per 100 grams. The daily human require- ment is 20 milligrams. They contain a Prune Products moderate amount of the vitamin pano- thenic acid. All of these vitamins are quite well retained through drying and improved processing and new storage. Vitamin C is completely lost in the uses developed by research usual methods of drying. It is possible that some vitamin C would be retained by steam blanching before drying. Pre- W. V. Cruess vious work showed that sulfuring before drying retains much of the vitamin C Molds and yeasts in packaged prunes may be packed in paper milk bottles or content of dried fruits. but it destroys can be destroyed by a few drops of propyl- similar paraffined containers or in jars vitamin B,. ene oxide. or cans and preserved by freezing. Partially dried prunes of 283 to 33'L While juice as such keeps well frozen moisture-directly off the dehydrater it is also very satisfactory when bottled or Granules and Powders trays and heated sufficiently to destroy canned in reenameled cans and preserved Prunes and other dried fruits processed enzymes--can be packed and sterilized to by heat sterilization. in water to about 30%' to 35% moisture, keep for months as a tender and juicy purbed, mixed with two to three parts by product of excellent eating quality. weight of dextrose, sieved, and dried also Research has demonstrated that it is Storage Deterioration can be broken up into granules or pow- perfectly feasible and practicable com- Dried fruits deteriorate in color, odor dered. The granules and powders are mercially to sterilize prunes in plastic- and flavor on prolonged storage and are suitable for preparing drinks simply by sheet lined cartons by adding a few drops also subject to infestation by insects, the addition of water or milk, and mixing of propylene oxide to the carton and heat sugar, molding and fermentation where to taste. sealing in the usual way. The fumigant conditions are favorable to these changes. The powdered product serves fairly destroys all molds and yeasts and then Even at moisture content below that well to flavor milk shakes and ice cream. evaporates through the walls of the con- ordinarily considered necessary for yeast Both granules and the powder can be used tainer, leaving the sterilized prunes ten- growth, prunes-particularly in bins and in candies, bread dough, cookie dough der and tasty. boxes-may undergo fermentation by and in other ways. The propylene oxide treatment may yeasts. revolutionize the prune processing and Contrary to previous belief, sulfur packing industry. dioxide will not permanently prevent Use in Confectionery prunes darkening in color as darkening Prunes may be used in preparing jel- is in part due to reactions between amino lied candies with pectin, sugar, citric acid, Prune Juice acids and sugars of the dried fruits. and corn syrup or invert syrup. The method of producing prune juice A prune jelly made with prune juice, in general use today consists in extract- fruit pectin, sugar, citric acid and corn ing the prunes three successive times with Dietary Value or invert syrup, cooked to the jellying water at or near the boiling point, coin- Prunes are high in readily digestible point and then mixed with about twice bining the three extracts, adjusting to 20" carbohydrates, chiefly invert sugar, that its weight of chopped pitted prunes gives Balling and canning or bottling, and ster- are useful sources of energy and tissue an excellent candy suitable for cutting ilizing. building materials. into bars or for boxing. Recently experiments were conducted It is possible that the vitamin B, con- to improve the quality of prune juice. tent of prunes may be concerned as one Flavor and aroma were superior when of the factors in the laxative value of Other Uses the prunes were extracted at 17s" to prunes. Canning of the prunes and juice Several other uses for prunes and 185°F instead of at the boiling point. does not affect the laxative value ad- prune pulp, as in catsup, chutney, jams, The juice retained its flavor, color and versely. butters, preserves, jelly, etc., have been aroma much longer and more satisfac- Prunes and prune juice do not cause developed. torily in reenameled tin cans than in plain dietary acidosis; that is, they do not re- Prune concentrate has been diluted and tin. Bottles were superior to tin cans in duce the carbon dioxide binding power carbonated in experiments and then bot- these respects. of the blood. Results of thorough tests tled as a carbonated beverage. It is re- The addition of about 0.2% of citric show that the common belief that prunes freshing and healthful. acid greatly improved the juice, for most lower the alkaline reserve of the blood is who unfounded and erroneous. W. V. Cruess is Professor of Food Technol- of those tasted the juices. Very small ogy and Biochemist in the Experiment Station, prunes gave a juice of poor flavor. The Prunes are a good source of iron and Berkeley. experimental juice prepared with these contain some copper. The propylene oxide treatment for packing various improvements was found to be It has been determined that prunes dried prunes was discovered and developed by considerably superior to several commer- are an excellent source of carotene-vita- Professor E. M. Mrak and Assistant Professor cial juices purchased in the local market. min A. Their B,-thiamin-content was H. J. Phaj, Division of Food Technology. fair, at 0.3 to 0.5 milligrams per 100 Associate Professor Gordon Mackinney and associates, Division of Food Technology are con- Frozen Juice and Concentrate grams; the human daily requirement be- ducting the research on the problem of color ing about 1.5 to 2.0 milligrams. They darkening in dried fruits mentioned in the fore- Juice and concentrate prepared by pro- were somewhat higher in vitamin B, or going report. gressive extractions at 180" to 190" F G-riboflavin-than in B,, that is 0.5 to The research on the dietary value of dried keep perfectly when stored at 0°F. Prune 1.8 milligrams per 100 grams. prunes was conducted by Professor Agnes Fay Morgan and staff of the Departnient of Home concentrate prepared to 50" to 60" Brix They were low in the anti-pellagra vita- Economics and Professor E. M. Mrak, Division by the progressive extraction procedure min, nicotinic acid; 1.5 to 2.2 milligrams of Food Technology.

12 CALIFORNIA AGRICULTURE, NOVEMBER, 1948