GB262988A - Process for treating raisins or other dried fruit - Google Patents

Abstract

262,988. Marks, E. C. R., (Sun-Maid Raisin Growers of California). Feb. 16, 1926. Conditioning dried fruit.-Raisins, currants, figs, prunes, or other dried fruit are treated by passage, with agitation, through an intense heat at such a speed that the duration of treatment is so short that injurious scorching of the fruit is prevented. The heat treatment may consist in passing the fruit over a heated surface, and the fruit may simultaneously be subjected to the action of heated vapour. The fruit may then be cooled in stages and otherwise treated. In the process described, dried stemmed unseeded raisins are passed through an apparatus C more fully described in Specification 262,989, in which the raisins are rapidly fed by a perforated screw conveyer 2 through a cylinder 1 provided with a heating jacket 4 through which gas or other fluid at about 800‹ F. is passed. Superheated vapour, preferably steam at atmospheric pressure or slightly above, is passed into the cylinder 1 through valve-controlled pipes 8. The combined heat and vapour treatment renders the raisins soft, resilient, and to some extent puffed up. The raisins are fed to and removed from cylinder 1 by gates B, D, D' of the revolving paddle type which seal the ends of the cylinder so as to prevent escape of heat or gases. Unabsorbed vapour is withdrawn from the raisins between gates D, D' by an exhaust pipe 10. The general temperature of the raisins in this treatment is only raised to about 142‹ F. They are next fed by a shaker feed table E to a de-seeder F, from which they pass through a shoot S and sealing gate G to cooling apparatus H, I which is more fully described in Specification 262,990. The apparatus consists of a cylinder 11 through which the raisins are fed by a perforated screw conveyer 12. In the portion H gradual cooling is obtained by the circulation of water in a jacket 16 in the direction opposite to that in which the raisins are fed. A more rapid and complete cooling to substantially room temperature is effected in portion I by the introduction of a refrigerant gas, preferably air, into the jacket 16 thereof through pipe 21, Fig. 2, the gas entering cylinder 11 through perforations 22 on one of its lower sides, and expanding through the raisins, banked up above the perforations, by action of the conveyer. The cylinder 11 is connected by a slot throughout its length with an upper cylinder 17 which in turn is connected at intervals by pipes 19, 19<1> with an exhaust pipe 18 having a vacuum pump Q, so that excess moisture is withdrawn from the raisins during cooling. The portions H, I of jacket 16 and cylinder 17 are separated by a transverse partition 20. Mineral or other oil, but preferably that extracted from the raisin seeds, is atomized and sprayed on the raisins at points 24-27 in the cooling apparatus. The oil nozzle 26 is situated adjacent the cold air pipe 21, so that the air carries the oil to the raisins. The oil forms an invisible coating on the raisins, rendering them substantially non-adherent, and also serves to lubricate the frictional surfaces of the apparatus. The raisins pass out through gate J to a shaker feed table K and to revolving screens L, N where they are treated with air blast at room temperature from perforated pipes 30, 31. These are preferably arranged to blow air through the screen fabric as the screens are rotated and the raisins are lifted against their sides, so that the temperature of the raisins is made more even and foreign matter removed before they pass to packages P. The screw conveyers 2, 11, the revolving gates B, D, D<1>, G. J and the fan Q are driven from pump R, and the shaker feed tables E, K from the driving motor U of the de-seeder F. In a modification. the cooling apparatus is formed bifurcated to enable it to be shortened.