Patent GB-940309-A (GB)
IPC: A23L3/42
Abstract: 940,309. Cooking in oil. PILLSBURY CO. Dec. 20, 1961 [Dec. 28, 1960 (2)], No. 45687/61. Headings A2B and A2D. [Also in Divisions A4 and F4]. A method for the dehydration of moist food particles, which may initially be in a frozen state, comprises enveloping particles of a moist food material in a hot fluid medium under partial vacuum, the medium comprising a foam-like mixture of vapour and hot oil, the oil being at a temperature substantially above the vapourization point of moisture in the material at the applied partial vacuum, whereby moisture is rapidly evolved from the material, and thereafter separating free oil from the dehydrated material. After a major part of the moisture has been thus removed, further moisture may be removed by contacting the material with clarified liquid oil, as a partial or complete replacement for the hot oil, under partial vacuum at a temperature (preferably 170-230‹ F.) substantially lower than the initial temperature of the hot oil (preferably 240-600‹ F.) but above the vapourization point of the moisture in the material at the applied partial vacuum. Preferably the material is centrifugally separated from free oil and the temperature of the material is reduced before the applied partial vacuum is released; this reduction in temperature is effected by evaporative cooling produced either by introducing water into the evacuated space occupied by the material whereby such water is flashed into steam, or by applying a partial vacuum higher than that (usually 22 to 29 inches mercury column) used in the main part of the dehydration. The partial vacuum may be broken by introducing an inert or fungicidal gas or by applying an impregnating medium including oils or fats, gelatin, aqueous liquids containing flavouring ingredients, volatile or aromatic flavourings, alcoholic liquors, concentrated sugar syrups, vitamins, tenderizing enzymes, preservatives and stabilizers. The material may finally be dried in a gaseous atmosphere. The dehydration may, if desired, result in a partial cooking of the material. Apparatus may consist of a tank 40, Fig. 3, provided with a removable cover 41, a perforated basket 42 with a collar 44 made of resilient synthetic material which basket is attached to a rotatable and slidable rod 43, and a connection 45 to vacuum. A perforated barrier screen 48 suspended by a winch 52 is provided for depressing particles below the surface of the oil when the drying at lower temperature is carried out, since at this stage the particles tend to float as a thick mat on the surface of the oil. In an alternative apparatus, the particles of material fall into a tank 61, Fig. 4, from a vacuum-connected charging container 66 and a centrifugal 75 is mounted in a removable housing 73 separated from the tank 61 by a butterfly valve 74; atmospheric air or other gas and cooling water may be introduced through conduits 78 and 82, respectively. Instead of a winch-operated, vertically movable barrier screen 64 depicted, a rotary screen 81, Fig. 5, may alternatively be employed; in this case, it is necessary to lower the level of oil before turning the screen into the operative (horizontal) position, after which the oil level can again be raised. The dehydrated product consists of particles having a form similar to the initial moist particles, each particle being porous, readily rehydratable and containing oil, usually to the extent of 100 to 255 milligrams per cubic centimetre, substantially in the form of randomly distributed minute e discrete masses, and the particles are further characterized by their ability to form on rehydration reconstituted moist t material similar in form and size to the particles of the initial material. Materials (many are particularly mentioned) include fruits, vegetables, m e a t (including fowl), seafood, condiments (spices and herbs), cereals and formulations from a number of such materials. A large number of suitable oils and fats, including blends with waxes, are mentioned. The many examples describe in detail a variety of operating procedures employed in conjunction with the apparatus of either Fig. 3 or Fig. 4 for the dehydration of the following materials: (1, 2, 3 and 4) frozen blueberries using hydrogenated cotton seed oil, sesame oil or hydrogenated vegetable oil shortening (in Example 3, the blueberries employed had been warmed, subjected to vacuum and then frozen under vacuum); (5, 6 and 7) frozen diced potatoes and frozen shreds of potatoes (some had previously been treated with sodium bisulphite solution) using hydrogenated vegetable oil shortening, (8 and 9) frozen sliced carrots using hydrogenated vegetable oil shortening; (10 and 11) frozen cut celery stalks using hydrogenated vegetable oil (some of the stalks had been blanched prior to freezing), (12) frozen shreds of green string beans using hydrogenated vegetable oil; (13) frozen mushrooms using hydrogenated vegetable oil<SP>-</SP> shortening, (14) canned water chestnuts using hydrogenated vegetable oil, (15) frozen lean beef (previously cooked and diced) using hydrogenated vegetable oil shortening, (16) frozen cooked chicken using hydrogenated vegetable oil, (17 and 18) frozen boiled shrimp and frozen, steam cooked salmon, respectively, using hydrogenated vegetable oil shortening, (19) chilled commercial maraschino cherries using hydrogenated vegetable oil, (20) frozen pineapple chunks using hydrogenated vegetable oil, (21) frozen dates using an unspecified oil; the dates had been prepared by soaking sundried, pitted and subdivided dates in cold water for two hours, draining off free water and freezing, (22) dried wheat using hydrogenated cotton seed oil; the wheat had been prepared by milling wheat for removal of the cortex and bran, soaking for one hour in an aqueous liquid maintained at about 200‹ F. and containing per 1b. of wheat, 1 oz. dried meat extract, ¢ OZ. of powdered gelatin and ¢ oz. salt, draining away the free liquid and freezing to form a free-flowing material, (23) frozen ravioli using hydrogenated vegetable oil, (24) frozen discs of moist dough using hydrogenated cotton seed oils; the dough was prepared from 2 cups wheat flour, <SP>2</SP>/ 3  cup whole milk and smaller proportions of baking powder, salt and shortening-the rehydrated product is stated to be particularly suitable for making dumplings and for use in stews and like food mixes, (25) as in (24) except that the discs were subjected to a short baking before freezing, (26 and 28) frozen sweet corn kernels using hydrogenated cotton seed oil, (27) as in (26) except that a puffed product was obtained by applying after centrifugal separation of the oil, a vacuum slightly above 29 inches mercury column for about three minutes, after which the vacuum was removed by admitting dehumidified air. Other pre-treatments of the materials prior to the dehydration also are disclosed.