Chemistry and Functional Properties of Carbohydrates and Sugars (Monosaccharides, Disaccharides, and Polysaccharides) - Sweeteners: Nutritional Aspects, Applications, and Production Technology - page 32

(cross-linking),alkalinegelatinization,orcertaincombinationsofthesetreatments.Thetwomajor
groups of chemically modiied starches are cross-linked and substituted (derivatized) starches.
Modiiedfoodstarchesareusuallyproducedaswhiteornearlywhite,tasteless,odorlesspowders,
asintactgranules,and,ifpregelatinized,aslakes,amorphouspowders,orcoarseparticles.They
areinsolubleinethanol,andifnotpregelatinized,theyarepracticallyinsolubleincoldwater(Lee
1975;PenieldandCampbell1990;Wurzburg1995).
Manymodiiedstarchesareonthemarket,butthosemostcommonlyusedinthefoodindus-
tryarethethinboilingtypes.Theyaretheresultofpartialhydrolysisofthestarch,usuallyusing
H 2 SO 4 orotheracids.Beforedrying,starchslurryistreatedwith0.1NH 2 SO 4 at50°Cfor6-24h.
Hydrolysisofsomeofthebondsinthestarchresultsinaproductthatwilldisperseinboilingwater
toyieldadispersionwithaviscositynotmuchgreaterthanwater.Themoreextensivethemodiica-
tionofthestarch,thegreatertheeffectonloweringviscosity(Meyer1987).
Starch syrups :Starchisalsousedinsweetcommodityproductsinaliquidformassyrup.Starch
syrupsareusedtoimpartsweettasteinfoods;theydonotcrystallizeeasily,theyretardsucrose
crystallization,andtheyactassofteningagents.
Theyarepreparedfromstarch,whichundergoespartialhydrolysis(withhydrochloricacidand/
ortheenzymeamylase)inordertoachievethedesiredproperties(Figure2.23).Hydrolysisisnot
complete,andthesyrupsareamixtureofglucose,maltose,andlongerchainsofglucoseunits.For
differentapplications,starchsyrupssubjectedtoextensive(softsyrups)andnonextensivehydrolysis
(hardsyrups)areavailablecommercially.Theextentofhydrolysisofastarchsyrupismeasured
intermsofitsdextroseequivalent(DE),whichisanestimateofthepercentageofreducingsugars
(small molecular weight) present in the total starch product. The DE is deined as the reducing
power,measuredinaspeciicwayandcalculatedasdextrose,expressedasapercentageofthedry
substance.ProductsofparticularlyhighDEareobtainedbyenzymeconversion.Thewiderange
ofstarchsyrupsstartswiththosewithaDEvalueof10-20(maltodextrins)andendswiththose
with a DE value of 96, while by deinition, the DE of dextrose is 100. High DE syrups contain

Starch slurry

α-Amylase Liquefaction

Maltodextrin

Glucoamylase/pullulanase

Saccharification

Maltose syrups

Purification

Glucose syrups

Mixed syrups

Glucose/isomerase Isomerization

Refining

Fructose syrups

Figure 2.23 Major steps in enzymatic starch conversion. (Adapted from Olsen, H. S., Enzymic Production of

Glucose Syrups , Chapman & Hall, London, 1995.)