MODIFIED STARCHES-变性淀粉

MODIFIED STARCHES Prepared at the 57th JECFA (2001) and published in FNP 52 Add 9 (2001) superseding specifications prepared at the 35th JECFA (1989), published in FNP 49 (1990) and in FNP 52 Add 5 (1997). An ADI “not specified” was established at the 26th JECFA (1982) for all modified starches listed below except for acetylated oxidized starch for which an ADI "not specified" was established at the 57th JECFA (2001). Modified starches comprise the following: Dextrin roasted starch: INS No. 1400 Acid treated starch: INS No. 1401 Alkaline treated starch: INS No. 1402 Bleached starch: INS No. 1403 Oxidized starch: INS No. 1404 Enzyme-treated starch: INS No. 1405 Monostarch phosphate: INS No. 1410 Distarch phosphate: INS No. 1412 Phosphated distarch phosphate: INS No. 1413 Acetylated distarch phosphate: INS No. 1414 Starch acetate: INS No. 1420 Acetylated distarch adipate: INS No. 1422 Hydroxypropyl starch: INS No. 1440 Hydroxypropyl distarch phosphate: INS No. 1442 Starch sodium octenylsuccinate: INS No. 1450 Acetylated oxidized starch: INS No. 1451 DEFINITION Food starches which have one or more of their original characteristics altered by treatment in accordance with good manufacturing practice by one of the procedures listed in Table 1. In the case of starches treated with heat in the presence of acid or with alkali, the alteration is a minor fragmentation. When the starch is bleached, the change is essentially in the colour only. Oxidation involves the deliberate production of carboxyl groups. Acetylation results in substitution of hydroxyl groups with acetyl esters. Treatment with reagents such as orthophosphoric acid results in partial substitution in the 2, 3- or 6- position of the anhydroglucose unit unless the 6-position is occupied for branching. In cases of cross-linking, where a polyfunctional substituting agent, such as phosphorus oxychloride, connects two chains, the structure can be represented by: Starch-O-R-O-Starch, where R = cross-linking group and Starch refers to the linear and/or branched structure. The article of commerce can be specified by the parameter specific for the particular type of modification as indicated in Column 3 of Table 1, and may also be further specified as to the loss on drying, sulfated ash, protein and fat. C.A.S. number Starch acetate: 9045-28-7 Acetylated distarch adipate: 68130-14-3 Hydroxypropyl starch: 9049-76-7 Hydroxypropyl distarch phosphate: 53124-00-8 Acetylated oxidized starch: 68187-08-6 DESCRIPTION Most modified starches are white or off-white, odourless powders. According to the drying method these powders can consist of whole granules having the appearance of the original native starch, or aggregates consisting of a number of granules (pearl starch, starch-grits) or, if pregelatinized, of flakes, amorphous powder or coarse particles. FUNCTIONAL USES Thickener, stabilizer, binder, emulsifier CHARACTERISTICS IDENTIFICATION Solubility (Vol. 4) Insoluble in cold water (if not pregelatinized); forming typical colloidal solutions with viscous properties in hot water; insoluble in ethanol. Microscopy Passes test See description under TESTS Iodine stain Passes test See description under TESTS Copper reduction Passes test See description under TESTS Differentiation test Passes test for type of starch See description under TESTS for: 1. Hypochlorite oxidized starch 2. Specific reaction for acetyl groups 3. Positive test for ester groups PURITY Sulfur dioxide Not more than 50 mg/kg for modified cereal starches Not more than 10 mg/kg for other modified starches unless otherwise specified in Table I See description under TESTS Lead (Vol. 4) Not more than 2 mg/kg Determine using an atomic absorption technique appropriate to the specified level. The selection of sample size and method of sample preparation may be based on the principles of the method described in Volume 4, “Instrumental methods”. Additional purity specifications for individual chemically modified starches See column 3 of Table I See description under TESTS TESTS IDENTIFICATION TESTS Microscopy Modified starches which have not been pregelatinized retain their granular structure and can be identified as starches by microscopic observation. Shape, size and sometimes striations are characteristics of the botanical origin. In polarized light under cross nicol prisms the typical polarization cross will be observed Iodine stain Add a few drops of 0.1 N potassium tri-iodide to an aqueous suspension of the sample. These starches stain with iodine in the same way as native starches. The colour can range from dark blue to red Copper reduction Place about 2.5 g of the sample previously washed with water, in a boiling flask, add 10 ml of dilute hydrochloric acid (3%) and 70 ml of water, mix, reflux for about three hours and cool. Add 0.5 ml of the resulting solution to 5 ml of hot alkaline cupric tartrate TS. A copious red precipitate is produced Differentiation test To differentiate between various treated starches perform the following tests: 1. Test for hypochlorite-oxidized starch (not for slightly oxidized potato starch) Principle: Because of the carboxyl group content, hypochlorite-oxidized starch has anionic properties. It can be dyed with positively charged dyes such as methylene blue. Procedure: 50 mg of the sample are kept in suspension for 5-10 min in 25 ml of a 1% aqueous dye solution and stirred occasionally. After decantation of the excess solution, the starch is washed with distilled water. Microscopic inspection clearly shows colouring, if the sample is hypochlorite-oxidized starch. By this test hypochlorite-oxidized starch is distinguished from native and acid modified starch of the same botanical origin. 2. Specific reaction of acetyl groups Principle: Acetate is liberated upon saponification of acetylated starch. After concentration the acetate is converted to acetone by heating with calcium hydroxide. The acetone thus produced stains blue with o- nitrobenzaldehyde. Procedure: About 10 g of the sample is suspended in 25 ml water to which is added 20 ml of 0.4 N NaOH. After shaking for 1 h the starch is filtered off and the filtrate evaporated in an oven at 110º. The residue is dissolved in a few drops of water and transferred to a test tube. Add calcium hydroxide and heat the tube. If the sample is acetylated starch, acetone vapours are produced. These produce a blue colour on a paper strip soaked in a fresh saturated solution of o-nitrobenzaldehyde in 2 N NaOH. The blue colour is more distinct when the original yellow colour of the reagents is removed with 1 drop of a 1 in 10 solution of hydrochloric acid. 3. Positive test for ester groups The infrared spectrum of a thin film gives a typical absorption band at about 1720 cm-1 which is an indication for ester groups. The limit of detection is about 0.5% acetyl, adipyl or succinyl groups in the product. PURITY TESTS Sulfur dioxide Scope: The method is applicable, with minor modifications, to liquid or solid samples even in the presence of other volatile sulfur compounds. Principle: The sulfur dioxide is released from the sample in a boiling acid medium and is removed by a stream of carbon dioxide. The separated gas is collected in dilute hydrogen peroxide where it is oxidized to sulfuric acid and titrated with standard alkali. Alternatively, the sulfuric acid may be determined gravimetrically as barium sulfate. Apparatus: “Monier-Williams" apparatus for the determination of sulfurous acid, constructed with standard-taper glass connections, can be obtained from any reliable scientific glass apparatus store. It is customary, however, to construct the apparatus with regular laboratory glassware using stopper connections (see Figure 1). . Figure 1 The assembly consists of a 1000-ml two-neck round-bottom boiling flask to which a gas-inlet tube, a 60-ml dropping funnel having a 2-mm bore stopcock, and a sloping Allihn reflux condenser are attached. A delivery tube connects the upper end of the condenser to the bottom of a 250-ml conical receiving flask, which is followed by a Peligot tube. In operation, carbon dioxide is passed through the scrubber and bubbled through the heated reaction mixture, sweeping sulfur dioxide through the condenser and into the receivers where it is absorbed quantitatively. Preparation of solutions: Sodium carbonate solution: Dissolve approximately 15 g of Na2CO3 or 40 g of Na2CO3·10H2O in distilled water, and dilute to 100 ml. Hydrogen peroxide, 3%: Dilute 10 ml of C.P. (Chemical Purity) neutral 30% hydrogen peroxide (H2O2) with distilled water to 100 ml. Procedure: Pass carbon dioxide from a generator or cylinder through the sodium carbonate scrubber solution to remove chlorine, thence into the gas-inlet tube of the boiling flask. Place 15 ml of the 3% hydrogen peroxide in the receiving flask and 5 ml in the Peligot tube. Connect the apparatus and introduce into the boiling flask, by means of the dropping funnel, 300 ml of distilled water and 20 ml of concentrated hydrochloric acid. Boil the contents approximately 10 min in a current of carbon dioxide. Weigh, to the nearest g, 100 g of the sample and disperse in approximately 300 ml of recently-boiled distilled water. Transfer the slurry to the boiling flask by means of dropping funnel, regulating the sample addition rate and the gas flow rate through the apparatus to prevent drawback of hydrogen peroxide, inclusion of air, or burning of sample. Boil the mixture gently for 1 h in a slow current of carbon dioxide. Stop the flow of water in the condenser just before the end of the distillation. When the delivery tube just above the receiving flask becomes hot, remove the tube from the condenser immediately. Wash the delivery tube and the Peligot tube contents into the receiving flask, and titrate with 0.1 N sodium hydroxide, using bromphenol blue indicator (see Note). Perform a blank determination on the reagents, and correct results accordingly. in which S = ml of 0.1 N sodium hydroxide used for the sample B = ml of 0.1 N sodium hydroxide used for the blank W = the weight (in grams) of the sample. Note. A gravimetric determination may be made after titration. Acidify with HCl, precipitate with BaC12, settle, filter, wash, ignite, and weigh as BaSO4. Table 1. Additional purity specifications for individual chemically modified starches (All percentages calculated on dry substance) Modification Process limitations End-product specifications Dextrin roasted starch Dry heat treatment with hydrochloric acid or ortho- phosphoric acid Final pH 2.5-7.0 Acid treated starch Treatment with hydrochloric acid or ortho-phosphoric acid or sulfuric acid Final pH 4.8-7.0 Alkaline treated starch Treatment with sodium hydroxide or potassium hydroxide Final pH 5.0-7.5 Bleached starch Treatment with peracetic acid and/or hydrogen peroxide, or sodium hypochlorite or sodium chlorite, or sulfur dioxide or alternative permitted forms of sulfites, Added carbonyl group not more than 0.1% No residual reagent or potassium permanganate or ammonium persulfate Residual sulfur dioxide not more than 50 mg/kg Residual manganese not more than 50 mg/kg Enzyme-treated starch Treatment in an aqueous solution at a temperature below the gelatinization point with one or more food- grade amyolytic enzymes Residual sulfur dioxide not more than 50 mg/kg Oxidized starch Treatment with sodium hypochlorite Carboxyl groups not more than 1.1% Residual sulfur dioxide not more than 50 mg/kg Monostarch phosphate Esterification with ortho-phosphoric acid, or sodium or potassium ortho-phosphate, or sodium tripolyphosphate Phosphate calculated as phosphorus not more than 0.5% for potato or wheat, and not more than 0.4% for other starches Distarch phosphate Esterification with sodium trimetaphosphate or phosphorus oxychloride Phosphate calculated as phosphorus not more than 0.5% for potato and wheat, and not more than 0.4% for other starches Phosphated distarch phosphate Combination of treatments for Monostarch phosphate and Distarch phosphate Phosphate calculated as phosphorus not more than 0.5% for potato and wheat, and not more than 0.4% for other starches Acetylated distarch phosphate Esterification with sodium trimetaphosphate or phosphorus oxychloride combined with esterification with acetic anhydride or vinyl acetate Acetyl groups not more than 2.5%; phosphate calculated as phosphorus not more than 0.14% for potato and wheat, and 0.04% for other starches; and vinyl acetate not more than 0.1 mg/kg Starch acetate Esterification with acetic anhydride or vinyl acetate Acetyl groups not more than 2.5% Acetylated distarch adipate Esterification with acetic anhydride and adipic anhydride Acetyl groups not more than 2.5% and adipate groups not more than 0.135% Hydroxypropyl starch Esterification with propylene oxide Hydroxypropyl groups not more than 7.0%; propylene chlorohydrin not more than 1 mg/kg Hydroxypropyl distarch phosphate Esterification with sodium trimetaphosphate or phosphorus oxychloride combined with etherification by propylene oxide Hydroxypropyl groups not more than 7.0%; propylene chlorohydrin not more than 1 mg/kg; and residual phosphate calculated as phosphorus not more than 0.14% for potato and wheat, and not more than 0.04% for other starches Starch sodium octenylsuccinate Esterification with octenylsuccinic anhydride Octenylsuccinyl groups not more than 3%; and residual octenylsuccinic acid not more than 0.3% Acetylated oxidized starch Treatment with sodium hypochlorite followed by esterification with acetic anhydride Acetyl groups not more than 2.5 % and carboxyl groups not more than 1.1 % METHODS FOR ADDITIONAL PURITY SPECIFICATIONS pH (Vol. 4) As specified in Column 3 of Table 1 Suspend 20 g of the sample with 80 ml of water, and agitate continuously at a moderate rate for 5 min (In the case of pregelatinized starches, 3 g should be suspended in 97 ml of water). Carboxyl groups As specified in Column 3 of Table 1. Principle: The carboxyl containing starch is equilibrated with mineral acid to convert carboxyl salts to the acid form. Cations and excess acid are removed by washing with water. The washed sample is gelatinized in water and titrated with standard alkali. Note: Native phosphate groups present in potato starch increase the titre found in this method (See note 6) Reagents: Hydrochloric Acid Solution, 0.10 N : Standardization unnecessary Sodium Hydroxide Solution, 0.10 N : Standardized Phenolphthalein Indicator, 1% Procedure: If necessary, grind sample completely through a laboratory cutting mill to 20 mesh or finer, taking precautions to prevent any significant change in moisture, and mix thoroughly. Weigh accurately a sample containing not more than 0.25 milliequivalent of carboxyl (Note 1), and transfer quantitatively to a 150-ml beaker. Add 25 ml of 0.1 N hydrochloric acid and stir occasionally over a period of 30 min. Vacuum filter the slurry through a medium porosity fritted-glass crucible or small funnel, using a fine stream of water from a wash bottle to aid quantitative transfer of the sample. Wash the sample with distilled water (300 ml usually sufficient) until the filtrate is free from chloride determined by silver nitrate test (Note 2). Transfer the demineralized sample quantitatively to a 600-ml beaker with the aid of distilled water, and slurry the sample in 300 ml of distilled water. Heat sample dispersion in a steam bath or boiling water bath (Note 3), stirring continuously until the starch gelatinizes, and continue heating for 15 min to ensure complete gelatinization (Note 4). Remove sample from bath and titrate while hot with standard 0.10 N sodium hydroxide solution to a phenolphthalein end-point. The end-point may be detected electrometrically at pH 8.3. A blank determination is run on the original sample to correct for native acid substances (Note 5). Weigh the same quantity of starch as taken for carboxyl titration, and slurry in 10 ml of distilled water. Stir at about 5-min intervals for 30 min. Vacuum filter the slurry quantitatively through a medium porosity fritted- glass crucible or small funnel, and wash sample with 200 ml of distilled water. Transfer, gelatinize, and titrate the sample with standard 0.10 N sodium hydroxide in the same manner as the demineralized sample. Calculation: Notes and Precautions: Sample size should not exceed 5.0 g for a mildly oxidized or less than 0.15 g for a highly oxidized commercial starch. Add 1 ml of 1% aqueous silver nitrate solution to 5 ml of filtrate. Turbidity or precipitation occurs within 1 min if chloride is present. Heating on a hot plate or over a Bunsen burner is not recommended. Over-heating or scorching in amounts too small to be visible will cause sample decomposition and apparent high carboxyl results. Thorough gelatinization facilitates rapid titration and accurate end-point detection. A blank titration is run on a water washed sample to correct for acidic components which are not introduced by oxidation or derivatization. Free fatty acids complexed with amylose in common corn starch are the principal contributors to the blank titer. A correction for phosphate content in potato starch (deduction) should be made after determining the phosphorus content of the sample being examined. The deduction is calculated: where: P = phosphorus content (%) Manganese As specified in Column 3 of Table 1. Instrumentation: Atomic absorption spectrophotometer with manganese hollow cathode lamp. Preparation of solutions: Standard solution: Prepare a solution containing 0.5 mg/l of manganese. Sample solution: Transfer 10.000 g of the sample into a 200-ml Kohlrausch volumetric flask, previously rinsed with 0.5 N hydrochloric acid, add 140 ml of 0.5 N hydrochloric acid, and shake vigorously for 15 min, preferably with a mechanical shaker. Dilute to volume with 0.5 N hydrochloric acid, and shake. Centrifuge approximately 100 ml of the mixture in a heavy-walled centrifuge tube or bottle at 650xg for 5 min, and collect the supernatant liquid. This supernatant comprises the “sample solution”. Procedure: Follow manufacturer's instructions for operating the atomic absorption spectrophotometer and aspirate distilled water through the air-acetylene burner for 5 min to obtain a base-line reading at 279.5 nm. In the same manner aspirate a portion of the "Standard solution" and note the reading. Finally, aspirate the "Sample solution" and compare the reading with the reading for the "Standard solution", and multiply this value by 20 to obtain mg per kg of Mn in the original sample taken for analysis. Phosphorus As specified in the Column 3 of Table 1. Reagents: Ammonium Molybdate Solution (5%): Dissolve 50 g of ammonium molybdate tetrahydrate, (NH4)6Mo7O24·4H2O, in 900 ml of warm water, cool to room temperature, dilute to 1000 ml with water, and mix. Ammonium Vanadate Solution (0.25%): Dissolve 2.5 g of ammonium metavanadate, NH4VO3, in 600 ml of boiling water, cool to 60 - 70o, and add 20 ml of nitric acid. Cool to room temperature, dilute to 1000 ml with water, and mix. Zinc Acetate Solution (10%): Dissolve 120 g of zinc acetate dihydrate, Zn(C2H3O2)2·2H2O, in 880 ml of water, and fil