Frank A. Lee

The Blanching Process

Publisher Summary This chapter discusses the process of blanching in the preparation of vegetables for freezing, canning, or dehydration. It describes blanching as a preliminary treatment in the canning process and freezing process. The objective of blanching as a pretreatment of vegetables for canning is the removal of tissue gases; the shrinking of the material so that adequate fills can be contained in the can; and the heating of the material prior to filling so that a vacuum will be obtained after heat processing and boiling. Blanching is necessary as a part of the preparation for freezing preservation to inactivate the enzymes in the tissues and to shrink the material so as to conserve space in packing. The inactivation of the enzymes is very important in this process because no final cook or sterilization is used previous to freezing, and freezing storage, at least at the temperatures commonly employed, does not prevent undesirable deterioration in flavor, odor, and color on the part of the enzymes in the tissues. Many studies have been conducted to determine the effects of steam and water blanching on the vegetables so processed. The relative merits of water-blanching versus steam-blanching have been studied. It seems that steam-blanching is the more effective of the two for the conservation of soluble nutrients. The chapter mentions some of the special techniques for blanching, such as steam pressure and electronic blanching. It presents investigations that have been conducted to determine the causes for the development of off -flavors, colors, and aromas when unblanched and underblanched vegetables are held in frozen storage.

Water and Solutions

Water is an important part of a large number of foods. It is not only an important component of these foods, it is necessary for the digestion of these foods in the body to sustain life. Without water, life as we know it would be impossible. Water is necessary in photosynthesis for the production of carbohydrates by this process. The deterioration of foods, both microbiological and chemical, is affected by the presence of water in the food. Dehydration, which is the elimination of most of the water present, permits food to be stored for relatively long periods of time.

Meat and Meat Products

Knowledge of animal muscle and the process by which it is converted to food has developed considerably. Much of this progress has resulted from the great strides that have been made in the basic understanding of proteins. Basic work of this character has already been discussed in Chapter 6 on proteins. The electron miscroscope has been instrumental in the understanding of the structure of muscles. Along with proteins, fats in meat are important from the nutritional as well as functional standpoint.

Fruits and Vegetables

Changes that occur in fruits and vegetables during the ripening process and after harvest influence their use as foods. Following harvest, the sources of nutrients and water that supplied the growing entities are no longer available. But life processes go on: respiration continues with the uptake of oxygen and loss of carbon dioxide and water. Deterioration accompanies the use of the reserves of respirable materials accumulated during photosynthesis that are no longer replenished. Under these conditions, while new compounds are formed by the continuation of anabolism, the major metabolic activity in this situation is catabolism. Fruit ripening is basically a process of aging. The ripening process is accompanied by developing senescence and then deterioration. The speed with which the reserve materials are used depends on the rate of respiration. In some species, change after harvest takes place much faster than in others. Apples will hold much longer in proper storage than strawberries, raspberries, or peaches. Also, deterioration by the growth of microorganisms in fruits and vegetables held in storage is a prominent factor.

Cocoa and Chocolate

Cacao originated in the Americas, probably in the jungles of the Orinoco and Amazon valleys. Cultivated by the Aztecs of Mexico and by the Mayas of Central America, cacao was being used by them at the time of the discovery of America by Columbus and the conquest of Mexico by Cortes. Columbus brought some cacao beans back to Europe. A beverage called chocolatl made from these beans was consumed in large amounts by the Emperor Montezuma. The basic concoction comprised cakes made from the fluid mass of ground chocolate, to which corn and spices as well as vanilla were added. Parts of the cakes were beaten with water and the other ingredients were added resulting in a final product that had the approximate consistency of honey. The Spaniards were said to have been attracted to it only when it was sweetened.

Zur chemischen Wirkung des Äthylens auf Gefrier-Erbsen während der Lagerung

ZusammenfassungDie beiden hervorstechenden Veränderungen, verursacht durch die Versuchsbedingungen, waren der Gehalt an Peroxid und ungesättigten Carbonylsubstanzen. Der Peroxidgehalt von nicht entschoteten und handentschoteten Erbsen war höher in Gasgemischen mit kleinen Mengen an Äthylen. Unterschiede an Gehalt ungesättigter Carbonylverbindungen wurden nur in nicht entschoteten Erbsen nach längerer Lagerung gefunden; sie enthielten weniger als andere Proben.[/p]Degustationen zeigten, daß Erbsen, die vor Beginn der Lagerung beschädigt wurden, oft schlechteren Geschmack entwickelten. Die Substanzen, die für den schlechten Geschmack verantwortlich sind, stumpfen anscheinend die Geschmacksnerven ab, so daß die Intensität des unangenehmen Geschmacks empfindlich abnimmt, wenn größere Mengen dieser Erbsen konsumiert werden.[/p]