How to Minimize Quality Losses by Gerald D. Kuhn and Louise W. Hamilton

All methods of preserving food will There is no single, ideal maturity alter, if not lower, the quality of for harvesting or preserving fruits fresh fruits and vegetables, but these and vegetables. Obviously, the qual- changes can be minimized. For prac- ity of canned or frozen products tical understanding of how to mini- made from any maturity other than mize quality changes you need to ideal for that specific commodity know something about: (1} natural lacks the ultimate potential of satis- differences in raw food, (2) natural faction for eating. causes of quality deterioration, and Three natural causes account for [3) how various food handling, prep- most quality changes in freshly har- aration, packaging and storage tech- vested fruits and vegetables — res- niques and conditions affect quality piration, enzymes and oxygen. Their retention. effects generally increase with the Because of insufficient research in- time between harvest and preserva- formation on home preserved foods, tion, and at higher temperatures.- some research findings of commer- Freshly harvested fruits and vege- cially processed food have been used tables are living organisms. They are to foster an increased awareness of sustained by cellular reactions known factors affecting the quality of home as '^respiration," in which native en- preserved food. zymes use oxygen and components Natural differences in quality and in food and give off heat, water and nutrient content in raw food often carbon dioxide. The energy needed exceed losses caused by preserving to sustain respiration is obtained food. Extreme variations (tenfold or from a storehouse of natural com- more) in vitamin A and C content ponents in food. As a result, natural have been found in some fruits and flavors and vitamins are diminished, vegetables. These natural differences sugars and sometimes acids decrease, are known to be caused singly or and texture may soften. The speed collectively by differences between of respiration and the onset of its varieties, climate changes between effects differs among various fruits seasons in the same region, and be- and vegetables, and is generally low- tween regions in the same year. They ered by refrigerator temperatures. are also influenced by some cultural Besides enzymes relating to respi- practices, and maturity of crops at ration, fruits and vegetables some- harvest. times contain other cellular enzymes Because of color, texture and es- associated with reducing food qual- pecially flavor qualities, some varie- ity. These enzymes act with oxygen ties are more suited for canning; to cause rapid discoloration of others are more suitable for freez- bruised, peeled and sliced tissue; oxi- ing. Few varieties possess the all- dation of flavors, and excessive purpose criteria needed to preserve softening. them as either high-quality canned or The roles of oxygen in respiration frozen products. and other enzyme reactions have been noted. Oxygen may react still another Gerald D. Kuhn is Professor, Food Sci- way to lower food quality: autoxida- ence Extension, and Louise W. Hamilton tion, where sensitive flavor, color and is Professor, Foods & Nutrition Exten- vitamin components are altered by sion, The Pennsylvania State University, oxygen. This causes fading of colors, University Park. off-flavors and, reduced vitamin re-

304 tention. These reactions occur quick- ly during canning and drying of foods, and also account for slow changes during storage of preserved food. Handling Raw Foods Because of the effects of respira- tion, other enzymes, autoxidation, and desiccation (loss of water), the raw product temperature and the time between harvest and preserva- tion are of utmost importance to pre- serving high-quality fruits and vegetables. Ideal handling conditions vary with the product. Small berry and stone Significant losses of water-soluble fruits, asparagus, green beans, beets, vitamins and minerals occur when broccoli, corn and leafy greens, to food contacts water, such as in wash- name a few, should be preserved the ing, blanching, cooking or canning same day of harvest, for highest qual- foods. As would be expected, losses ity. Apples, peaches, pears, plums due to leaching of water-soluble vita- and tomatoes, if harvested at firm mins and minerals rise with in- maturity, should be ripened a few creased cut or exposed food surface days before preserving them. Other areas, repeated exposures to water, fruits and vegetables may be stored and more time in water, especially from a week to months before pres- when heated. ervation without significantly lower- The effects on fiber in preserved ing their quality. food is much the same as in fresh From a nutritional standpoint, if cooked foods. after harvest the handling and pres- ervation of these crops are carefully Canning planned and implemented, quality of Home canned foods should have a the preserved products can be equal bright color, characteristic texture, to food prepared from fresh market pleasant flavor and contain nutrients fruits and vegetables. naturally present. When all steps of Fruits and vegetables are recog- scientifically based canning direc- nized as significant sources of vita- tions are carefully followed, color, mins A, the B family, C, minerals, texture and flavor will be optimum. and fiber. These observable signs of quality are Vitamin A, pro-carotene, is also an index to nutrient retention of heat-stable and insoluble in water that canned food. but is subject to a minor loss caused Proper pretreatment of the fruit or by autoxidation. Therefore, losses vegetable being canned is essential in home preserved foods are for top quality. This includes using insignificant. only good, wholesome food at peak Of the water-soluble vitamins, as- eating quality. Any trace of moldy or corbic acid (C) and thiamin (Bi) are otherwise spoiled food should be subject to serious loss upon heating completely removed. All food must foods. Riboflavin {B2) is subject to be washed thoroughly. loss when raw or preserved foods Removing the skins from peaches before are exposed to light. canning.

305 Removal of skins from thin-skinned vegetables may be safely canned foods such as tomatoes and peaches without salt, but when salt is used, is important. A short blanching time better flavor results. Salt is essential in boiling water loosens the skins, for slow process pickles; vinegar is and a short cooling time in cold or ice needed for quick process pickles. water stops the cooking of the food. Canning or pickling salt should al- Because water leaches out vitamins, ways be used. Iodized salt will inhibit , dilutes color and flavor, and results proper fermentation and react with in a mushy product, do not allow the starch in some foods, causing foods to soak unnecessarily in either them to turn pink or blue. hot or cold water. Sugar concentration in sirups is Air is an enemy of light-colored important to appearance of the fruit. foods, and should be kept from the With a light sirup, fruits are less peeled or cut food. This can be done likely to float than with a heavier with a commercial antioxidant (as- sirup. And with a light sirup, fewer corbic acid), lemon juice, or a simple calories are added. Then too, the solution of two tablespoons each of cost is less than with a medium or vinegar and salt per gallon of water. heavy sirup. Peel or cut food directly into such a solution for maximum protection Headspace from air. When enough food for a Using the proper amount of head- canner load is prepared, drain and space pays off in quality products. rinse the food for best flavor. Adequate headspace is needed so The packing method used is one of food has enough room for expansion the most important factors in quality during heat sterilization. canned products. Foods that are Generally, more headspace is heated before being put in jars have needed for foods heat-sterilized in a better quality than foods packed raw pressure canner than those in a boil- in jars. Heating destroys enzymes and ing water canner, because of in- removes much of the air from food creased expansion of foods at the tissues. higher temperature. Enzymes must be destroyed quickly With too little headspace, liquid is for top-quality food. Removal of air more likely to cook out of the jars not only shrinks the,food, but leads during heat sterilization. This in- to better color, flavor and nutrient re- creases the danger of seal failure due tention, and too, fruits are less likely to food particles that may be trapped to float. Hot packed jars also have at the interface of the sealing surface. higher vacuums, thus less oxidation With too much headspace, air remain- can take place. ing in the jar can cause darkening of Tomatoes and tomato juice are less the food, oxidized flavor, and lower likely to separate if tomatoes are cut vitamin retention, especially in food and heated at once. Cutting activates at the top of the jar. enzymes in tomatoes which then Pressure canning low-acid foods is change the pectins in the tomatoes receiving increased emphasis today, and causes separation. Heating right mainly based on the greater safety of after cutting inactivates the enzymes this technique. The method also and minimizes separation. offers an additional advantage that Sugar, salt and vinegar play impor- is little known to home canners— tant roles in quality canned foods. improved quality and nutrient While sugar is not needed to safely retention. can fruits, it contributes to better Generally an 18" F (10" C] rise in color, flavor and texture. Likewise, canner temperatures increases the

306 destruction of bacteria tenfold. At must allow air, but not liquid, to es- the same time, chemical changes cape during heat sterilization. A low that affect color, flavor, texture and liquid level in the jar may indicate the nutrients of the food are only lid did not function properly, pres- doubled. sure was allowed to fluctuate in the This means that for every 18° F pressure canner, or the canner wasn't [10° C) increase in canning tempera- cooled completely before opening, or ture, bacteria are destroyed five raw pack was used. Foods not cov- times faster than are vitamins, flavor, ered with liquid will have poorer color and texture. Accordingly, in quality. contrast to boiling w^ater canning, Jars must be air-cooled naturally heat sterilizing in a pressure canner after heat sterilization to maintain at 240° F [116° C] (10 p.s.i.) destroys quality as well as for safety. Delayed bacteria about 17 times faster than cooling in tightly enclosed areas, such chemical changes are effected, ac- as cardboard cartons, will decrease counting for better nutrient and qual- quality of the product. ity retention of pressure canned low- Storage conditions are vital to qual- acid foods. ity of canned foods. If stored in a Be cautious about interpreting this light, rather than a dark place, light- as an advantage in pressure sterilizing sensitive colors will darken gradu- acid foods. This technique can in- ally. Some colors, such as carot- crease quality and nutrient losses be- enoids in tomatoes and carrots will cause of the total time the jars of gradually fade with prolonged storage. food v^ill be near or above boiling Storage temperatures between 40 water temperature. to 50° F (4.5° to 10° G). if the spot For example, with tomatoes it takes is dry, are best for quality retention. about 5 minutes until steam begins to Quality losses are increased when escape, 10 minutes to exhaust the air, canned foods are stored at higher about 5 minutes to build up pressure, temperatures. For example, about a 5 minutes for heat sterilizing at 240° F third of the vitamin C is lost if foods [116° C) and 30 to 45 minutes cool- are stored a year at temperatures of ing before opening the canner. That 80° F (26° C) or higher. adds up to about 55 to 80 minutes at Storage temperatures between 50° temperatures near or above 212'' F to 70° F (10° to 21° C) are accept- (100° C), as compared to the recom- able. mended 35 minutes for heat steriliz- Properly canned and stored foods ing in a boiling water canner. Assum- should be safe to eat for more than ing the average product temperature two years. However, for top quality, is elevated above 212° F (100° C) it is best to can only the amount to about half of this total time, the loss be used in one year. in quality could be at least doubled. Top quality home canned foods Properly managed heat steriliza- have rich, jewel-like colors, character- tion has a great deal to do with the istic of the food canned. Colors are quality of canned food. If the tem- those of well-prepared foods ready to perature is too high or the time of be served, rather than fresh uncooked sterilization too long, the result is a foods or over-cooked foods. Light- product with poor color, soft texture, colored foods should retain their and less flavor. Tomatoes canned in color with no signs of darkening at the pressure canner are an example. tops of jars. Fruits should look nei- After heat sterilization, a quality ther under-ripe and hard, nor over- canned food will have liquid cover- ripe and mushy. Vegetables ought to ing the solid food in the jar. The lid look young and tender, rather than

307 old and starchy. Vegetables and fruits aging quaUty frozen foods. If the seal should be free of stems, cores, seeds, itself is not moisture-vapor-proof, it or pieces of skin, and be of uniform becomes the weakest part of the pack- size, shape and color. age and poorer quality results. Adequate labeling helps assure that Freezing each package of food is used while Freezing, like canning, does not at top quality. Packages kept too long improve food quality. Top quality will be of poor quality. Even with the fresh fruits and vegetables are essen- finest produce and use of the best tial for premium frozen products. preparation and packaging pro- Quality factors include a suitable cedures, retention of quality in frozen variety for freezing, optimum matur- food is affected by how quickly food ity, and freshness of the product. is frozen, the temperature of food Even with high quality, fresh produce, stored in the freezer, and how long it is imperative to freeze foods on the it is frozen before eating. day when they are at their peak of For top quahty, avoid freezing per maturity or ripeness for eating fresh. day, more than two pounds of fresh Selection; sorting and trimming of packaged food per cubic foot capacity produce and the quality control steps of your home freezer. Food packages as related to color, flavor, and nutri- to be frozen should be spread one ent retention described for canning package deep over the bottom or high quality fruits and vegetables other areas designated by your apply equally to preservation by freezer manufacturer. The freezer freezing. However, most vegetables should be regulated to a uniform must be blanched before packaging temperature between 0° F [—18° C) and freezing to prevent slow but ac- and minus 5° F (—21° C). A freezer cumulating effects of enzyme activity temperature fluctuation of more than and autoxidation. These effects, if 5° F should be avoided if possible. not prevented, will cause discolora- Freezing too slowly, temperatures tion, oxidized flavors [sometimes de- above 0° F, and temperature fluctua- scribed as tasting grassy or hay-hke), tions in freezers increase the ice and increased loss of vitamins, espe- crystal size in frozen food, lower the cially A and G. Proper blanching rec- quality and shorten the shelf life of ommendations are contained in the food. Frozen foods should be used ac- USDA Home and Garden Bulletin No. cording to the guidelines in the 1974 10, Home Freezing of Fruits and Yearbook of Agriculture, Shoppers Vegetables. Guide. The quality of packaging materials QuaHty frozen fruits and vegetables used is reflected in overall quality of should have the natural color, texture the frozen product. Packaging ma- and flavor of the individual food. terials must be moisture-vapor-proof. There should be a minimum of ice This means there is no transfer of crystals inside the package and no hquids or vapors from the inside to sign of freezer burn. the outside, or from the outside to the Frozen foods should be higher in inside of the frozen packages. ascorbic acid and thiamin than In addition, fruits and vegetables canned foods. Vitamin C, including must be packaged in containers with that leached into the juices, ap- as little air inside as possible. Air proaches 90 percent of the value of left inside will oxidize the food, caus- raw fruits. ing deterioration of color, flavor and nutrients. Drying Proper sealing is essential for pack- Quality fruits and vegetables can

308 be sun-dried or dried inside using an or vegetable, whether fresh or pre- oven or a food dehydrator. As with served, may be about the same. other methods of preservation, Top quality, garden fresh foods, quality of the final product will de- served in season, provide the greatest pend greatly on quality of the fresh satisfaction when served fresh as food being dried. Drying does not im- table-ready food. Individual prefer- prove the quality of any food. ences for market fresh, frozen canned, A top quality dried product re- or dried food will differ. Since nu- flects suitable pre-treatment before trient content is nearly the same, the drying, and adequate drying under choice is up to the consumer. Even proper conditions. Also, appropriate more important is the choice of vege- storage after drying is vital to keep tables and fruits for a good diet. moisture from re-entering the dried product. For Further Reading: Fruits may be dried more easily Food editors of Farm Journal, How to than vegetables, because of their high Dry Fruits and Vegetables at Home, sugar content and since not as much Countryside Press and Doubleday & moisture must be removed to get a Company {Dolphin Books), 1975. $2.95. quality product. When properly dried, Hamilton, Louise W., Kuhn, Gerald D., fruits should be leathery and pliable, Rugh, Karen A., with the food editors of Farm Journal, Home Canning—The and have a color characteristic of the Last Word, Countryside Press and fruit. Excessive darkening indicates Doubleday & Company (Dolphin a less desirable, poorer quality Books], 1976. $2.95. product. U.S. Department of Agriculture, Home Vegetables must be dried until they Canning of Fruits and VegetabJes, are brittle. The color should be char- H&G Bui. No. 8, on sale by Superin- acteristic of the vegetable and not tendent of Documents, U.S. Govern- excessively dark. ment Printing Office, Washington, To sum up, nutrient content of D.C. 20402, 45í¿. foods depends on natural differences, U.S. Department of Agriculture, Home control of deterioration, and handling Freezing of Fruits and Vegetabies, H&G Bui. No. 10, on sale by Superin- techniques of food preparation as tendent of Documents, U.S. Govern- well as preservation. Therefore, over- ment Printing Office, Washington, all nutrient content of a specific fruit D.C. 20402. 75^.

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