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{{Short description|Edible mixture of glucose and fructose, obtained from sucrose hydrolysis}}
{{Use mdy dates|date=January 2017}} 
{{chembox
| Name = Invert sugar 
| Watchedfields = changed
| ImageFileL1 = Alpha-D-Glucopyranose.svg
| ImageSizeL1 = 100
| ImageCaptionL1 = Glucose (α-{{sm|d}}-glucopyranose form)
| ImageClassL1 = skin-invert
| ImageFileR1 = Beta-D-Fructofuranose.svg
| ImageSizeR1 = 120
| ImageCaptionR1 = Fructose (β-{{sm|d}}-fructofuranose form)
| ImageClassR1 = skin-invert
| OtherNames = 
| IUPACName = 
| SystematicName = 
| Section1 = {{Chembox Identifiers
| CASNo = 8013-17-0
| CASNo_Ref = {{cascite|correct|CAS}}
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = ED959S6ACY
| ChEMBL = 1201647
| ChEMBL_Ref = {{ebicite|changed|EBI}}
| PubChem = 21924868
| ChemSpiderID = none}}
| Section2 = {{Chembox Properties
| MolarMass = 360.312 g/mol }}
| Section3 = 
| Section4 = 
| Section5 = 
| Section6 = {{Chembox Pharmacology
| ATCCode_prefix = C05
| ATCCode_suffix = BB03
}}
}}
[[File:Inverted sugar syrup (Trimoline).jpg|thumb|Dense inverted sugar syrup (Trimoline)]]

'''Inverted sugar syrup''' is a [[syrup]] [[mixture]] of the [[monosaccharide]]s [[glucose]] and [[fructose]], made by splitting [[disaccharide]] [[sucrose]]. This mixture's [[optical rotation]] is opposite to that of the original sugar, which is why it is called an ''invert'' sugar. Splitting is completed through [[hydrolytic]] [[saccharification]].

It is 1.3x [[Sweetness|sweeter]] than [[table sugar]],<ref>{{cite web|title= Making simple syrup is an exercise in chemical reactions |work= A Word from Carol Kroskey |url= http://www.bakers-exchange.com/articles/2000/april.html |access-date=May 1, 2006 |archive-url= https://web.archive.org/web/20070714004114/http://www.bakers-exchange.com/articles/2000/april.html |archive-date= July 14, 2007 |quote=In addition to increased moisture retention ability, converting sucrose to invert syrup has two other interesting results: increased sweetness and better solubility. On a sweetness scale where sucrose is set at 100, invert syrup ranks about 130.}}</ref> and foods that contain invert sugar retain moisture better and crystallize less easily than those that use table sugar instead. [[Baker]]s, who call it '''invert syrup''', may use it more than other [[sweeteners]].<ref>{{Cite book |first1=Hubert |last1=Schiweck |first2=Margaret |last2=Clarke |first3=Günter |last3=Pollack |chapter=Sugar |title=Ullmann's Encyclopedia of Industrial Chemistry |year=2007 |publisher=Wiley-VCH |location=Weinheim |doi=10.1002/14356007.a25_345.pub2 |isbn=978-3527306732 }}</ref>

Other names include '''invert sugar''',<ref>{{cite web |title=What are the types of sugar? |url=http://www.sugar.org/consumers/sweet_by_nature.asp?id=275 |url-status=dead |archive-url=https://web.archive.org/web/20090301033842/http://www.sugar.org/consumers/sweet_by_nature.asp?id=275 |archive-date=March 1, 2009 |publisher=The Sugar Association |df=mdy-all}}</ref> '''simple syrup''', '''sugar syrup''', '''sugar water''', '''bar syrup''', and '''sucrose inversion'''.

==Production==

===Additives===
Commercially prepared [[enzyme]]-catalyzed solutions are inverted at {{convert|60|°C|°F}}. The optimum pH for inversion is 5.0. [[Invertase]] is added at a rate of about 0.15% of the syrup's weight, and inversion time will be about 8 hours. When completed the syrup temperature is raised to inactivate the invertase, but the syrup is concentrated in a vacuum evaporator to preserve color.<ref name="Minifie">{{cite book |first=Bernard |last=W. Minifie |title=Chocolate, Cocoa and Confectionery: Science and Technology |date=1989 |publisher=Aspen Publishers, Inc. |isbn=083421301X |page=246 |edition=3rd |url= https://books.google.com/books?id=qdjh_W4uYS0C&pg=PA246 |access-date=July 3, 2014 |via=[[Google Books]] }}</ref>

Though inverted sugar syrup can be made by heating table sugar in water alone, the [[Chemical reaction|reaction]] can be sped up by adding [[lemon juice]],  [[cream of tartar]], or other [[Catalysis|catalyst]]s, often without changing the flavor noticeably.{{citation needed|date=April 2024}} Common sugar can be inverted quickly by mixing sugar and [[citric acid]] or [[cream of tartar]] at a ratio of about 1000:1 by weight and adding water. If [[lemon juice]], which is about five percent citric acid by weight, is used instead then the ratio becomes 50:1. Such a mixture, heated to {{convert|114|°C|°F}}<ref name="eddy.van.damme">{{cite web |url= http://www.chefeddy.com/2009/11/invert-sugar/ |title=Invert sugar recipe |first=Eddy |last=Van Damme |access-date=September 27, 2012 }}</ref> and added to another food, prevents crystallization without tasting sour.

Commercially prepared [[hydrochloric acid|hydrochloric-acid]] catalyzed solutions may be inverted at the relatively low temperature of {{convert|50|°C|°F}}. The optimum pH for acid-catalyzed inversion is 2.15. As the inversion temperature is increased, the inversion time decreases.<ref name="Minifie"/> They are then given a pH neutralization when the desired level of inversion is reached.<ref>{{cite book |editor1-first=Michael D. |editor1-last=Ranken |editor2-first=R.C. |editor2-last=Kill |editor3-first=C. |editor3-last=Baker |title=Food Industries Manual |date=1997 |publisher=Blackie Academic & Professional |location=London |isbn=0751404047 |pages=407–408 |edition=24th |url= https://books.google.com/books?id=iG3wx9Wh5N4C&pg=PA408 |access-date=June 30, 2014 |via=Google Books |quote=Commercially, invert sugar is prepared as a syrup of about 70% soluble solids concentration. Invert sugar can be produced by holding a 65% sucrose solution containing 0.25% hydrochloric acid at 50°C (122°F) for one hour. Sodium bicarbonate should then be added to neutralize the acid. }}</ref><ref name="sugar.beet">{{cite magazine |date=1904 |title=The Sugar Beet |url=https://books.google.com/books?id=tdrmAAAAMAAJ&pg=PA171 |access-date=July 4, 2014 |magazine=The Sugar Beet |publisher=H.C. Baird & Company |location=Philadelphia |pages=171–172 |via=Google Books |volume=25 |issue=10}}</ref>

In confectionery and [[Candy making#Sugar stages|candy making]], [[cream of tartar]] is commonly used as the acidulant, with typical amounts in the range of 0.15–0.25% of the sugar's weight.<ref>{{cite book |last1=Lean |first1=Michael E.J. |title=Fox and Cameron's Food Science, Nutrition & Health |date=2006 |publisher=CRC Press |location=Boca Raton, FL |isbn=9780340809488 |page=110 |edition=7th |url= https://books.google.com/books?id=wMX8769CSTAC&pg=PA110 |access-date=July 1, 2014 |via=Google Books }}</ref> The use of cream of tartar imparts a honey-like flavor to the syrup.<ref name="sugar.beet" /> After the inversion is completed, it may be neutralized with [[sodium bicarbonate|baking soda]] using a weight of 45% of the cream of tartar's weight.<ref>{{cite book |last1=Morrison |first1=Abraham Cressy |title=The Baking Powder Controversy |volume=1 |date=1904 |publisher=The American Baking Powder Association |location=New York |page=154 |url= https://books.google.com/books?id=Xc3VAAAAMAAJ&pg=PA154 |access-date=July 2, 2014 |via=Google Books |quote=The best cream of tarter baking powder on the market contains about 28 per cent of bicarbonate of soda.  To neutralize this quantity ... 62.6 per cent of cream of tartar is required.  This quantity will leave in the food 70 per cent of anhydrous Rochelle Salts. }}</ref><ref>{{cite book |editor1-first=Joseph A. |editor1-last=Maga |editor2-first=Anthony T. |editor2-last =Tu |title=Food Additive Toxicology |date=1995 |publisher=Marcel Dekker |location=New York |isbn=0824792459 |page=71, table 24 |url= https://books.google.com/books?id=6mGmxYqqiREC&pg=PA71 |access-date=July 3, 2014 |via=Google Books }}</ref>

===For fermentation===
{{main|Syrup#For fermentation}}

All constituent sugars (sucrose, glucose, and fructose) support [[fermentation]], so invert sugar solutions of any composition can be fermented.

Syrup is used to feed microbiological life, which requires oxygen found in the water. For example, [[kombucha]] is produced by fermenting inverted sugar syrup with [[tea]] using a ''[[symbiotic]] culture of bacteria and yeast'' ([[SCOBY]]), and [[yeast in winemaking]] is used for [[ethanol fermentation]]. Cold water can hold more dissolved oxygen than warm water, but granulated sugar does not dissolve easily in cold water.

Water in a container with wide bottom [[surface area]] allows for faster dissolving of the sucrose, which only has to be mixed a few times periodically to form a homogeneous solution. Also, a [[Mixer (appliance)|mixer]] or [[blender]] may be used to rotate the sugar, in turns, if necessary.

==In other foods and products==
{{see also|Free sugar}}
[[File:Cadbury-Creme-Egg-Whole-&-Split.jpg|thumb|right|Two [[Cadbury Creme Egg]]s, one opened to show the [[fondant]] filling, which uses inverted sugar syrup as a key ingredient]]
*[[Honey]] which is mostly a mixture of glucose and fructose, being similar to invert syrup therefore, can remain a liquid for longer periods of time.
*[[Fruit preserves|Jam]] contains invert sugar formed by the heating process and the acid content of the fruit. This sugar preserves the jam for long periods of time.
*[[Golden syrup]] is a syrup of about 55% invert syrup and 45% table sugar (sucrose).
*[[Fondant icing|Fondant]] filling for chocolates is unique in that the conversion enzyme is added, but not activated by acidification (microenvironment pH adjustment) or [[cofactor (biochemistry)|cofactor]] addition depending on the enzymes, before the filling is [[enrober|enrobed]] with chocolate.  The very viscous (and thus formable) filling then becomes less viscous with time, giving the creamy consistency desired. This results from the sub-optimal enzymes conditions purposely created by withholding activation factors, which allows only a fraction of the enzymes to be active, or allows all enzymes to proceed at only a fraction of the biological rate [biologically, it's realistically a combination of both: a reduced number of functional enzymes, with the ones that do function having reduced catalytic kinetics/rates].
*[[Cadbury Creme Egg]]s are filled with inverted sugar syrup produced by processing fondant with invertase.<ref>{{cite web |title=Creme Egg |url=https://www.cadbury.co.uk/products/Creme-Egg-2392?p=2392 |url-status=live |archive-url=https://web.archive.org/web/20141216222828/https://www.cadbury.co.uk/products/Creme-Egg-2392?p=2392 |archive-date=December 16, 2014 |access-date=April 10, 2015 |publisher=Cadbury}}</ref><ref>{{cite web |last=LaBau |first=Elizabeth |url=http://candy.about.com/od/candyglossary/g/What-Is-Invertase.htm |title=What is Invertase? |work=About.com |access-date=April 10, 2015 |archive-date=April 6, 2015 |archive-url=https://web.archive.org/web/20150406171447/http://candy.about.com/od/candyglossary/g/What-Is-Invertase.htm |url-status=dead }}</ref>
*[[Sour Patch Kids]] also contain inverted sugar to add sweet flavor.

===Sweetened beverages===
Inverted sugar syrup is the basis in [[sweetened beverage]]s.

* [[Sweet reserve]] is a [[wine]] term referring to a portion of selected [[Fermentation (wine)|unfermented]] grape [[must]], free of microorganisms, to be added to wine as a sweetening component. When wine ferments, glucose is fermented at a faster rate than fructose. Thus, arresting fermentation after a significant portion of the sugars have fermented results in a wine where the residual sugar consists mainly of fructose, while the use of sweet reserve will result in a wine where the sweetness comes from a mixture of glucose and fructose. 
* Alcoholic beverage manufacturers often add invert sugar in the production of drinks like gin, beer and sparkling wines for flavoring. [[Candi sugar]], similar to invert sugar, is used in the brewing of Belgian-style beers to boost alcohol content without drastically increasing the body of the beer; it is frequently found in the styles of beer known as [[dubbel]] and [[tripel]].<ref name="sugar.beet" />

==Chemistry==
{{more citations needed section|date=November 2019}}
Table sugar (sucrose) is converted to invert sugar by [[hydrolysis]]. Heating a mixture or [[Solution (chemistry)|solution]] of table sugar and water breaks the [[chemical bond]] that links together the two simple-sugar components.

The [[Chemical equation|balanced chemical equation]] for the hydrolysis of sucrose into glucose and fructose is:

:[[File:Sugar-inversion.png|left|500px]]{{clear left}}

:C<sub>12</sub>H<sub>22</sub>O<sub>11</sub> (sucrose) + H<sub>2</sub>O (water) → C<sub>6</sub>H<sub>12</sub>O<sub>6</sub> (glucose) + C<sub>6</sub>H<sub>12</sub>O<sub>6</sub> (fructose)

=== Optical rotation ===
Once a sucrose solution has had some of its sucrose turned into glucose and fructose the solution is no longer said to be pure. The gradual decrease in purity of a sucrose solution as it is hydrolyzed affects a [[chemical property]] of the solution called [[optical rotation]] that can be used to figure out how much of the sucrose has been hydrolyzed and therefore whether the solution has been inverted or not.

==== Definition and measurement ====
[[Polarization (waves)#Plane waves|Plane polarized light]] can be shone through a sucrose solution as it is heated up for hydrolysis. Such light has an 'angle' that can be measured using a tool called a [[polarimeter]]. When such light is shone through a solution of pure sucrose it comes out the other side with a different angle than when it entered, which is proportional to both the concentration of the sugar and the length of the path of light through the solution; its angle is therefore said to be 'rotated' and how many degrees the angle has changed (the degree of its rotation or its 'optical rotation') is given a letter name, <math>\alpha</math> (alpha). When the rotation between the angle the light has when it enters and when it exits is in the clockwise direction, the light is said to be 'rotated right' and <math>\alpha</math> is given to have a ''positive'' angle such as 64°. When the rotation between the angle the light has when it enters and when it exits is in the counterclockwise direction, the light is said to be 'rotated left' and <math>\alpha</math> is given a ''negative'' angle such as −39°.

==== Definition of the inversion point ====
When plane polarized light enters and exits a solution of ''pure'' sucrose its angle is rotated 66.5° (clockwise or to the right). As the sucrose is heated up and hydrolyzed the amount of glucose and fructose in the mixture increases and the optical rotation decreases. After <math>\alpha</math> passes zero and becomes a negative optical rotation, meaning that the rotation between the angle the light has when it enters and when it exits is in the counter clockwise direction, it is said that the optical rotation has 'inverted' its direction. This leads to the definition of an 'inversion point' as the per cent amount sucrose that has to be hydrolyzed before <math>\alpha</math> equals zero. Any solution which has passed the inversion point (and therefore has a negative value of <math>\alpha</math>) is said to be 'inverted'.

==== Chirality and specific rotation ====
As the [[Chemical structure|shapes of the molecules]] ('chemical structures') of sucrose, glucose, and fructose are all [[Asymmetry|asymmetrical]] the three sugars come in several different forms, called [[stereoisomers]]. The existence of these forms is what gives rise to these chemicals' optical properties. When plane polarized light passes through a pure solution of one of these ''forms'' of one of the sugars it is thought to hit and 'glance off' certain asymmetrical [[chemical bond]]s within the molecule of that form of that sugar. Because those particular bonds (which in [[Cyclic compound|cyclic sugars]] like sucrose, glucose, and fructose include an [[Anomer|anomeric bond]]) are different in each form of the sugar, each form rotates the light to a different degree.

When any one form of a sugar is purified and put in water, it rapidly takes other forms of the same sugar. This means that a solution of a pure sugar normally has all of its stereoisomers present in the solution in different amounts which usually do not change much. This has an [[Mutarotation|'averaging' effect]] on all of the optical rotation angles (<math>\alpha</math> values) of the different forms of the sugar and leads to the pure sugar solution having its own 'total' optical rotation, which is called its 'specific rotation' or 'observed specific rotation' and which is written as <math>[\alpha]</math>.

In the circumstance of 20&nbsp;°C, the specific optical rotation of sucrose is known to be 66.6°, glucose is 52.2°, and fructose is −92.4°.<ref>{{cite journal | pmc=7867249 | year=2021 | last1=Li | first1=D. | last2=Weng | first2=C. | last3=Ruan | first3=Y. | last4=Li | first4=K. | last5=Cai | first5=G. | last6=Song | first6=C. | last7=Lin | first7=Q. | title=An Optical Chiral Sensor Based on Weak Measurement for the Real-Time Monitoring of Sucrose Hydrolysis | journal=Sensors (Basel, Switzerland) | volume=21 | issue=3 | page=1003 | doi=10.3390/s21031003 | pmid=33540721 | bibcode=2021Senso..21.1003L | doi-access=free }}</ref>

==== Effects of water ====
Water molecules do not have [[Chirality (chemistry)|chirality]], therefore they do not have any effect on the measurement of optical rotation. When plane polarized light enters a body of pure water its angle is no different from when it exits. Thus, for water, <math>[\alpha]</math> = 0°. Chemicals that, like water, have specific rotations that equal zero degrees are called 'optically inactive' chemicals and like water, they do not need to be considered when calculating optical rotation, outside of the concentration and path length.

==== Mixtures in general ====
The overall optical rotation of a mixture of chemicals can be calculated if the proportion of the amount of each chemical in the solution is known. If there are <math>N</math>-many optically active different chemicals ('[[chemical species]]') in a solution and the [[molar concentration]] (the number of [[Mole (unit)|moles]] of each chemical per [[Litre|liter]] of liquid solution) of each chemical in the solution is known and written as <math>C_i</math> (where <math>i</math> is a number used to identify the chemical species); and if each species has a specific rotation (the optical rotation of that chemical were it made as a pure solution) written as <math>[\alpha]_i</math>, then the mixture has the overall optical rotation<math display="block">\displaystyle \alpha = \frac{\sum_{i=1}^N C_i [\alpha]_i}{\sum_{i=1}^N C_i} = \sum_{i=1}^N \left(\frac{C_i}{\sum_{i=1}^N C_i}\right)[\alpha]_i = \sum_{i=1}^N \chi_i[\alpha]_i</math>Where <math>\chi_i</math> is the [[mole fraction]] of the <math>i \mathrm{^{th}}</math> species.

==== Fully hydrolyzed sucrose ====
Assuming no extra chemical products are formed by accident (that is, there are no [[side reaction]]s) a completely hydrolyzed sucrose solution no longer has any sucrose and is a half-and-half mixture of glucose and fructose. This solution has the optical rotation
<math display="block">\displaystyle \alpha = \frac{1}{2}[\alpha]_{\text{glucose}} + \frac{1}{2}[\alpha]_{\text{fructose}} = \frac{1}{2}(52.7^\circ - 92.0^\circ) = -19.7^\circ</math>

==== Partly hydrolyzed sucrose ====
If a sucrose solution has been partly hydrolyzed, then it contains sucrose, glucose and fructose and its optical rotation angle depends on the relative amounts of each for the solution;<math display="block">\displaystyle \alpha = \chi_s[\alpha]_s +\chi_g[\alpha]_g +\chi_f[\alpha]_f</math>Where <math>s</math>, <math>g</math>, and <math>f</math> stand for sucrose, glucose, and fructose.

The particular values of <math>\chi</math> do not need to be known to make use of this equation as the inversion point (per cent amount of sucrose that must be hydrolyzed before the solution is inverted) can be calculated from the specific rotation angles of the pure sugars. The reaction [[stoichiometry]] (the fact that hydrolyzing one sucrose molecule makes one glucose molecule and one fructose molecule) shows that when a solution begins with <math>x_0</math> [[Mole (unit)|moles]] of sucrose and no glucose nor fructose and <math>x</math> [[Mole (unit)|moles]] of sucrose are then hydrolyzed the resulting solution has <math>x_0-x</math> moles of sucrose, <math>x</math> moles of glucose and <math>x</math> moles of fructose. The total number of moles of sugars in the solution is therefore <math>x+x_0</math>and the [[Reaction progress kinetic analysis|reaction progress]] (per cent completion of the hydrolysis reaction) equals <math>\frac{x}{x_0} \times 100 \%</math>. It can be shown that the solution's optical rotation angle is a [[Function (mathematics)|function]] of (explicitly depends on) this per cent reaction progress. When the quantity <math>\frac{x}{x_0}</math> is written as <math>r</math> and the reaction is <math>r \times 100\%</math> done, the optical rotation angle is
<math display="block">\displaystyle \alpha_{r} = \frac{(x_0-x)[\alpha]_s +x[\alpha]_g +x[\alpha]_f}{x_0 + x} = \frac{1}{1 + r}\left([\alpha]_s +  ([\alpha]_g + [\alpha]_f - [\alpha]_s) r\right) </math>

By definition, <math>\alpha</math> equals zero degrees at the 'inversion point'; to find the inversion point, therefore, alpha is set equal to zero and the equation is manipulated to find <math>r</math>. This gives<math display="block">\displaystyle r_{\text{inversion}} = \frac{[\alpha]_s}{[\alpha]_s - [\alpha]_g - [\alpha]_f} = 0.629 </math>Thus it is found that a sucrose solution is inverted once at least <math>62.9 \%</math> of the sucrose has been hydrolyzed into glucose and fructose.

==== Monitoring reaction progress ====
Holding a sucrose solution at temperatures of {{convert|50|-|60|°C|°F}} hydrolyzes no more than about 85% of its sucrose. Finding <math>\alpha</math> when r = 0.85 shows that the optical rotation of the solution after hydrolysis is done is −12.7° this reaction is said to invert the sugar because its final optical rotation is less than zero. A polarimeter can be used to figure out when the inversion is done by detecting whether the optical rotation of the solution at an earlier time in its hydrolysis reaction equals −12.7°.

==See also==
* [[High fructose corn syrup|High-fructose corn syrup]]
* [[List of syrups]]

==References==
{{Reflist|30em}}

==External links==
{{sister project links|b=Cookbook:Simple Syrup|d=Q412082|c=Category:Inverted sugar syrup|n=no|q=no|wikt=simple syrup|s=no|m=no|mw=no|species=no|v=no}}
*{{cite web |title=Invertase |url=http://greenwoodhealth.net/np/invertase.htm |website=Greenwood Health Systems |access-date=November 27, 2012 |archive-date=May 29, 2017 |archive-url=https://web.archive.org/web/20170529133633/http://greenwoodhealth.net/np/invertase.htm |url-status=dead }}

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[[Category:Brewing ingredients]]
[[Category:Monosaccharides]]
[[Category:Food science]]
[[Category:Types of sugar]]
[[Category:Syrup]]