THE PATENTS ACT, 1970

COMPLETE
SPECIFICATION




SECTION 10
TITLE
Process For The Making Of Invert Sugar Syrup In Mixed Solvent Systems Using Strong Mineral And Weak Organic Acids
-APPLICANTS
( Lali A. M., Sunita V. and Lodha D. B. c/o Chemical Engineering Division, University Department of Chemical Technology, Nathalal Parikh Marg, Matunga, Mumbai
Maharashtra, India 400 019 *c/o M.B. Chemicals, Malegaon, Nasik, Maharashtra

The following Specification Particularly describes and ascertains the nature of this invention and the manner in which it is to be performed.

20 AUG 2001

3. Description of Invention
PROCESS FOR THE MAKING OF INVERT SUGAR SYRUP IN MIXED
SOLVENT SYSTEMS USING STRONG MINERAL
AND WEAK ORGANIC ACIDS
FIELD OF INVENTION
This invention relates to the use of mixed solvents for producing clear, colourless invert sugar, which may be used in a variety of beverage, food and pharmaceutical industries.
BACKGROUND

Reaction: Inversion of sucrose
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Sucrose when hydrolyzed produces invert sugar, which is an equimolar mixture of the constituent monosaccharide sugars glucose and fructose. Sucrose is readily hydrolyzed in acidic solutions at rates that increase markedly with increasing temperature, yielding the monosaccharide constituents. Acids vary in their ability to invert sugar, almost in the same order of their degree of ionization [Kurudis and Mauch, 1991].

Sugar is the most popular sweetener in the market. It also possesses preservative, bulking, flavor enhancing, and texturing properties. The major reasons for its popularity are its ready availability, low cost, simplicity of production, purity and long history of usage. When hydrolyzed, sucrose produces invert syrup, an equimolar mixture of glucose and fructose. While sucrose is sweet, fructose is 1.5 times sweeter and can substitute cane sugar or sucrose in many applications like foods, beverages and pharmaceutical formulations. Important properties exhibited by invert sugar are chemical similarity to sucrose, greater solubility in water, higher sweetness, flavor, storage stability and ease of mixing. These beneficial properties led to the development of invert sugar in the 1960's. The demand potential for invert sugar is estimated at about 20 lakh tons per annum. About 40 lakh tons of crystal sugar is used in the non-domestic sector and at least about 50% of this market could be easily captured by Invert sugar syrup [Gehlawat, 1991],
In the chemical sense, the word inversion means changing of the dextrorotatory optical activity to laevorotatory. This term was used to describe the rotational change following acid hydrolysis of a sugar solution when the strong dextrorotation of sucrose is inverted to the laevorotation of the resulting mixture of glucose and fructose. Usage of the term 'inversion' in sugar technology now has an extended application and encompasses hydrolysis of sucrose by both acidic or the enzymatic routes.
Traditionally, the acid hydrolysis process used for inversion of sucrose involves use of strong mineral acids like hydrochloric acid (HCl) and sulfuric acid (H2SO4), or occasionally weaker organic acids such as citric acid and acetic acid in case of some specific end uses of the invert sugar. The traditional acid inversion process however, has the following inherent problems [Newton and Wardip, 1974]:
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• High acidity of the final product
• High ash content
• Corrosivity of the acid
• Large volume of effluent generated
• Formation of undesirable coloured products (7-8%) resulting in coloured final product
• Problems associated in de-ionization of the final product
The pH of the resultant acid hydrolyzed invert sugar is less than 3, which is generally unacceptable. The problem of incomplete acid removal in sugar and sugar products has been a topic of concern in the sugar industry. De-ionization of the reaction mixture can be performed by neutralization of the acid by an alkali or by ion exchange. The most common method of acidity removal involves neutralization of the acid with an alkali. This however results in residual salt (as ash content) in the invert sugar syrup and the syrup can be used only for applications where salt (generally NaCl) is acceptable in the end use. In addition, presence of residual acid or alkali if used for neutralization, results in an unusually large increase in colour formation during the subsequent syrup concentration stages carried out at higher temperatures through the Lobry van Eickenstein transformation [Imming, 1994]. Removal of the acid by ion exchange leads to significant adsorption of the product to the resin through mechanisms of sugar occlusion and adsorption. Therefore post reaction removal of the acid catalyst and/or the salt is a decisive factor in product economics and acceptability. Sugar syrups and invert sugar are most stable within a pH range of 5.0 to 5.5 [Shallenberger, and Birch, 1975].
During the manufacture of invert sugar, both the inversion process and concentration of the final product by evaporation have been implicated as the major colour forming steps [Monsan and Combes. 1985]. Colour is an important decisive factor in the acceptability of the product. The causes of the formation of colour and the preventive measures have been the focus of a
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large number of theoretical and industrially relevant investigations. Higher inversion temperatures required for acid conversion and subsequent product concentration results in product loss via formation of various colour forming compounds. These compounds also impart an off flavor to the invert sugar formed. The main precursor in the pathway of colour formation is the neurotoxin; hydroxy methyl furfural (HMF) formed from fructose [Hodge, 1963; Moye and Krzeminski, 1962]. Colour formation during the inversion reaction is generally less with dilute sugar solutions. However, since most commercial grades of invert sugar require a product concentration of ca 75% w/v, use of low reaction concentrations of sugar entails large energy requirement, and results in higher colour development during the long concentration process at high temperature.
The colour forming reactions occur at high temperatures between sucrose, the hydrolysed products and acid, resulting in the concomitant loss of both sucrose and invert sugar to form high molecular weight dark coloured polymers. The loss in sucrose is mainly due to the caramelization reactions and the product loss is through the formation of colour complexes initiating from hydroxy methyl furfural formed principally from fructose. As a result the colour of invert sugar may range from colourless to pale yellow to dark brown. Colour formation has generally been found to increase with an increase in sucrose concentration, and accelerates in the presence of acidic ions and/or metal ions (primarily Fe) at higher temperatures [Barnes and Kaufman, 1947].
Most acid catalyzed sugar inversion processes use dilute sugar concentrations in order to avoid colour formation at reaction stage. This results in a need to further concentrate the invert sugar syrup by evaporation of water which makes the production an energy intensive process that increases the product cost. Use of higher initial sucrose concentration (>60%w/v)
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can be a feasible solution to avoid the further downstream concentration if colour formation at the inversion stage can be arrested.
Despite all the problems associated with a typical acid inversion process, the bulk of the invert sugar manufactured globally still uses acid as the inversion catalyst. Many of the problems encountered in the acid catalyzed inversion of sucrose could be remedied if inversion is carried under "controlled" conditions of acidity and at lower temperatures. Controlled acidity implies smaller quantities of the dissociated proton in the inverting solution. This condition would exist in solutions of weak organic acids where the dissociation of the acid is lower than strong mineral acids. It is known that dissociation of an acid can be suppressed by the addition of an organic solvent to its aqueous solution [Vinnik, 1987]. This phenomenon is more significant in solutions of weaker organic acids that already have low degrees of dissociation in aqueous solutions.
The first of our claims relates to invention of a process for acid inversion of sucrose wherein a mixed solvent/s is used as the reaction medium for sucrose hydrolysis with two objectives: (1) Decrease or control of the acidity of the acid catalyst, and (2) Facilitate concentration of the invert sugar at lower temperatures with lower energy requirement. By the phrase "mixed solvent system' we mean use of an organic solvent or mixture of organic solvents in a homogeneous mixture with water, the mixture then being used to provide the dissolution medium for sucrose used for making the invert sugar. The solvent/s used has to fulfill the following criteria:
a. The solvent/s should be miscible with water.
b. The solvent/s should have lower boiling point than water (as pure solvent, or as
azeotrope with water).
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c. The solvent/s should have solubility for the acid to be used as catalyst in the
sucrose inversion process.
d. The solvent/s should, either as pure solvent or in a mixture with water in one or
the other proportion, exhibit high solubility for sucrose and invert sugar (glucose
and fructose).
e. The solvent/s should be non-toxic.
f. The solvent/s should possess a latent heat of vaporization of less than 200 kcal/kg.
The second of our claims relates to invention of a process for the acid catalyzed manufacture of invert sugar wherein a post hydrolysis partial neutralization to a pH of 5.0-5.5, is effected along with removal of the acid catalyst as an insoluble calcium or any other metal salt. The acid from the salt precipitate may then be regenerated to yield the free acid for subsequent reuses. The careful monitoring of pH after the addition of a stoichiometric quantity of the precipitating/neutralizing agent effectively neutralizes the invert sugar formed. The insoluble acid precipitate is then separated and may be regenerated for subsequent batches.
OBJECTS OF THE INVENTION
This invention relates to a process for streamlining the entire acid inversion process using an acid catalyst in mixed solvent system to yield invert sugar of acceptable quality (Table 1). The primary objective of this invention is to propose a new process for acid catalyzed inversion of sucrose to invert sugar under controlled conditions. The objective of using the controlled conditions is to reduce or avoid colour-forming reactions in the inversion step, and later in the syrup concentration step. The controlled conditions are effected through the use of mixed solvent system as solvent for the sucrose and the resulting invert sugar; and use of an appropriate acid catalyst that can be quantitatively precipitated after the inversion reaction.
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Another objective of inventing the process that uses the controlled conditions through the use of mixed solvent/s system is to facilitate concentration of the invert syrup at temperatures lower than 100°C and using lesser energy on account of lower latent heat of vaporization of the solvent/s used.
DESCRIPTION OF THE PROCESS
According to this invention there is provided a process for the preparation of commercially acceptable grades of invert sugar (Table 1) through a modified acid hydrolysis process that uses a mixed solvent system. The process comprises of the hydrolysis of sucrose dissolved in a concentration range of 5% w/v to 75% w/v in a mixed solvent/s, and using an acid catalyst at typical temperatures ranging from 35°C to 75°C and at any pressure (preferably atmospheric pressure). The mixed solvent system is a homogenous solution of an organic solvent or a mixture of organic solvents and water in any proportion from 1:10 to 10:1. The various solvents that can be used are from ethanol, methanol, isopropyl alcohol, dimethyl formamide, dimethyl sulfoxide, and acetone. The choice of the acid catalysts used is based on the ability of the acid to form insoluble calcium or any other metal salt, and hence enable its quantitative separation by precipitation from the mixed solvent system. The acid catalyst chosen can be from strong mineral acids such as hydrochloric acid, sulphuric acid, nitric acid and perchloric acid; or from weak monobasic acids such as acetic acid and oxalic acid; or from weak dibasic acids or tribasic acids such as citric acid or tartaric acid. The acid catalyst in the sucrose inversion process may either be used in its pure form or as an aqueous solution that is recycled from the previous inversion batches.
In a typical process the sucrose hydrolysis reaction is carried out in batch mode in a stirred or mixed vessel of any type under controlled temperature conditions, and provided with suitable



solvent condensation system. The reaction is performed preferably at atmospheric pressure. In accordance with the invention, the reaction mixture comprising a homogenous solution of sucrose (in 5% w/v to 75% w/v final concentration) and the chosen acid catalyst from those mentioned above (in 0.001 gmoles/L to 0.05 gmoles/L final concentration), dissolved in a mixed solvent system as described above, is subject to an optional pre-hydrolysis clrificatio step consisting of decolorisation and deionisation using ion exchange and/or metalchelating resins before being heated to the inversion temperature. The decolourizing agents employed could be any one of the commonly used decolourants such as activated carbon, talc, talofloc, kieselguhr, activated clays, and zeolites.
The reaction of sucrose hydrolysis is carried out at temperatures ranging from 30°C to 75°C at any pressure, preferably atmospheric. The reaction can be followed by estimating the degree of conversion/inversion through analysis of the reducing sugar by the DNSA method in periodically withdrawn samples. The reaction is stopped when the inversion of sucrose is complete to near complete, by the addition of a pre-calculated amount of the acid precipitating or acid neutralizing agent like calcium carbonate. The pH of the reaction mixture is continuously monitored and maintained not above 5.5. The reaction mixture is adjusted to pH of 5.0 to 5.5, and cooled, and then filtered to remove insoluble acid salt precipitate. The quantitative removal of the acid salt from the invert sugar syrup is verified through an appropriate analytical procedure.
The residual trace amount of metal ion, if any, in the invert sugar thus obtained is removed by a second clarification step comprising deionisation using an ion exchange and/or metal chelating resins. The metal chelating resins also adsorb any residual colour developed in the invert sugar during the hydrolysis and neutralization stages. At this stage any change in pH of
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the final syrup from the range of 5.0-5.5 is remedied by a readjustment of the pH to 5.0-5.5 by the addition of dilute acid or alkali.
The invert sugar syrup thus obtained is now ready to be concentrated to the desired commercially acceptable concentration of ca 75% w/w product concentration. The concentration stage involves recovery of the solvent/s, and may be performed under atmospheric conditions or under vacuum. The typical temperature utilized in the concentration stages are in the range of 30°C-60°C to avoid color formation and product loss in the invert sugar syrup through caramelization reactions.
The acid salt precipitate obtained in the neutralization step can be subjected to a regeneration process to recover the acid catalyst if desired, for recovery or reuse in the subsequent batches. Sulphuric acid (concentrated or dilute) can be employed as the hydrolytic agent in the recovery of the acid catalyst from the acid salt insoluble complex. Hydrolysis of the acid salt complex results in the recovery of the acid in its soluble form leaving calcium sulphate or any other insoluble acid salt complex as the insoluble precipitate. This solution of the acid may then be recycled as inversion catalyst in further inversion batches.
Example
In a typical example, inversion of sucrose to invert sugar syrup is performed in a baffled glass reactor equipped with a four-blade turbine agitator containing a homogenous solution of 35% w/v sucrose solution in a mixed solvent system with a chosen acid catalyst at a concentration of 0.001 gmoles/L to 0.05 gmoles/L, after being optionally treated to an initial clarification step consisting of decolorization and deioiniation. The acid catalyst chosen in the sugar inversion process may be one of strong mineral acids such as hydrochloric acid, sulphuric

acid, nitric acid and perchloric acid, or weak, monobasic acids such as acetic acid and oxalic acid, or dibasic acids and tribasic acids. The mixture of sugar and acid in a mixed solvent system is heated to the desired reaction temperature (in the range of 35°C-80°C) and the reaction carried till near complete conversion of 95%+ is attained. A calculated quantity of calcium carbonate is then added to the cooled reaction mixture, and neutralization of the acid monitored till the pH of the invert syrup attains a value between 5.0 and 5.5. The insoluble acid precipitate, if formed, is filtered and the resultant clear invert sugar syrup may be optionally subjected to a second step of deionisation and decolorization using metal chelating resins or any other means. Any change in pH is corrected to between 5.0-5.5. The invert sugar syrup is then concentrated under appropriate pressure (ImBar-lBar) at temperatures ranging from 30°C to 60°C, to the desired commercially specified concentration. The above preparation process can give an invert sugar syrup with any of the following specifications:
Table 1: Commercial Specifications for Different Grades of Invert Sugar Syrup

Parameters Bakery grade Pharma grade Special Intravenous
Colour Golden yellow (100+/- lOIC'USMA*) Off white (40+/- 10ICUSMA) Ciolden yellow (40 +/- 5 1CUSMA) Off white (30+-/-5ICI/SMA)
Total solids (wt%) 74 +/- 1.0 74 +/- 1.0 78.5 +/-0.5 74 +/- 0.3
Inversion (wt%) > 95% > 95% > 95% > 95%
Free sucrose (wt%) < 2-3 % < 2-3 % < 2-3 % < 2-3 %
Brix** 72.4 +/- 0.3% 72.4 )•/- 0.3% 76.4 +/- 0.3% 72.4 +/- 0.3%
pll 3.5 - 5.5 3.5-5.5 4.0 - 4.8 3.5-5.5
Specific gravity (20/20°C) 1.36 1.36 1.39 1.36
Ash content (wt%) <-0.2 <0.2 <0.15 <0.2
Solubility Water, glycerine, glycols Water, glycerine, glycols Water, glycerine, glycols Water, glycerine, glycols
*ICUSM A: Colour determination for sugar solutions can be represented as a? -logts'be As he
where Tx and As are the transmittancy and absorabancy as measured at 420nm, b is the cell length in cm and c
is the concentration of the total solids (g/cm3) and calculated from density. ICUSMA - as x 1000
** Brix: Degree Brix is the % by weight of sucrose in a pure sugar solution. But in the sugar industry it is usually considered to the he % by weight of solid matter or total solids, implying that the non-sucrose solids are of the specific gravity as cane sugar although this is true only of solutions of pure sugar.

CLAIMS We claim,
1. A reaction process for the manufacture of invert sugar from sucrose using strong mineral acid or weak organic acid in mixed solvents, with typical starting sucrose concentrations ranging between 5%w/v to 75%w/v, with preferred reaction temperatures being in the range of 35°C to 75°C, at any pressure, resulting in a product, the 'invert sugar syrup' having a total dissolved solid concentration of up to 75% w/v, comprising of >95% sugars as monosaccharides, and having a specific gravity of >1.35, and a Brix value >72%, and colour ranging from near colourless to pate, or golden yellow.
2. The process according to claim 1 wherein, the sucrose inversion is performed in a mixed solvent system that is composed of a homogenous solution of water and a non-aqueous organic solvent/s, in a ratio ranging from 1:10 to 10:1, with the solvent/s selected from the group of ethanol, methanol, isopropyl alcohol, dimethyl formamide, dimethyl sulfoxide, and acetone; as a single solvent or in any combination with each other.
3. process as claimed in claim 1 and claim 2, wherein the process uses an acid catalyst that is selected on the basis of its ability to form an insoluble or sparingly soluble salt with calcium, or any other metal, in mixed solvent systems/described claim 2( with the acid being selected from any of the mineral acids, or monobasic or polybasic organic acids.

4 A process as claimed in claim 1 claim ? and claim 3? therein the metal salt of acid is formed and removed from the product mixture after the reaction by simple filtration or any other solid-liquid separation operation to result in the product mix at pH between 5.0
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and 5.5, and enabling a possible recovery and/or regeneration of the acid catalyst and a possible subsequent reuse of the acid catalyst in subsequent batches.
5. That the mixed solvent 'process as claimed in claim 1 and claim 2 results in low-colour
formation during the hydrolysis reaction and yields invert sugar that can be concentrated
by distillation/removal of the solvent with lower energy requirement and at temperatures less than 100C (generally in the range from 30C to 60C) thereby resulting in decreased colour formation in the final product 'invert sugar' during concentration.



(Lali A. M) (Sunita V) (Lodha D. B)
Applicant Applicant Applicant

References
Barnes HM and Kaufman CW, 1947, Industrial aspects of browning reaction, Ind. Eng.
Chem. Vol 39. 1167-1170
• Gehlawat JK, 1991, Sugar cane: A cost effective source of invert syrups and high fructose syrups, J Sci Ind Res, Vol 50, 989-997
• Hodge JE, 1953, Chemistry of browning reactions in model systems, J. Agr. Food. Chem, Vol 1,928-943
• Imming R, Bliesener K and Buchholz K, 1994, The fundamental chemistry of colour formation in highly concentrated sucrose solutions, Zuckerind, Vol 11, 915-919
• Kurudis S and Mauch W, 1991, Studies for the calculation of the intensity of the browning reaction in sucrose containing model solutions, Zuckerind, Vol 116,261-265
• Monsan P and Combes D, 1984, Application of immobilized invertase to the continuous hydrolysis of a concentrated sucrose solution, Biotechnol and Bioeng, Vol 26, 347-354
• Moye CJ and Krzeminski ZS, 1962, The formation of 5-Hydroxymethylfurfural from Hexoses, Aust. J. Chem, Vol 16, 258-268
• Newton JM. and Wardip EK. (1974)"High Fructose Corm Syrup," in Symposium: Sweeteners, G.E.Inglett, Ed. (Westport, CT: AVI Publishing Company), pp.87-96
• Shallenberger J and Birch KT, 1975, Sugar Chemistry, The Avi Publishing Co. Inc. Wetport, Connecticut
• Vinnik MI, 1987, Catalytic action of acids in aqueous organic media, Kinetika I Kataliz, Vol 28 (English Transalation), 100-115