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.