BACKGROUND

The invention relates generally to steam cooking and more particularly to methods for heating almonds to condition them for cutting into, for example, slices, slivers, or dice.

It is known that preheating almonds at temperatures below 85°C (185°F) in a low- humidity, dry-air preheating chamber, or preheater, before they are conveyed into a pasteurizer reduces the uptake of moisture during pasteurization. For example, instead of pasteurizing room-temperature almonds in the low-temperature pasteurizing region for 4 min at 79°C (175°F), almonds preheated to a surface temperature of about 54°C (130°F) at a relative humidity of between 1% and about 60% can be pasteurized at 95°C (203°F) in under 2 min. The preheater heats the surfaces of the almonds to a temperature below the dew point, or condensation temperature, to ensure that condensation forms on the almonds' outer surfaces during pasteurization.

Almonds are sold whole, slivered, sliced, chopped, or ground. In the production of sliced almonds, for example, whole pasteurized almonds are sliced into thin sheets, or slices, by slicer blades in slicers. Before being sliced, the whole almonds are first treated in a steam blancher to add moisture to and kill pathogens in the almonds. Then the almonds undergo dry-heat roasting in a plasticizer that evaporates surface moisture that would otherwise cause a pasty build-up in the slicer. Although most of the slices exiting the slicer are whole slices, i.e., complete cross sections of the almonds, some are not. The thin, sliced sheets are prone to damage. Damage is especially likely if the moisture content of the almonds is too low, which makes the almonds brittle. The quality of a batch of sliced almonds is measured by the percentage of whole slices. And the better the quality, the higher the price they can command.

SUMMARY

One method for slicing, slivering, or chopping almonds comprises: (a) preheating whole almonds in a dry-air preheater at a first temperature for a first dwell time; (b) pasteurizing the preheated whole almonds in a steam heating chamber at a second temperature for a second dwell time; (c) sending the pasteurized whole almonds without further heating to a cutting apparatus; and (d) cutting the pasteurized whole almonds into slices, slivers, or dice in the cutting apparatus. Another method for conditioning almonds for slicing, slivering, or chopping, comprises: (a) moving whole almonds continuously through a dry-air preheater; (b) preheating the almonds in the dry-air preheater at a first temperature for a first dwell time; (c) moving the preheated almonds from the dry-air preheater continuously through a heating chamber that forces a gaseous atmosphere comprising a steam mixture through the almonds in the heating chamber along a convection path intersecting the almonds moving through the heating chamber to heat the outer skins of the almonds and limit the amount of water condensation enrobing the almonds; (d) controlling the temperature of the gaseous atmosphere in the heating chamber to a heating temperature of greater than 85°C and less than 99°C for a second dwell time to pasteurize the almonds; and (e) sending the pasteurized almonds from the heating chamber without further heating to a cutting apparatus to be cut into slices, slivers, or dice.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a portion of a steam cooker, with its facing sidewall removed for clarity.

FIG. 2 is an axial cross-sectional view of the steam cooker of FIG. 1.

FIG. 3 is a block diagram of a steam cooker as in FIG. 1 and a dry-heat preheater for preparing almonds for cutting.

DETAILED DESCRIPTION

A steam cooker that operates according to and embodies features of the invention is shown in FIG. 1 with its facing side wall removed to better illustrate its components. The cooker 14, which is open to the atmosphere, has an enclosure 16 that is supported on legs 17 and extends from an entrance end 18 to an exit end 19. A for aminous conveyor belt 20 is trained around drive and idle sprockets 22, 23 at opposite ends of an upper carryway 24 that traverses the cooker. Diverting rollers or drums 26 guide the endless belt loop along a returnway 28 below the cooker. A network of steam pipes 30 injects steam supplied by a boiler or other steam source into the cooker through the bottom of the enclosure. The injection of steam is regulated by valves 31 (in FIG. 2) in the steam network.

The cooker shown is modular with one or more identical heating modules 32, 32'.

Modules may be connected in series to lengthen the total low-temperature heating region. A single module could be used for almonds that require only a brief heating time. Each module is individually controlled with its own steam valves. A feedback signal from a temperature-sensing probe 34 in each heating module is used by a controller, such as a programmable logic controller, to control the opening of the steam-injector valve to admit more steam from a steam source, such as a boiler, to maintain a predetermined heating temperature in each module. The probe, the controller, and the valve provide a means for maintaining a pre-selected temperature in each module. Air circulators, such as fans 36 or blowers, draw air 37 into the cooker through one of the side walls 38, as also shown in FIG. 2. The fan also draws steam 40 injected into the cooker through openings in a plenum 42, in which the air and steam are mixed. The fan blows the air-steam mixture through openings in the top of the plenum. The air-steam mixture then circulates along a convection path, indicated by arrows 44, that intersects almonds 46 being conveyed atop the conveyor belt 20 along the carryway. The belt is foraminous to allow the air-steam mixture to pass through and also to allow any condensation to drain. Other features of such a forced-convection cooker as described thus far are given in U.S. Patent No. 6,274,188, "Method for Steam- Cooking Shrimp at Reduced Temperatures to Decrease Yield Loss," August 14, 2001, incorporated herein by reference. One example of such a cooker is the CoolSteam® cooker manufactured and sold by Laitram Machinery, Inc., of Harahan, Louisiana, U.S.A. Because of the thoroughness of the forced-convection heat treatment described, heat-treating at temperatures of less than 100°C (212° F) at atmospheric pressure is effective in blanching or pasteurizing almonds without blistering or loosening their skins because the low temperatures minimize the uptake of moisture by the almonds.

During the operation of the cooker, almonds are conveyed into the steam cooker 14 by the conveyor belt 20 along a conveying path 56. The almonds are heated in a low- temperature cooking region 58 that may include one or more identical forced-convection heating modules 32, 32'. Air is drawn into the modules and mixed with steam to form a substantially homogeneous gaseous atmosphere of air (or other gas, such as nitrogen) and steam or water vapor. This steam mixture is circulated by an air circulator, such as a fan, in a convection path that intersects the almonds. In this example the convection path is perpendicular to the conveying path 56, but it could intersect or cross the conveying path from other directions. Along with the low-temperature heat treatment, the forced- convection flow through the almonds shears condensation enrobing the almonds and inhibits the uptake of moisture. The duration of the heating— the dwell time— is set by one or more of: (a) the length of the low-temperature heating region 58, (b) the speed of the conveyor belt 20, (c) the temperature of the heating region, (d) the size and kind of almond, and (e) the thickness of the mat of almonds on the conveyor belt. The dwell time is long enough to achieve sufficient lethality, e.g., a 5-log reduction in a target organism, such as salmonella. The temperature of the heating region is measured by a temperature probe and controlled by the amount of steam introduced into the cooker in each module.

Low-temperature pasteurization as described is effective in minimizing the deleterious uptake of water by the almonds. But pasteurizing almonds at lower temperatures requires a longer dwell time in the cooker to achieve the desired kill of pathogens. And longer dwell times lower product throughput.

Preheating almonds in low-humidity, heated dry air before pasteurization in a steam cooker is effective in conditioning whole almonds for slicing, slivering, or chopping in a cutting apparatus: a cutting apparatus for slicing slices whole almonds into thin sheets; a cutting apparatus for slivering cuts whole almonds into sticks; or a cutting apparatus for chopping chops whole almonds into dice. First, as shown in FIG. 3, whole almonds are preheated in a dry-air preheating module 60 of the steam cooker or a separate dry-air preheater. Second, the preheated almonds are conveyed into a steam heating chamber, or module, 62 of the steam cooker for pasteurization. After pasteurization the pasteurized almonds are sent to a cutting apparatus 64 without being subjected to further heating. The preheating reduces the uptake of moisture during pasteurization at high temperatures, such as temperatures between 90°C (194°F) and 99°C (210°F). The preheater 60 heats the surfaces of the almonds to a temperature below the dew point, or condensation temperature, to ensure that condensation forms on the almonds' outer surfaces during pasteurization. The quality of sliced, slivered, or chopped almonds is improved by preheating the whole almonds with heated dry air at temperatures above 85°C before sending them to the cutting apparatus 64. Preheater dwell times from about 4 min to about 10 min are adequate for preheating at those temperatures. To facilitate the cutting of the pasteurized almonds, the preheated almonds are also then pasteurized at higher temperatures and/or for longer dwell times, such as from about 2 min to about 6 min, than would be used merely to pasteurize almonds. Thus, dry-air preheating before steam pasteurizing, as opposed to blanching before heated dry-air surface drying, is effective in conditioning whole almonds for slicing, slivering, or chopping. Although the almonds have been described as being conveyed continuously through the preheater and the heating chamber on conveyor belts, they can alternatively be moved continuously through the preheater and the heating chamber by other conveying means, such as screw conveyors, vibration conveyors, or air conveyors, for example. Furthermore, the almonds can alternatively be conditioned by a preheater and a heating chamber in a batch process rather than in a continuous process.