Patent Description:
Tofu is a highly nutritious, protein-rich food that is made from the curds of soybean milk. It is believed to have been invented in China around <NUM> years ago. Basic tofu is a white, essentially bland, soft product.

Tofu production starts with a soybean soaking process to prepare the soybeans for extraction of soy protein. Whole, dry soybeans are saturated with water at ambient temperature for <NUM>-<NUM> hours although soybean flakes or "grits" can also be used. The soaked beans or flakes are ground. The ground soybean slurry is then cooked, typically with direct or indirect heat or steam up to <NUM> or <NUM> for <NUM> to <NUM> minutes. During the cooking process, soy protein is denatured and some of the volatile flavors are removed. The resultant soy slurry may be filtered to remove the soy pulp or fiber or the slurry may be filtered prior to cooking. The resulting product, referred to as soymilk, is then coagulated to form curds and whey. Whey is removed before or during pressing of the curds. The finished, pressed curds are referred to as tofu.

Tofu-like products have been made from a variety of non-soybean sources, for example, egg tofu, sesame tofu, peanut tofu and Burmese tofu (which uses yellow split pea flour and is set in a manner similar to soft polenta).

Canola meal, a by-product of canola oil processing, is high in protein and is typically used as a feed ingredient for livestock animals, due to its low cost.

Successful preparation of a canola based tofu has not previously been reported.

<CIT> teaches that solubilised residue of rapeseed (canola), can be separated from insoluble residue by acid extraction, centrifugation or filtration or a combination thereof, to produce a dry protein extract.

<CIT> teaches a process for aqueous extraction, fractionation and enzymatic treatment of oil-extracted non- or lightly toasted flakes from rapeseed (canola), to produce a hard curd that can be pressed to form dried animal feed.

<CIT> teaches a food composition containing a coagulated dried soy protein and a process for making the composition.

<CIT> discloses a structured protein, including canola protein, which can be combined with tofu, soy whey, or soymilk and a coagulant to form a structured protein composition.

<CIT> discloses extracting oleosin from canola meal. <CIT> concerns oilseed processing. <CIT> concerns a process for preparing a curd-like product from cottonseed and other oilseeds. <CIT> concerns a method for producing a soy milk. <CIT> concerns aqueous processing of oilseed press cake.

According to one aspect of the description, there is provided a method of making a tofu-like canola meal food product comprising the sequential steps of:.

The canola meal can be cold pressed canola meal, or canola meal cake.

Before step (a), the method can include grinding a quantity of canola to produce the canola meal. Fine ground meal is preferred, and more preferred is medium ground meal. Sieving can be done to remove larger fragments. If sieving is done, about a <NUM> to <NUM> sieve can be used. The canola meal can be ground by a hammer mill, a roller mill or a pin mill. The canola meal cake may be ground such that the hull fragments will be retained by a <NUM> sieve.

During soaking, the ground canola water:meal can be a ratio of <NUM>:<NUM> to <NUM>:<NUM>, preferably <NUM>:<NUM> to <NUM>:<NUM>, more preferably about <NUM>:<NUM>.

The liquid can be removed by draining the mixture and/or pressing and/or filtration. The separation of liquids and solids can also be done by centrifugation.

The cooling can be done to a temperature of about <NUM>-99C, preferably <NUM>-90C. The aqueous ground canola meal can be soaked for <NUM>-<NUM> hours, preferably <NUM>-<NUM> hours, more preferably <NUM>-<NUM> hours.

The coagulant can be selected from the group consisting of: calcium sulfate; magnesium chloride; magnesium sulfate (MgSO<NUM>), calcium chloride; glucono delta-lactone (GDL); acetic acid; citric acid; papain; vinegar, an alkaline protease; a neutral protease; and mixtures thereof. Preferably, the coagulant is selected from one or more of calcium sulfate anhydrous (CaSO<NUM>), glucono delta-lactone (GDL), and a combination of the two coagulants. Preferably, the coagulant is between <NUM>% and <NUM>% (v/v) of the canola milk.

The invention also teaches a canola based food product obtained by the methods of the invention.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are now described.

The present invention, which is defined by the claims, relates to a method of making a tofu-like canola meal product from ground canola meal, and to a tofu-like food product obtained by that method when the coagulant is glucono delta lactone and/or calcium sulfate.

Canola meal, a by-product of canola oil processing is typically used as a feed ingredient for livestock animals.

Canola meal has not previously been used for preparation of a tofu-like product because of several concerns regarding the nature of the canola meal itself and the process of preparing tofu from soybean. Specifically, compared to whole soybean (typically used in tofu production), canola meal has lower protein content (<NUM>% for cold press canola meal; <NUM>% for solvent extracted canola meal, compared to <NUM>-<NUM>% crude protein for whole soybean), and much higher fiber content (<NUM>% crude fiber for cold press canola meal, versus <NUM>% crude fiber for whole soybean). Accordingly, there were problems with coagulation of the canola proteins, as well as concerns regarding the difficulties in processing such a high fiber meal and the ability to form a suitable tofu cake from a meal having these characteristics. Furthermore, canola meal proteins are more soluble than soy meal proteins, which have prevented the preparation of a tofu-like product from canola meal, specifically, during the coagulation of the canola milk.

Assuming that a tofu-like product could be made from the high fiber, low protein content, high soluble protein canola meal, an additional consideration is the fact that canola meal cake has a dark, gritty appearance, meaning that the meal cake would be expected to produce a product with an unappetizing appearance as well as a gritty texture in the mouth. Furthermore, the canola meal also has a bitter taste, meaning that any tofu-like product produced therefrom would be expected to be unpalatable.

For conventional processing of canola, the seed is initially rolled or flaked. This ruptures cells and makes the oil easier to extract. Next the flaked or rolled seeds are cooked. Cooking thermally ruptures any oil cells that have survived flaking. It also reduces oil viscosity, which promotes oil collection, and inactivates the myrosinase enzyme which can hydrolyze glucosinolates found in canola resulting in undesirable breakdown products affecting oil and meal quality. Temperatures used during this stage range from <NUM>-<NUM>, with an optimum temperature of about <NUM>. The cooking cycle usually lasts <NUM>-<NUM> minutes.

The cooked canola flakes are then pressed in a series of screw presses or expellers which removes <NUM>-<NUM>% of the oil while avoiding excessive pressure and temperature. The resulting compressed "cake fragments" undergo further processing to remove the remaining oil by treating the cake with hexane that is specially refined for the vegetable oil industry. After this process, the solvent is removed in a desolventizer-toaster. Most of the solvent is flashed from the meal by a heating process. The final stripping of the solvent is completed by injecting steam through the meal, a process called toasting. During the desolventization-toasting process, the meal is heated to <NUM>-<NUM> and moisture increases to <NUM>-<NUM>%. This process takes about <NUM> minutes. The final stage involves blowing air through the meal to cool it and dry to about <NUM>% moisture. It is then ground to a uniform consistency using a hammer mill, and then either pelletized or sold as a granular product to the feed industry.

Alternatively, canola oil can be extracted by cold pressing. Cold pressing does not involve heating of the canola seeds/meal before, during, or after the pressing process. Seeds are selected, cleaned, and rolled or crushed. The seeds are then mechanically pressed at a slow speed to limit friction and avoid elevating temperatures above <NUM>. The screw presses are often water cooled to ensure the temperature of the pressed cake does not exceed <NUM> during mechanical processing. The resulting meal is much higher in oil than the meal obtained from conventionally processed canola.

The present inventor has found that, the canola meal cake used in the manufacture of the tofu-like product can be either a solvent-extracted canola meal cake or a cold press canola meal cake, although in preferred embodiments, cold press canola meal cake is used.

In an embodiment of the invention, there is provided a method of making a tofu-like canola meal food product which can comprise:.

The canola curd may be placed into a mold prior to pressing so that the tofu-like product has the desired shape.

The canola meal cake may be ground by any suitable means known in the art, for example, a hammer mill, a roller mill or a pin mill. Preferably, the canola meal cake is ground until the canola meal cake is in the form of individual particles and does not contain any clumps. Alternatively, the canola meal cake may be ground such that the hull fragments will be retained by a <NUM> sieve (that is, will not pass through a <NUM> sieve).

Sieving is not essential, as the solid parts of the meal will be separated from the canola milk in any event. However, for some canola meals (e.g. Landmark™), it is desirable to remove large pieces of non-protein material from the meal. If sieving, sieves between US Standard <NUM> (<NUM>) and US Standard <NUM> (<NUM>) can be used, and even larger. If sieving, sieve size in not critical.

In some embodiments, approximately <NUM>% of the canola meal cake is removed by the sieving process. This <NUM>% is composed primarily of hull fragments which are high in bran.

The present inventor has found that the ground meal cake can optionally be soaked for any suitable period of time, for example, for <NUM>-<NUM> hours, preferably <NUM>-<NUM> hours. Variations in soaking time have been used, ranging from <NUM> to <NUM> hours. Prolonged extraction generally does not result in more protein in the extracted milk. It is possible that materials in addition to protein are solubilized during the long process. Handling of the material can be more difficult with longer soaking times. This is believed to result from increased swelling of starch or fibrous material that may be present, making the separation step more of a challenge.

According to the present invention, a preferred ratio of water to ground meal cake is of <NUM>:<NUM> to <NUM>:<NUM>. If too little water is added, some of the soluble material may fall out of solution and be lost during filtering. Alternatively, if too much water is added, the canola milk may be too dilute to coagulate.

The milk is then separated from the meal. Separation of milk from the insoluble material, in particular the dark seed coat can be accomplished by a variety of techniques including filtration and centrifugation. Many different separation devices and methods will work. One preferred method is the use of a nut bag. Nylon mesh is easier to work with and removes more of the small black bits than, for example, cheese cloth. Centrifugation was also very effective.

The filtering of the soaked ground meal cake is carried out so that only the soluble material passes through the filter and insoluble material such as hull fragments are removed.

The canola milk concentrate is heated to a temperature between <NUM>-<NUM>, preferably to a temperature between <NUM>-<NUM> for an appropriate time. Preferably, the temperature of the canola milk is increased gradually, to promote coagulum formation. Once the canola milk reaches the desired temperature, the canola milk is removed from heat prior to the addition of the coagulant, as discussed below.

The present inventor tested multiple different coagulants. The coagulant may be any suitable coagulant known for the production of tofu or similar products may be used in the invention. For example, the coagulant may be selected from the group consisting of: calcium sulfate; calcium chloride, magnesium sulfate, magnesium chloride; calcium chloride; glucono delta-lactone (GDL); acetic acid; citric acid; papain; an alkaline protease; a neutral protease; a vinegar, and mixtures thereof. Alternative salts of the coagulants may be used.

A combination of coagulants is generally preferred. Preferred coagulants are calcium sulfate and glucono delta-lactone (GDL). However, using <NUM>% GDL only is particularly preferred, based on the quality of the resulting product. Yield is often higher with calcium sulfate, however, the solubility of CaSO<NUM> can be a concern as some of the precipitate CaSO<NUM> may contribute to the yield and leave a white powdery residue on the tofu like product. The coagulant may be added at <NUM>-<NUM>% (v/v) of the heated canola milk. <NUM>-<NUM>% is preferred. Yields were better with a <NUM>% coagulant addition.

The conditions for the preparation of the canola meal tofu-like product may be varied to produce different results, specifically, different textures and firmness for the end product. For example, mixtures of the coagulants and different quantities of the coagulants, both individually and relative to one another may be used. For example, a combination of calcium sulfate and GDL produced an end product with a texture similar to silken tofu. Other firmness and textures can be obtained by varying the parameters discussed herein.

Calcium sulfate or calcium chloride may be used to produce a tofu-like product that is high in calcium whereas magnesium chloride may be used to produce a tofu-like product that is high in magnesium.

The ideal temperature to which the canola milk is heated and the temperature at which the coagulant is added may depend in part on the coagulant selected. For example, calcium sulfate may be added at a temperature of <NUM>-<NUM> and the mixture mixed at a temperature of <NUM>; a combination of calcium sulfate and GDL may be added at a temperature of <NUM> and the mixture mixed at a temperature of <NUM>; or GDL may be added at a temperature of <NUM>-<NUM> and the mixture mixed at a temperature of <NUM>. Suitable temperatures for other coagulants and coagulant mixtures may be determined by following the methods described herein.

The invention will now be further illustrated by way of examples; however, the invention is not necessarily limited to the examples.

Canola press cake provided by the Food Development Centre in Portage La Prairie, Manitoba was used. The variety from which the seed cake was derived for this example was Invigor™ L150 Lot <NUM> certified seed variety. The methods described herein are not specific for this variety and may be used with any canola variety.

Food grade Calcium Sulfate Anhydrous (CaSO<NUM>) and Glucono delta-Lactone (GDL) was purchased from Spectrum Laboratory Products in Gardena CA.

Prior to working with the press cake it was further ground to pass through a <NUM> sieve. As the hull particles tended to be larger, as discussed above, hull particles were removed by the sieving process prior to the initial soak. Approximately <NUM>% of the press cake was removed by this sieving step in this trial.

The ground press cake was then soaked in water for approximately <NUM> hours (overnight). Ranges of press cake to water ratios were evaluated. A ratio of water to press cake of between <NUM>:<NUM> and <NUM>:<NUM> was found to be suitable. A ratio of <NUM>:<NUM> was used for those products that were evaluated in Example <NUM>, below.

The mixture was filtered through a cloth lined with two layers of cheesecloth to obtain canola milk concentrate.

The canola milk was slowly heated with gentle agitation to between <NUM>° and <NUM>. It was then removed from the heat and coagulant, which had been dissolved in water at a ratio of <NUM> parts water to <NUM> part coagulant and a temperature appropriate for the coagulant (Table <NUM>). The mixture was then stirred gently for <NUM> seconds at the appropriate temperature (Table <NUM>).

Gentle agitation kept the soluble protein in solution; however, too much agitation produces a froth or foam which will reduce yield as will no agitation (due to precipitation).

Once the coagulant was incorporated into the mixture, it was left to set at room temperature for <NUM> minutes and then transferred to refrigerator and set for an additional <NUM> hours.

The resulting coagulum was drained through <NUM>-<NUM> layers of cheesecloth for <NUM> to <NUM> hours to produce a curd. The curd, wrapped in two layers of cheesecloth, was transferred to a mold and pressed overnight in refrigerator. Press time was extended to <NUM> hours to create firmer texture.

Texture was analyzed with a TA-XT Plus™ texture Analyzer (Texture Technologies, Hamilton MA) and associated software. A penetration system with a <NUM><NUM> uniaxial compression ball, starting at a distance of <NUM> from the sample and compressing at a rate of <NUM> per second was used. Samples were held at refrigerated temperatures until tested to maintain consistent results.

The maximum applied force (firmness) and stress to strain ratio of elastic modulus (elasticity) were evaluated and are summarized in Table <NUM>. Tests were performed on full size samples in triplicate.

The colour of the canola tofu was measured using a Minolta cm-3500d spectrophotometer with Spectramagic nx™ software. CIE lightness (L*), yellow-blue (a*) and red-green (b*) values were determined in triplicate. Results of these analyses are summarized in Table <NUM>.

Texture measurements indicated that it was possible to create a canola tofu with a texture similar to that seen for a commercial soft (or silken) tofu. This could be obtained either with <NUM>% GDL or the combination of <NUM>% CaSO<NUM> + <NUM>% GDL, with values for the latter being closer to the commercial product. Firmer and more elastic gels could be obtain with CaSO<NUM>, but even with levels of <NUM>% CaSO<NUM> both firmness and elasticity were considerably lower than that seem for the hard commercial soy tofu.

The colour of the canola tofu was noticeably difference from the soy tofu; however, surprisingly, the colour was not as dark as expected. L* values ranged from <NUM> to <NUM> indicating a reasonably light product, but considerably lower than the soybean controls. A values were close to zero (a* scale goes from -<NUM> to +<NUM>), suggesting little in the way of green and red colours; some were close to those for the control and some a little higher. The b* values were distinctive for the canola products and the high values were indicative of a strong yellow colour, which appeared to be a golden colour. The lowest b* value was obtained with the mixture of <NUM>% CaSO<NUM> and <NUM>% GDL, suggesting this may be the preferred combination for the preparation of a golden soft canola tofu.

Cold pressed canola meal was provided by the Manitoba Food Product Development Centre.

Grinding and sieving was not necessary when using the cold press canola meal. The raw material was soaked for <NUM> to <NUM> hours with cold tap water at a ratio of <NUM>:<NUM> (w/v) or <NUM>:<NUM> (w/v) prior to blending; the <NUM>:<NUM> ratio is preferred due to a higher yield of Tofu produced. A <NUM>:<NUM> ratio has also been tried for all three raw materials (Cold Press Canola Meal, Extruded Canola Meal (Viterra™), and Solvent Extracted Canola meal (Fine fraction; Landmark Feeds), but after blending, the texture of the mixtures was too thick to extract milk.

The canola meal and water mixture was blended for <NUM> minutes at "liquefy" mode using an Oster™ blender. The slurry was then filtered and squeezed manually through a nut milk bag (Aviva™ Nut Milk Bag, made of sturdy nylon). Previously, cheese cloth was used, which performed well with respect to removing insoluble material, including bits of seed coat. Any cloth or polymer based filtration should have a similar effect. The milk was then heated to boiling (<NUM> - <NUM>) for <NUM> minutes with constant stirring. During heating, milk would get more turbid and milky, between room temperature and around <NUM>-50C. At around 50C, coagula separation began, and this became more pronounced through the heating process.

Coagulants were prepared based on the volume of the milk, and coagulants were mixed with 5x their volume of water prior to mixing with the milk. For example, if the amount of milk was <NUM> and the concentration of coagulants <NUM>%, the amount of coagulants needed was <NUM> * <NUM>% = <NUM>, plus <NUM> of water. The two coagulants can be used separately or in combination. Using CaSO<NUM> as a coagulants resulted a lighter coloured final products, and white powder residue in the final products. However, using CaSO<NUM> as a coagulant seemed to result in a higher yield. Milk was poured into the coagulants at <NUM> - <NUM> for CaSO<NUM>, and <NUM> - <NUM> for GDL.

After the addition of coagulants, the mixture was set undisturbed for <NUM> hour at room temperature before filtering through one layer of cheese cloth. The curd was then pressed for <NUM> hours in a fridge (<NUM>).

Solvent Extracted Canola Meal (Landmark Feeds) was used. The methods of Example <NUM> were followed, with the following modifications.

Sieving was performed as there was a substantial quantity of fiber and other debris in the sample provided. Three fractions were obtained:.

Both the medium and fine part of the canola meal can be used to extract milk. The fine fraction showed better promise. Protein extractions were lower than for the initial press cake and as a result, it was difficult to get a firm texture after pressing. This material looked more like a spread and may have potential in other applications.

Milk extracted from Solvent Canola Meal (Landmark Feeds) was darker than the milk extracted from using the cold press canola meal.

Extruded Canola Meal (Viterra) was obtained by oil extraction using extrusion. The methods of Example <NUM> were followed, with the following modifications.

Milk extracted from the Extruded Canola Meal from Viterra (finely ground when received) was darker than the milk extracted from using the cold press canola meal.

Both were from Spectrum Laboratory Products in Gardena CA and were of food grade.

Extruded Canola Meal (Viterra) was obtained by oil extraction using extrusion by traditional oil extraction method, heat treatment included. The methods of Example <NUM> were followed.

A thin layer appeared on the cheesecloth that could not be pressed. This was primarily due to the lack of solubility of the protein.

Claim 1:
A method of making a tofu-like canola meal food product comprising the sequential steps of:
a) placing ground canola meal in an aqueous solution to form a aqueous ground canola meal;
b) separating insoluble materials from liquids of the aqueous ground canola meal to isolate a canola milk;
c) heating the canola milk to <NUM>-100C to induce protein unfolding;
d) cooling the canola milk to allow coagulation;
e) adding a coagulant to the canola milk to induce coagulation; and
f) removing liquid from the curd to produce a soft solid product, preferably wherein the canola meal is cold pressed canola meal, preferably wherein the canola meal is canola meal cake.