EP3392352B1

EP3392352B1 - Process for preparing raw sugar from sugar beet

Info

Publication number: EP3392352B1
Application number: EP17167505.1A
Authority: EP
Inventors: Riccardo CASONI; Fabio Filippini; Giorgio Pezzi
Original assignee: CoProB Soc Coop Agricola
Current assignee: CoProB Soc Coop Agricola
Priority date: 2017-04-21
Filing date: 2017-04-21
Publication date: 2020-11-25
Anticipated expiration: 2037-04-21
Also published as: PL3392352T3; EP3392352A1

Description

TECHNICAL FIELD

The present invention relates to a process for preparing raw sugar from sugar beet.

PRIOR ART

In the food industry, as well as in common language, the term "sugar" indicates sucrose, a disaccharide consisting of a unit of glucose and a unit of fructose. Sucrose is amply available on the market, especially in crystallised granular form (granulated sugar) and is used in many food preparations, especially sweets and confectionary. For the sake of simplicity, in the context of the present invention as well, the term "sugar" will be meant to refer to sucrose.
Sugar is obtained by extraction from plant raw materials, mainly from sugar beet (Beta vulgaris saccharifera) and sugar cane (Saccharum officinarum). Hereinafter, "beet" will refer to sugar beet, even where not expressly indicated.
The raw sugar extracted from beet or cane can be purified (or "refined") into "white sugar", whose sucrose content is equal to about 99.9% by weight. Refinement has the disadvantage of eliminating also substances that are useful from a health and nutritional standpoint, such as, for example, mineral salts, in particular potassium, sodium, calcium and magnesium, organic acids such as citric acid, polyphenols and betaine, a molecule present mainly in beets which is capable of protecting cells from osmotic stress. US 2016/0108437 A1 relates to raw sugar and ethanol production using selective fermentation. WO 2013 /116113 A1 concerns a process and apparatus for producing ethanol from sugar beets. US 2015/0159230 A1 relates to methods of microbiological control in beet sugar. Henke et al., Journal of Food Engineering; 77; 2006; pages 416-420, relates to the application of the program Sugars for modelling and simulation of a sugar factory. Mhemdi et al., Food and Bioproducts Processing; 95, 2015; pages 323-331, concerns the impact of pulsed electric field and pre-heating on the lime purification of raw sugar beet expressed juices.
Raw sugar thus offers a better nutritional contribution than refined sugar. At present, the raw sugar used in the food industry is derived from sugar cane; with the exception of a few typical regional products, in fact, the raw sugar obtained from beets contains several components which impart organoleptic characteristics (above all odour) that are inappropriate for a sweetening product. Hence, the need to refine raw beet sugar arises. Refined beet sugars dyed with various natural or artificial colourants also exist on the market; in particular, refined sugars dyed with caramel take on a yellow-brown colour that makes them visually similar to raw sugar, though they cannot be classified as raw sugars.
The traditional process presently used to extract sugar from sugar beet comprises the following steps:

a) extraction from the roots of the beet plant by diffusion in hot water so as to obtain the so-called "raw juice";
b) purification of the raw juice by treatment with calcium oxide and carbon dioxide and concentration by eliminating water so as to obtain the so-called "thick juice";
c) crystallisation of the thick juice so as to obtain a so-called "massecuite" for the first crop of raw sugar;
d) centrifugation of the massecuite for the first crop of raw sugar to separate the first crop of raw sugar crystals from the crystallisation liquid (called "green drain" or "mother drain");
e) dissolution of the first crop of raw sugar in water to form a syrup (liquor);
f) crystallisation of the syrup so as to obtain a so-called "white sugar massecuite";
g) centrifugation of the white sugar massecuite so as to separate the crystals of refined white sugar from the drain (called "eliminated drain").

The process generally also comprises a step that enables further product to be recovered: typically, the green drain is crystallised in order to obtain the so-called "massecuite" for the second crop of raw sugar, from which the second crop of raw sugar and molasses are separated by centrifugation.
The raw juice obtained through extraction by diffusion from the roots of the beet plant in step (a) is a dark brown-coloured syrup which contains most of the extracted substances, including the sugar.
The thick juice obtained in step (b) is a concentrated sugar syrup (approx. 65-75°Bx) comprising about 64% by weight of sucrose, in addition to mineral salts and other organic substances (organic acids, amino acids, betaine).
The thick juice undergoes a first crystallisation (step (c)), at the end of which a "massecuite" for the first crop of raw sugar is obtained, containing raw sugar crystals and the so-called "green drain" or "mother drain", a sugar syrup that has a low sucrose content and comprises above all the above-mentioned mineral salts and organic substances. The raw sugar crystals present in the massecuite for the first crop are covered by a thin layer of green drain, which is deposited and adheres to the crystals themselves: the subsequent centrifugation (step (d)) thus removes the excess drain, which has not adhered to the sugar crystals, from the massecuite, enabling a first crop of raw sugar to be obtained.
The first crop of raw sugar is dissolved in water (step (e)), thus forming a sugar syrup, which then undergoes crystallisation and centrifugation to obtain a refined sugar (white sugar) and a drain ("eliminated drain"). The eliminated drainis generally mixed with the thick juice coming from another extraction and purification cycle and then treated again so as to optimise product recovery.
Following refinement, the sugar takes on a white colour, having a sucrose concentration of about 99.9% by weight. White sugar of an inferior quality can also be obtained by "washing" the raw sugar crystals with water during the centrifugation step, without carrying out any recrystallisation.
The raw sugar extracted from sugar cane is obtained by crystallisation and centrifugation of a partially purified and concentrated cane "juice" using a process similar to the one described above for obtaining raw beet sugar. Raw cane sugar can be subsequently purified in order to obtain refined cane sugar, but some varieties of raw cane sugar can be intended directly for human consumption, as they have organoleptic characteristics appreciated by consumers.
The different organoleptic characteristics of raw beet sugar and raw cane sugar (above all odour and flavour, extremely important for the use for which sugar is intended) depend on the different composition of the cane and beet juices from which the crystallisation process starts off.
Both juices obviously contain sucrose as the prevalent component, glucose and fructose, but they differ in the content, both qualitative and quantitative, of "non-saccharidic" substances, due to the botanical distance between the two plants. While the non-saccharidic components of cane juice (aldehydes, polyphenols) impart organoleptic characteristics appreciated by consumers to the resulting raw sugar, the non-saccharidic components of beet juice lend the resulting raw sugar an unpleasant aftertaste, unsuitable for food use. In particular, the amino acids present in beet juice with a percentage content about three times higher than in cane juice, are degraded releasing ammonia, a substance that is unpleasant both in terms of odour and flavour.
For the reasons illustrated above, there are no raw sugars originating from beet processing on the market today, whereas raw sugars obtained by extraction from sugar cane are widely available.
It thus appears of great interest to provide a process allowing a raw sugar to be obtained also from sugar beet, thus solving the known problems tied to the organoleptic properties and to the storage of the raw beet sugar obtainable with the current processes.
One of the objects of the present invention is to provide a process for preparing a raw beet sugar which is suitable for human dietary consumption and overcomes the limits and disadvantages of the traditional raw beet sugar extraction process.
Another object of the invention is to provide a process for preparing raw beet sugar without the non-saccharidic components that render the aroma and flavour thereof unpleasant.
In greater detail, the present invention has the object of providing a process for preparing raw beet sugar with a reduced amino acid content. Another object of the invention is to provide a process for preparing raw beet sugar which retains the nutritional elements that are generally lost with refinement, namely, mineral salts (above all potassium salts) and betaine.
Furthermore, the present invention has the object of providing a process for preparing raw beet sugar which does not have an odour, flavour and/or aftertaste that is unpleasant for the human palate, but rather has an appealing odour and flavour and can therefore be used in the food industry, especially in confectionery.
A last but not least object of the invention is to provide a process for preparing raw sugar from sugar beet with the above characteristics, which is highly reliable and easy to implement, entails low costs and can be carried out without any need for complex instruments or equipment.

SUMMARY OF THE INVENTION

The present invention relates to a process for preparing raw sugar from sugar beet comprising the steps of:

(i) subjecting at least a liquid obtained from the process of extracting beet sugar to a heat treatment at a temperature comprised between 120°C and 150°C, for a time comprised between 30 minutes and 120 minutes, to obtain a boiled syrup;
(ii) mixing the boiled syrup obtained in step (i) with sugar crystals, thus obtaining a mixture comprising sugar crystals coated by a layer of boiled syrup;
(iii) centrifuging the mixture prepared in step (ii) to separate the coated sugar crystals from any excess boiled syrup;
(iv) recovering the sugar crystals coated with boiled syrup separated in step (iii).

The invention also relates to a raw sugar from sugar beet with an α-amino nitrogen content of less than 20 mg/kg, as well as the use of said raw sugar for human consumption.

DETAILED DESCRIPTION OF THE INVENTION

As has been said, cane and beet juices contain qualitatively and quantitatively different components on which the organoleptic characteristics (pleasant or unpleasant) of the corresponding raw sugars depend. Although it is not possible to lend raw sugar extracted from beets the flavour and aroma of raw sugar extracted from cane, the inventors of the present invention have conceived a process which makes it possible to reduce, in the liquids obtained from the beet sugar extraction process, the content of the components on which the unpleasant organoleptic characteristics of the raw sugar derived therefrom depend.
Step (i) of the process developed by the inventors of the present invention consists in subjecting at least a liquid obtained from the beet sugar extraction process according to the traditional process to a heat treatment, carried out in a particular temperature interval and for a given time.
During the heat treatment, the Maillard reaction and Strecker degradation occur. Sugar caramellisation reactions, on which the formation of a brown-coloured product depends, at least in part, are also triggered.
As is known in the art, "Maillard reaction" refers to a complex series of phenomena which are triggered as a result of the interaction between sugars and proteins at high temperatures, for example during boiling. The substances that form as a result of the Maillard reaction (such as melanoidins) have a brown colour and a characteristic odour of freshly baked bread. The Strecker degradation, instead, is a chemical reaction in which an α-amino acid is converted into an aldehyde through the formation of an imine.
In the heat treatment carried out in the process according to the invention, the amino acids and monosaccharides (prevalently glucose and fructose) contained in the liquid obtained from the sugar extraction process react with one another, giving rise on the one hand to aldehydes and other substances having an odour and flavour that are pleasing to the human palate and on the other hand to ammonia, which is removed by stripping. The heat treatment takes place at a temperature comprised between 120°C and 150°C; preferably, it can be carried out at a temperature comprised between 125°C and 140°C and more preferably at a temperature of 131-133°C.
The duration of the heat treatment is comprised between 30 minutes and 120 minutes; preferably, the duration can be comprised between 45 minutes and 80 minutes, and more preferably between 45 minutes and 70 minutes. In a particularly preferred embodiment, the duration of the heat treatment can be comprised between 55 minutes and 65 minutes, for example it can be equal to about 60 minutes.
A particularly preferred embodiment of the process of the invention provides for the heat treatment to be carried out at a temperature of 131-133°C for a time comprised between 45-70 minutes.
The heat treatment allows to obtain a reduction in the content of amino acids present in the liquid obtained from the beet sugar extraction process, thus preventing the resulting raw sugar from having unpleasant organoleptic characteristics. Furthermore, the aldehydes and other substances that form due to the Maillard reaction render the resulting raw sugar appreciable in terms of odour and flavour, and thus suitable for human consumption.
In order to evaluate the content of amino acids in the liquid before and after the heat treatment, the α-amino nitrogen can be conveniently measured, for example using the Sörensen method. It has been observed that a 50% decrease in α-amino nitrogen in the boiled syrup obtained at the end of the heat treatment compared to the content in the initial liquid ensures a sufficient reduction in amino acids and the production of substances that are pleasing to the palate. This 50% decrease in α-amino nitrogen is reached after about 30 minutes of heat treatment. After a decrease of about 50% compared to the initial value of the α-amino nitrogen content, the rate of reduction greatly decreases until nearly reaching a stop.
For example, a thick beet juice having a purity quotient (Q, percentage content of sucrose relative to the dry substance) of about 90, a concentration of about 70 Bx and an α-amino nitrogen content comprised between 1 and 1.4 g/kg of dry substance, subjected to a heat treatment at a temperature comprised between 125°C and 140°C, will have a rate of reduction of the α-amino nitrogen comprised between 0.2 and 1.0 mmols*kg^-1*min^-1.
The liquid obtained from the beet sugar extraction process which undergoes the heat treatment can be, for example, the thick juice or the green drain. Preferably, the liquid undergoing the heat treatment can be the thick juice. When the liquid undergoing the heat treatment is thick juice, it is preferably obtained after the steps of purifying and concentrating the raw beet juice.
The heat treatment is preferably carried out in the absence of air (preferably under water-steam pressure).
At the end of the treatment the pressure in the reactor is gradually decreased until atmospheric pressure and then further decreased until vacuum conditions. The pressure reduction in the reactor, above all to values lower than atmospheric pressure, favours the discharge of the reaction gases, such as carbon dioxide and ammonia, from the reactor.
In one embodiment, at the end of the heat treatment, the pH of the boiled syrup can be modified by adding a base so as to bring the pH back to values close to neutrality (pH of about 7) to prevent a further inversion of the sucrose from occurring. Furthermore, at the end of the heat treatment the concentration of the boiled syrup can be modified by adding water. The boiled beet syrup obtained at the end of the heat treatment comprises sucrose, monosaccharides (mainly glucose and fructose), substances that are useful from a nutritional standpoint, such as mineral salts (above all sodium, potassium, calcium and magnesium salts), and betaine, as well as aldehydes and other organoleptically appreciable substances generated by the Maillard reaction. However, the content of monosaccharides is particularly high relative to the sucrose content, since the high temperature used during the heat treatment favours the hydrolysis of sucrose into the corresponding monosaccharides. Typically, monosaccharides represent about 20% by weight of the dry substance, and sucrose about 60% by weight of the dry substance. Furthermore, the boiled syrup has a low purity quotient (Q about 60%) and it is therefore not possible to obtain sucrose by crystallisation of this syrup.
The process of the invention thus provides for the boiled syrup to be mixed with sugar crystals (step (ii) of the process).
Step (ii) can be carried out in two alternative ways:

(iia) by adding the boiled syrup to the sugar crystals during the step of centrifuging the massecuite for the first crop of raw sugar, preferably after the so-called "green drain" has been partially eliminated;
or
(iib) by adding the boiled syrup to the sugar crystals obtained after centrifuging the massecuite for the first crop of raw sugar, i.e. after complete removal of the "green drain".

In case (iia) the boiled syrup is added when the green drain has been partly eliminated, and preferably when most of the green drain has been eliminated; the boiled syrup must however be added before the sugar crystals become too compact. At the end of the addition of boiled syrup, the centrifugation is completed, as per step (iii), to separate any excess added syrup. A raw beet sugar is thus obtained which comprises about 2% by weight of boiled syrup, deposited as a thin layer on the sucrose crystals: the total sucrose content (crystals+syrup) is about 99.4% by weight.
In case (iib) the sugar crystals obtained after centrifugation of the massecuite for the first crop of raw sugar are mixed with the boiled syrup (for example in a mixer) so as to form a "magma", i.e. a mixture comprising sugar crystals and boiled syrup. As a result of the mixing, the boiled syrup is deposited on the sugar crystals, coating them with a thin layer and replacing the green drain. The magma is then centrifuged, according to step (iii), to obtain a raw beet sugar that comprises about 2% by weight of boiled syrup and has a total sucrose content (crystals+syrup) of about 99.4% by weight.
The liquid obtained from the centrifugation step (iii) (i.e. the excess boiled syrup) represents a waste product called "boiled drain" or "treated drain", which can be recycled by joining it to subsequent batches of boiled syrup. In one embodiment of the process, in fact, the boiled drain obtained in step (iii) of a first preparation can be mixed with the boiled syrup obtained in step (i) of a second preparation, and the resulting mixture can then be mixed with sugar crystals. Practically speaking, according to this embodiment of the process, in step (ii) the sugar crystals are mixed with a mixture comprising the boiled syrup obtained in step (i) and the excess boiled syrup (i.e. the boiled drain) obtained in step (iii) of a previous preparation.
Since, as has been said, boiled drain means the boiled syrup recovered at the end of centrifugation, in this manner sugar crystals coated with a thin layer of boiled syrup are obtained as well.
The sugar crystals with which the boiled syrup is mixed in step (ii) of the process according to the invention can preferably be raw sugar crystals; however, they can also be white sugar crystals obtained at the end of refinement, after centrifugation of the white sugar massecuite (step indicated as g) in the known sugar extraction and purification process described above). If white sugar crystals are used, in step (ii) the sugar crystals are simply mixed with the boiled syrup (for example in a mixer), with the formation of a "magma" according to what was described for step (iib) of the process.
In one embodiment, the centrifugation performed in step (iii) of the process according to the invention can be carried out in a centrifuge of a continuous type, for example in a centrifuge of the conical basket type.
In a preferred embodiment, the centrifugation performed in step (iii) of the process according to the invention can be carried out in a centrifuge of a discontinuous type, thus operating in batches.
If batch centrifuges are used, the boiled syrup is mixed with the sugar crystals present in the centrifuge when the rotation speed of the centrifuge is comprised between 400 and 600 rpm, preferably between 450 and 550 rpm. Once the boiled syrup is added into the centrifuge, the rotation speed is increased until reaching 1000-1200 rpm. At the end of centrifugation, i.e. when the excess of boiled syrup has been eliminated, the rotation speed is gradually slowed until the centrifuge comes to a stop and then is unloaded.
The raw sugar obtained with the process of the invention is then sent off for the subsequent drying, screening and packaging steps, carried out according to known processes commonly employed in the sugar industry. The process for preparing raw sugar from sugar beet comprises the initial steps of:

a) extraction from the roots of the beet plant by diffusion in hot water, so as to obtain the so-called "raw juice";
b) purification of the raw juice by a treatment with calcium oxide and carbon dioxide and concentration by eliminating water, so as to obtain the so-called "thick juice".

In one embodiment, the thick juice obtained at the end of these initial steps can be divided into two parts: one part of the thick juice undergoes the heat treatment according to step (i) of the process of the invention, and the resulting boiled syrup is used in the subsequent steps (ii)-(iv). The other part of the thick juice is crystallised to obtain the so-called "massecuite" for the first crop of raw sugar, which contains raw sugar crystals and is centrifuged. As envisaged in the process of the invention, the boiled syrup prepared in step (i) can be added during this centrifugation (according to step (iia)); alternatively (step (iib)), the boiled syrup prepared in step (i) can be mixed with the sugar crystals at the end of centrifugation, that is, after the crystals have been separated from the crystallisation liquid (the "green drain" or "mother drain"); this mixing can take place, for example, in a mixer.
In another aspect, the present invention relates to a raw sugar from sugar beet comprising 2% by weight of the boiled syrup obtainable from the heat treatment of a liquid deriving from the sugar beet processing according to step (i) of the process of the invention. The total sucrose content (crystals+syrup) of this raw sugar is about 99.4% by weight.
Since the boiled syrup described above comprises glucose, fructose, water, mineral salts (for example potassium, sodium, calcium and magnesium), aldehydes deriving from the heat treatment of the amino acids contained in the starting liquid and betaine, such substances are thus present in the raw sugar according to the invention.
The raw sugar of the invention has a lower α-amino nitrogen content than the raw sugar obtained with the traditional sugar extraction process. More particularly, the invention relates to a raw beet sugar whose α-amino nitrogen content is 50% lower compared to the raw sugar obtained with the traditional extraction process. In particular, the raw beet sugar according to the present invention is characterised in that it comprises α-amino nitrogen in an amount of less than 20 mg/kg. Furthermore, in one embodiment, the raw sugar according to the invention can have a betaine content equal to or greater than 500 mg/kg. In another embodiment, the raw sugar according to the invention can have a solution colour equal to or greater than 1000 ICUMSA units, determined according to the ICUMSA method GS1/3-7 (2011).
Preferably, the sugar with the characteristics described hereinabove is obtainable by the process of the present invention.
Said sugar, despite being raw, is suitable for dietary consumption, because the reduced α-amino nitrogen content lends it organoleptic properties that are pleasing to the human palate. Furthermore, precisely because it is not refined, said sugar retains a series of nutritional substances which would otherwise be lost during refinement.
Another aspect of the invention thus relates to the use of the raw sugar as described here for human consumption. Preferably, the sugar according to the invention can be used in sweet and confectionery preparations, at a domestic, artisanal or industrial level.
Below are some examples of implementation of the process according to the invention for the preparation of raw beet sugar suitable for human dietary consumption; these examples are obviously not intended to limit the scope of the invention.

EXAMPLES:

Example 1: laboratory preparation of raw beet sugar (according to the invention) starting from green drain.

The beet juice undergoing the heat treatment is the so-called "green drain", i.e. the liquid that is obtained following crystallisation of the thick juice and centrifugation to separate the raw sugar crystals.
549 grams of beet green drain(a) underwent the heat treatment in an autoclave at a temperature of 132°C for 60 minutes, in a Pyrex glass vessel with a 1 litre capacity and a loosened polypropylene (PP) lid. The time was measured from the moment at which the temperature reached the set value. At the end of this process a boiled syrup (b), derived from the "green drain", was obtained.
399 grams of this boiled syrup were mixed at room temperature with 401 grams of white beet sugar so as to obtain 800 grams of magma.
The magma was centrifuged for 10 minutes at room temperature in a laboratory centrifuge having a basket diameter of 22 cm and at a rotation speed of 3000 rpm.

383 grams of wet raw beet sugar (d) and 324 grams of residual treated drain (c) were unloaded from the centrifuge. 93 grams were missing from the mass; this amount corresponds to the mass remaining inside the containers and the centrifuge. The raw sugar obtained (d) has pleasing organoleptic characteristics (appearance, odour and flavour) and a very bright colour.

		(a) Beet green drain	(b) Boiled syrup derived from the green drain	(c) Treated drain (after centrifuging)
Pol	°Z	53.23	38.57	39.98
Bx		75.51	77.86	78.83
Apparent Q		70.50	49.54	50.72
pH		7.88	5.00
D-Glucose	% dry	0.15	3.36
Colour	UI	41,780	321,510

		(d) Raw sugar
Pol	°Z	98.90
ashes	%	0.187
Moisture	%	0.253
pH		5.43
D-Glucose	%	0.076
Colour	UI	5,080

Example 2: laboratory preparation of raw beet sugar (according to the invention) starting from thick juice.

In this case, the beet juice undergoing the heat treatment is the "thick juice", i.e. the liquid that is obtained following purification of the raw juice with calcium oxide and subsequent concentration.
1,897 grams of thick juice (a) underwent the heat treatment in an autoclave under the same conditions as in example 1. A boiled syrup (b) derived from thick juice was obtained, with a 96.4% mass recovery and a 98.4% dry substance recovery .
1,779 grams of boiled syrup (b) and 601 grams of "boiled drain" (c) from previous preparations (batches) using boiled syrup were mixed with white sugar in a 1:1 ratio by weight so as to form a series of batches of magma, each weighing about 1 kg. These batches of magma were centrifuged as in example 1 and raw sugar and other boiled drain (d) were obtained.
1,623 g of boiled drain (d) were recovered and again mixed with white sugar in a 1:1 ratio by weight; the resulting magma was centrifuged and other raw sugar and a second boiled drain were obtained.
1,015 g of this second boiled drain were again mixed with white sugar in a 1:1 ratio by weight and the resulting magma was centrifuged and other raw sugar and a final boiled drain (e) were obtained.

Altogether, 9 batches of magma (total weight 10,245 grams) were centrifuged and a total of 5,092 grams of raw sugar was obtained. The analysis of this raw sugar following drying (f) is shown in the table below. This raw sugar has pleasing organoleptic characteristics and the crystals "flow" freely on one another ('free flowing').

		(a) Initial beet thick juice	(b) boiled syrup derived from thick juice	(c) boiled drain from previous preparations	(d) Boiled drain recovered from this preparation	(e) final drain of this preparation
Pol	°Z	59.30	37.94	48.73	42.88	45.99
Bx		65.35	68.06	73.56	70.76	73.45
Apparent Q		90.74	55.74	66.25	60.60	62.62
pH		8.28	4.72	4.88	4.73	4.79
D-Glucose	% dry	0.14	12.49
Colour	UI	6,130	80,420

		(f) Raw sugar
Pol	°Z	99.34
ashes	%	0.039
moisture	%	0.127
pH		5.63
D-Glucose	%	0.140
Colour	UI	1,150

Example 3: preparation of raw beet sugar (according to the invention) starting from thick juice in an industrial plant.

The industrial trial was carried out over six days in the Coprob sugar refinery in Minerbio (Bologna) using the equipment present therein.

a) Heat treatment for the preparation of the boiled syrup

Four batches of thick juice weighing about 9 t each were prepared using a steam-heated stainless steel concentrator at a pressure of 2.5 bar. The chamber containing the juice was kept closed at a pressure of 2 bar and a temperature of 132°C (±1°C). The duration of the treatment was measured starting from the moment at which the temperature of 132°C was reached. Cooling was performed by shutting off the steam and gradually lowering the pressure in the chamber containing the juice to the atmospheric value and then to vacuum pressure until reaching a temperature of about 75°C. The juice concentration was corrected by adding water (evaporated because of the slight boiling occurred during the lowering of the pressure). The pH was corrected by adding caustic soda.

The analysis of the characteristics of the starting thick juice and of the four batches of boiled syrup is shown in the following table:

		Thick juice prior to treatment	Boiled syrup
		Thick juice prior to treatment	Batch 1	Batch 2	Batch 3	Batch 4
duration of treatment	minutes	-	60	70	60	60
Pol	°Z	63.37	49.30	31.90	46.60	54.67
Bx		69.11	72.12	71.60	72.60	73.03
Apparent Q		91.69	68.36	44.55	64.19	74.86
pH		8.71	5.10	4.82	4.99	5.11
Colour	UI	10,350	40,682	97,188	65,455	47,558
D-Glucose	g/100 g dry	0.09	6.34	16.38	9.90	5.81
α-amino nitrogen	mg/g dry	1.064	0.338	0.315	0.359	0.382
Acidity	mmol/g	-	0.042	0.076	0.056	0.041

b) Crystallisation (according to the prior art)

Batch pans with automatic control were used, each with a capacity of 30 m³. Boiling was carried out in the traditional manner, adjusting the parameters in such a way as to favour the formation of raw sugar crystals with a large grain size (mean diameter (MD) of sugar crystals equal to about 0.8 mm). Over the six days of the trial, 24 boiled batches were prepared , corresponding to a total of about 1,050 t of massecuite.
The analysis (mean values) of the thick juice which underwent crystallisation and the massecuite obtained after crystallisation is shown below:

Thick juice Massecuite

Pol °Z 60.62 83.53

Bx 66.04 91.13

Q 91.79 91.66

pH 8.71

Colour UI 10,350

c) Centrifugation

BMA batch centrifuges with a basket diameter of 132 cm, operating at a maximum speed of 1200 rpm and with a maximum load of 1000 kg/cycle, equipped with washing nozzles were used. The amount of water used was about 6-7% by weight of the massecuite, most of it (85%) to clean the basket after unloading and before the subsequent cycle.
The green drain derived from the massecuite obtained at the end of the crystallisation step was separated by centrifugation of the raw sugar crystals. The rotation speed of the centrifuge was gradually increased to about 500 rpm; once this value was reached, the boiled syrup prepared as described in step a) was added in the centrifuge and mixed with the raw sugar crystals in an amount comprised between 4 and 6% by weight of the sugar crystals, maintaining the rotation speed constant for the entire duration of the mixing. At the end of the addition of boiled syrup, the rotation speed of the centrifuge was gradually increased again to about 1200 rpm.
The boiled syrup was added by means of the water nozzles present in the centrifuge. The mean Bx and pH values of the boiled syrup used to spray the raw sugar are the following:

day 1 day 2 day 3 day 4 day 5 day 6

Bx 68.59 69.19 70.42 69.03 67.29 67.87

pH 5.72 5.44 5.83 5.90 6.29 6.46

A total of about 500 t of raw sugar and 650 t of drain were produced using 1500 t of thick juice. Daily average data of the raw sugar and drain separated in the centrifuge are shown in the following table:

		day 1	day 2	day 3	day 4	day 5	day 6
Raw sugar
Pol	°Z	99.30	99.22	99.15	99.07	99.17	99.47
ashes	%	0.194	0.095	0.074	0.082	0.106	0.119
Moisture	%	0.103	0.098	0.079	0.078	0.096	0.120
pH		7.30	7.03	6.90	6.73	7.30	7.70
D-Glucose	%	0.070	0.150	0.172	0.151	0.048	0.045
Colour	UI	1,130	1,390	1,570	1,240	940	1,100

Drain
Pol	°Z	60.65	56.83	61.61	62.80	63.27	60.41
Bx		73.00	68.33	74.28	76.25	76.85	74.58
Q		83.08	83.17	82.94	82.36	82.33	81.00
pH		8.82	8.12	8.57	8.67	8.78	8.55
D-Glucose	% dry	0.248	0.573	0.502	0.344	0.179	0.182
Colour	UI	26,270	30,980	26,719	25,490	26,470	29,610

The drain obtained at the end of the above-described process has the characteristics of a green drain and can be used in the crystallisation of low-purity sugar.
The raw sugar obtained was packaged in big bags. The search for any chemical or biological contaminants gave a negative result.
Unlike white sugar, the raw sugar obtained at the end of processing retains some nutritional elements of plant origin present in beet juice, such as, for example, potassium salts and betaine.
A sensory analysis performed according to standard ISO 13299:2003, in comparison with raw cane sugar of the "Demerara" variety and white beet sugar, revealed the absence of unpleasant aromas and/or aftertastes and a better degree of sweetness compared to raw cane sugar.
It was ascertained, in practice, that the process according to the invention wholly fulfills its objects as it allows to obtain a raw beet sugar which retains many of the substances typical of unrefined sugar (such as mineral salts) but is at the same time devoid of the components that make the raw sugar obtained with the traditional process unsuitable for human consumption. In particular, the process according to the invention makes it possible to reduce the content of amino acids (and hence of α-amino nitrogen, on which the undesirable organoleptic characteristics depend) present in the raw sugar. The process described herein thus satisfies the need to obtain a beet sugar that is unrefined but nonetheless suitable for human dietary consumption and appropriate for applications in the confectionery industry.
The process for preparing raw beet sugar suitable for human dietary consumption according to the present invention, and the raw sugar itself, conceived as described herein, are susceptible of numerous modifications and variants, all falling within the scope of the inventive concept; moreover, all of the details can be replaced by other equivalent elements whose correspondence is known to the person skilled in the art.

Claims

A process for preparing raw sugar from sugar beet, comprising the steps of:
(i) subjecting at least a liquid obtained from the process of extracting beet sugar to a heat treatment at a temperature comprised between 120°C and 150°C, for a time comprised between 30 minutes and 120 minutes, to obtain a boiled syrup;

(ii) mixing the boiled syrup obtained in step (i) with sugar crystals, thus obtaining a mixture comprising sugar crystals coated by a layer of boiled syrup;

(iii) centrifuging the mixture prepared in step (ii) to separate the coated sugar crystals from any excess boiled syrup;

(iv) recovering the sugar crystals coated with boiled syrup separated in step (iii).
The process according to claim 1, wherein step (ii) is carried out by adding the boiled syrup to the sugar crystals according to a method selected between:
(iia) adding the boiled syrup to the sugar crystals during the centrifugation of the massecuite for the first crop of raw sugar;
or

(iib) adding the boiled syrup to the sugar crystals at the end of centrifugation of the massecuite for the first crop of raw sugar, wherein said centrifugation of the massecuite for the first crop of raw sugar is a step of the beet sugar extraction process.
The process according to claim 2, wherein the boiled syrup is added to the sugar crystals during the step of centrifuging the massecuite for the first crop of raw sugar in a centrifuge when the rotation speed of the centrifuge reaches 400-600 rpm.
The process according to claim 1, wherein step (ii) is carried out by adding the boiled syrup to white sugar crystals obtained from the refinement of the beet sugar.
The process according to any one of the preceding claims, wherein the at least a liquid obtained from the beet sugar extraction process undergoing the heat treatment in step (i) is selected from the group consisting of thick juice and green drain.
The process according to any one of the preceding claims, wherein the heat treatment in step (i) is carried out at a temperature comprised between 125°C and 140°C.
The process according to claim 6, wherein the heat treatment in step (i) is carried out at a temperature comprised between 131°C and 133°C.
The process according to any one of the preceding claims, wherein the heat treatment in step (i) has a duration comprised between 45 minutes and 70 minutes.
The process according to claim 8, wherein the heat treatment in step (i) has a duration comprised between 55 minutes and 65 minutes.
The process for preparing raw sugar from sugar beet according to any one of the preceding claims, comprising the following steps:
- preparing a thick juice by extraction of a raw juice from the roots of the beet plant and subsequent purification and concentration;

- separating the thick juice into two portions;

- subjecting one portion of the thick juice to step (i) of the process according to claim 1, thereby obtaining a boiled syrup;

- subjecting the other portion of the thick juice to subsequent refinement steps in order to obtain white sugar from sugar beet.
The process according to claim 10, wherein said subsequent refinement steps comprise the steps of:
- crystallising the thick juice, so as to obtain a so-called "massecuite" for the first crop of raw sugar;

- centrifuging the massecuite for the first crop of raw sugar in order to separate the first crop of raw sugar crystals from the crystallisation liquid (called "green drain" or "mother drain");

- dissoving the first crop of raw sugar in water in order to form a syrup (liquor);

- crystallising the syrup in order to obtain a so-called "white sugar massecuite";

- centrifuging the white sugar massecuite in order to separate refined white sugar crystals from the drain (called "eliminated drain").
A raw sugar from sugar beet with an α-amino nitrogen content of less than 20 mg/kg.
The raw sugar from sugar beet according to claim 12, wherein said raw sugar has a betaine content equal to or greater than 500 mg/kg.
The raw sugar from sugar beet according to claim 12 or 13, wherein the solution colour of said raw sugar is equal to or greater than 1000 ICUMSA units, determined according to the ICUMSA method GS1/3-7 (2011).
The raw sugar from sugar beet according to any one of claims 12 to 14, wherein said raw sugar is obtainable by the process according to any one of claims 1 to 10.
The raw sugar from sugar beet according to claim 15, comprising 2% by weight of boiled syrup, wherein said boiled syrup is obtainable through step (i) of the process according to any one of claims 1 to 10.
Use of the raw sugar from sugar beet according to any one of claims 12 to 16, for human consumption.