STARCH-BASED FOOD PRODUCTS
FIELD OF THE INVENTION
The present invention relates to food products which are intended as an alternative for normal rice or wheat based pasta and to a process for making them.
BACKROUND OF THE INVENTION
There is an increasing demand for food products which are easily produced on an industrial scale and subsequently easily prepared in the home but which are still nutritious and have an acceptable taste and/or texture. Furthermore, there is an increasing demand for nutritious food products which can be produced by relatively simple production techniques; this is true especially for undeveloped countries where there is an emphasis on using inexpensive production methods and inexpensive and/or local ingredients. In particular, there is a need for food products which can be produced by relatively simple production processes (ideally using inexpensive and/or local ingredients) and which retain a high level of their nutritive value, especially protein value, upon cooking.
Many foods do not provide a good protein quality to the consumer and improving this is of particular importance, especially, in the developing or third world countries where food from single raw material sources (e.g. cassava, yams, etc.) is used to provide the basis of nutritional intake and good nutrition from the food which is available is vital .
Another problem which exists in the art is to provide acceptable alternatives to wheat based food products which are suitable for people suffering from dietary wheat intolerences . Such alternative products should ideally be easily digestible,
have an acceptable taste and/or texture and be relatively easy to prepare on a commercial scale .
Attempts have been made to address one or more of the aforementioned problems.
US 3,615,674 discloses a blend of milled wheat fractions which are chosen so as to provide a well-balanced combination of calorie content, protein content and quality, fibre content and nutrient availability. These wheat fractions can be used to produce pasta and other products. It is suggested that such a product could be used to help address world food shortages and nutritional problems.
US 4,158,069 discloses enriched wheat macaroni products comprising a major proportion of milled wheat ingredients and a predetermined amount of L-Lysine to provide a fortified protein content. The product is disclosed to be an economical, easily manufactured, high protein content pasta.
WO 92/15203 discloses non-wheat containing pasta products prepared from urad legumes, prepared by mixing urad legumes flour with water to form a dough which is formed into a pasta shape and dried. The product is intended to be easily prepared in undeveloped countries.
US 4,440,798 discloses the preparation of low cost textured vegetable protein products which are intended for use particularly in undeveloped countries to improve the protein quality and content of consumers' diets. A proteinaceous material, such as soy beans, is mixed with water and a protein coagulating agent is added. The material is then cooked to form
textured vegetable protein which has a high protein content, generally of at least 64%.
US 4,923,709, US 5,789,012 and EP-A-0 290,471 (all in the name of Slimak) disclose food products prepared from starch containing foods such as cassava, white sweet potatoes or yams etc as alternatives to wheat based products. The products are prepared by methods wherein the starch containing foods are fully gelatinised either during the single cooking step of the food product, or, before undergoing a further cooking step to produce the food product .
US 4,325,976 discloses pre-formed, easily rehydrateable, rice products which contain a mixture of pregelatinised and ungelatinised flour, with the pregelatinised flour being present in an amount of at least 30% of the flour.
However, despite the above proposals, there remains in the art a need for a food product which has at least one of the following features: are easily produced on an industrial scale and subsequently easily prepared in the home. are nutritious, easily digestible and have acceptable taste and/or texture . - can be produced using inexpensive production methods and inexpensive and/or local ingredients such as those typically found in undeveloped countries . which retain a high level of their nutritive value, especially protein value (quality and quantity) upon cooking, that is, they have a low cooking loss for nutrients .
- are acceptable alternatives to food products comprising substantial levels of wheat and thus are suitable for people wishing to reduce their wheat intake.
In particular, there still exists a need in the art for a food product which combines any two or more of the above advantages . Furthermore, there still exists a need for food products which can be easily and inexpensively industrially produced, which are easily cooked or prepared at home, which are nutritious and easily digestible with acceptable taste and/or texture, which can be produced from inexpensive and/or local ingredients and which retain a high level of their nutritive value, especially protein quality and quantity upon cooking. This is especially so for the undeveloped countries .
There is also a need in the art for food products which are suitable for consumers wishing to control or reduce their intake of wheat. Such products should ideally not comprise high levels of wheat, be easily produced on an industrial scale and subsequently easily prepared in the home, be nutritious, easily digestible and have acceptable taste and/or texture and retain a high level of their nutritive value, especially protein quality and quantity, upon cooking.
The present invention seeks to address one or more of the above problems.
SUMMARY OF THE INVENTION
We have surprisingly found that a food product which contains certain levels of starch and protein, a protein coagulating agent, no more than a certain amount of wheat and with the starch pregelatinised to within given amounts is beneficial in addressing one or more of the aforementioned problems.
The present invention therefore provides, according to a first aspect, a food product comprising: a) an amount of from 50 to 90 %wt starch, and b) an amount of from 1 to 50 %wt protein, and c) an effective amount of a protein aggregating agent, and wherein the product comprises 10 %wt or less of wheat, all amounts based upon the weight of the product dried to constant weight, and further wherein from 2 to 35%wt of the amount of starch in the product is gelatinised.
According to a second aspect, the present invention provides a food product obtainable by the process of at least partially cooking the food product according to any one of the preceding claims, wherein the at least partially cooked food product comprises a greater amount of gelatinised starch than the uncooked food product of any one of the preceding claims .
The products of the second and first aspect of the invention have several advantages including; they are easily digestible, have good texture and taste and resist the leeching of starch and/or protein during the cooking process so that they deliver good amounts of protein and also good protein quality to the consumer .
According to a third aspect, the present invention provides a process to produce the food product according to the first aspect of the invention, wherein the process comprises the steps : a) mixing a starch source comprising 2 to 35%wt gelatinised starch, a protein source and a protein aggregating agent together, and
b) forming a dough from the mixture of step a. c) optionally shaping the dough by extrusion wherein further gelatinisation of the starch is avoided and cutting to the desired size. d) optionally drying the dough.
The process is easy to apply without the need for sophisticated equipment, inexpensive and gives good results. It is especially suitable for use in undeveloped countries.
Except in the operating and comparative examples, or where otherwise explicitly indicated, all numbers in this description indicating amounts of material or conditions of reaction, • physical properties of materials and/or use are to be understood as modified by the word "about." All amounts in the food product are by weight, based on the weight of the food product dried to constant weight, unless otherwise specified.
DETAILED DESCRIPTION OF THE INVENTION The invention will now be discussed in greater detail.
The food product is preferably formed as a pasta-type product (including noodles) or a rice-type product. These products may be used as an alternative to normal rice and to wheat-based pasta. Other forms of food products may be made according to the invention, for example puddings, confectionery, cous-cous and other grain-type products. The food product of the invention may itself be incorporated into other food products, or used in their preparation, for example in spreads, dressings and mayonnaises, ice creams, cream alternatives, health bars, bakery products, soups, sauces, fillings and coatings.
(i) starch
The food product comprises an amount of from 50 to 90 %wt starch, preferably from 55 to 85 %wt , most preferably 60 to 80%wt. Levels of more than 68 %wt starch have been found to be especially beneficial .
Any suitable starch source may be used to prepare the product. It is preferred that the starch source comprises one or more of cassava, yam, sorghum, potato, sweet potato, corn, millet, lotus, malanga, amaranth, maize, plantain, bananas, edible aroids and rice. Members of the cassava family are especially preferred.
The starch source may be used in any suitable form to produce the food product; for example as a dried starch source such as flour or as the fresh starch source pulp. In the case of cassava, the starch used to produce the product may be a cassava flour or fresh cassava pulp, or, a mixture thereof. One advantage of the invention is that good results can be obtained from unrefined, or partially refined starch sources; this is especially useful for developing countries where good starch refining processes are not always available or are too expensive. For this reason, according to one aspect of the invention it is preferred that the product comprises unrefined, or partially refined starch.
In the food product from 2 to 35%wt of the total amount of starch is gelatinised starch, preferably 2 to 30%wt, more preferably 3 to 25%wt, most preferably 5 to 20 %wt . The remaining starch is ungelatinised starch. Without wishing to be bound by theory, it is believed that the presence of the gelatinised starch in the food product helps to avoid excessive water loss during the manufacture of the food product, e.g.
during extrusion to make pasta-shaped or rice-shaped products. If an excess of water is lost, then the product becomes difficult to shape and the texture may suffer. Too high an amount of pregelatinised starch is however disadvantageous because it increases dough viscosity and results in impaired texture of the finished cooked product .
Upon at least partial cooking by the consumer prior to eating, the level of gelatinised starch in the product increases. This at least partially cooked product forms the second aspect of the invention. As the cooking conditions determine the level of gelatinised starch in the Λcooked' product, the level will be greater than the uncooked product which forms the first aspect of the invention but the actual level of gelatinised starch will depend upon the cooking conditions employed. It is preferred that this at least partially cooked product comprises at least 50% of the total amount of starch as gelatinised starch, more preferably at least 60%, such as 70 to 95% or 100%.
The weight average particle size of the starch source from which the product is produced is preferably in the range of 1 to 250 microns, more preferably 2 to 200 microns, most preferably 5 to 100 microns, such as 5 to 50 microns. It has been found that if such particle sizes are used, the texture of the product can be favourably affected. If the particle size is too large, the texture tends to become course and not homogeneous .
(ii) protein
The food product comprises an amount of from 1 to 50 %wt protein, preferably from 2 to 40%wt, most preferably 3-35 %wt, especially 4 to 30 %wt . The exact level of protein used will
in part depend upon the type of protein source used and the level used should be selected so that a good texture of the food product is obtained for the desired application. For example, if making a pasta-type or rice-type product where a glutinous product is not desired, the amount of protein is preferably in the range 10 to 25 %wt, more preferably 15 to 20 %wt .
Any suitable protein source may be used. The proteins are preferably not fully denatured. It is especially preferred that the protein comprises one or more of vegetable protein, egg protein, milk or milk derived protein, fish protein and meat protein. Especially preferred are vegetable proteins especially those which plentiful and inexpensive such as those derived from beans, peas, pulses and legumes. Soya protein is a particularly suitable vegetable protein. It has been found that using vegetable proteins, especially soya proteins, in an amount of from 5 to 35 %wt is especially effective.
The protein sources may used in any suitable form, for example combined with some oil to help the preparation of the food product. For soya this includes as whole soy beans, extracted soy beans, soy protein concentrates and soy protein isolates.
As for the starch, good results can be obtained from using unrefined, or partially refined protein sources and it is preferred that the product comprises unrefined, or partially refined protein. Of course unrefined, or partially refined, starch and proteins may both be used in the product .
It has been found that if the protein has a high protein solubility then particularly good results are obtained, especially if vegetable protein is used. It is thus preferred
that the protein has a Nitrogen Solubility Index value in the range of from 40% to 100%, especially 50% to 100%, most preferably 60% to 100%.
A further preferred feature of the food product is that the protein quality thereof is greater than 65%, more preferably in the range 70-100%, most preferably 80-100%, especially 85-100%. The protein quality refers to the available essential amino acid content of the food product. Essential amino acids are those which cannot be synthesized by the body and which have to be obtained from dietary sources. A protein quality of 100% represents a food product comprising the correct ratio/amount all of the essential amino acids. A protein quality of 50% represents a food product wherein the relative amount of one or more of the essential amino acids is limited to 50% of the human requirement .
The definition of protein quality is given in the paper by Schaafsma, "The Protein Digestibility - Corrected Amino Acid Score", J. Nutr. 130 p 18655-18675, 2000. The human requirements of essential amino acids are given by the WHO/FAO/UNV recommendations in 1985 and described by Tome et al in the paper "Protein quality and FAO/WHO recommendations", Sciences des Aliments, 22, p. 395-405, 2002.
According to a particular embodiment of the present invention, it is preferred that the food product has a protein content in the range of from 5 to 35 %wt and a protein quality of preferably in the range 70-100%.
By comprising good levels of protein, good protein quality and good levels of starch, the food product is nutritious for the consumer as it provides not only a good level of protein and
starch to the consumer but also good protein quality. This is especially important in developing countries where the average diet is often poor in protein content and in protein quality.
Without wishing to be bound by theory, it is believed that the advantages exhibited by the food products are obtained, at least in part, from the combination of the controlled amount of pregelatinised starch and the formation (during further cooking of the food product) of a protein network achieved by the presence of the protein and the protein coagulating agent. Thus the at least partial network is predominantly formed during the further cooking of the product of the first aspect of the invention to provide the advantages referred to hereinabove. It is believed that this combination contributes to the food products having controlled cooking loss of nutrients (good resistance to a leeching of the starch and/or protein content into the cooking medium, e.g. water, during cooking by the consumer) and/or good protein quality. The cooking loss is expressed as the percentage of the nutrient from the food product present in the cooking water, but expressed as the equivalent percentage which would be present in the food composition. For example, a cooking loss of 1% starch means that in the cooking water, 1% of the starch (based on the weight of the dried food product) leached out of the product and into the water. It is especially preferred that the products of the invention have a cooking loss independently for starch and protein of less than 5 %wt, more preferably less than 3 %wt, most preferably less than 2 %wt . Results for both starch and protein are ideally less than 1.5 %wt, such as less than 1 %wt .
Furthermore the products are endowed with good texture (especially good bite' and no stickyness) and taste and are digestible. In particular, the products of the invention have been found to exhibit a lower cooking loss than other non wheat pasta-type products and rice-type products which do not comprise a protein coagulating agent. It has also been found that the products of the invention have at least the same, and preferably a lower cooking loss than wheat pasta and ordinary rice .
The weight average particle size of the protein source form which the product is produced is preferably the same as that recited above for the starch. The effects found are also the same.
(iii) Wheat
The food products comprise 10 %wt or less of wheat, preferably 5 %wt or less. It is most preferred that the food product is substantially free of wheat. The lower the concentration of wheat in the food product, the more suitable it will be for people wishing to control or restrict their dietary intake of wheat, for example because of a dietary intolerance to wheat.
Furthermore, the food products preferably comprise 10 %wt or less of rice products. In some products the presence of rice flour is an advantage as it can help to improve texture of the food product. Typically, in such products, the rice flour is present in an amount of from 5 to 10 %wt of the food product.
(iv) protein aggregating agent
The food products of the invention comprise an effective amount of a protein aggregating. By an effective amount is meant an amount which is sufficient to form at least a partial protein
network in the food product. It is preferred that the products comprise an amount of from 0.01 to 2 %wt of the protein aggregating agent, more preferably 0.02 to 1.5 %wt, most preferably 0.05 to 1 %wt .
One form of the protein aggregating agent preferably comprises at least one inorganic or organic alkaline earth metal salt. Suitable examples include calcium chloride, calcium sulphate, magnesium chloride, magnesium sulphate, barium chloride, barium sulphate, calcium acetate, calcium lactate, calcium citrate and other alkaline earth salts of organic or inorganic acids which are capable of supplying alkaline earth metal / divalent metal cations. Other suitable examples include calcium phosphate salts such as tricalcium phosphate which has been found to be especially suitable.
The purpose of the protein aggregating agent e.g. alkaline earth metal salt is to form at least a partial protein network in the product. The alkaline earth metal salts are believed to achieve this by the interaction between the salt cation and the protein. The believed effect of this protein network is discussed hereinabove.
If this type of protein aggregating agent does not readily dissociate in water to provide cations which help to form the protein network, then different methods may be employed to allow this to occur. One suitable method is to bring the pH of the mixture from which the food product is produced into a suitable pH range so that the protein aggregating agent undergoes a degree of disassociation and is then able to form the at least partial protein network. The determination of the pH range and how to effect the necessary adjustments is well within the skill of the person skilled in the art and does to
need to be further explained here. For example, when tricalcium phosphate is used, it has been found to be beneficial to adjust the pH of the food product to less than pH 7.5, preferably in the range 4 to 7 and this can be achieved by using the appropriate amount of an edible acid, such as 0.05 - 0.5% wt.
For readily water-soluble salts, pH adjustment is often not required as the salts readily dissociate in the presence of water.
The salts can be used in any suitable form, for example as a solid or a solution of the salt.
Alternatively the protein aggregating agent may be an agent which reduces the solubility of the protein by adjusting the pH of the medium surrounding the protein. Such suitable agents include edible organic acids such as acetic acid, citric acid, lactic acid, malic acid etc and edible inorganic acids such as phosphoric acid, hydrochloric acid, nitric acid, sulphuric acid.
(v) optional ingredients
The food products preferably comprise hydro-colloids such as pectins, gums or alginates . Preferred amounts are in the range of from 0.01 %wt to 1 %wt, more preferably 0.05 %wt to 0.5 %wt . Pectin and alginates are most suitable, especially pectin.
The food products may contain any of the usual minor food ingredients in conventional amounts, for example added vitamins and minerals, flavourings, colourings, aromas etc.
Other food ingredients may also be included in suitable amounts, for example fats /lipids preferably in an amount of 0.5 to 10 %wt.
It is preferred that the food products contain less than 0.5 %wt of added amino acids such as L-Lycine, most preferably that they are essentially free of such materials. L-lycine is a relatively expensive amino acid and during the cooking process the majority thereof is leached out into the cooking water.
(vi) water content
The food product according to the first aspect will typically be dried to facilitate transport and storage. The consumer then re-hydrates the product at home during the cooking process. It is of course possible that the food product will be sold, transported, used etc in a semidried or non-dried state. In this case it may contain up to 40 %wt water, preferably up to 35 %wt, more preferably up to 30 % wt, most preferably up to 25 %wt . The minimum amount of water for these products is likely to be at least 10%wt, preferably at least 15% wt . It has been found that it is advantageous to firstly dry the products without very elevated temperatures being applied (e.g. by sun drying) , preferably to a water content in range 5 to 20 %wt followed by machine drying. The products, if dried, will of course have a reduced water content preferably to a water content in range 1 to 15 %wt .
(vii) production of the food product
The food product may be produced by any suitable method and then may be subsequently shaped and/or dried as desired. If the product is shaped to produce a pasta-shaped or rice-shaped product, it is preferred that the moisture content of the food product prior to extrusion is in the range of from 20 to 40%wt, preferably 10 to 35%wt water, more preferably 25 to 35 %wt . It is also preferred that the food product is shaped by a means that does not apply undue pressure to the food product, otherwise moisture is lost during processing and product texture has been found to suffer therefrom. Suitable processes include extrusion under relatively low pressures. The pressure to be applied will depend upon the food product in question. However, if excessive water loss occurs, or, the temperature during extrusion rises above the gelation temperature of the starch in the food product so that the product texture suffers then the pressure applied is too great . Such routine optimisation is will within the skill of the skilled person.
It is preferred that the starch source is a flour or a starch pulp. Mixtures thereof can also be used. Preferably the gelatinised starch is prepared by cooking it in water, for example as a 10 - 35 %wt dispersion in water. Gelatinised starch and non-gelatinised starch can be prepared and mixed to be used as the starch source. Alternatively a starch source can be prepared with the required level of gelatinisation using careful control of the gelatinisation conditions. It is preferred that the protein source is a solid or semi solid, for example a flour or a paste, especially a finely ground flour of paste. As described above with respect to the protein agglomerating agent, the pH of the mixture may be adjusted for the addition of the protein aggregating agent. Where the agent
does not readily disassociate, this is preferred. Preferably the dough has a water content of from 20 to 40 %wt, more preferably of from 25 to 35 %wt . The dough may optionally be further shaped and/or dried. Suitable extrusion and drying techniques are well known in the art.'
One suitable method is:
Step 1 - the starch source is prepared as necessary. Fresh, raw and/or unrefined starch source or powder material may be used. Preferably the particle size is reduced to 200 microns or less.
Step 2 - at least a part of the starch is partly gelatinised. Step 3 - the starch is mixed with at least a part of the protein source. Water and the protein aggregating agent are added, if necessary adjusting the pH so that the protein network can later be formed. All other ingredients are also added. Step 4 - the mixture from step 3 is mixed with water to form a dough, preferably having a water content in the range of from 20 to 40 wt%, more preferably 25 to 35 %wt . Step 5 - optionally the product may be shaped to a rice-shaped product or a pasta-shaped product, for example by a suitable extrusion process.
Step 6 - optionally the product may be dried.
(viii) test procedures a) Determination of Cooking Yield
Weigh 10 grams of (dry) product (wl) , cook for 10 minutes in
400 ml of water, drain, weigh amount of cooked product (w2)
Calculate yield: W2/W1 * 100 = cooking yield
b) Determination of hardness after cooking
Calibrate texture analyzer (force and height) . Take 3 grains of product and place on base of Texture analyzer. Compress to 10 % of height with 1 inch cylinder probe. Measure the maximum force needed for the compression using Texture Expert software. Repeat 5 time and calculate average Hardness = average of 5 measurements. Expressed as grams.
c) Calculation of Firmness Factor Divide hardness by cooking yield and by 100
The present invention will be further explained with reference to the following non-limiting examples. Further examples within the scope of the present invention will be apparent to the person skilled in the art.
E AMPLES
Example 1 Two food products were made with the compositions as given in table 1 and by the method as described in example 2.
Table 1
*1 - ex Cargil USA, nitrogen solubility index > 85% *2 - available from Obipectin
*3 & *4 - available from National Starch.
*5 - available from Dunkwa Goldfields Ltd., Ghana
The products were found to have good taste and texture. Furthermore, they had a good protein quality level and had very good cooking loss results (resistance to starch and protein being leached during cooking) . For both examples after 6 minutes cooking, the cooking loss was found to be less than 0.7% wt starch and less than 1.5 %wt protein in the cooking water (expressed as levels that would be present in the food product) . Normally the cooking loss for starch and protein for similar products is much higher than this as much more of these nutrients are leeched out of the product.
Example 2
The products of the invention may be prepared according to the following process. Examples 1A and IB were prepared following this method.
Step 1 - starch source (e.g. cassava) is peeled, washed and crushed with Hammer mill or grates or grates and the coarse pulp is milled further to below 50 micron particle size. Alternatively a powder starch source can be used which is milled and subsequently sieved to below 50 microns particle size. Step 2 - a suspension with 25 %wt dry matter is made with the starch source (cassava pulp, flour or tapioca starch) and water, this is heated for about 10 minutes at about 85oC and cooled to less than 30oC. Step 3 - any other starch and the protein (e.g. soya protein) are mixed in Stephan mixer along with the gelatinised starch from step 2 is added along with the palm oil (and water) , any acid solution, any other powdered ingredients and the other minor ingredients such as vitamin mixes and salt etc.
Step 4 - a dough is formed and is mixed at 3000 rpm for a maximum of 1 minute. Step 5 - the dough is extruded through an industrial extruder suitable for making pasta-type products. Low shear extrusion at less than 40oC is used.
Step 6 - drying in air at less than 35oC to -18% moisture, final drying in hot air(~60oC domestic drum dryer to final moisture of less than <10%.
Example 3
Products were prepared according to the following compositions using the proceedure of Example 1.
Table 2
PARTS BY WEIGHT
t
The products were analysed and the results are given in Table 3. Table 3
t
Table 4 - Ingredients
NJ UI
The comparative example, containing 1% gelatinised starch (of the total starch) showed much higher starch and protein loss from the product into the cooking water and also did not give a good firmness factor. The products according to the invention all gave good results for the firmness factor and for the starch and protein loss in cooking water.