Chemistry and Functional Properties of Carbohydrates and Sugars (Monosaccharides, Disaccharides, and Polysaccharides) - Sweeteners: Nutritional Aspects, Applications, and Production Technology - page 40

DuringMaillardreactions,theaminogroupreactswithsugartoformcondensationproducts,
which act as autocatalysts for further reactions such as enolization reaction, Amadori rearrange-
ment,anddehydration.Thepresenceofcarbonylcomponentsisnecessaryintheirsttwotypesand
attheirststageofthethirdtype.Theinalproductsofthesereactionsarebrownpigments,which
arecalledmelaninsormelanoidins.TherateoftheMaillardreactionsisinluencedbythetempera-
ture, pH, the type and concentration of reducing sugar and amino compound, the water activity,
andthepresenceofmetalions.TheMaillardreactionsarefavoredbyintermediatehumidity(aw=
0.6-0.8).TheacidsinhibitorpreventtheMaillardreactionsbecausetheyinactivatethefreeamino
groupsofaminoacids,peptides,andproteinsbyformingsaltswiththem.Thebasesincreasethe
reactionbecausetheyreleaseaminogroupsthatareprobablyinactivatedinasaltform.Blocking
ofthereactioncanbecausedbychemicalmeans,forexample,withNaHSO 3 ,whichreactswiththe
carbonylgroupofthereducingsugars.Thestudyofparametersaffectingthereactionisveryuseful
forthedesignofmanyfoodproducts(especiallydehydratedandintermediatemoistureones)and
thedeterminationoftheirpreservation(Coultate2002).
2.9 CarBOhYDrate MetaBOLISM—hUMaN NeeDS IN CarBOhYDrateS
Thecarbohydratesduringmetabolismarehydrolyzedbyenzymesoracidstoglucose,whichis
neededforthephysiologicaloperationsofthebody.Duringchewing,foodismixedwithsalivary
amylase,sostarchisbrokendowninsmallextenttomaltose.Afterswallowing,foodreachesthe
stomach,whereitisbeingacidiied,andthedegradationofstarchcontinuesbythepancreaticamy-
lases.Afterthecompletionofdigestion,themacromolecularcomponents,havingbeenbrokendown
intosmallercomponents,canbeabsorbedbythebodythroughtheintestinalwalls,somonosaccha-
ridespassthroughthebloodvesselsoftheintestinalwallandleadtotheliver,whilethenondigest-
iblecomponents(iber)areremovedfromtheintestine(GamanandSherrington1990).
Thenondigestivecarbohydratesconsistmainlyofnonstarchpolysaccharides,resistantstarch,
andnondigestiveoligosaccharides.Carbohydratesprovidethebodywithenergy(4kcal/g).Along
with fat, they cover most of the energy needs of the human body. A normal diet should contain
10%ofcarbohydrates.Theminimumdailyrequiredamountofcarbohydrateis40g.Thecalories
obtained from carbohydrates should be 55%-65%, and the indicative daily requirement is 300-
400 g.Bothlackandexcessiveconsumptionofcarbohydratescancauseadverseeffectsonthebody,
suchaslackofglucoseorobesity(BeMiller2007).
2.10 aLterNatIVe SUGarS—SWeeteNerS
Alternativesugarsarefoodconstituentsoradditivesusedtosubstitutesugarandduplicateits
effectintaste,usuallywithlessenergyintake.Theyarederivedfromtherequirementsofreduc-
ing sucrose in the diet of diabetics, avoiding risks connected with obesity or overweight caused
by the excessive caloric intake and reactive hypoglycemia, and preventing dental caries. These
substances can either be carbohydrates or carbohydrate derivatives [glucose, fructose, l-sugars,
invertsugarsyrup,polyols(lactitol,maltitol,mannitol,sorbitol,xylitol)]ornoncarbohydratesub-
stances(aspartame,acesulfame-K,cyclamate,saccharin,stevioside,thaumatin,etc.).Theycanalso
be categorized as nutritive and nonnutritive sweeteners. Nonnutritive sweeteners are usually not
carbohydrate-basedandthereforehavedifferentchemicalandphysicalproperties.Theyalsooften
havelavorcharacteristicsthatdifferfromthoseofcarbohydratesweetenersandareintenselysweet
comparedwithcarbohydratesweeteners(SalminenandHallikainen2002).
Themainalternativesugarsarethefollowing.