Process for producing a peanut protein food gel, gel obtained and use thereof

The present invention relates to a process for the preparation of a food gel from a crushed peanut seed, as well as gels obtainable by this method.

Protein, along with carbohydrates and lipids, is one of three major macro-nutrient families that contribute to energy intake.

Essential to the body, they play a structural role (muscular or cutaneous) but are also involved in many processes such as the immune response (antibodies), the transport of oxygen in the body (hemoglobin ), or digestion (digestive enzymes).

There are two major classes of protein, animal protein and vegetable protein.

Animal proteins come from milk, eggs, fish and meat.

Vegetable proteins come mainly from cereals and legumes.

It has been established that more than 70% of the protein consumed in Western societies is of animal origin, compared with only 15-20% in developing countries.

This difference between industrialized and developing countries can be explained by the fact that the production of animal proteins is more expensive than the production of vegetable proteins.

On the other hand, animal raw materials such as milk, fish or meat are much more difficult to preserve than vegetable raw materials.

In addition, the negative environmental impacts of both intensive and intensive meat production are increasingly being promoted. They mainly result in a risk of degradation of water quality, a substitution of forests by grasslands, a reduction of biodiversity or even a production of greenhouse gases.

Finally, the availability of animal products will decrease in the next 50 years.

It would thus be desirable to find an alternative to food products based on animal proteins such as, for example, cheeses or dairy desserts.

However, the main difficulty with this alternative lies in the presence of antinutritional factors such as phytic acid, flatulence factor and antitrypsic factor present in plant proteins. In addition, vegetable proteins, unlike animal proteins, when mixed with other ingredients, hardly get in shape because vegetable proteins have a lower functionality than animal proteins that are inherently structured.

There are forms of structuring of vegetable protein products that are poorly developed and whose market supply is limited in developing countries.

Transglutaminase, often called "meat glue" is an enzyme widely used in the food industry. This enzyme is composed of amino acid chains and acts on the proteins contained in the food products in order to stick them together.

Transglutaminase also improves the texture of protein-rich products. For example, transglutaminase has been shown to improve the texture of tofu (Liu, Chang & Tatsumi, 2004). food science and technology, 7p).

In this document, soy juice is extracted and is then transformed into tofu. When processed into tofu, the serum that is rich in nutrients is removed by dripping. The tofu thus obtained is very poor in nutrients.

Peanuts are an important resource and their consumption is widespread. The protein content of peanuts, although lower than that of soybeans, remains high. Peanuts would therefore be good candidates for the preparation of vegetable food gel. However peanuts are difficult to treat. Conventionally, peanuts are roasted and possibly salted before being consumed. Studies have focused on the gelation of isolated peanut proteins or peanut protein concentrates. However, for reasons of industrial and economic viability, it would be important to be able to obtain a peanut protein gel directly from the raw peanut seed.

Thus, it would be interesting to have a low-cost, nutritionally complete food that is highly concentrated in peanut protein and that has a texture that is adapted to the type of food desired and that could be substitutes for the food. food products based on animal proteins.

It is disclosed in WO 2015/145089 that a nutrient-rich food comprising predominantly plant-derived proteins that have been treated with transglutaminase partially meets these needs.

The present inventors have found that by improving the solubilization of peanut proteins, it is possible to more finely control the gelation of a suspension of ground peanut seed meal and to provide gels which can be used to improve texture of food products.

SUMMARY OF THE INVENTION

The object of the present invention therefore relates to a process for preparing a food gel of peanut protein by treatment with a transglutaminase of an aqueous suspension of a crushed peanut seed deed .

The present invention also relates to a food gel rich in peanut protein. Finally, it relates to the use of said food gel to improve the texture of food products.

DETAILED DESCRIPTION

The object of the present invention therefore relates to a process for preparing a food gel of peanut protein by treatment with a transglutaminase of an aqueous suspension of a crushed peanut seed deed .

In the present invention, food gel is understood to mean a crosslinked polymerized structure capable of retaining water. A gel according to the invention has a water retention capacity of at least 50%, preferably at least 60% and even more preferably at least 80%, when subjected to minute centrifugation. at 2000rpm.

The aqueous suspension of ground peanut seed meal comprises substantially all or all of the nutrients of peanut seeds and especially proteins.

However, these are not completely solubilized in the aqueous phase.

Without wishing to be bound by any theory, the inventors are of the opinion that the formation of the gel by the action of transglutaminase will be all the more effective if the peanut proteins are solubilized in the aqueous phase. Thus, according to an advantageous embodiment of the invention, prior to said transglutaminase treatment, the solubilization of the peanut proteins in the aqueous suspension is increased.

In order to increase the solubilization of the peanut proteins, one of the following means can be used alone or in combination: addition of ions in the aqueous medium, in particular sodium chloride, salts of phosphates or polyphosphates, other molecules loaded with food quality; addition of mineral or organic acids, organic or inorganic bases, free amino acids, food grade solvents having a different polarity of the water; heating the medium to a temperature of 40 to 140 ° C; mechanical shear treatment of the suspension, such as homogenization at limited pressure; ultrasonic treatment; biological treatment such as enzymatic hydrolysis prepared for example by means of a protease or a bacterial fermentation.

According to an advantageous embodiment for its simplicity, the solubilization of proteins in water is increased by adding sodium chloride. The amount of sodium chloride added can be adjusted according to the desired protein concentration in the aqueous phase.

According to another advantageous embodiment, the solubilization of the proteins in the water is increased by heating the suspension at a temperature T1 of 40 to 140 ° C. for a period of time of 5 to 60 minutes, preferably at a temperature Tl of 70.degree. at 105 ° C. for a period of about 10 minutes. This increase in the solubilization of the proteins by heating can also be carried out on a suspension which has previously been concentrated.

Treatment with transglutaminase is advantageously at a transglutaminase concentration of between 0.05 and

<td> 1</td><td colspan="2">%, preferentially between</td><td> 0,</td><td>1 and 0.5%,</td><td>mass of</td>

<td colspan="2">transglutaminase by</td><td>report to</td><td>the</td><td>total quantity</td><td>extract</td>

<td>dry</td><td>peanut.</td><td></td><td></td><td></td><td></td>

<td>In</td><td>using this</td><td>amount</td><td>of</td><td>transglutaminase</td><td>he is</td>

It is possible to prepare a gel with a minimum concentration of total peanut protein of the order of 5%, preferably of the order of 8%, and more preferably of the order of 9%.

According to a particular embodiment, the method according to the invention comprises the steps of:

a) separating the peanut seeds and removing the fibrous film;

b) grinding said de-lined seeds into water to form a suspension;

c) increasing the solubilization in water of the proteins present in said suspension

d) optionally concentrating said suspension;

e) bringing said suspension obtained in step (c), or optionally in step (d), at a temperature T of 20 to 70 ° C, preferably of 30 to 70 ° C, more preferably still of 45 ° C;

f) add transglutaminase; and

g) recovering the food gel thus formed comprising peanut proteins.

The recovery step of the food gel is done after incubating the medium in the presence of transglutaminase for a sufficient time, for example of the order of 24 hours.

According to another embodiment, the method according to the invention comprises the steps of:

a) separating the peanut seeds and removing the fibrous film;

b) grinding said de-lined seeds into water to form a suspension;

c) increasing the solubilization in water of the proteins present in said suspension by addition of sodium chloride and / or by heating the suspension at a temperature Tl of 40 to 140 ° C for a time tl of 5 to 60 minutes, preferably at a temperature T1 of 70 to 105 ° C for a time of about 10 minutes;

d) optionally concentrating said suspension;

e) bringing said suspension obtained in step (c), or optionally in step (d), at a temperature T of 20 to 70 ° C, preferably 30 to 70 ° C, more preferably still about 45 ° C;

f) add transglutaminase; and

g) recovering the food gel thus formed comprising peanut proteins.

According to a particular embodiment, the process according to the invention may comprise an additional step of adding to the mixture of step (b), (c), (d) and / or (e) an acidifier so that the transglutaminase is added in a medium having an acidic pH ranging from 3.6 to 5.2.

The acidifier may be any organic acid or mineral food grade agent. By way of example, mention may be made of fermentative acids such as acetic acid, lactic acid, malic acid, carbonic acid and other fermentative acids; phosphoric acids, citric acid, hydrochloric acid, sulfuric acid; and their mixtures.

The order of steps c) and d) can be reversed.

The method according to the invention may further comprise, at the end of step (g), an additional heating step at a temperature T2 of between 80 and 140 ° C. for a duration t2 of between 1 and 60 minutes. This final heating step makes it possible to finalize the structuring of the gel.

The invention also relates to a food gel that can be obtained by the method described above.

The food gel according to the invention may contain from 5 to 30%, preferably from 6 to 20%, and more preferably still from 8 to 15% by weight of peanut protein.

The gel according to the invention can be used to modify the texture of a food in which it is incorporated. It can thus allow the realization of food, such as products type: yogurts, cream desserts, cheeses, sauces, etc., without resorting to products of animal origin

The invention will be described in more detail by means of examples which are not limiting.

FIGURES

Figure 1 is a diagram showing the firmness of a gel as prepared according to Example 1 as a function of its ionic strength.

Fig. 2 is a diagram showing the water retention capacity of peanut polymers at various dry extracts in the presence and absence of transglutaminase, according to Example 2.

EXAMPLES

Example 1

De-lined peanut seeds are ground with water to obtain a suspension (S0) having a solids content of 40% by weight.

To promote the solubilization of peanut proteins, the ionic strength is varied by adding NaCl to the aqueous suspension. Five different suspensions (SI to S5) having a solids content of 40% by weight and different ionic strengths are thus prepared.

The ionic strength μ in mol / L corresponds to the following formula: μ = 1 / 2Σσι *_Ζ1²

Ci being the molar concentration in Na ion⁺ (in mol / L) and zi being the Na load⁺.

The mixture is heated to 45 ° C. and 0.3% (w / w) of transglutaminase is added. Incubate for 45 minutes at 45 ° C. Then left to stand for 24 hours at room temperature.

The firmness of each of the structured gels obtained using a Stable Micro Systems TAX.XT device is measured at a distance of 5 mm and a speed of 0.5 mm / s.

The results are reported in the table below and in Figure 1.

<td>suspensions</td><td>Ionic strength (Mol / L)</td><td>Firmness (N)</td>

<td>SO</td><td> 0</td><td> 0,21</td>

<td>IF</td><td> 0,24</td><td> 0,42</td>

<td>S2</td><td> 0,38</td><td> 0,56</td>

<td>S3</td><td> 0,48</td><td> 0, 77</td>

<td>S4</td><td> 0,57</td><td> 0,50</td>

<td>S5</td><td> 0,72</td><td> 0,63</td>

It is observed that a maximum of firmness is obtained for an ionic strength of 0.48 mol / L.

Example 2

Different concentrations of ground peanut seeds of peanut were ground in water to give solids of 5, 10, 15, 20, 25, 30, 35, 40 and 50% (w / w).

The ionic strength of each suspension is adjusted to 1 mol / L by addition of NaCl.

Each suspension is mixed and heated at 45 ° C., then each suspension is divided into 2 batches. In a series, 0.3% (w / w) of microbial transglutaminase is added and incubated for 20 minutes at 45 ° C.

The series are allowed to stand for 24 hours at room temperature.

For each batch, the formation of a gel is then determined by determining the maximum water retention capacity C of the formed structure, when 30 g of the structure are placed in a test tube and subjected to centrifugation. minutes at 2000 rpm according to the following formula:

C (%) = (pellet mass after centrifugation / initial mass) * 100.

The results obtained are shown in FIG.

A gel is formed only in batches treated with transglutaminase having a solids content greater than or equal to 30%.