TEKNOLOGI PENGOLAHAN DAN PENGAWETAN PANGAN (TPG 630) Dr. Ir. Sugiyono, M.AppSc. Departemen Ilmu dan Teknologi Pangan Fateta IPB Kampus IPB Darmaga PO Box 220 Bogor Telp/Fax

Starch  Complex carbohydrate made up of two components  Components: –Amylose –Amylopectin  Properties depend on amounts of the components

Sources  Roots/Tubers –Potato –Arrowroot –Cassava –Sweet potato  Cereal –Corn –Waxy corn –Wheat –Rice –Waxy rice

Starch vs Flour  Starch is obtained from extraction with water, e.g. tapioca, corn starch, etc.  Flour is produced by milling process, e.g. wheat flour, rice flour, etc. wheat flour, rice flour, etc.

Amylose  Linear component of starch  Contains 1,4- alpha-glucosidic bonds  Molecular weight: less than 0.5 million  Can form coils which will trap iodine and turn blue

Amylopectin  Branched component of starch  Contains 1,4-alpha- glucosidic as well as 1,6-alpha-glucosidic bonds  Molecular weight: million  Limited coiling causes purplish-red color when iodine added

Amylose vs. Amylopectin  Starches usually contain more amylopectin than amylose  Generally roots/tubers contain more amylopectin than cereals  Roots/tubers: 80% amylopectin  Cereals: 75% amylopectin  Waxy corn and rice contain virtually all amylopectin

Starch Composition

Starch Granule  Made in the cytoplasm of plant cells  Amylopectin forms in concentric circles with amylose dispersed in between  Held together by hydrogen bonds  The granule swells when heated in water

Starch Granule

Functions  Gelatinization –Structure in baked products –Thickener in sauces, soups, and dressings  Dextrinization  Gelation –Pie filling

Gelatinization  When starch is heated in water  Hydrogen bonds break, allowing water to enter the granule and the granule swells  Amylose migrates out of the granule  H-bonding between water and amylopectin increases  Reduced free water changes the viscosity of the starch mixture, thickening it

Gelatinization and Temperature  Gradually thicken with temperature  Can be heated to 100 o C without much granule rupture  If held at 95 o C will implode and lose viscosity

Gelatinization and Type of Starch  Best thickening ability: potato starch  Worst thickening ability: wheat starch  More amylopectin=more translucent=more stringy

Viscosity and Type of Starch

Gelatinization and Sugar  Used together in pie fillings and puddings  Sugar competes with the starch for water so less water available for gelatinization  Delays gelatinization and decreases viscosity  Increases gelatinization temperature  The more sugar added, the longer the delay  Disaccharides have a stronger effect than monosaccharides

Gelatinization and Acid  Used together in fruit pie fillings, specifically lemon fillings  Acid breaks down starch molecules so the paste is thinner  Decreases viscosity  Acid effect can be minimized by adding after gelatinization or heating rapidly

Gelation  As a starch paste cools, a gel is formed  Free amylose molecules lose energy as the temperature decreases and form hydrogen bonds  The bonds create a network that holds the swelled granules in place

Gelation and Starch Source  The more amylopectin (less amylose), the softer the gel  Potato starch=high amylopectin=good thickening agent=soft gel  Corn starch=less amylopectin=less effective thickening agent=strong gel

Gelation and Other Effects  Heating –Moderate temperature and rate of heating –Enough amylose needs to be released from the granule without the granule bursting  Agitation –Agitation during cooling disrupts amylose network –Should mix flavorings immediately after removing from heat

Gelation and Other Effects  Sugar –Decreases gelatinization and amylose release –Softer gel  Acid –Decreases gelatinization by hydrolysis of granules –Softer gel

Aging Gels  Syneresis –Loss of water from a gel –Amylose molecules pull together, squeezing water out  Retrogradation –Realignment of amylose molecules –Hydrogen bonds break and reform into more orderly crystals –Can by reversed by gently heating –Examples: refrigerated pudding, stale bread

Dextrinization  When starch is heated without water  A higher temperature is reached than with water  Bonds break throughout the starch forming dextrins

Genetically-modified Starches  Waxy starch –High in amylopectin –Used in fruit pies because thickens well, but does not gel well –Have good freeze-thaw stability  High amylose starch –Amylose creates strong bonds to form strong gels –Used in edible films to coat food

Starch Characterization  Line spread test: –Measures thickening power –Poor heated starch into cylinder, lift cylinder and measure spread after specified time using concentric circles  Universal Texture Analyzer: –Measures gel strength  Percent sag: –Measures gel strength –Measure molded gel height and compare to unmolded gel height –Stronger gel=small % sag, weaker gel=large % sag

Modified Starches  Physically or chemically modifying native starches  Are used for specific applications in the food industry, Why?  Native starches have undesirable qualities: –Poor processing tolerance to heat, shear and acid –Poor textures –Do not store, hold, and freeze/thaw well

Starch Modification 1.Acid hydrolysis 2.Cross linking 3.Oxidation 4.Substitution 5.Pre-gelatinization 6.Hydrothermal treatment

- meningkatkan kejernihan gel / pasta - dpt dilakukan dg cara kering atau basah - asam : -

Acid hydrolysis (Acid Thinning) or Thin-Boiling Starches  Process : dry or wet using HCl, H 2 SO 4 HCl, H 2 SO 4  Use: –Pass freely through pipes  Acid-hydrolyzed starch –Hydrolyzes 1,6-alpha-glucosidic bonds –Amylopectin in smaller pieces –Decreases thickening power, but makes a strong gel because hydrogen bonds form more readily –Increases clarity of gel –Used in candy products

Cross linking -cross links between hydroxyl ends of two starch molecules in a starch granule - use acetic anhydride, succinic anhydride, or ethylene oxide, phosphorus chloride, sodium trimetaphosphate, epichlorohydrin, etc, -Wet and alkali conditions - pH, temperature, and process duration affect cross linking process

Cross-linked Starch  Use: –Increases storage time because of reduced retrogradation –More stable at high temperature, with agitation, and with acid addition –Salad dressings, baby foods, pie fillings  Cross-linked starch molecules –Alter hydroxyl ends under alkaline conditions by acetic anhydride, succinic anhydride, or ethylene oxide

-Example : 2 StOH + Na 3 P 3 O 9 StO-P-OSt + Na 2 H 2 P 2 O 7 Catalist : NaOH, Na 2 CO 3, Ca(OH) 2 Catalist O ONa

Cross linked Starches  Vary in degree of cross linking  May be double modified – substituted starches  Reduce elasticity found in native starches  More tolerant to high shear in processing  Less effected by acid, sugar  More resistant to heat  Not easily swell  High viscosity

Cross Linked Starch Degree of cross linkingApplication Lightly cross linkedNeutral and slightly acidic foods Medium cross linked High acid foods;delay gelation for some canned foods; foods stored at low temperature; Highly cross linkedHigh shear, high temperature

Viscosity and Cross-linked Starches

Oxidation (Bleaching) - Uses hydrogen peroxide, perasetic acid, ammonium persulphate, sodium hypochlorite - Wet conditions - Pigment and hydroxyl oxidation - Pigment and hydroxyl oxidation -More whiteness -Not easily retrograde -Softer gel

Pre-gelatinized Starches  Use: –Instant pudding  Dehydrated gelatinized starch –Heated so granule swells and then dehydrated –Swells when water added, no heat necessary –Decreases preparation time –Physical change

Substitution -changes hydroxyl groups with other functional groups

Example : hydroxypropylatin using propylene oxide propylene oxide St - OH + CH 2 – CH – CH 3 St – OCH 2 OH - O CH – CH 3 OH

Substituted Starches  Starch esters –Acetate Starch –Starch phosphate –Succinylated  Starch ethers –carboxy methyl starch –hydroxyl propyl starch

Substituted Starches  Made from starch in granule form  Low level subsitution interupts linearity and – –retards retrogradation, –increase water binding capacity, –lowers gelation temperature, –introduction of hydrophobic groups impart emulsification properties –Alters clarity

Acetate starch Class: Substituted starch  Acetylated starch. Granular starch ester with a CH 3 CO-group introduced  Improves paste stability and clarity.  The acetate groups act as pegs on the amylopectin chains to reduce or prevent retrogradation. Acetate starches are used in chilled or frozen preparations such as icecream cheesecakes etc.  The level of acetelation can be altered to tailor the properties.

Phosphate starch  There are two classes of phosphate starches.  Substituted starch phosphate esters. eg. monostarch phosphate. –Similar in function to starch acetate. The phosphates act as pegs to prevent retrogradation. – Improves paste stability and clarity  Crosslinked starch esters. Crosslinks starch chains to stabilize viscosity and reduce shear thinning.

Succinylated starch  This is a substituted starch ester  Retards retrogradation  Increases hydrophobicity and can assist in emulsification

Substituted starch ether  General term for three classes of starch ether substitution are: – Anionic (Carboxy methyl starches), –cationic (Quaternery ammonium) and –Non-Ionic (Hydroxy alkyl starches).

Substituted starch ether (cont)  Substituted starch ethers have improved clarity, better resistance to retrogradaion and improved viscosity  The substituted starch ethers (carboxy methyl starch and hydroxyl propyl starch) are generally preferred as they offer improved functionality compared with the substituted starch esters (starch acetate and monostarch phosphates). Crosslinked hydroxyl-propyl starches are among the most functional of the food grade modified starches.

Hydroxypropyl starch.  The hydroxyl-propyl groups act as pegs to prevent retrogradation.  Similar to the starch acetates above but the substituted group is larger,

Substituted or Cross Linked?  Crosslinking protects against high shear, acid processing and prolonged heating. It depends on the food or other use, processing conditions and the cost of the modified starch.  Most modified starches are BOTH crosslinked and substituted, It is the level of each of these processes that is used to adjust functionality. The levels of both crosslinking and substitution are adjusted depending on end use.

Hydrothermal Treatment : -Annealing : dilakukan dengan mengkondisikan pati pada kadar air tinggi kemudian dipanaskan pada suhu di bawah titik gelatinisasi -Annealing : dilakukan dengan mengkondisikan pati pada kadar air tinggi kemudian dipanaskan pada suhu di bawah titik gelatinisasi - Heat moisture treatment (HMT) : dilakukan dengan cara memanaskan pati di atas titik gelatinisasinya pada kadar air yang terbatas (kurang dari 35%). - Heat moisture treatment (HMT) : dilakukan dengan cara memanaskan pati di atas titik gelatinisasinya pada kadar air yang terbatas (kurang dari 35%).

Resistant Starch  Small intestine is unable to digest, limited digestion in large intestine  Classifications –RS1: trapped in cells (seeds/legumes) –RS2: native starch (raw potatoes, bananas, waxy maize) –RS3: crystalline, non-granular starch (cooked potatoes) –RS4: chemically modified  Can contribute fiber to food without the fat that bran has  Takes up less water than other fiber, making dough less sticky  Smooth even texture  Less than 3 cal/g

Glucose / Fructose Syrup from Starches Glucose / Fructose Syrup from Starches - hydrolysis using acid, acid – enzyme, or enzyme –enzyme enzyme –enzymeStarch Glucose syrup Fructose syrup  -,  -amylase, glucoamylase Glucose isomerase

Glucose Production Process EmulsionCornstarch Convert Glucoamylase Add in Clean and Dry Filter Discolor Ion exchange Inspissation Crystallization and separation Glucose 53