Food or edible material: processes – compositions – and products – Fermentation processes – Of plant or plant derived material
Reexamination Certificate
2000-08-07
2003-04-29
Hendricks, Keith (Department: 1761)
Food or edible material: processes, compositions, and products
Fermentation processes
Of plant or plant derived material
C426S052000, C426S629000
Reexamination Certificate
active
06555147
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to methods for making enzyme-treated unpopped popcorn kernels for improving the yield of popped popcorn.
2. Description of the Related Art
Popcorn is different from other types of maize by its capacity to form large flakes when popcorn kernels are subjected to heat, an effect known as popping expansion. Popcorn kernels consist of three main structural parts: pericarp, germ, and endosperm (Reeve and Walker, 1969
, Cereal Chemistry
46: 227-241; Hoseney et al, 1983
, Journal of Cereal Science
1: 43-52). The pericarp serves as a tough protective layer surrounding the kernel and participates directly in the popping action of popcorn. The pericarp is composed of many tightly packed layers which depending on the variety consists of both thick and thin pericarps. Immediately inside the pericarp is a single layer of thick-walled aleurone cells, these being the outer layer of the endosperm. The endosperm consists of two types: mostly translucent endosperm and smaller amounts of opaque endosperm. The translucent endosperm contains closely arranged polygonal starch granules while the opaque endosperm contains large, smooth spherical granules with many intergranular spaces. The proportion of translucent endosperm appears to be closely associated with popping expansion. The germ affects the texture of the flakes, but contributes the least to the popping.
Most popcorn in use today is hybrid popcorn that replaced the open-pollinated varieties. Hybrid popcorn is characterized as having improved yield, better standing ability, more uniform kernel type, and better popping expansion. The maximum popping potential of hybrid popcorn can be achieved only if it reaches full maturity. Popcorn hybrids move through commercial channels as three kernel types, which include white, small yellow, and large yellow, but now some medium kernel yellows are available. White popcorn characteristically has a rice-shaped kernel, while yellow popcorn kernels are pearl-shaped.
Hoseney el al., 1983, supra, have described the mechanism of popcorn popping. The popping expansion results from a small amount of water stored in a circle of soft starch inside the kernel's pericarp or hull wall. When heated, the water expands until the pericarp ruptures wherein the water vaporizes providing the driving force for expansion of the kernel leading to the explosion of the kernel into a flake. The pericarp or hull serves as a pressure vessel that allows the moisture held in the kernel to turn into superheated steam. Eventually the hull can no longer withstand the internal pressure and the wall of the hull ruptures. The rupture occurs at temperatures in the range of 350-375° F. These temperatures correspond to saturated steam pressures inside the kernel of 135-185 psi.
When the kernel pops, the pericarp separates between the seed coat and the aleurone cells where the pericarp is blown free and appears to undergo no change in structure other than the fracture failure. Popping does not alter the germ chemically or physically. The aleurone cells as well as the outer edge of the endosperm undergo minimal change in structure. However, deeper in the endosperm, the starch in the translucent endosperm greatly expands due to gelatinization, whereas in the opaque endosperm large voids are produced and the starch remains unchanged.
The maximum popping yield of a batch of popcorn kernels is generally reported to be greater than 90%, even though in practice this percentage can be much lower. The reduction in maximum popping yield is primarily attributed to the loss of moisture content of the kernel where 13.5% is optimal for achieving maximum popping yield. It is known that a 1% drop below 13.5% in moisture can harm the popping quality, and a 3% drop in moisture can render popcorn unpoppable. However, the kernels can be partially or completely rejuvenated by rehydration.
It is an object of the present invention to improve the yield of popped flakes from popcorn kernels.
SUMMARY OF THE INVENTION
The present invention relates to methods for making enzyme-treated unpopped popcorn kernels, comprising: (a) contacting the kernels with an aqueous solution comprising an effective amount of one or more hull wall-degrading enzymes for a period of time sufficient to weaken the hull wall of the kernels; and (b) recovering the enzyme-treated popcorn kernels.
The present invention also relates to popcorn kernels obtained by the methods of the present invention.
DESCRIPTION OF THE INVENTION
The present invention relates to methods for making enzyme-treated popcorn kernels by sufficiently degrading the hull wall of the kernels with an aqueous solution comprising an effective amount of one or more hull wall-degrading enzymes and recovering the enzyme-treated kernels, wherein the enzyme treatment increases the yield of popped flakes from a given weight of popcorn kernels.
In the methods of the present invention, the popcorn may be of any type, such as open-pollinated varieties or hybrid varieties. The popcorn is preferably a hybrid popcorn, and more preferably white, small yellow, medium yellow, and/or large yellow popcorn.
The cultivation of popcorn with regard to soil type, soil fertility, planting, weed control, insect control, disease control, irrigation, harvesting, conditioning, and storage are well known in the art.
The popcorn kernels may be harvested by hand, on the ear, or by combine. Popcorn can be hand-harvested anytime after it reaches maturity (i.e., 35% moisture) or ear-harvested at 25% moisture. Combine-harvested kernels should have a field moisture of about 14% to about 18%, with the optimum being about 16% to about 17% moisture. Above 18% moisture, the kernels may undergo physical damage, which lowers popping volume. Below 14% moisture, the kernels are susceptible to impact damage especially from combining and associated handling operations, which can also lower popping volume.
In the methods of the present invention, the kernels prior to enzyme treatment preferably have a moisture content in the range of about 10 to about 25%, more preferably about 14% to about 20%, even more preferably about 14% to about 18%, and more preferably about 15% to about 17%.
Kernels with an unsuitable moisture content may be partially dried using a heated or unheated forced-air system or natural ventilation known in the art for such purposes. The drying process should be such that it does not affect the potential popping yield of the kernels.
Higher quality kernels can be expected if drying is performed in several stages with a 12-24 hour tempering period between stages to allow for moisture redistribution within the kernels. An alternative to this is a two-stage combination drying system where a heated-air dryer is used to reduce moisture content to approximately 17-18%. then a natural air or low temperature drying system finishes the conditioning process.
If the kernels are over-dried, they can be re-hydrated to the desired moisture content, but generally they will not recover their initial popping volume. Any method known in the art for re-conditioning over-dried kernels may be used. It is preferable to pass 70-85% relative humidity through the kernels for a sufficient period of time, which depends on the air flow rate and the amount of re-hydration needed until the desired moisture content is achieved.
The term “effective amount of one or more hull wall-degrading enzymes” is defined herein as the amount of one or more enzymes that is sufficient for weakening the pericarp component of popcorn kernels to increase the yield of popped flakes from a given weight of unpopped popcorn kernels when subjected to heat in the range of 350-375° F. The effective amount of the one or more hull wall-degrading enzymes will depend on the enzyme(s) and the period of time desirable for degrading the hull wall. High amounts of the enzyme(s) will likely require shorter times of treatment while low amounts longer times.
In the methods of the present invention, one or more enzymes may be used whi
Hendricks Keith
Novozymes Biotech Inc.
Starnes Robert L.
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