FILTERS INCLUDING MAGNESIUM SILICATE

This invention relates to filters for treating used cooking oil. More particularly, this invention relates to cooking oil filters which contain magnesium silicate.

In recent years there has been a growth in the use of cooking oils and fats for cooking of foods such as chicken, potatoes, pies, fish, etc.

In the frying operation, large quantities of edible cooking oils or fats are heated in vats to temperatures in the order of 315°-375°F, and the food is immersed in the oil or fat for cooking. During repeated use of the cooking oil or fat, high temperatures, as well as air and water, cause the breakdown of triglyceride molecules.

The hydrolysis of triglycerides causes the formation of free fatty acids (FFA). An increase in the FFA decreases the oil's smoke point and results in increasing smoke as the oil ages. In addition, when cooking, there is an oxidative decreneration of fats which results form contact of air with hot oil producing oxidized fatty acids (OFA) . Heating transforms the OFA into secondary and tertiary by-products such as aldehydes, ketones, and polymers. Moreover, caramelization (which is a browning reaction which occurs when foods containing carbohydrates and proteins are exposed to heat) occurs during the use of the oil over a period of time, resulting in a very dark color of the oil which, combined with other by-products, produces dark,

unappealing fried foods. These degradation compounds are classified as polar compounds which correlate to the taste and odor characteristics of fried foods.

Because of the tremendous cost resulting from the replacing of the cooking fats and oils after use thereof (normal useful life generally in the order of 2-10 days), the industry has searched for an effective and economical way to slow degradation of fats and oils and extend their usable life.

Filtering oil has long been recognized as being beneficial to extending the life of a usable frying oil. The use of powdered filter aids in combination with a cloth, paper, or wire septum removes particulate impurities from the oil, and in the case of activated filter aids, removes-dissolved products of oil degradation as well.

U.S. Pat. No. 4,112,129, granted on September 5, 1978, discloses that a composition comprised of diatomite, synthetic calcium silicate hydrate and synthetic magnesium silicate hydrate may be employed for reclaiming used fats and oils. The patent further indicates that a synthetic magnesium silicate hydrate may not be used, by itself, for such purposes.

U.S. Patent No. 4,988,440, issued to Bernard, et al., discloses a filter for treating used cooking oil which comprises a porous sheet of substantially uniform thickness, and includes from 15 wt.% to 35 wt.% activated carbon; from 15 wt.% to 40 wt.% calcium silicate, magnesium silicate, or mixtures thereof; from 25 wt.% to 40 wt.% cellulosic fiber; up to 2 wt.% resin binder, and, optionally, up to 30 wt.% diatomaceous earth.

It is an. object of the present invention to provide an improved filter for the treatment of used cooking oils and fats.

In accordance with an aspect of the present invention, there is provided a filter which consists essentially of cellulosic fiber and magnesium silicate.

In general, the magnesium silicate is present in the filter in an amount effective to reduce the content of polar compounds.

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in the oil or fat and permit reuse of the oil or fat for cooking. In one embodiment, the cellulosic fiber is present in an amount of from about 10 wt.% to about 40 wt.%, preferably at about 20 wt.%, and the magnesium silicate is present in an amount of from about 60 wt.% to about 90 wt.%, preferably at about 80 wt.%.

In general, the magnesium silicate is a magnesium silicate which is accpetable as a filter aid in food processing applications. For example, the Food Chemical Codex, Third Edition, gives the following specifications for a magnesium silicate which is acceptable in food processing operations: Loss or Drying 15% max

Loss on Ignition 15% max (dry basis)

% MgO 15% mi-n. (ignited basis)

% Si0 ₂ 67% min. (ignitied basis)

Soluble salts 3% max.

Mole ratio MgO:SiO- 1:1.36 to 1:3.82 In one embodiment, the magnesium silicate is an amorphous synthetic magnesium silicate having a surface area of at least 300 square meters per gram, and preferably has a surface area from about 400 square meters per gram to about 600 square meters per gram. In addition, such magnesium silicate is preferably employed as coarse particles, with at least 75%, and preferably at least 85% of the particles having a particle size which is greater than 400 mesh, and with no more than 15%, and preferably no more than 5%, all by weight, having a particle size greater than 40 mesh. In most cases, the average particle size of the magnesium silicate employed in accordance with the present invention is in the order of but not limited to 20-75 microns. It is to be understood, however, that the magnesium silicate may have a particle size different than the preferred size. For example, the magnesium silicate may be used as a finely divided powder, i.e., 50% or more passes through a 325 mesh screen. In addition, the hydrated magnesium silicate which is employed in accordance with the present invention generally has a

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bulk density in the order of from 15-35 lbs/cu.ft., a pH of 7-10.8 (5% water suspension) and a mole ratio of MgO to SiO_ of 1:1.8 to 1:4.

The following is a specification and typical value for a magnesium silicate which is employed in accordance with the present invention:

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Parameter Specification Typical Value

A representative example of such a magnesium silicate having a surface area of at least 300 square meters per gram is available as Magnesol Polysorb 30/40, a product of the Dallas Group of America, Inc., Liberty Corner, N.J.

In another embodiment, the magnesium silicate is an amorphous, hydrous, precipitated synthetic magnesium silicate which has been treated to reduce the pH thereof to less than about 9.0. As used herein; the term "precipitated" means that the amorphous hydrated precipitated synthetic Magnesium silicate is produced as a result of precipitation formed upon the contact of a magnesium salt and a source of silicate in an aqueous medium.

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For purposes of the present invention, the pH of the magnesium silicate is the pH of the magnesium silicate as measured in a 5% slurry of the magnesium silicate in water. The pH of the treated magnesium silicate in a 5% slurry preferably is from about 8.2 to about 8.9, and more preferably from about 8.5 to about 8.8. An example of such a treated amorphous hydrous precipitated synthetic magnesium silicate is available as Magnesol XL, a product of the Dallas Group of America, Inc., Liberty Corner, N.J.

In yet another embodiment, the magnesium silicate is a magnesium silicate which has a surface area of from about 50 square meters per gram to about 150 square meters per gram. Preferably, such a magnesium silicate has" a mole ratio of MgO to Si0 ₂ of from about 1:2.6 to about 1:3.4, and a pH (5% water suspension) of from about 9.5 to about 10.5. An example of such a magnesium silicate is available as Magnesol HMR-LS, a product of the Dallas Group of America, Inc., Liberty Corner, N.J.

The cellulosic fiber provides a support matrix to which the magnesium silicate can bind. Examples of cellulosic fibers include, but are not limited to wood pulp fiber and hemp fiber. In one embodiment, the cellulosic fiber is in the form of bleached wood pulp fiber. Typically, the wood pulp fiber has an average fiber length of from about 1.75 millimeters to about 3.00 millimeters, preferably from about 1.80 millimeters to about 2.80 millimeters, and an average diameter of from about .020 millimeters to about .035 millimeters, preferably from about .025 to about .030 mm.

In accordance with another aspect of the present invention, there is provided a filter which consists essentially of cellulosic fiber, magnesium silicate, and a binder component. The magnesium silicate and cellulosic fiber may be as hereinabove described.

In one embodiment, the cellulosic fiber is present in the filter in an amount of from about 10 wt.% to about 40 wt.%,

preferably from about 15 wt.% to about 20 wt.%, the magnesium silicate is present in an amount of from about 55 wt.% to about 85 wt.%, preferably from about 75 wt.% to about 80 wt.%, and the binder component is present in an amount of from about 1 wt.% to about 5 wt.%, preferably from about 1 wt.% to about 3 wt.%.

The binder component aids in binding the magnesium silicate to the cellulosic fiber, thereby preventing magnesium silicate particles from detaching from the filter, as well as providing structural stability to the filter. The binder is one which is food compatible. Examples of binders which may be employed include, but are not limited to, starch, polyvinyl alcohol, or other non-toxic and food compatible binders. An example of a polyvinyl alcohol binder which may be employed is Airvol 523, a product of Air Products, Allentown, PA, and an example of a vinyl acetate polymer which may be a vinyl acetate polymer emulsion in water is known as Airflex 109, also a product of Air Products, Allentown, PA.

Applicant has found that when one contacts used cooking oil or fat with a filter which consists essentially of cellulosic fiber and magnesium silicate, or of cellulosic fiber, magnesium silicate, and a binder component, one obtains improved reduction of the content of free fatty acids in the oil or fat.

The filter employed in accordance with the present invention, therefore, can be used to treat used cooking oil and/or fats in conjunction with any one of the wide variety of operations for filtering used cooking oils and fats.

The filters of the present invention are applicable to continuous filtration systems in which the used oil is continuously circulated through filtration units and back to the frying vats and/or batch systems wherein one or more times a day the contents of each frying vat are filtered through a batch type ilter.

Thus, in accordance with yet another aspect of the present invention, there is provided a process for treating used cooking

oil or fat by contacting used cooking oil or fat with a filter such as those hereinabove described, wherein the magnesium silicate is present in the filter in an amount effective to reduce the polar compound content of the used cooking oil or fat.

The filters of the present invention may be produced by many standard methods of fabrication, and may consist of the proportions of the components hereinabove described.

In one embodiment, a slurry of a liquid medium (such as alcohol or water, preferably water) is created in a mixer by adding to water in the following proportions: 80% magnesium silicate and 20% wood pulp. The component percentages are based on the total components added to the water. Sufficient water is employed to adjust the solids content of -the slurry to about 2% by weight based on the total slurry. A period of thorough mixing follows. When the mixture appears to be thoroughly mixed, it is then subjected to a shearing action in a refiner.

The final, refined slurry is poured onto a screen to dewater, thereby forming a desired sheet as an endproduct. The uniformity of thickness of the sheet is achieved through the use of moving rakes which uniformly distribute the refined slurry over the surface of the screen. After sufficient dewatering, the moist sheet is dried in an oven. Thereafter, the dried sheet is cut into filter pads, or wafers, of the peripheral size and shape necessary to fit the desired filtering application. The trimmings, or scrap left from cutting the finished sheets may be added as feedstock to make up part of the 2% solids of a subsequent batch of water slurry created in the mixer.

The formation of the filter may be carried out on an apparatus which makes one filter sheet at a time or a continuous filter sheet may be made on a machine similar to a Fourdrinier (paper making) machine. With such a machine, the uniformity of sheet thickness is controlled by maintaining a uniform discharge of the refined slurry across the width of an underlying moving screen. The porosity of the sheets may be adjusted by varying

the amounts of cellulosic fiber and magnesium silicate, and by varying the degree of refining.

In another embodiment, a slurry of solids in a liquid medium such as those hereabove described (preferably water) is formed in a mixer by adding wood pulp to water to form a slurry having a solids content of from about 0.5% to about 5% by weight, preferably at about 2% by weight. A period of mixing follows. After mixing, the slurry is added to a vacuum mold chamber which contains a vacuum-backed screen. A filtrate collector in the form of a funnel and a vacuum motor are located beneath the screen. Before the slurry is added to the vacuum mold chamber, water is added to the vacuum mold chamber to a depth such that the water occupies from about 25% by to about 40% by volume above the screen. The slurry of water and wood pulp is then added. Upon addition of the slurry, magnesium silicate is then added to the vacuum mold chamber so that the composition of the solids is 80 wt.% magnesium silicate and 20 wt.% wood pulp. A vacuum is then applied to the slurry, and water is drawn through the screen and into the funnel, whereby a filter of magnesium silicate and wood pulp is formed. The filter is then removed from the vacuum mold chamber and oven dried.

In another alternative, fiberized wood pulp is deposited on a vacuum-backed framing screen. The magnesium silicate is then metered into the fiberized pulp mat. The pulp and the magnesium silicate are then compressed to form a filter pad.

Filters formed in accordance with the present invention may be employed for filtering and treating cooking oil or fat used in frying operations. In general, the cooking oil or fat is not cooled to a temperature which is below 150°F. In most cases, the treatment temperature should not exceed 375°F; however, it may be possible to expose the oil and/or fat to higher temperatures for a period of time during the treatment cycle without an adverse effect on the oil.

The filters of the present invention are capable of maintaining contaminant levels below the point of discard for an extended period of time. Such filters may be used to remove contaminants from used cooking oil or fat without affecting food quality adversely.

The filters of the present invention may also be employed to treat fruit-based or vegetable-based beverages to remove chill haze components therefrom. Thus, in accordance with another aspect of the present invention, there is provided a process for treating a fruit-based or vegetable-based beverage to remove chill haze components therefrom by contacting the beverage with a filter such as those hereinabove described, wherein the magnesium silicate is present in the filter in an amount effective to remove chill haze components from the fruit-based or vegetable-based beverage. Examples of fruit-based beverages which may be treated include, but are not limited to, wine, apple juice, grape juice, pineapple juice, apple cider, etc. Examples of vegetable-based beverage which may be treated include, but are not limited to, beer, ale, porter, stout, malt liquor, etc.

The invention will now be described with respect to the following example; however, the scope of the present invention is not intended to be limited thereby.

Example

Ten gallons of water are added to a vacuum mold chamber having a diameter of 21.875" and a depth of 16" (1.63 gallons per 1 inch of depth). A 24 X 110 mesh screen is contained at the bottom of the chamber. A slurry of 0.375 lb. of wood pulp and water is then formed in a mixer wherein the slurry has a wood pulp content of 2%. The slurry has a total volume of 2.21 gallons. After mixing, the slurry is added to the vacuum mold chamber. Magnesium silicate ( Magnesol XL) is then added to the vacuum mold chamber such that the composition of the solids is 80 wt.% magnesium silicate and 20 wt.% wood pulp. The total amount of magnesium silicate added was 1.5 lbs. A vacuum is then

applied against the screen of the vacuum mold chamber, whereby - the solids are drawn against the screen at the bottom of the chamber, and water is drawn out of the chamber through the screen. After all of the water is drawn out of the vacuum mold chamber, the vacuum is stopped and the resulting filter pad, having a thickness of 9/16" (+/- 3/32") is removed from the chamber. The pad is then oven dried to provide a filter consisting of magnesium silicate and wood pulp.

It is to be understood, however, that the scope of the present invention is not to be limited to the specific embodiments described above. The invention may be practiced other than as particularly described and still be within the scope of the accompanying claims.

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