Potato Processing

Potato Processing

1. 5/6/2017
1
Potato Processing
Md rahmatuzzaman Rana
Assistant Professor, Dept of FET, SUST
•Semi-perishable, contains approx 80% water
•Under tropical and sub-tropical conditions 40-50 % lossesoccur due
to poor handling and storage.
•Processing of potatoes is advantageous, because it reduce bulkiness
and increase shelf-life.
•Potatoes are processed into-
1.friedproducts such as wafers/chips etc.;
2.dehydratedproducts such as dice etc.
3.Frozen products such as French fries, patties, puffs, dice etc.
4.Canned.
Md rahmatuzzaman Rana
Assistant Professor, Dept of FET, SUST

2. 5/6/2017
2
Consideration in potato processing
1.Specific gravity:
High:chips, French fries. Due to higher yield, low uptake of fat/oil, low
mc need to be removed.
Low: Canning. Cause firm piece is desirable.
But!!! too high (1.106) is not suitable for French fries, chips because of
biscuit like hardness and hard chips.
Measured by-
a)brine solution of known sp. Gravity
b)Hydrometer
c)Archimedes principle
d)Variable load hydrometer
e)Ordinary scale
Md rahmatuzzaman Rana
Assistant Professor, Dept of FET, SUST
Consideration in potato processing
2.Dry matter:
Important because of its high yield of potato chips or wafers, and
texture of chips and reconstituted dried products.
Measured by-
a)Oven drying but non-destructive method
Md rahmatuzzaman Rana
Assistant Professor, Dept of FET, SUST

3. 5/6/2017
3
Consideration in potato processing
3.Sugar content
Sugarcontentinfluencesthecoloroftheprocessedproducts.
Highglucose,fructosecontainingpotatoesarenotsuitableforchipsand
Frenchfriesbecauseofthereactionbetweenreducingsugarandamino
acidandcausesdiscoloration
Generally,freshlyharvestedmaturepotatoescontainacceptablelevelof
reducingsugarbutwhenstoredatlowtemperature(-5oC)sugarcontent
increase.
Ontheotherhand,whenstoredatambienttemperaturethensugar
contentarenotincreasedthatmuchbutsproutingandweightlossare
excessive.
Md rahmatuzzaman Rana
Assistant Professor, Dept of FET, SUST
Consideration in potato processing
3.Sugar content
Sugarcontentinfluencesthecoloroftheprocessedproducts.
Highglucose,fructosecontainingpotatoesarenotsuitableforchipsand
Frenchfriesbecauseofthereactionbetweenreducingsugarandaminoacid
andcausesdiscoloration
Generally,freshlyharvestedmaturepotatoescontainacceptablelevelof
reducingsugarbutwhenstoredatlowtemperature(-5oC)sugarcontent
increase.
Ontheotherhand,whenstoredatambienttemperaturethensugarcontent
arenotincreasedthatmuchbutsproutingandweightlossareexcessive.
Evaporativecooledstoragesystemhasstillsimilarchangeinsugarcontent
andproblemswithlowerweightlossbutstillsproutingproblemremained.
Md rahmatuzzaman Rana
Assistant Professor, Dept of FET, SUST

4. 5/6/2017
4
Consideration in potato processing
3.Sugar content
ToovercometheseproblemspotatoesareoftentreatedwithCIPC
(Isopropyl-N-chlorophenylcarbamate)andstoredatlowtemperature.
Butunderthisconditionpotatoesareunfitforprocessingwithinshort
period.
Reconditioning:coldstoredpotatoesarestoredat15-20oCfor2-3weeks
andreductioninsugarcontenttakeplace.
Toovercomeunacceptablecolorproblem,chipsoftenfriedatlower
temperaturebutitcontain30%moreoilthannormalcondition.
Discolorationduetosugarcontentiscopeupbyselectionofrightvariety
whichaccumulateslesssugarcontent.
Md rahmatuzzaman Rana
Assistant Professor, Dept of FET, SUST
Consideration in potato processing
4.Discoloration
Problemsaffectingappearanceandacceptability.
Potatoesandpotatoproductsareproneto3typesofdiscoloration-
a.Enzymaticdiscoloration:PPOenzymeactsonpolyphenolcontentin
presenceofairandoxygen.
Exclusionofoxygenandair:inactivatingenzymewithheatorlowering
thepH;treatthewholepotatowithSO2gasandstored;highconc.of
CO2alsocanbeused.
Potashfertilizeroftenusedonfieldtoovercomeenzymaticdiscoloration
butstilllowdrymatercontentproblemmayoccur.
Chemicalslikesulfiteoftenusethoughithashealthhazardproblemsesp.
forasthmaticpatient.
Md rahmatuzzaman Rana
Assistant Professor, Dept of FET, SUST

5. 5/6/2017
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Consideration in potato processing
4.Discoloration
b.Aftercookingdiscoloration:Nonenzymaticbrowningreactiontakeplaceathigh
temperatures.
Ithappenduetotheformationofdarkcoloredcomplexofferricironand
phenoliccompound.
Factorssuchasironcontent,organicacid,phenoliccompoundsandpHislessin
immaturethanmaturetubers.
Darkeningcanbepreventedifthepotatoinsolutionisacidicthannormal
condition.
Organicacidsuchasasparticacidaffectsdiscolorationaftercookingattributedto
pHorabilitytochelateiron.Themorecitricacidlessercontentofdarkening.
Thisproblemswithdifferentvarietiescanbeovercomebystoringathigh
temepratureorbyreconditioningat3035oCfortwoweeks.
Md rahmatuzzaman Rana
Assistant Professor, Dept of FET, SUST
Consideration in potato processing
4.Discoloration
b.Discolorationoffriedanddehydratedproducts:highsugar
contentanddiscoloredduringdehydrationandtoturndarkduring
storage.
i.Fermentation:excessquantityofsugarscanbefermentedtolactic
acidbyLactobacillusplantarum.
ii.Washingrawslicesinwater:50%oftheRSand40%offreeAAare
removed.
Md rahmatuzzaman Rana
Assistant Professor, Dept of FET, SUST

6. 5/6/2017
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Consideration in potato processing
5.Peeling
Idealpeelingoperationshouldonlyremoveaverythinouterlayer
ofthepotato,leavingnoeyes,blemishes,orothermaterialfor
laterremovalbyhandtrimming.Itshouldnotsignificantlychange
thephysicalorchemicalcharacteristicsoftheremainingtissue.
Theeffectivenessofpeelingdeterminetheyieldoffinished
product,theamountofwaste,andcostofwastedisposal.
Md rahmatuzzaman Rana
Assistant Professor, Dept of FET, SUST
Consideration in potato processing
5.Peeling
A.Abrasive peeler: designed to uniformly contact the surface of
tubers with abrasive discs or rollers so that, while peeling, the
losses are minimum.
The peel fragments are flushed out by water sprays.
Works best with uniform size of tubers.
Suitable for chips/wafers, since other peeling processes which use
heat, give a coated layer of tissue, or a visible heat ring.
Md rahmatuzzaman Rana
Assistant Professor, Dept of FET, SUST

7. 5/6/2017
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Consideration in potato processing
5.Peeling
B.Lye peeling: NaOH solution is used at a high temperature, i.e. 160 oFor
lower temperature, i.e. 120-160 oF.
Potaoesmay be preheated for a short period of time in water at
temperature ranging from 140-190 oF. This minimize cooling effect and
help to maintain uniform temperature.
Use of low temperature reduces the heat ring or cooked surface layer on
peeled potato.
Lye peeling softens the surface of the potato and the color changes to
deep yellow due to reaction of the lye with potato constituents.
After lye peeling, potatoes are washed to remove lye solution.
Md rahmatuzzaman Rana
Assistant Professor, Dept of FET, SUST
Consideration in potato processing
5.Peeling
C.Brine peeling: Brine solution maintained near boiling or saturation
points.
However, evaporation of water happen continuously hence it is necessary
to prevent over saturation and crystallization.
Immersion time: 3-10 minutes.
D.Steam peeling: High pressure steam for short time.
Hydrates potatoes and soften surface tissue and loosen the peel. The
softened tissue removed by brushes or water sprays.
This method leaves heat ring on outer surface which is not objectionable
for many products exception in chips/wafers.
Md rahmatuzzaman Rana
Assistant Professor, Dept of FET, SUST

8. 5/6/2017
8
Consideration in potato processing
5.Peeling
C.Brine peeling: Brine solution maintained near boiling or saturation
points.
However, evaporation of water happen continuously hence it is necessary
to prevent over saturation and crystallization.
Immersion time: 3-10 minutes.
D.Steam peeling: High pressure steam for short time.
Hydrates potatoes and soften surface tissue and loosen the peel. The
softened tissue removed by brushes or water sprays.
This method leaves heat ring on outer surface which is not objectionable
for many products exception in chips/wafers.
Md rahmatuzzaman Rana
Assistant Professor, Dept of FET, SUST
The potato verities criteria for processing
1)High degree of maturity, round or oval shape, medium to large
with fleet eyes, and free from diseases.
2)Long dormancy
3)High sp. Gravity and dry matter content.
4)Low sugar content
5)Free from after cooking discoloration
6)Low peeling losses.
Md rahmatuzzaman Rana
Assistant Professor, Dept of FET, SUST

9. 5/6/2017
9
Processing of potato chips/wafers
Potatoes (fully mature)
Washing
Sorting
(Removal of defective and small tubers)
Peeling (abrasive)
Trimming
(Removal of residual skin, discolored
area, green portion)
Slicing
(1/5 to 1/25 inch thick slices by rotary
slicer)
Drying
(Optional process may be done by drum
dryer)
Frying
(In continuous or batch type fryers using
refined oil)
Salting and addition of flavoring
(immediate after frying)
Cooling and inspection
Packaging and storage
Md rahmatuzzaman Rana
Assistant Professor, Dept of FET, SUST
•Also look for processing of French fries.
Md rahmatuzzaman Rana
Assistant Professor, Dept of FET, SUST