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173.350 Combustion product gas.

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[Code of Federal Regulations]
[Title 21, Volume 3]
[Revised as of April 1, 2006]
From the U.S. Government Printing Office via GPO Access
[CITE: 21CFR173.350]

[Page 146-147]
                        TITLE 21--FOOD AND DRUGS
                          SERVICES (CONTINUED)
CONSUMPTION--Table of Contents
                   Subpart D_Specific Usage Additives
Sec.  173.350  Combustion product gas.

    The food additive combustion product gas may be safely used in the 
processing and packaging of the foods designated in paragraph (c) of 
this section for the purpose of removing and displacing oxygen in 
accordance with the following prescribed conditions:
    (a) The food additive is manufactured by the controlled combustion 
in air of butane, propane, or natural gas. The combustion equipment 
shall be provided with an absorption-type filter capable of removing 
possible toxic impurities, through which all gas used in the treatment 
of food shall pass; and with suitable controls to insure that any 
combustion products failing to meet the specifications provided in this 
section will be prevented from reaching the food being treated.
    (b) The food additive meets the following specifications:
    (1) Carbon monoxide content not to exceed 4.5 percent by volume.
    (2) The ultraviolet absorbance in isooctane solution in the range 
255 millimicrons to 310 millimicrons not to exceed one-third of the 
standard reference absorbance when tested as described in paragraph (e) 
of this section.
    (c) It is used or intended for use to displace or remove oxygen in 
the processing, storage, or packaging of beverage products and other 
food, except fresh meats.
    (d) To assure safe use of the additive in addition to the other 
information required by the act, the label or labeling of the combustion 
device shall bear adequate directions for use to provide a combustion 
product gas that complies

[[Page 147]]

with the limitations prescribed in paragraph (b) of this section, 
including instructions to assure proper filtration.
    (e) The food additive is tested for compliance with paragraph (b)(2) 
by the following empirical method:

    Spectrophotometric measurements. All measurements are made in an 
ultraviolet spectrophotometer in optical cells of 5 centimeters in 
length, and in the range of 255 millimicrons to 310 millimicrons, under 
the same instrumental conditions. The standard reference absorbance is 
the absorbance at 275 millimicrons of a standard reference solution of 
naphthalene (National Bureau of Standards Material No. 577 or equivalent 
in purity) containing a concentration of 1.4 milligrams per liter in 
purified isooctane, measured against isooctane of the same spectral 
purity in 5-centimeter cells. (This absorbance will be approximately 
    Solvent. The solvent used is pure grade isooctane having an 
ultraviolet absorbance not to exceed 0.05 measured against distilled 
water as a reference. Upon passage of purified inert gas through some 
isooctane under the identical conditions of the test, a lowering of the 
absorbance value has been observed. The absorbance of isooctane to be 
used in this procedure shall not be more than 0.02 lower in the range 
255 millimicrons to 310 millimicrons, inclusive, than that of the 
untreated solvent as measured in a 5-centimeter cell. If necessary to 
obtain the prescribed purities, the isooctane may be passed through 
activated silica gel.
    Apparatus. To assure reproducible results, the additive is passed 
into the isooctane solution through a gas-absorption train consisting of 
the following components and necessary connections:
    1. A gas flow meter with a range up to 30 liters per hour provided 
with a constant differential relay or other device to maintain a 
constant flow rate independent of the input pressure.
    2. An absorption apparatus consisting of an inlet gas dispersion 
tube inserted to the bottom of a covered cylindrical vessel with a 
suitable outlet on the vessel for effluent gas. The dimensions and 
arrangement of tube and vessel are such that the inlet tube introduces 
the gas at a point not above 5\1/4\ inches below the surface of the 
solvent through a sintered glass outlet. The dimensions of the vessel 
are such, and both inlet and vessel are so designed, that the gas can be 
bubbled through 60 milliliters of isooctane solvent at a rate up to 30 
liters per hour without mechanical loss of solvent. The level 
corresponding to 60 milliliters should be marked on the vessel.
    3. A cooling bath containing crushed ice and water to permit 
immersion of the absorption vessel at least to the solvent level mark.
    Caution. The various parts of the absorption train must be connected 
by gas-tight tubing and joints composed of materials which will neither 
remove components from nor add components to the gas stream. The gas 
source is connected in series to the flow-rate device, the flow meter, 
and the absorption apparatus in that order. Ventilation should be 
provided for the effluent gases which may contain carbon monoxide.
    Sampling procedure. Immerse the gas-absorption apparatus containing 
60 milliliters of isooctane in the coolant bath so that the solvent is 
completely immersed. Cool for at least 15 minutes and then pass 120 
liters of the test gas through the absorption train at a rate of 30 
liters per hour or less. Maintain the coolant bath at 0 [deg]C 
throughout. Remove the absorption vessel from the bath, disconnect, and 
warm to room temperature. Add isooctane to bring the contents of the 
absorption vessel to 60 milliliters, and mix. Determine the absorbance 
of the solution in the 5-centimeter cell in the range 255 millimicrons 
to 310 millimicrons, inclusive, compared to isooctane. The absorbance of 
the solution of combustion product gas shall not exceed that of the 
isooctane solvent at any wavelength in the specified range by more than 
one-third of the standard reference absorbance.

Additives that reference this regulation:

Source: U.S. Code of Federal Regulations - CFR Title 21, Part 173, Section 350

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