Corn Syrup
(korn sir' up).
[8029-43-4].
DEFINITION
Corn Syrup is an aqueous solution of saccharides obtained by partial hydrolysis of edible corn starch by food grade acids and/or enzymes. It contains NLT 20.0% reducing sugar content (dextrose equivalent) expressed as d-glucose, calculated on the dried basis.
IDENTIFICATION
•  A.
Analysis:  Add a few drops of a solution of Syrup (1 in 20) to 5 mL of hot, alkaline cupric tartrate TS.
Acceptance criteria:  A copious, red precipitate of cuprous oxide is formed.
ASSAY
•  Reducing Sugars (Dextrose Equivalent)
Apparatus:  Mount a ring support on a ring stand 1–2 inches above a gas burner, and mount a second ring 6–7 inches above the first. Place 6-inch open-wire gauze on the lower ring to support a 250-mL conical flask, and place a 4-inch watch glass with a center hole on the upper ring to deflect heat. Attach a 25-mL buret to the ring stand so that the tip just passes through the watch glass centered above the flask. Place an indirectly lighted white surface behind the assembly for observing the endpoint.
Standard solution:  6 mg/mL of USP Dextrose RS
Sample solution:  10 mg/mL of Corn Syrup
Analysis:  Transfer 25.0-mL portions of alkaline cupric tartrate TS to each of two flasks, and boil. Immediately place one flask on the wire gauze of the Apparatus, and adjust the burner so that the boiling point is reached in about 2 min. Titrate with the Standard solution to within 0.5 mL of the anticipated endpoint. Heat the flask, with swirling, boil moderately for 2 min, and add 2 drops of methylene blue solution (1 in 100). Immediately add 2 drops of the Standard solution from the buret, and bring to a boil. Allow the cuprous oxide to settle slightly, and observe the color of the supernatant. Complete the titration within 1 min by adding the Standard solution dropwise, and boil after each addition to the disappearance of the blue color, as determined by viewing against a white background in daylight or under equivalent illumination. If more than 0.5 mL of the titrant is required after the addition of the indicator, repeat the titration, adding the necessary volume of titrant before adding the indicator. Bring the contents of the second flask to a boil, and similarly titrate with the Sample solution.
Calculate the percentage of reducing sugars as d-glucose, calculated on the dried basis, in the portion of Corn Syrup taken:
Result = (CS/CU) × (VS/VU) × [1/(0.01 × A)] × 100
CS== concentration of USP Dextrose RS in the Standard solution (mg/mL)
CU== concentration of Corn Syrup in the Sample solution (mg/mL)
VS== titrated volume of the Standard solution (mL)
VU== titrated volume of the Sample solution (mL)
A== percentage of dry solids in Corn Syrup measured by the refractive index
Acceptance criteria:  NLT 20.0% reducing sugar content on the dried basis
IMPURITIES
•  Residue on Ignition 281: NMT 0.5%, determined on 20 g of Corn Syrup
•  Heavy Metals, Method II 231: NMT 5 ppm
•  Limit of Lead
[Note—For the preparation of all aqueous solutions and for the rinsing of glassware before use, use water that has been passed through a strong-acid, strong-base, mixed-bed ion-exchange resin. For digestion, use acid-cleaned, high-density polyethylene, polypropylene, polytef, or quartz tubes. Select all reagents to have as low a content of lead as practicable, and store all reagent solutions in borosilicate glass containers. Cleanse glassware before use by soaking in warm 8 N nitric acid for 30 min and rinsing with deionized water. Store final diluted solutions in acid-cleaned plastic or polytef tubes or bottles. ]
Modifier solution:  200 mg/mL of magnesium nitrate. Just before use, transfer 1.0 mL of this solution to a 10-mL volumetric flask, and dilute with 5% nitric acid to volume.
Standard stock solution:  Transfer 10.0 mL of Lead Nitrate Stock Solution, prepared as directed in Heavy Metals 231, to a 100-mL volumetric flask, add 40 mL of water and 5 mL of nitric acid, and dilute with water to volume. Transfer 1.0 mL of this solution to a second 100-mL volumetric flask, dilute with 5% nitric acid to volume, and mix. This solution contains 0.1 µg/mL of lead.
Standard solutions:  Transfer portions of Standard stock solution to four suitable containers, and dilute with 5% nitric acid to obtain Standard solutions having lead concentrations of 100, 50, 25, and 10 ng/mL, respectively.
Sample solution:  [Note—Perform this procedure in a fume hood. ] Transfer 1.5 g of Corn Syrup to a digestion tube, and add 0.75 mL of nitric acid to the tube. Warm the solution slowly (to avoid spattering) to 90–95. Heat until all brown vapors have dissipated and any rust-colored tint has disappeared from the tube (20–30 min). Cool, add 0.5 mL of 50% hydrogen peroxide, dropwise, to the solution, heat to 90–95 for 5 min, and cool. Add a second 0.5-mL portion of 50% hydrogen peroxide dropwise to the solution, and heat to 90–100 until clear (5–10 min). Cool and transfer the solution to a 10-mL volumetric flask. Rinse the digestion tube with 5% nitric acid, add the rinse to the volumetric flask, dilute with 5% nitric acid to volume, and mix.
Standard blank:  5% nitric acid
Sample blank:  Transfer 1.5 g of water to a digestion tube, and proceed as directed for the Sample solution, beginning with “add 0.75 mL of nitric acid”.
Instrumental conditions 
Mode:  Graphite furnace atomic absorption with pyrolytically coated graphite tubes and adequate means of background correction
Lamp:  A lead hollow-cathode lamp
Analytical wavelength:  Lead emission line of 283.3 nm
Furnace program:  See Table 1. [Note—The temperature program may be modified to obtain optimum furnace temperatures. ]
Table 1
Step Dry Ash Purge Atomize
Temperature () 200 750 Cool down, and purge the air from the furnace
20
1800
Ramp time (s) 20 40 0
Hold time (s) 30 40 60 10
Argon flow rate
(mL/min)
300 300 300 Argon gas flow stopped
Injection volume:  20 µL
Analysis  
[Note—Use peak area measurements for all quantitations. ]
Samples:  Add 5 µL of the Modifier solution to 20 µL each of the Standard solutions, the Sample solution, the Standard blank, and the Sample blank, and mix.
Separately inject equal volumes (about 20 µL) of the Samples into the instrument for analysis.
Using the Standard blank to set the instrument to zero, determine the integrated absorbances of the Standard solutions. Plot the integrated absorbances of the Standard solutions versus their contents of lead, in ng/mL, and draw the line best fitting the four points to determine the calibration curve. Similarly determine the integrated absorbances of the Sample solution and the Sample blank. Correct the absorbance value of the Sample solution by subtracting from it the absorbance value obtained from the Sample blank.
Calculate the concentration, in ppm (µg/g), of lead in the portion of Corn Syrup taken:
Result = (CL × V/W) × F
CL== concentration of lead in the Sample solution, as determined from the calibration curve (ng/mL)
V== volume of the Sample solution, 10 mL
W== weight of Corn Syrup taken to prepare the Sample solution (g)
F== conversion factor, 10-3 µg/ng
Acceptance criteria:  0.5 ppm (µg/g)
•  Limit of Sulfur Dioxide
Starch indicator solution:  Mix 10 g of soluble starch with 50 mL of cold water, transfer to 1000 mL of boiling water, stir until completely dissolved, cool, and add 1 g of salicylic acid preservative. [Note—Discard this solution after 1 month. ]
Sample:  100 g
Blank:  200 mL of water
Titrimetric system 
Mode:  Direct titration
Titrant:  0.005 N iodine VS
Endpoint detection:  Visual
Analysis:  Transfer the Sample to a 250-mL conical flask, add 100 mL of water, and mix. Cool to 5–10. While stirring with a magnetic stirrer, add 10 mL of cold (5–10) 1.5 N sodium hydroxide. Stir for an additional 20 s, and add 10 mL of Starch indicator solution. Add 10 mL of cold (5–10) 2.0 N sulfuric acid, and titrate immediately with Titrant until a light blue color persists for 1 min. Perform a blank determination, and make any necessary correction.
Calculate the concentration, in ppm (µg/g), of sulfur dioxide (SO2) in the Sample taken:
Result = [(VS VB) × N × F1/W] × F2
VS== Titrant volume consumed by the Sample (mL)
VB== Titrant volume consumed by the Blank (mL)
N== actual normality of the Titrant (mEq/mL)
F1== equivalency factor, 32.0 mg/mEq
W== Sample weight (g)
F2== conversion factor, 103 µg/mg
Acceptance criteria:  NMT 40 ppm (µg/g)
•  Absence of Soluble Starch
Analysis:  Dissolve 1 g in 10 mL of water, and add 1 drop of iodine TS.
Acceptance criteria:  A yellow color indicates the absence of soluble starch.
SPECIFIC TESTS
•  Microbial Enumeration Tests 61 and Tests for Specified Microorganisms 62: The total aerobic microbial count does not exceed 103 cfu/g, and the total combined molds and yeast count does not exceed 102 cfu/g.
•  Total Solids
Instrumental conditions 
Mode:  Refractometer equipped with a jacket for water circulation or some other mechanism for maintaining the sample at 20 ± 0.1 or 45 ± 0.1
Before proceeding with measurements, ensure that the sample and the prism have reached the equilibrium temperature and that the instrument has been properly checked and calibrated against a standard provided by the manufacturer.
Analysis:  Measure the refractive index of Corn Syrup, and convert the value to approximate percent solids value using Table 2 and Table 3. [Note—Table 2 covers the approximate total solids levels of these products in commerce. If the ash or dextrose equivalent of the sample differs from that of the product in Table 2, use Table 3 for the ash and dextrose equivalent correction. ]
Table 2. Reference for Converting the Refractive Index to Approximate Percent Solids
Dextrose Equivalent (DE) Dry Substance (DS)
Refractive
Index
at 20
Refractive
Index
at 45
Degrees Baumé
at 140 F
(60 C) + 1
28 DE Corn syrup—0.3% ash 76.0 1.4888 1.4837 40.98
77.0 1.4915 1.4864 41.49
78.0 1.4943 1.4892 42.00
79.0 1.4971 1.4919 42.51
80.0 1.4999 1.4947 43.01
34 DE High-maltose corn syrup—0.3% ash 78.6 1.4933 1.4882 41.99
79.6 1.4960 1.4909 42.49
80.6 1.4988 1.4936 42.99
81.6 1.5015 1.4964 43.49
82.6 1.5043 1.4992 43.99
36 DE Corn syrup—0.3% ash 78.4 1.4938 1.4887 42.01
79.4 1.4965 1.4914 42.52
80.4 1.4993 1.4941 43.02
81.4 1.5021 1.4969 43.52
82.4 1.5049 1.4997 44.02
43 DE High-maltose corn syrup—0.3% ash 78.9 1.4934 1.4883 42.00
79.9 1.4961 1.4910 42.51
80.9 1.4988 1.4937 43.01
81.9 1.5016 1.4964 43.51
82.9 1.5044 1.4992 44.01
43 DE Corn syrup—0.3% ash 78.7 1.4933 1.4882 42.01
79.7 1.4960 1.4909 42.51
80.7 1.4988 1.4936 43.02
81.7 1.5015 1.4964 43.52
82.7 1.5043 1.4992 44.01
43 DE (Ion-exchanged)
Corn syrup—0.03% ash
78.8 1.4935 1.4884 41.99
79.8 1.4962 1.4911 42.50
80.8 1.4990 1.4938 43.00
81.8 1.5018 1.4966 43.50
82.8 1.5045 1.4994 43.99
53 DE Corn syrup—0.3% ash 80.5 1.4962 1.4911 42.64
81.5 1.4989 1.4938 43.14
82.5 1.5016 1.4965 43.64
83.5 1.5044 1.4992 44.13
84.5 1.5072 1.5020 44.63
63 DE Corn syrup—0.3% ash 81.0 1.4955 1.4904 42.53
82.0 1.4982 1.4931 43.02
83.0 1.5009 1.4958 43.52
84.0 1.5037 1.4985 44.01
85.0 1.5064 1.5012 44.50
63 DE (Ion-exchanged)
Corn syrup—0.03% ash
81.3 1.4963 1.4912 42.60
82.3 1.4990 1.4939 43.10
83.3 1.5017 1.4965 43.59
84.3 1.5044 1.4993 44.09
85.3 1.5072 1.5020 44.58
66 DE Corn syrup—0.3% ash 81.0 1.4949 1.4898 42.36
82.0 1.4975 1.4924 42.86
83.0 1.5002 1.4951 43.36
84.0 1.5029 1.4978 43.85
85.0 1.5056 1.5005 44.35
95 DE Corn syrup—0.3% ash 69.0 1.4598 1.4550 35.46
70.0 1.4621 1.4573 35.96
71.0 1.4644 1.4596 36.46
72.0 1.4668 1.4619 36.96
73.0 1.4692 1.4643 37.45
95 DE (Ion-exchanged)
Corn syrup—0.03% ash
69.0 1.4597 1.4549 35.39
70.0 1.4620 1.4572 35.89
71.0 1.4644 1.4595 36.39
72.0 1.4667 1.4619 36.89
  73.0 1.4691 1.4642 37.38
Table 3. Ash and Dextrose Equivalent (DE) Corrections for Corn Syrup: Changes in Refractive Index for an Increase in Dry Substance (DS)
Dry Substance (DS)
1% Ash 1 Dextrose Equivalent (DE)
2 0.000000 –0.000001
4 0.000000 –0.000003
6 0.000001 –0.000005
8 0.000002 –0.000007
10 0.000003 –0.000010
12 0.000004 –0.000012
14 0.000006 –0.000015
16 0.000008 –0.000017
18 0.000010 –0.000020
20 0.000013 –0.000023
22 0.000016 –0.000026
24 0.000019 –0.000029
26 0.000022 –0.000033
28 0.000026 –0.000036
30 0.000030 –0.000040
32 0.000034 –0.000044
34 0.000039 –0.000048
36 0.000044 –0.000052
38 0.000049 –0.000057
40 0.000055 –0.000061
42 0.000061 –0.000066
44 0.000068 –0.000071
46 0.000074 –0.000076
48 0.000082 –0.000081
50 0.000089 –0.000087
52 0.000097 –0.000093
54 0.000105 –0.000099
56 0.000114 –0.000105
58 0.000123 –0.000112
60 0.000133 –0.000118
62 0.000143 –0.000125
64 0.000153 –0.000132
66 0.000164 –0.000140
68 0.000175 –0.000147
70 0.000187 –0.000155
72 0.000199 –0.000163
74 0.000212 –0.000172
76 0.000225 –0.000181
78 0.000239 –0.000190
80 0.000253 –0.000199
82 0.000268 –0.000208
84 0.000283 –0.000218
Acceptance criteria:  The total solids value is NLT 70.0%.
ADDITIONAL REQUIREMENTS
•  Packaging and Storage: Preserve in tight containers. No storage requirements specified.
•  Labeling: Label it to indicate its nominal dextrose equivalent. Label it also to indicate the presence of sulfur dioxide if the residual concentration is greater than 10 ppm (µg/g).
•  USP Reference Standards 11
USP Dextrose RS
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