CA1049320A - Preparation of ready-to-eat puffed cereal flakes - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A ready-to-eat puffed cereal flake is prepared by selecting a mid-sized corn meal which is then continuously cooked and pelletized and thereafter dried and tempered prepara-tory to flaking in order that the specially treated flakes may be blistered in a first temperature zone of fluidizing heated air and toasted in a second zone to produce improved uniformly blistered and curled product.

Description

The art of preparing a ready-to-eat pufed cereal product has advanced significantly from its inception in the early part of the 20th century. This cereal form has now assumed the prominence of being a standard in the industry having certain characterizing structural and eating features which may be stated as follows; the flake is uniformly blist-ered as well as uniformly colored and has the appearance of substantially uniform thickness as a consequence of such blistering, the edges of the flake being preferably scalloped or irregular and the flake itself being generally curled if not cupped. Good manufacturing practice requires that such a flake be produced by a process which is sanitary, easily controlled and continuous.
Processes have been described which enable the con-tinuous cooking of a ready-to-ea-t breakfast cereal product, i.e., United States No. 3,062,657 issued November 6, 1962 to Vollink for Process for Producing Breakfast Cereal Flakes.
This process describes means whereby a farinaceous cereal material may be advanced in a continuous, high-temperature extrusion path that eventuates into a low-temperature termina-tion point, whereupon the cooked mass is pelletized and con-verted into flakes. The cooked material is typically extruded through a cooling zone and a die plate whereby the dough mass does not undergo expansion but rather substantially retains its doughy plastic cooked condition in an unexpanded condition.
The art involved in providing a highly blistered surface after rolling the flakes to a condition wherein they may be toasted at elevated temperatures using radiant heat or forced hot air . .

still leaves something to be desired in achieving the foregoing objective of breakfast cereal flake crispness and uniformly blistered and colored appearance.

Uniformity of cooking coupled with control of toasting are important considerations to achieving a uniformly blistered structure and yet there remains a need to ad~ance the art of achie~ing such uniformity in a continuous cooXing system.
More recently invented processes described in U.S.
No. 3,453,115 issued July 1, 1969 to Clausi et al. for prepara-tion of Ready-to-Eat Puffed Cereals provide means whereby the cooked pellets may be flaked and fluidized in a hot air stream and thereafter toasted to achieve a golden puffed corn flake product.
The merging of these arts would pro~ide a significant advance in ready-to-eat puffed cereal flake manufacture, and yet improvements remained prior to the present invention in respect of a need for a uniformly puffed flake structure as aforementioned.
In accordance with this invention, a blistered uniform preferred eating texture is afforded a cornflake by converting a mid-sized cereal meal that is comprised predominantly of corn meal substantially free of free starch and grits into a coo~ed cereal dough wherein fla~oring syrup is infused. The cooked dough is pelletized after being cooled to below 210F., the pellets are dried to less than 20~ but above 13% moisture, and the dried pellets are then tempered to be plastic preparatory to flaking. The flakes are then subjected to fluidized bed blister-ing in a first zone wherein water vapor is caused to be uniformly flashed from the surfaces thereof in less than one minute with a collateral 25% - 75~ moisture reduction, the blistered fla~e being thereafter toasted to a stable moisture content, preferably in a second fluidizing toasting zone.
The foregoing narrative statement of the key steps in the process merges some arts that are known ~o skilled art work-ers including those of continuous cooking, p~lleting and flaking:
accordingly, a detailed description of such arts is unnecessary `~` ` : ` : ' .

and may be drawn from the operative best mode described herein-after, the practices of coo~ing, pelleting and flaking not being critical to this invention except as disclosed.
One necessary feature that is uncommon and is not fully understood is the requirement that farinaceous cornmeal flour ~e of a size which is substantially free of very fine flour and coarse grit particles. The most preferred blistered flake has only been pxoduced when such a particle size distribution in the starting material is employed, although less than 15% by weight of said very fine and coarse particles in combination as speci-fied in the operative example can be present in the starting meal. By selecting the mid-sized corn meal, as specified herein, combined with syrup and 25~ - 35% added moisture and cooking it in a continuous reactfon vessel such as positively and consist-ently advances the dough undergoing gelatinization, there is a uniform cooking and infusion of flavoring in the farinaceous particles. This is significant since it is important not only to cook the dough uniformly but also to avoid overcooking it, whereby the eventual toasted puffed flake retains a texture which causes the rehydrated flake to disintegrate through fracture of flake structure per se rather than conversion to a mush. This rehydration characteristic -~s afforded by pressure cooking the hydrated corn dough mass with a minimum of mechanical shear intermediate continuously rotating blades and a circum-jacent heating barrel. A minimum of fine flour particles avoids overgelatinization such as detracts from this intended flake struc'cure; a minimum of oversized grit particles likewise assures intended flake disintegration and uniform gelatinization.
Mid-si~e corn meal fraction also assure that the cooled extrudate can be col}ected and handled without excessive subse-quent clustering of the pellets. To explain, it's important that , . . .

the pellets of cooked material remain essentially discrete so that they can be pneumatically conveyed or otherwise trans~erred to the next primary station where they are partially dried.
Sticky pellets can adhere to one another and clog a system; in like manner, sticky moisture-laden pellets of overgelatinized material can cluster and dry as such. A uniformly cooked pellet is important to insure smooth and consistent downstream proces-sing. Thus, it is important to pr~vide a discrete partially dried pellet which can be individually flaked and will toast pneumatically as such.
In this regard it will also be advantageous to employ 0.1 to 1.0~ of mono- and or a mono- and diglyceride emulsifier in the starting meal; the cooked cooled pellets are less sticky and will dry discretely, permitting facility in recovery from drying screens and a discrete condition for later flaking and fluidized bed toasting. It appears that the mono-glycerides comple~es the free starch sufficiently to result in such smooth cooking as will minimize any tendency in the pellets to stick by reason of overgelatinization of the starch.
The screen fractions of a typical corn meal used for pelletized corn flakes in accordance with this invention, will ~e as follows:
SCREEN FRACTIONS OF CORN MEAL USED FOR
PELLETIZED CORN FLAKES
on USS 16 mesh 11.0%
" " 18 " 30.0%
" " 20 " 17.0%
" " 25 " 31.0%
" " 30 " 10.0%
thru " 30 " ~.D~
These fractions are determined by conventional Rotap sieve procedure using a 5 minute tap.

-. . ~ . , ~049320 In general, at least 85% by weight of the ~eal will pass a USS 16 mesh screen and essentially at least 5~% by weight of the meal used will be retained on a USS 25 mesh screen after passing a USS 16 mesh screen. Thus, as seen from the foregoing typical screen analysis, a major weight percent of the corn meal particles will not only be free of very fine essentially endo-sperm starch-containing granules, but also a large majority of the granules will be distributed uni~ormly in a particle size distribution pattern, despite the coarseness of the meal. While it is difficult to establish and only a theoretical ~bser~ation, it is believed that in a continuous cooking operation where sus-tained processing to achieve the ultimate cook is required absent a sticky condition, such uniform corn meal particle size granula-tions will assure even distribution of the chemical and corresponding physical properties of the particles providing ideal pelleting, flaking, toasting and incidental handling properties.
Also, as indicated herein, it will be desired that a majority of the uniformly cooked starch granules will have been gelatinized to the point that they will lose their birefringence as viewed under polarized light: on the other hand, avoidance of excessive mechanical shear is believed important to avoid the presence of high order of free starch that has been overgelatin-ized.
The cooked dough, produced by continuously heating the meal and syrup is converted into a pelletized mass that should be cooled ~o well below 210F (e.g. 100 - 185F) preparatory to issuance from an extrusion nozzle or shaping die whereby the extrudate does not undergo su~stantial puffing or moisture loss;
for this purpose, therefore, the cooled dough will be at a temperature well below that point at which the water vapor of the dough mass will flash; ideally the dough will be cooled to 104~3Z0 about 150F as it is admitted to atmospheric conditions it has been observed that at product temperatures above 185F there is a noticeable tendency of the pellets to stick with the afore-mentioned processing difficulties resulting.
The cooked pellets should be dried in as discrete a physical state as possible to between 13~ - 20~ H2O. A distilled monoglyceride in a level of about 0.75% of the meal aids in pro-cessing to permit such ideal drying conditions.
An important refinement will be the tempering of the pelletized dough over a sustained period under ambient conditions wherein the product will have a uniform plasticity rendering it flakable to a point where the cooked dough moisture is uniformly distributed; generally, this is evidenced by a scalloped appear-ance at the edge of flaked, tempered pellets and by a uniform flaked pellet surface free of breaks. In this context, the phrase "ambient conditions" is intended to connote that no external heat of any consequence is applied, it being a preferred embodiment of this invention that the pellets be flaked at a temperature about 90 - 150F whereat they exhibit sufficient plasticity incident to rolling to uniformly respond to the rol-ling pressures of the fla~ing rolls after tempering for one to three hours.
Tempering of the pellets is quite consequential when related to the blistering conditions that are employed to set the flake structure upon introduction to the fluidized high tempera-ture drying gas; this gas is typically air. The jets of fluidizing medium are directed into a vibrating trough or similar - vessel operative to reflect the high velocity gas jets and redirect the volume of drying gas back upwardly in the direction of the flake charge admitted over this fluidizing medium. The flakes are preferably advanced through a plurality of such fluidizing zones as described hereinafter and are sequentially 104913Z~
turned so that water vapor is uniformly generated within the flake and is uniformly expanded as can be practiced in apparatus for this function described in U.S. 3,060,590 to Wolverine Equipment Co. for Method of Treating Discrete Particles issued October 30, 1962. This treatment causes uniform discrete blistering as specified herein. It is believed critical to this fluidizing invention that fluidized blistering be caused to transpire over a period less than a minute preferably less than 45 seconas, the minimum time for blistering being to some degree a function of the limitations of the fluidizing gas temperature which exceeds 300F and its velocity; generally at least 15 seconds is required for proper blistering of flakes to cause moisture content reduction between 25% - 75%, typically about 50%, and until a moisture co~tent of between 5% - 10% and typically 8% is achieved. The extent of blistering will be dependent upon the initial moisture content of the flakes and its distribution - through tempering: as indicated, the pellets are dried prepara-tory to being tempered and the extent to which the pellets are dried has a bearing on the degree to which the flakes should be dehydrated incident to being blistered; it is believed that at higher moisture contents a higher level of moisture reduction and a higher rate of evaporation will produce preferred flake blistering.
The flaXe temperatures reguired to achieve this uniform blistering will be such that the blistered flake charge will exhibit a sensible heat of at least 250F when measured by a thermocouple inserted into a bed thereof after the zone of fluidiæation has been rendered inoperative; generally, the blis-tered flake at this point should not exceed 350F. Once the fluidized and blistered flake is produced, it is ideally consecu-tively rapidly toasted in a second like fluidizing toasting zone wherein fluidizing gas temperatures are operative to carmelize the product to a brown golden hue and result in terminal moisture reduction to 2~ - 3~, the product blisters being thereby hardened and flavor and color being uniformly developed. The preferred fluidizing toasting zone may be dispensed with and in lieu thereof a more conventional toasting oven employed. In all of the toasting applications, product temperature will ~e elevated to above 275~F and commonly in the neighborhood of 300 - 370F, measured as before in the case of blister fluidization. In this art product temperature is the ambient temperature of the fluid-izing gaseous medium, which the product will substantiallyapproàch the term product temperature is thus reasonably under-stood by workers to be the gas temperature in the plenum chamber for entering fluidizing gas. Generally, toasting should consecutively follow fluidized blistering with a minimum of elapsed time such that blistered flakes are above ambient temperatures as they are delivered from the fluidizing zone to the toasting zone.
A corn flour meal having the aforementioned size distribution wherein 90% is retained on a USS No. 30 mesh screen and 85~ passes a USS ~o. 16 mesh screen is formulated as follows:
Formula - 80% corn flour, 8% sugar, 1~ salt, 1% malt flavoring, 0.75~ distilled mono-glyceride and trace ~ coloring.
Processing - Sufficient water is added to the ingredi-ents to form a mixture containing approximately 30% moisture.
The wetted mixture is fed into a screw type pressure lock wherein the mixture form a continous pressure charge entering a contin-uous cooker of the type described in U.S. Patent No. 3,062,657 cited hereinabove and generally comprising a rotating screw within a steam jacketed complementary ~arrel serving to contin-uously heat and gelatinize the syrup produced ~y dissolving thesugar-salt flavoring in the make-up water. This mass is heated for approximately 15 minutes at 20 pound steam pressure and the starch content will be substantially digestible and fully cooked.

The cook-in~ mixture does not fully occupy the chamber space intermediate the rotor blades a~d the chamber itself and the bla~es serve to advance the mix~ure with a tumbling mixing action to uniformly treat all of the particles and cause them to merge with one another in producing the intended dough, there being virtually no localized accumulations of flavoring syrup and instead a rather uniform impregnation thereof in the cooked dough mass. The dough mass is then gravity-discharged with a free-fall to an extruder wherein the cooked dough under-goes a gradual cooling between the screw and barrel surfaces asit advances to a die plate; the cooling of the dough serves to assure that it will not expand subsequent to issuance from the cooker to an extent greater than that which it has achieved through the effects of hydration in the cooker per se.
Although the temperatures to which the dough mass is elevated during cooking is not a critical aspect of the inven-tion, a preferred upper temperature limit will be 300F gen-erally whereat earmelization and other flavor reactions are minimized and only that amount of heat treatment is provided to gelatinize and develop intended flavor. The discharged cooked mass that is cooled by the extruder issues therefrom at about 150F and has a moisture content of about 30%.
The cooked pellets, say 3/16 long and of li~e dia-meter, are next pneumatically conveyed to a through-circulation belt drier wherein they are dried in an oven to broadly 14% -20%, preferaly 15% - 18% moisture and thereafter tempered for a period of about two hours until the pellets have a uniform dis-tribution of the moisture content herein and are uniformly plastic and non-sticky. The pellets are thereby in a condition ~ g _ ,.

~ 0493ZO
to be ~laked between a pair of oppositely rotating flaking r~lls set at a gap thickness commensurate with producing a flake having a thickness of about 0.018 inch and - 9a -A .
.. , . ~

exerting a fla~ing pressure of about 36,000 psi at the nip; the rolls may be adjusted to have variable rolls speeds where accentuated curling is desired in the flake preparatory to blistering and toasting. At this point the flaked dough sur-face is uniform and free of surface breaks on the flattened regions thereof whereas the perimeter of the flakes are essen-tially shape-retaining and in a condition to be subjected to the blistering and toasting practices of the invention.
A charge of the tempered flakes is introduced in a first fluidizing zone wherein a plurality of high velocity air jets are admitted proximate one another downwardly over in proximate relation to a bed of the f la~es at an air temperature of approximately 400F for about 30 seconds; in this zone the flakes will be retained on a vibrating trough-conveyor adapted to fluidize the flakes by deflection of the high velocity air flow around and upwardly through the charge. The velocity of the circulating air within the bed is such as to provide an air pressure of about 2.0" to 2.7" of water as measured by a magnihelic gauge connected to Pitot tubes inserted into the plenum supplying the air to the aforesaid air jets; velocity in relationship to the charge material will be such that substantially all of the tempered flakes will be fluidized and the flakes themselves will undergo uniform flashing of water vapor therefrom, thereby resulting in a discrete yet uniform blistered appearance while being only slightly changed in color.
The bed of flakes is more or less randomly poised above the trough area, the suspensibility of the flakes being such that they turn individually and independently of one another in random manner to provide uniform surface blistering on both surfaces thereof. In the trough flakes are advanced horizon-tally and initially intercept a vertical series of fluidizing nozzles which cause the fla~e to be elevated under influence of ~04~13ZO
trough vibrations. Once the thrust of a series o~ vibration causes the flakes to be fluidized, they are sequentially exposed to alternating zones of fluidization defined by staggered sequential rows of high air velocity iets poised a~ove the trough and creating the fluidized condition just described.
As a result of fluidized bed blistering as just described, the product will undergo a flashing of approximately S0~ of its moisture content and thus will be of a moisture content of about 8~.
~pon completion of the 30 second blistering cycle, the flakes will be transferred by a conveyor to a second zone, a fluidized toasting oven like the first, operating at a fluidizing air pressure of 1 to 1.5" of water wherein the flakes will be toasted by hot air at 275F - 370F or approximately 310F for 30 seconds or until a uniformly golden hue results and during which toasting virtually no further consequential blistering may be observed. Proauct passing the toasting zone undergoes a further moisture reduction to about 3%.
The toasted blisters per se are discrete and the walls therefore relatively continuous in that they have a minimum of visible broken areas, although some isolated instances of blister rupture may be apparent on each flake.
The product when consumed in milk retains its crispness for a reas~nable recipe period~ is quite flavorful and has the preferred blistered corn flaXe texture described in the preamble of this specification.
While the invention has been described by a detailed depiction of the best mode for practicing it, variations will occur to men skilled in the art.

.. . . .

Claims (10)

The embodiment of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. The process of preparing a uniformly blistered cereal flake which comprises selecting a mid-sized corn meal flour substantially free of free starch and having less than 15% in combination of fine flour and large-sized grits, at least 85% by weight of the meal passing a USS 16 mesh screen and at least 50% by weight of the meal being retained on a USS
25 mesh screen after passing a USS 16 mesh screen mixing the flour and syrup flavoring ingredients; continuously heating the flour and syrup to produce a cooked dough that is extrudable into pellets, continuously cooling the dough while extruding it into pellets at below the gelatinization temperature as admitt-ed to an atmospheric zone; drying the pellets to 12% - 20%
moisture; tempering the pellets until they have the moisture content thereof uniformly distributed throughout and are uni-formly plastic; flaking the tempered pellets; introducing the flaked tempered pellets to a zone of fluidizing heated drying gas wherein the flakes are heated to a temperature of from about 250°F to about 350°F and are caused to undergo discrete uniform blistering on both surfaces thereof in a period of less than one minute while undergoing a reduction in moisture con-tent exceeding 25% but less than 75% of the initial moisture content thereof; and toasting the fluidized flake to a stable moisture content at an elevated carmelizing temperature ranging from about 300°F to 370°F.

2. The process of Claim 1 wherein the flakes are dehydrated to 6% - 10% moisture incident to blistering.

3. The process of Claim 1 wherein the blistered flakes are toasted in a second fluidized toasting zone,

4. The process of Claim 1 wherein a major weight percent of the corn flour meal retained is on a USS No. 25 mesh screen and 85% passes a USS No. 16 mesh screen.

5. The process of Claim 4 wherein the dough is cooled to below 185°F prior to being pelleted.

6. The process of Claim 5 wherein the pellets are dried to 14% - 20% moisture before tempering.

7. The process of Claim 6 wherein the pellets are tempered 1 - 3 hours.

8. The process of Claim 7 wherein the pellets are dehydrated to 5% - 10% moisture as a result of blistering.

9. The process of Claim 1 wherein an emulsifier selected from the class of monoglycerides and mixtures thereof and diglycerides are added to the mixture of flour and syrup prior to cooking the dough.

10. The process of Claim l wherein the mixture of flour and syrup are cooked under pressure in a confined zone wherein the ingredients are advanced with a tumbling action without mechanical shearing of the ingredients while being cooked to the extent that the majority of the starch granules in the dough produced lose their birefringence.