Carbohydrates

1. Carbohydrates • Pectins • Starches • Sweeteners

2. Sensory characteristic • Taste • Color (Maillard browning reaction, caramelization) • Flavor ( products of Maillard reaction)

3. Preservation • High sugar content (syrups) • Fermentation (conversion of sugar to ethanol or lactic acid)

4. Functional • tenderizer • bulking agent • fat substitute • to entrap flavours and enzymes • texturizer • humectant • leavening agent

5. Functional Properties of Sugars

6. Structural • Cellulose • Hemicelluloses • Pectins • Starches

7. Storage • Starches • Glycogen

8. Classification • Simple sugars (hexoses, pentoses) • Oligosaccharides (sucrose, maltose, lactose, flatulence-causing sugars: raffinose, stachyose, verbascose) • Polysaccharides=complex carbohydra-tes (heteropolysaccharides: pectins, vegetables gums, homopolysacchari- des: cellulose, starches, glycogen)

9. Sugars Monosaccharides (glucose, fructose, galactose) Disaccharides (sucrose, maltose, lactose) Trisaccharides (raffinose) Tetrasaccharides (stachyose) Pentasaccharides (verbascose) Glucose Fructose

10. Simple sugars D-ribose D-arabinose D-xylose D-glucose D-mannose D-gulose D-galactose D-fructose

11. Oligosaccharides sucrose sucrose maltose lactose raffinose

12. Homopolysaccharides

13. Hemicelluloses and b-glucan b-glucan xylan arabinoxylan

14. Sugars in Fruits and Berries

15. Pectins A complex, high molecular weight polysaccha- ride mainly consisting of the partial methyl esters of polygalacturonic acid and their so- dium, potassium, and ammonium salts. In some types (amidated pectins) galacturonamide units occur in polysaccharide chain. The product is obtained by aqueous extraction of appropriate plant material usually citrus fruits and apples)

16. Pectin content [% • Potato 2.5 • Tomato 3 • Apple 5 - 7 • Apple pomace 15 - 20 • Carrot 10 • Sunflower heads 25 • Sugar beets pulp 15 - 20 • Citrus albedo 30 - 35

19. Pectic substances • Protopectins - highly esterified pectic substances, insoluble in water. • Pectinic acids - Less highly esterified pectic substances. Also known as pectins. Form colloidal dispersions or are water soluble. • Pectic acids - Pectic substances with 0% degree esterification

20. Enzymes • Protopectinase • Pectin esterase or pectase or pectin methyl esterase (deesterifying) • Polygalacturonase (depolymerizing)

23. Pectins • Pectin grades are the number of part of sugar required to gel one part of pectin to acceptable firmness. • The degree of esterification (DE) is defined as the ratio of esterified galacturonic acid to total galacturonic acid units in pectin molecule.

24. Pectins • High-Ester Pectins DE >50% • Rapid set pectins DE - 70-75% • Slow set pectins DE 55-65% • Low-Ester Pectins DE<50% • Rapid set pectins 25-35% • Slow set pectins 35-45%

26. High-Ester Pectins • Increase of DE leads to higher gel setting temperature and setting rate. • Decrease of pH leads to increase in gelling temperature and setting rate. Commercial pectins do not gel at pH>4.0. Normal application conditions usually require a pH around 3.0. • Increase in sugar content leads to increase in gelling temperature and setting rate. Practical working range is between 55 and 80%. Above 80% setting occurs at boiling point. Below 55% no gel formation.

27. High-ester pectins

28. Low-Ester Pectins • Optimum gels may be obtained at pH 3.0-3.5, but excellent gels may be obtained at higher pH by increasing the pectin dosage or calcium level • Calcium increases the gel strength, but to high levels of calcium lead to gels with syneresis • Increasing the amount of solids leads to less brittle gel and reduced syneresi tendency but increases setting temperature. • Unlike high ester pectins, low-ester pectin gels weaken with increasing temperature and will usually melt when temperature is 5-10C above the setting temperature

29. Low-ester pectins

30. Starches

31. Native Starches- Problems • The lack of free flowing properties or water repellency of starch granules • insolubility or failure of granules to swell and develop viscosity in cold water • excess or uncontrolled viscosity upon cooking • cohesive or rubbery texture of cooked starches • the sensitivity of cooked starches to breakdown during extended cooking when expose to shear or low pH • the lack of clarity and the tendency of starch sols to become opaque.

32. Modified Starches • Cross-linking • Stabilization • Pre-gelatinization • Oxidation • Conversion • Cyclization

33. Crosslinked/Inhibited starches • Reinforces the natural H-bonds, • Retards the rate of granule to swell • Reduces sensitivity of swollen granules to rupture • Adds greater stability to heat and prolonged cooking, • Adds stability to agitation • Improves stability to damage from hydrolysis. • Modified starch pastes are unclear.

34. Crosslinked starches are obtained by : • Reacting starch (dry or aqueous suspension) with difunctional agents such as phosphorus oxychloride, adipic acid anhydride, or epichlorohydrin. • These agents are capable of reacting with hydroxyl groups of two different molecules in granule.

36. Inhibited starches are used as: • Thickener or stabilizers in: • baby foods, cream-style corn, fruit pie fillings.

37. Stabilization of starches • By introduction of constituent groups on hydroxyl groups: • Distorts linearity • Interrupts association through steric hindrance

38. Stabilization of starches reduces their tendency • to gel • to lose hydrating ability and clarity on storage at low temperatures • lower gelatinization temperature of starch • this treatment is often used in combination with cross linking

40. Examples of stabilized starches • Starch phosphate monoesters are obtained by heating a dry mixture of starch and acid salts of ortho-, pyro- or tripolyposphate at 50-60 for 1 hr. • This process lower gelatinization temperature, improves swelling in cold water, increases paste viscosity and clarity, lower tendency of starch to gel and retrograde.

41. Example of stabilized starches • Hydroxyethyl starches ethers (starch + ethylene ether at 50 C) • lower gelatinization temperature • lower the tendency of starch pastes to gel and retrograde. • Uses: salad dressings, pie fillings, other food thickening applications

42. Pregelatinization • Done by simultaneous cooking at temperatures below gelatinization and drying starches on hot drums or in spray dryers. • Pregelatinized starches can swell in cold water

43. Oxidation • Done by treatment of starches with chlorine or sodium hypochlorite • lower viscosity • decrease tendency of amylose to retrograde • sols have intermediate viscosities and form a soft gels.

44. Conversion • These are thin boiling starches and are prepared by mild acid acid treatment of aqueous starch suspensions. • This treatment reduces viscosity • These starches can be used at much higher concentrations • most common use - manufacture of gum candies - cooked at high sugar concentrations to form strong gels

45. Other modified starches • Lipophylic substitutions • Hydrophobic starches • Schandinger dextrins also known as cyclodextrins. Cyclodextrins may contain from 6-10 glucose units. They are obtained from starches by the action of Bacillus macerans amylase.

47. Starch selection • Marketing/formulation requirements • Production requirements

48. Marketing/formulation requirements: • Product properties: structural, aesthetics, organoleptic, shelf stability • Product form: dry, semimoist, liquid • Utilization: ready-to-eat, requires additional preparation • Economics • Legality

49. Production requirements: • Physical abuses: temperature, shear (agitation) • Chemical abuses: pH, oxidation

50. Product may take one of the following forms: • Gelled • Flowable • Expanded • Rigid • Rubbery