Chemistry Reference
In-Depth Information
Apples
received
Washing,
drying
Quality
control
Apples
grinding
Juice
filtration
Pulp
pressing
Pasteurization
Centrifugation
Aromatic
substances
recovery
Tanks
Filtration
Evaporation
Freezing,
canning
Natural juice
Figure 7.5
Flow diagram of apple juice manufacture.
The main constituents of fruit juices are sugars; inorganic salts and other elements, such as
potassium, calcium, sodium, phosphorous, chlorine, and iron; and vitamins such as vitamins A,
B,C,andD.Thequalityofjuiceisdirectlyrelatedtothequalityofrawmaterials,i.e.,thenatural
juicesthatwillbeaddedtotheinalproduct.Factorsaffectingthequalityofthenaturaljuicesare
thefollowing:
•
Ratioofsugarstoacids,wherethestarchofunripefruitsduringmaturationisbrokendowntoglu-
cose,which,inconjunctionwithothersolublesugarssuchasfructoseandsaccharose,arerespon-
sibleforthesweettaste.
•
Organic acids of fruits, such as citric acid (citrus fruits), tartaric acid (grapes), and malic acid
(apples),whichhaveahighconcentrationwhentheyareunripeandfalldownduringmaturityin
balancewithsugars.
•
Pectinsubstances,whereprotopectinsduringfruitmaturationconvertintosolublepectins,which
affectthetextureofleshandfruitprocessing.
•
Phenolicsubstances,suchastanninsandcoloringagents,thataffectcolorandtaste.
•
Aromatic compounds, such as alcohols, esters, aldehydes, and ketones, which consist of a large
number of volatile compounds (in trace quantities, they contribute in the formation of the inal
aromaofjuices).
•
Proteinsintraceamounts,causingproblemsinjuiceclarity.
7.4.2 Manufacturing
Harvestingofmaturefruitswithagoodbalanceofsugarsandacidsisfollowedbysamplingfor
qualitycontrol,washingtoremoveimpuritiesandpesticideresidues,andmashingtoremovethe
pulp.Thisbreakingcolonizescellularstructureandbringsenzymes(phenoloxidases)incontact
withtheirsubstrate,causing,withtheeffectofoxygen,theenzymicbrowning.Juicecomesoutof
pressing,mistyandmuddy,andthenisilteredwiththeadditionofgelatin,albumin,orenzymes.
PackagingiscarriedoutinTetraPakmachinesaseptically.
7.4.3 preservation and Storage
Pasteurizationiscarriedoutat93°Cfor30s,whichdestructspathogenicmicroorganismsand
inactivates enzymes. Another preservation method is the addition of benzoic acid (antibacterial),
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