STARCHES

• Food Source and Kind of Starches

  • corn
  • tapioca (cassava)
  • potato
  • rice
  • wheat
  • Other
• Starch is a solid carbohydrate that is granular in form and naturally present in many plants such as grains (wheat or rice), pulses (corn), tubers (potatoes), and numerous other plant species
• Native starch


  Originally derived from its plant source; a powder obtained from plants containing starch
• Modified starch


  Has structures altered by treatment with physical or chemical agents; also called starch derivatives, are prepared by physically, enzymatically, or chemically treating native starch to change its properties
• Slowly Digested Starch (Amylose)


  Contains 500 to 20,000 molecules of glucose connected together in a straight chain that twists into a helix and then two chains bond together, forming a structure that resists the digestive enzymes trying to break the glucose molecules apart
• Rapidly Digested Starch (Amylopectin)


  Significantly larger than amylose, with a structure made up of millions of glucose molecules that branch out and form a crystalline structure. Its glucose units are easily cleaved during digestion, which makes it a rapidly digestible starch
• Resistant Starch (RS)


  Any starch or starch digestion products that are not digested and absorbed in the stomach or small intestine and pass on to the large intestine
• Categories of Resistant Starch

  • RS1 - Physically inaccessible or undigestible resistant starch
  • RS2 - Resistant starch is inaccessible to enzymes due to starch conformation
  • RS3 - Resistant starch that is formed when starch-containing foods are cooked and cooled
  • RS4 - Starches that have been chemically modified to resist digestion
• Types of Starches


  • Cornstarch
  • Tapioca Starch
  • Potato Starch
  • Sweet White Rice Flour
  • Arrowroot Starch
• Cornstarch


  • Has a neutral flavor as long as it has been fully cooked
  • Can withstand low-acid fat
  • Does not work well with acidic ingredients
  • The best choice for thickening dairy-based sauces
• Potato Starch


  • Has a neutral flavor
  • Provides a balance of structure and tenderness in gluten free baked goods
  • Replace 1 tablespoon cornstarch with 1.5 tablespoons potato starch
  • Sauces thickened with potato starch should never be boiled
• Tapioca Starch


  • Has a neutral flavor
  • Provides elasticity and structure in gluten-free baking
  • Helps baked goods develop a golden brown crust
  • Thickens quickly at a relatively low temperature
• Sweet White Rice Flour

  • Has a neutral rice-like flavor
  • Can replace wheat flour in a 1:1 ratio for thickening
  • Cannot be used as a replacement for white rice flour
  • Acts as a strong binder in gluten-free baked goods
• Production of Starch


  1. Starch is an end product of photosynthesis

  2. Starch is synthesized in special cell plastids of plants and is intended as the energy reserve for the germination of new plants

  3. Glucose molecules polymerize or combine into two basic structures: amylose (linear glucose chain) and amylopectin (highly branched chain)

  4. Starch has significant value for humans as the main carbohydrate source in diet and as a renewable raw material for industries
• Biosynthesis of starch involves converting glucose-1-phosphate to ADP-glucose using the enzyme glucose-1-phosphate adenylyl transferase, then adding the ADP-glucose via a 1,4-alpha glycosidic bond to a growing chain of glucose residues to create amylose, and finally introducing 1,6-alpha glycosidic bonds between the amylose chains to create the branched amylopectin
• Amylose


  Linear, helical chains of roughly 500 to 20,000 alpha-D-glucose monomers linked together through alpha (1-4) glycosidic bonds
• Amylopectin


  A branched-chain polysaccharide composed of glucose units linked primarily by a-1,4-glycosidic bonds but with occasional α-1,6-glycosidic bonds, which are responsible for the branching
• Amylose


  Starch molecule composed of 500 to 20,000 alpha-D-glucose monomers linked together through alpha (1-4) glycosidic bonds; has spiral structure that contains six glucose units per turn due to hydrogen bonding
• Amylopectin


  Branched-chain polysaccharide composed of glucose units linked primarily by a-1,4-glycosidic bonds but with occasional α-1,6-glycosidic bonds, which are responsible for the branching; a molecule may contain many thousands of glucose units with branch points occurring about every 25-30 units, major polymer in most starches with 70-85% in non-waxy starches and 100% in waxy(malagkit) varieties
• Starch granule structure


  1. Granule swelling

  2. Crystallite or double helical melting

  3. Amylose leaching
• Complete gelatinization


  • Loss of birefringence
  • Increase in viscosity
  • Increase in clarity
• Gelation


  Cooling process of formation of a gel from a system with polymers; branched polymer materials form linkages (hydrogen bonding) between branches which leads to the formation of large polymer networks
• Retrogradation


  Process where disaggregated amylose chains begin to (re)associate by hydrogen bonding into an ordered 3-dimensional structure; amylose retrogradation is considered complete by the time the product has been cooled to room temperature
• Syneresis


  Expulsion of moisture from the gel; leaking of water from the gel which occurs in all kinds of gel such as puddings, jellies, gelatin, agar
• Dextrinization


  Also known as pyroconversion, it involves the heat treatment of a dried starch with or without adding acid leading to the structural modification of starch; reduces the larger starch molecules into smaller dextrin molecules
• Enzyme reaction


  Most commonly used enzymes include a-amylases, ẞ-amylases, and glucoamylases; a-amylase is an endo-amylase responsible for the initial hydrolysis of starch granules to soluble products; glucoamylase is an exo-amylase that can hydrolyze both alpha (1-4) and alpha (1-6) linkages
• Amylopectin molecules increase the tendency to form strong and stable gels, but will be softer than high amylose gels while longer amylose molecules will form a stiff gel
• Pure amylopectin starches do not gel upon cooling but remains a paste; its retrogradation is due to the association with its outer branches, occurs much more slowly and can happen at low storage freezing temperatures; example is the staling of bread wherein the crumb becomes firm and fall easily and crust dries up
• Scanning electron micrographs of starches separated from different sources: rice, wheat, potato, and maize
• Photomicrographs of native starches observed in an optical microscope: cassava, sweet potato, Peruvian carrot, and potato
• ₂OH


  Chemical formula for water
• H OH


  Chemical formula for water
• Dextrin


  Partially hydrolyzed starches that are prepared by dry roasting starch
• Dextrin


  • Have sweet taste and nutty flavor
  • Readily soluble in water and gels have lower solubility
  • Less susceptible to lumping
• Hydrolysis


  1. Occurs during cooking (prolonged heating), processing or storage

  2. The breaking up of the glycosidic bonds that join the glucose molecules using acids and enzymes (amylase) catalysts
• POLVORON COOKIES
• Enzyme reaction


  Most commonly used in the industry include a-amylases, ẞ-amylases, and glucoamylases
• Alpha-Amylase


  An endo-amylase responsible for the initial hydrolysis of starch granules to soluble products; act on alpha (1-4) linkages of amylose and amylopectin, but cannot cleave the branched alpha (1-6) linkages; release linear short chain dextrans, oligosachharides, maltose and glucose
• Glucoamylase


  Also known as amyloglucosidase; an exo-amylase that can hydrolyze both alpha (1-4) and alpha (1-6) linkages; works on non-reducing endings of the polysaccharide and releases glucose units
• Starch


  Polymer of glucose