Manures on the Yield of Wheat. 271. Feeding Dairy Calves in California. 272. Commercial Fertilizers. 273. Preliminary Report on Kearney Vine- yard Experimental Drain. 274. The Common Honey Bee as an Agent in Prune Polination. 275. The Cultivation of Belladonna in Cali- fornia. 276. The Pomegranate. 277. Sudan Grass. 278. Grain Sorghums. 279. Irrigation of Rice in California. 280. Irrigation of Alfalfa in the Sacramento Valley. 282. Trials with California Silage Crops for Dairy Cows. 283. The Olive Insects of California. No. 285. 286. 288. 290. 297. 298. 299. 300. 301. 302. 303. 304. 308. I. 309. I. 310. 311. 312. 313. 314. 316. 317. 318. 319. 320. 321. 322. 323. 324. 325. The Milch Goat in California. Commercial Fertilizers. Potash from Tule and the Fertilizer Value of Certain Marsh Plants. The June Drop of Washington Navel Oranges. The Almond in California. Seedless Raisin Grapes. The Use of Lumber on California Farms. Commercial Fertilizers. California State Dairy Cow Competition, 1916-18. Control of Ground Squirrels by the Fumigation Method. Grape Syrup. A Study on the Effects of Freezes on Citrus in California. Fumigation with Liquid Hydrocianic Acid. II. Physical and Chemical Pro- perties of Liquid Hydrocianic Acid. The Carob in California. II. Nutri- tive Value of the Carob Bean. Plum Pollination. Investigations with Milking Machines. Mariout Barley. Pruning Yound Deciduous Fruit Trees. Cow-Testing Associations in California. The Kaki or Oriental Persimmon. Selections of Stocks in Citrus Propagation. The Effects of Alkali on Citrus Trees. Caprifigs and Caprification. Control of the Coyote in California. Commercial Production of Grape Syrup. The Evaporation of Grapes. Heavy vs. Light Grain Feeding for Dairy Cows. Storage of Perishable Fruit at Freezing Temperatures. Rice Irrigation Measurements and Ex- periments in Sacramento Valley, 1914- 1919. No. 65. 70. 76. 82. 87. 109. 111. 113. 114. 115. 117. 124. 126. 127. 128. 129. 130. 131. 133. 135. 136. 137. 138. 139. CIRCULARS No. The California Insecticide Law. 140. Observations on the Status of Corn Growing in California. Hot Room Callusing. 143. The Common Ground Squirrels of California. 144. Alfalfa. 147. Community or Local Extension Work by 148. the High School Agricultural Depart- 152. ment. The use of Lime and Gypsum on California 153. Soils. Correspondence Courses in Agriculture. 154. Increasing the Duty of Water. Grafting Vinifera Vineyards. 155. The Selection and Cost of a Small Pump- 156. ing Plant. 157. Alfalfa Silage for Fattening Steers. 158. Spraying for the Grape Leaf Hopper. 159. House Fumigation. 160. Insecticide Formulas. 164. The Control of Citrus Insects. 165. Cabbage Growing in California. Spraying for Control of Walnut Aphis. 167. County Farm Adviser. 168. Official Tests of Dairy Cows. Melilotus Indica. 169. Wood Decay in Orchard Trees. 170. The Silo in California Agriculture. The Generation of Hydrocyanic Acid Gas 172. in Fumigation by Portable Machines. 173. The Practical Application of Improved Methods of Fermentation in California Wineries during 1913 and 1914. Control of Grasshoppers in Imperial Valley. Oidium or Powdery Mildew of the Vine. Tomato Growing in California. "Lungworms". Some Observations on the Bulk Handling of Grain in California. Announcement of the California State Dairy Cow Competition, 1916-18. Irrigation Practice in Growing Small Fruits in California. Bovine Tuberculosis. How to Operate an Incubator. Control of the Pear Scab. Home and Farm Canning. Agriculture in the Imperial Valley. Lettuce Growing in California. Small Fruit Culture in California. Fundamentals of Sugar Beet Culture under California Conditions. Feeding Stuffs of Minor Importance. Spraying for the Control of Wild Morning- Glory within the Fog Belt. The 1918 Grain Crop. Fertilizing California Soils for the 1918 Crop. Wheat Culture. The Construction of the Wood-Hoop Silo. CIRCULARS— Continued No. 174. Farm Drainage Methods. 175. Progress Report on the Marketing and Distribution of Milk. 176. Hog Cholera Prevention and the Serum Treatment. 177. Grain Sorghums. 178. The Packing of Apples in California. 179. Factors of Importance in Producing Milk of Low Bacterial Count. 181. Control of the California Ground Squirrel. 182. Extending the Area of Irrigated Wheat in California for 1918. 183. Infectious Abortion in Cows. 184. A Flock of Sheep on the Farm. 185. Beekeeping for the Fruit-grower and Small Rancher or Amateur. 187. Utilizing the Sorghums. 188. Lambing Sheds. 189. Winter Forage Crops. 190. Agriculture Clubs in California. 191. Pruning the Seedless Grapes. 193. A Study of Farm Labor in California. 195. Revised Compatibility Chart of Insecti- cides and Fungicides. 197. Suggestions for Increasing Egg Produc- tion in a Time of High-Feed Prices. No. 198. Syrup from Sweet Sorghum. 201. Helpful Hints to Hog Raisers. 202. County Organization for Rural Fire Control. 203. Peat as a Manure Substitute. 204. Handbook of Plant Diseases and Pest Control. 205. Blackleg. 206. Jack Cheese. 207. Neufchatel Cheese. 208. Summary of the Annual Reports of the Farm Advisors of California. 210. Suggestions to the Settler in California. 213. Evaporators for Prune Drying. 214. Seed Treatment for the Prevention of Cereal Smuts. 215. Feeding Dairy Cows in California. 216. Winter Injury or Die-Back of the Walnut. 217. Methods for Marketing Vegetables in California. 218. Advanced Registry Testing of Dairy Cows. 219. The Present Status of Alkali. 220. Unfermented Fruit Juices. 221. How California is Helping People Own Farms and Rural Homes.