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DESCRIPTION

The present invention falls into the field of compositions for food use. In particular, it relates to a salt with a reduced sodium content and a process for obtaining it that makes use of microwaves. The salt according to the present invention is characterised by a pleasant flavour and a high level of saltiness.

State of the art

Sodium chloride is a flavour enhancer widely used in cooking and in the canning industry, both as an ingredient and a preservative.

However, a salt-rich diet can favour the onset of cardiovascular and brain diseases, correlated in particular to arterial hypertension. There is a close link between dietary salt intake and arterial pressure; it has in fact been demonstrated that an excessive daily intake of sodium is among the causes of the onset of hypertension.

For this reason, the World Health Organization recommends a daily salt intake of less than 5 g.

Decreasing the daily salt intake can be achieved both by reducing of the amount of salt manually added to food as a condiment and by reducing the non-discretionary amount, i.e. that is already contained in foods.

For this purpose, there are different types of commercially available salts with a reduced sodium content, in which varying percentages of sodium chloride are substituted with potassium chloride.

However, although potassium chloride has a salty flavour, it possesses a bitter aftertaste, as a result of which low-sodium salts containing potassium chloride are not well accepted by people who need to follow a low-sodium diet.

Moreover, high concentrations of potassium are absolutely to be avoided in patients with chronic kidney failure or who undergo dialysis. In this context, the object of the present invention is to provide a salt with a reduced sodium content that is pleasing to the taste, and which can be used both as a table salt and in industrial food preparations.

Moreover, a further object that the present invention aims to achieve is to provide a salt with a reduced sodium content that can be enriched with further nutritional elements having a beneficial effect on human health. Summary of the invention

In a first aspect, the present invention therefore relates to a process for producing salt with a reduced sodium content comprising the following steps:

(i) mixing a composition comprising sodium chloride and calcium D- gluconate with water, so as to obtain a paste;

(ii) subjecting said paste to melting by microwave irradiation so as to obtain a molten product;

(iii) drying said molten product; and

(iv) cooling the dried product.

In a further aspect, the present invention relates to a salt with a reduced sodium content obtained or obtainable with the process according to the invention, as well as a preparation for food use comprising said salt.

Detailed description of the invention

Additional features and advantages of the present invention will become more apparent from the description that follows.

In the present description and in the appended claims, the percentages are expressed in weight, unless specified otherwise.

In the present description and in the appended claims, the term "salt with a reduced sodium content" and the term "low-sodium salt" refer to a product based on NaCI (salt) in which a part of the sodium chloride is substituted with a compound not containing sodium. Therefore, a salt with a reduced sodium content (or low-sodium) contains a lower amount of sodium, weight for weight, than a salt of marine or terrestrial origin. In the present description and in the appended claims, the term "microwaves" refers to electromagnetic radiation with a frequency comprised between 10 MHz and 10 GHz.

Step (i) of the process according to the invention entails mixing a composition comprising sodium chloride and calcium D-gluconate with water, so as to obtain a paste.

In one embodiment, the composition of step (i) can comprise

(a) 30 - 80%, preferably 30 - 50%, of sodium chloride; and

(b) 20 - 70%, preferably 30 - 60%, of calcium D-gluconate,

the percentages by weight stated above referring to the solid composition, prior to mixing with water.

Preferably, the sodium chloride used in step (i) is selected from among sea salt, rock salt (or halite) and mixtures thereof.

It has been observed that by adding a small percentage of sodium chloride in the form of sea salt to sodium chloride in the form of rock salt, preferably in percentages < 5% by weight relative to the total weight of the sodium chloride, one can obtain a salt with a reduced sodium content with a higher degree of saltiness than a low-sodium salt prepared using exclusively rock salt as the raw material. This is because sea salt adds weak anions, originating from seawater, which increase the ionic mobility of the sodium ion, strengthening its salty flavour.

According to one embodiment, the composition of step (i) can comprise calcium D-gluconate anhydrous (CAS No. 299-28-5), calcium D-gluconate monohydrate (CAS No. 66905-23-5) and mixtures thereof; preferably, said composition can comprise calcium D-gluconate monohydrate.

The Applicants have surprisingly found that, in order to obtain complete melting of the paste during step (ii), and thus a molten product having a homogeneous composition, only the D form of calcium gluconate can be used in step (i) of the process according to the invention, since both the L form and the racemate (DL) lead to incomplete or almost no melting of the paste under the operating conditions of step (ii). The water used in the mixing of step (i) can be osmotised or distilled water, typically with a conductivity < 10 μβ.

In one embodiment, during step (i) the composition can be mixed with an amount of water equal to 20 - 50%, preferably comprised between 20 and 30%, relative to the final paste, about 25% of water being a an optimal value of humidity.

Below a value of 20% of water in the paste, during the next step (ii), a molten product is not obtained, or melting takes place only partially, compromising the characteristics of the low-sodium salt obtained at the end of the process. In pastes comprising an amount of water greater than 50%, although a molten product is obtained at the end of step (ii), the amount of energy necessary to dry the molten product during step (iii) is extremely high, making the implementation of the process according to the invention of little interest from an economic viewpoint. The Applicants have observed that 25% of water represents the best compromise between complete melting of the solid and the amount of energy required to carry out step (iii).

In one embodiment, the paste of step (i) can further comprise variable amounts of iodine, preferably < 35 ppm, more preferably comprised in the range of 25-35 ppm, said amount referring to the final paste. More preferably, the amount of iodine can be about 30 ppm, said value being a regulatory limit, not a technological one.

The iodine can be mixed with other raw materials such as iodine salt, preferably potassium iodide. The iodine can be mixed with the raw materials both in solid form and in the form of an aqueous solution.

To carry out the mixing step (i), any apparatus for mixing solids and liquids can be used, for example a mixer or a kneader, provided that they are suitable for preparing products for food use and able to assure homogeneous mixing of the raw materials. The person skilled in the art, depending on the amount of raw materials employed and the apparatus used will be able, using his or her own technical skills, to identify the operating parameters of step (i) (duration of mixing, speed, etc.) that will enable a paste with a homogeneous composition to be obtained.

Optionally, and preferably, the paste obtained in step (i) can be crushed, for example with a scrap recovery machine or a lump breaker, before the melting step (ii).

Step (ii) of the process of the invention entails subjecting the paste obtained in step (i) to melting by microwave irradiation with microwaves. Preferably, the microwaves used in step (ii) of the process can have frequencies comprised between 2000 MHz and 5000 MHz.

When the paste is subjected to the action of the microwaves, thanks also to the presence of water molecules, a product is obtained which melts at a considerably lower temperature than the melting point of the individual components (801 °C for NaCI and about 120°C for calcium D-gluconate). Melting of the paste in fact occurs at a temperature generally comprised between 85° and 100°C, depending on the composition of the paste.

The Applicants have surprisingly found that the molten product obtained in step (ii) by irradiation with microwaves, after drying and cooling, exhibits specific physicochemical characteristics which differentiates it both from products obtainable by heating the same raw materials with other sources of heat and simple mechanical mixtures of the raw materials.

Microscopic observation of the crystals of the salt with a reduced sodium content obtainable with the process according to the invention did not reveal morphological differences among the crystals making up said salt. Step (ii) of melting the paste can be implemented in a conventional microwave oven, provided that it is suitable for the processing of raw materials for food use. On an industrial level, the process can be implemented in a continuous or discontinuous manner, preferably a continuous manner, using for example a tunnel oven. Said ovens generally operate at ambient pressure. The operating conditions of the process according to the invention, in particular the power of the microwave oven and irradiation time, depend on the mass of the paste subjected to step (ii).

The irradiation step (ii) ends when the paste is completely melted.

Next, the molten product is dried during step (iii) of the process according to the invention. During the step of drying the molten product, it solidifies and the water present in the molten product is released in the form of steam.

During step (iii) the molten product can be dried using different sources of heat, for example hot air or infrared irradiation or, preferably, by irradiation with microwaves. Using microwave irradiation considerably reduces the drying times for the molten product compared to the drying times necessary if other heat sources are used. If microwaves are used to dry the molten product in step (iii), the power of the oven used can be less than or equal to the power used to melt the product in step (ii).

In a preferred embodiment, the steam released during the drying step (iii) can be conveyed towards a condenser that brings the water into a liquid state. The recovered water can subsequently be used to produce the paste in step (i) of the process. This embodiment makes it possible to minimise the atmospheric emissions and consumption of water of the process according to the invention, thereby diminishing its environmental impact and increasing its efficiency.

At the end of step (iii), the dried product is cooled, generally by means of a stream of air at a temperature lower than the temperature of the dried product, until reaching a temperature comprised between 20° and 40°C, preferably until reaching a thermal equilibrium between the product and the environment.

According to one embodiment, steps (iii) and (iv) of the process according to the invention are conducted in such a way as to obtain a product, i.e. a salt with a reduced sodium content, with a residual humidity < 4%. According to one embodiment, at the end of step (iv) of the process according to the invention, the salt with a reduced sodium content can optionally be ground in a conventional salt mill, so as impart the desired particle size to the product. The product to be ground is introduced at the centre of the machine and is projected by the rotor against a shell with teeth disposed at the periphery of the grinding chamber. Positioned in the lower part there is a grid which serves to hold back the material until it has reached the desired fineness.

According to a further variant of the process, the "microfine" material obtained by grinding the product, i.e. the fraction of ground product with a particle size < 200 μιη, can be used as a raw material in the mixing step (i). An amount of microfine material < 30% can be added in the composition of step (i), as a partial replacement for the sodium chloride and calcium D-gluconate, said percentage referring to the composition prior to mixing with water.

At the end of the grinding step, and optionally after a sieving step, generally conducted by means of vibrating screens with a defined particle size, the salt with a reduced sodium content obtained with the process according to the invention can have a particle size comprised in the range of 0.2-3.5 mm. The salt with a reduced sodium content placed on the market as fine table salt can have a particle size comprised in the range of 0.2-1 .5 mm; the salt with a reduced sodium content placed on the market as coarse cooking salt can have a particle size comprised in the range of 1 .5-3.5 mm.

The salt with a reduced sodium content obtained or obtainable with the process according to the invention can contain from 20 to 70% less sodium than traditional table salt and can be used as a total replacement for traditional salt. Moreover, it differs fundamentally from the dietetic salts currently on the market by virtue of its pleasant flavour and high level of saltiness. Another salient characteristic of this low-sodium salt is that it is rich in calcium. The dietary intake of calcium is fundamental for human health. Calcium is a mineral that participates in the metabolic functions necessary for the regular activity of the nerves, muscles and skeletal system. It plays an important role in regulating heart and kidney functions, in coagulation, and in the integrity of blood vessels. It cooperates in the utilisation of vitamin B12.

Furthermore, the low-sodium salt obtained or obtainable with the process according to the invention can also be enriched with iodine up to the limits established by the applicable legislation. Low-sodium salt supplemented with iodine is the solution proposed by the World Health Organization (WHO) for eradicating disorders due to iodine deficiency. Iodine is fundamental for our body, because it is an element present in the hormones produced by the thyroid, involved particularly in the growth and development of the nervous system and maintenance of a metabolic balance. Iodine deficiency has particularly grave repercussions on the mental and physical development of children. In adults, on the other hand, it gives rise to goitre, whose consequences are of varying severity according to the subject's age and sex.

Therefore, in a further aspect, the present invention relates to a salt with a reduced sodium content obtained or obtainable with the process according to the invention.

The salt with a reduced sodium content according to the invention can be employed as a flavour enhancer to be added manually to foods, i.e. as a table salt, or else as an additive in industrial food preparations.

In a further aspect, the present invention relates to a low-sodium preparation for food use comprising the salt with a reduced sodium content according to the invention as described above.

In one embodiment, the low-sodium preparation for food use according to the invention can moreover comprise further food additives, preferably selected from among colourings, preservatives, antioxidants, acidity correctors and regulators, thickening agents, stabilisers, emulsifiers, anti- caking agents and mixtures thereof.

For example, spicy low-sodium salts can be obtained by adding to the low- sodium salt of the invention natural and/or artificial flavourings such as mint, pepper, chilli pepper, lemon essence, etc.

Furthermore, the low-sodium salt according to the present invention can be used as an ingredient in the preparation of granular stock.

The present invention is described below through some examples of implementation which have a non-limiting illustrative purpose.

Measurement methods

Particle size: particle-size analysis is performed by sieving using a normalised series of sieves.

Example 1

Preparation of a low-sodium salt with a sodium chloride content equal to 70%, using a mixture of sea salt and rock salt.

A laboratory mixer was used to mix 75g of a composition containing 70% sodium chloride, made up of a mixture of sea salt and rock salt, and 30% calcium D-gluconate monohydrate with 25 g of osmotised water.

The paste obtained had the following composition by weight:

-Sea salt 2.5%

-Rock salt 50.0%

-Calcium D-gluconate monohydrate 22.5%

-Osmotised water 25.0%

The paste was distributed in a container for microwave ovens, so as to reach a total depth of 2 cm of paste.

The material thus disposed was introduced into a microwave oven (model Panasonic NN-GD462M, maximum power 1000 W) for a first 3-minute operating cycle at 300W. After this time had elapsed, the paste was completely melted. For the subsequent drying step the same microwave oven was used for a 7-minute cycle at 100W. The drying brought about the complete removal of the water added during mixing (25 g).

The dry product was cooled to room temperature and subsequently ground and sieved to obtain a low-sodium salt with a particle size in the range of 0.2-1 .0 mm.

Example 2

Preparation of a low-sodium salt with a 50% content of sodium chloride, using only sodium chloride from rock salt.

A laboratory mixer was used to mix 71 .4g of a composition containing 50% sodium chloride from rock salt, and 50% calcium D-gluconate monohydrate with 28.6g of osmotised water.

The paste obtained had the following composition by weight:

-Rock salt 35.7%

-Calcium D-gluconate monohydrate 35.7%

-Osmotised water 28.6%

The paste was distributed in a container for microwave ovens, so as to reach a total depth of 2 cm of paste.

The material thus disposed was introduced into a microwave oven (model Panasonic NN-GD462M, maximum power 1000 W) for a first 4.5-minute operating cycle at 300W. After this time had elapsed, the paste was completely melted.

For the subsequent drying step the same microwave oven was used for a 3-minute cycle at 300W. The drying brought about the complete removal of the water added during mixing (28.6 g).

The dry product was cooled to room temperature and subsequently ground and sieved to obtain a low-sodium salt with a particle size in the range of 1 .5-3.5 mm.

Example 3

Preparation of a low-sodium iodised salt, with a 40% content of sodium chloride. A laboratory mixer was used to mix 71 .4g of a composition containing 40% sodium chloride, made up of a mixture of sea salt and rock salt, and 60% calcium D-gluconate monohydrate with 25.9 g of osmotised water.

The paste obtained had the following composition by weight:

-Sea salt 1 .1 %

-Rock salt 28.5%

-Calcium D-gluconate monohydrate 44.5%

-Osmotised water 25.9%

2.93 g of an aqueous solution of Kl at 0.1 % wt./wt., equal to 2.24 mg of iodine, was further added to the paste.

The paste was distributed in a container for microwave ovens, so as to reach a total depth of 2 cm of paste.

The material thus disposed was introduced into a microwave oven (model Panasonic NN-GD462M, maximum power 1000 W) for a first 4.5-minute operating cycle at 300W. After this time had elapsed, the paste was completely melted.

For the subsequent drying step, lasting 20-min., hot air was used, at a temperature of about 90°C. The drying brought about the complete removal of the water added during mixing (25.9 g).

The dry product was cooled to room temperature and subsequently ground and sieved to obtain a low-sodium salt with a particle size in the range of 0.2-1 .0 mm.