Modern Food Processing MILDRED M. BOGGS AND CLYDE L. RASMUSSEN A FEW of the 5 thousand-odd food water or warmth. Both processes items sold in a modern super- destroy some organisms but not all. ^ market are fresh, but most of The organisms grow again if water or them are processed—canned, waxed, warmth is restored. dried, frozen, bottled, pickled, pack- Some common ways to slow down aged, wrapped, baked, changed in one chemical changes are to keep foods way or another. cool, protect them from light, add Stabilization of foods, which keeps chemicals that interfere with reactions, them from spoiling, is a main purpose and minimize contact of the food with of processing. air—by driving the air off with heat, Micro-organisms are the first thing removing it with vacuum, or replacing we think of in connection with deteri- the air of the package with an inert oration of food. Yeasts and molds work gas, such as nitrogen, which does not primarily on acid fruits and cause combine with foods. them to become soured, yeasty, or To cut down the loss of vitamins and moldy. Bacteria, the main trouble- minerals, a processor has to keep in makers in most other foods, cause mind that all B vitamins, vitamin G, changes all the way from lower quality and some of the minerals dissolve in to putrefaction. water and may be thrown away in Other chemical changes go on all the water. Vitamins A and D dissolve in the time—before, during, and after fat—for example, in the oil on canned processing and when there is no fish. Contact with air is damaging processing. Enzymes, present in every to vitamins A, C, and D. Vitamin Bj living cell, speed up some of the is destroyed by heat in nonacid foods, chemical reactions. even in the absence of air. Light is bad When food is canned, heat destroys for vitamin Bg and perhaps also for A the micro-organisms that cause food and G. All these losses occur faster in to spoil. Hermetic sealing of the cans warm foods than in cold foods. prevents later contamination. The first limitation on the quality of Preservation by dehydrating and a processed food is the raw material freezing deprives the organisms of from which it was made. some condition they need for growth— If a turkey to be frozen has eaten 418 MODERN FOOD PROCESSING 419 food that produces the kind of fat that they are processed promptly or kept becomes rancid rapidly, or if the peas cool. * are starchy, the fruit is green, the Peas present a special problem be- variety of strawberries is low in flavor cause some are vined (threshed from and color, the final product will be no vines and pods) at stations some dis- better. tance from the plant. An objectionable Just as not all apples are good for flavor develops quickly in bruised, eating and not all potatoes are good warm peas. The trend has been to vine for baking, not all types of raw mate- at the plant or to water-cool the peas rial are good for processing. Fresh- at the vining stations. market potatoes are produced in The first procedures in the process- nearly all States, but a few varieties ing plant are cleaning, sorting, grad- grown only in special areas are best ing, and preparing the foods as for for drying and freezing. table use—eviscerating the poultry, Different processes for the same food peeling the fruit, straining the milk, may have different requirements. and so on. Mealy potatoes with a low water The foods must be clean. An inspec- content are best for dried mashed tor can easily see whether a plant is potatoes. The waxy type is best for clean. Standards of cleanliness usually canning. These two types can be sep- are high. arated with salt brines, because the Sorting and grading have a good mealy potatoes sink in it and the others deal to do with the uniformity of packs. float. The extent to which a processor can Economic considerations sometimes afford to separate material into sublots dictate the use of varieties other than adapted to different uses depends those known to be best. Less desirable largely on the diversity of his line of varieties may be included in the total products. Some persons believe that pack in a year in order to extend the separations based on appearance have processing season beyond the short been carried too far and those on flavor time the best variety is available. not far enough. Having decided what raw material Many foods are transported in the to buy, the processor must next make plant in a trough—a flume—of water. sure it arrives at the plant in good Some of the flavoring constituents and condition—as quickly and as cool as vitamin C, the B vitamins, and min- possible. erals are lost thereby. Some processors Fish and shellfish used to be subject have replaced flumes with conveyor to long delays, but the situation has belts. improved. Much fish is packed heavily After they are prepared for table use, with crushed ice immediately after it most foods receive some kind of treat- is caught. Large quantities are frozen ment, such as blanching, pasteurizing, on ships and are thawed and eviscer- concentrating, or sulfiting. (Each of ated in plants on shore. Some is com- these terms we explain later.) pletely processed—canned or frozen— Many liquid products—milk, cream, aboard ship. These procedures help eggs, fruit juices—are pasteurized. preserve flavor and quality. Pasteurization is mild heating, which Rapid cooling and refrigeration of destroys all or most micro-organisms, milk, eggs, meat, and poultry are nec- depending on the product. It also in- essary whether they are used in fresh activates enzymes and so helps in re- form or in processing. tention of flavor and color of the foods. Asparagus, sweet corn, peas, and Pasteurization of orange juice that is lima beans are the most perishable of to be concentrated and frozen reduces the processed vegetables. They rapidly the amount of separation into pulp and lose flavor, sweetness, general excel- clear layers during storage but tends lence, and vitamins B2 and C unless to take away the fresh flavor. 420 YEARBOOK OF AGRICULTURE 1959 Batch pasteurization, which involves is lost. Sulfite aids in the retention of heating Hquids at about 165° F. for 15 vitamin C, but it destroys vitamin Bj. or 30 minutes, is giving way to con- Too much sulfite gives a flavor that tinuous high-temperature, short-time most persons consider objectionable. procedures, in which the fluid is rapid- Because we want berries, peaches, ly heated and then cooled as it flows apricots, and cherries for dessert to through a series of coiled tubes. It may taste as uncooked as possible, they arc take only a fraction of a second and not blanched, but are covered with gives better flavor and color. sugar sirup, which shuts out air and Most vegetables and some fruits are gives them some protection from blanched. Blanching consists of cook- oxidation. ing pieces of food for a short time in Vitamin C sometimes is added to the water or steam. Small pieces, such as sirup for apricots, peaches, and cher- peas, are cooked for about a minute at ries to increase their stability. Oxygen the boiling temperature or for a slight- combines with the added vitamin ly longer time at lower temperatures. instead of with the fruit constituents. Larger pieces are cooked longer. The The vitamin may be used up during purpose of blanching is to inactivate storage. enzymes and thus enhance the reten- Soups, milk, fruit juice, and other tion of color and flavor during storage. liquids sometimes are partly concen- Blanching procedures are not stand- trated before they are canned and ardized. Some processors have a leach- frozen in order to reduce the amount of ing loss of 5 to 10 percent of each material to be packaged, shipped, and water-soluble vitamin or other con- stored. The water is removed at a re- stituent. Others have losses of 40 to 50 duced temperature by means of a percent—or even higher with the same vacuum. There is little impairment of food. quality or nutritive value in this step. Losses are larger in water blanch- The recovery of fruit essence is a ing than in steam blanching and larger special application of concentrating. with long-low temperature treatment It saves the components of flavor. The than with quick-high temperature flavorful vapors that boil oflf during treatment. Industry has changed large- the early cooking of jelly and other ly to quick-high temperature blanch- fruit products are collected, con- ing for frozen green beans, and the densed, and concentrated. The essence color of the product has been greatly may be added to jelly in the final improved. cooking stage, to fruit beverages and Considerable research has been con- juices, fruit-flavored ice creams, and ducted to develop electronic blanch- other fruit products. ing, which would avoid losses through leaching, but a satisfactory procedure IRRADIATION is a potential process- had not been worked out in 1959. ing method for foods. Although no Some dehydrated and frozen fruits irradiated food was on the market in and vegetables are sulfited instead of 1958—in fact, the law did not permit blanched. A few are both blanched and it—millions of dollars have been spent sulfited. Sulfiting consists of exposing on research on irradiation. the food to sulfur dioxide gas or Just as X-rays can be used to destroy dipping the food in a liquid containing cancer cells in the human body, a similar substance.