abstraction of cream or sweet skim milk, or the addition of concentrated sweet skim milk.

(3) Milk fat is determined by the method prescribed in "Official and Tentative Methods of Analysis of the Association of Official Agricultural Chemists," Fourth Edition, 1935, page 281 [Ed. note, 10th edition, 1965, p. 240, sec. 15.112] under "Fat-Official."

$18.535 Condensed milks which contain corn sirup; identity.

(a) Condensed milks which contain corn sirup are the foods each of which conforms to the definition and standard of identity prescribed for sweetened condensed milk by § 18.530 except that corn sirup or a mixture of corn sirup and sugar is used instead of sugar or a mixture of sugar and dextrose. For the purpose of this section the term "corn sirup" means a clarified and concentrated aqueous solution of the products obtained by the incomplete hydrolysis of cornstarch, and includes dried corn sirup; the solids of such corn sirup contain not less than 40 percent by weight of reducing sugars, calculated as anhydrous dextrose.

%

(b) The name of each such food is: (1) "Corn sirup condensed milk," "condensed milk with corn sirup," or "condensed milk prepared with corn sirup," if corn sirup alone is used; or (2) "____% Corn sirup solids ----% sugar condensed milk," "Condensed milk with % corn sirup solids sugar," or "Condensed milk prepared with --% corn sirup solids ----% sugar," if a mixture of corn sirup and sugar is used, the blanks being filled in with the whole numbers nearest the actual percentages of corn sirup solids and sugar in such food; alternately ---% sugar” may precede“. -% corn sirup solids" in such names.

§ 18.540 Dried skim milk, powdered skim milk, skim milk powder; identity.

Dried skim milk, powdered skim milk, skim milk powder, is the food made by drying sweet skim milk. It contains not more than 5 percent of moisture, as determined by the method prescribed in "Official and Tentative Methods of Analysis of the Association of Official Agricultural Chemists," Fourth Edition, 1935, page 282 (Ed. note, 10th edition, 1965, p. 240, sec. 15.119], under the caption "Moisture-Tentative." The term

19.600

Mozzarella cheese, scamorza cheese; identity.

19.601 Part-skim mozzarella cheese, partskim scamorza cheese; identity. 19.605 Low moisture mozzarella cheese, low moisture scamorza cheese; identity. 19.606 Low moisture part-skim mozzarella cheese, low moisture part-skim scamorza cheese; identity.

19.610 Romano cheese; identity; label statement of optional ingredients.

19.615 Asiago fresh cheese, asiago soft cheese; identity; label statement of optional ingredients.

19.620 Asiago medium cheese; identity; label statement of optional ingredients.

19.625 Asiago old cheese; identity; label statement of optional ingredients. Cook cheese, koch kaese; identity. 19.637 Sap sago cheese; identity.

19.635

19.639

Gammelost cheese; identity. 19.650 Hard cheeses; identity; label statement of optional ingredients. 19.655 Semisoft cheeses; identity; label statement of optional ingredients. 19.660 Semisoft part-skim cheeses; identity; label statement of optional ingredients.

19.665 Soft ripened cheeses; identity; label statement of optional ingredients. 19.670 Spiced cheeses; identity; label statement of optional ingredients. 19.675 Part-skim spiced cheeses; identity; label statement of optional ingredients.

19.680 Hard grating cheeses; identity; label statement of optional ingredients. 19.685 Skim-milk cheese for manufacturing; identity.

19.750 Pasteurized process cheese; identity; label statement of optional ingredients.

19.751 Pasteurized blended cheese; identity; label statement of optional ingredients.

19.775 Pasteurized process cheese spread; identity: label statement of optional ingredients.

19.776 Pasteurized cheese spread; identity, label statement of optional ingredients.

19.780 Pasteurized process cheese spread with fruits, vegetables, or meats; identity; label statement of optional ingredients.

19.781 Pasteurized cheese spread with fruits, vegetables, or meats; identity;

19.782

label statement of optional ingredients.

Cream cheese with other foods; identity: label statement of optional ingredients.

19.783 Pasteurized neufchatel cheese spread with other foods; identity; label statement of optional ingredients. 19.785 Cold-pack cheese, club cheese, comminuted cheese; identity; label statement of optional ingredients. 19.787 Cold-pack cheese food; identity; label statement of optional ingredients.

19.788 Cold-pack cheese food with fruits, vegetables, or meats; identity; label statement of optional ingredients. 19.790 Grated American cheese food; identity; label statement of optional ingredients.

AUTHORITY: The provisions of this Part 19 issued under secs. 401, 701, 52 Stat. 1046, as amended, 1055, as amended; 21 U.S.C. 341, 371.

CROSS REFERENCE: For other regulations in this chapter concerning cheese see §§ 3.19 and 5.4.

the same physical and chemical properties as the cheese produced when the procedure set forth in paragraph (b) of this section is used. It contains not more than 39 percent of moisture, and its solids contain not less than 50 percent of milk fat, as determined by the methods prescribed in paragraph (c) of this section. If the milk used is not pasteurized, the cheese so made is cured at a temperature of not less than 35° F. for not less than 60 days.

The

(b) Milk, which may be pasteurized or clarified or both, and which may be warmed, is subjected to the action of harmless lactic-acid-producing bacteria, present in such milk or added thereto. Harmless artificial coloring may be added. Sufficient rennet (with or without purified calcium chloride in a quantity not more than 0.02 percent, calculated as anhydrous calcium chloride, of the weight of the milk) is added to set the milk to a semisolid mass. The mass is so cut, stirred, and heated with continued stirring, as to promote and regulate the separation of whey and curd. The whey is drained off, and the curd is matted into a cohesive mass. mass is cut into slabs, which are so piled and handled as to promote the drainage of whey and the development of acidity. The slabs are then cut into pieces, which may be rinsed by sprinkling or pouring water over them, with free and continuous drainage; but the duration of such rinsing is so limited that only the whey or the surface of such pieces is removed. The curd is salted, stirred, further drained, and pressed into forms. A harmless preparation of enzymes of animal or plant origin capable of aiding in the curing or development of flavor of cheddar cheese may be added during the procedure, in such quantity that the weight of the solids of such preparation is not more than 0.1 percent of the weight of the milk used.

(c) Determine moisture by the method prescribed on page 262 (15.124) [Ed. note, 10th edition, 1965, p. 247, sec. 15.157], under "Moisture-Official," and milk fat by the method prescribed on page 263 (15.131) [Ed. note, 10th edition, 1965, p. 248, sec. 15.164], under "FatOfficial," of "Official Methods of Analysis of the Association of Official Agricultural Chemists," Seventh Edition, 1950. Subtract the percent of moisture found from 100; divide the remainder into the percent milk fat found. The quotient, multiplied by 100, shall be

considered to be the percent of milk fat contained in the solids.

(d) Cheddar cheese in the form of slices or cuts in consumer-sized packages may contain an optional mold-inhibiting ingredient consisting of sorbic acid, potassium sorbate, sodium sorbate, or any combination of two or more of these, in an amount not to exceed 0.3 percent by weight, calculated as sorbic acid.

(e) For the purposes of this section: (1) The word "milk" means cow's milk, which may be adjusted by separating part of the fat therefrom or by adding thereto one or more of the following: Cream, skim milk, concentrated skim milk, nonfat dry milk, water in a quantity sufficient to reconstitute any concentrated skim milk or nonfat dry milk used.

(2) Milk shall be deemed to have been pasteurized if it has been held at a temperature of not less than 143° F. for a period of not less than 30 minutes, or for a time and at a temperature equivalent thereto in phosphatase destruction. Cheddar cheese shall be deemed not to have been made from pasteurized milk if 0.25 gm. shows a phenol equivalent of more than 3 micrograms when tested by the method prescribed in paragraph (f) of this section.

(3) During the cheese-making process the milk may be treated with hydrogen peroxide solution followed by addition of a suitable catalase preparation to eliminate the hydrogen peroxide. The hydrogen peroxide solution shall comply with the specifications of the United States Pharmacopeia, except that it may exceed the concentration specified therein and it does not contain added preservative. The amount of the hydrogen peroxide solution used shall be such that the weight of the hydrogen peroxide added thereby does not exceed 0.05 percent of the weight of the milk treated. The catalase preparation used shall be stable, and in potency, for eliminating added hydrogen peroxide from milk, it shall not be less than equivalent to livercatalase preparation testing 100 Keil units per grain. It shall be either a preparation that is not a food additive within the meaning of section 201(s) of the Federal Food, Drug, and Cosmetic Act, or a preparation that is a food additive but which is used in conformity with regulations promulgated pursuant to the authority of section 409 of the act. The amount of catalase preparation used

shall be such that the weight of the catalase added thereby does not exceed 20 parts per million of the weight of the milk treated.

(f) The method referred to in paragraph (e) (2) of this section is as follows:

I. Reagents-1. Buffers-a. Barium boratehydroxide buffer. Dissolve 25.0 gm. of c. p. barium hydroxide (Ba(OH),:8H.O, fresh, not deteriorated) in distilled water and dilute to 500 ml. Dissolve, in another flask or cylinder, 11.0 gm. of c. p., boric acid (HBO) and dilute to 500 ml. Warm each to 50° C. (122⚫ F.), mix the two together, stir, cool to approximately 20° C. (68° F.), filter, and stopper the filtrate tightly (pH approximately 10.6). The buffer prepared thus is designated as the 25-11 buffer, the figures indicating the grams per liter of each of the respective reagents.

b. Color-development buffer. Dissolve 6.0 gm. of sodium metaborate (NaBO2) and 20 gm. of sodium chloride in water and dilute to a liter with water (pH 9.8).

c. Color-dilution buffer. Dilute 100 ml. of color-development buffer 1-b to a liter with

water.

d. Standard borax buffer, 0.01-molar, for checking pH meter, pH 9.18 at 25° C. Dissolve 0.9544 gm. of pure borax (Bureau of Standards Sample 187) in distilled water (distilled recently or freshly boiled and cooled) and dilute to 250 ml. Keep stoppered tightly.

2. Buffer substrates. Specify phenol-free crystalline disodium phenyl phosphate.

a. For evaluating pasteurization. Dissolve 0.10 gm. of the phenyl phosphate in 100 ml. of the appropriate (table 1) barium boratehydroxide buffer 1-a.

b. For quantitative results with raw-milk cheese. Dissolve 0.20 gm. of the phenyl phosphate in 100 ml. of the appropriate (table 1) barium borate-hydroxide buffer 1-a.

3. Protein precipitants-a. Zinc-copper precipitant for unripened cheese. Dissolve 6.0 gm. of zinc sulfate (Zn80, 7HO) and 0.1 gm. of copper sulfate (CuSO, 5H,O) in water and dilute to 100 ml. with water. The precipitant prepared thus is designated as the 6.0-0.1 precipitant.

b. Zinc precipitant for ripened cheese. Dissolve 6.0 gm. of zinc sulfate in water and dilute to 100 ml. with water. This precipitant is designated as the 6.0 precipitant. 4. BQC (2,6-dibromoquinone-chlorotmine solution) (Gibbs' reagent): Dissolve 40 mg. of BQC powder in 10 ml. of absolute methyl alcohol and transfer to a dark-colored dropper bottle. This reagent remains stable for at least a month if kept in the ice tray of a refrigerator. Do not use it after it begins to turn brown.

All pH values reported herein were determined at 25° C. or corrected to that temperature.

5. Other reagents-a. Copper sulfate, 0.05 percent, for standards. Dissolve 0.05 gm. of copper sulfate in water and dilute to 100 ml. b. Butyl alcohol. Specify n-butyl alcohol, boiling point 116°-118° C. To adjust the pH, mix 50 ml. of the color-development buffer 1-b with a liter of the butyl alcohol.

6. Phenol standards-a. Stock solution. Weigh accurately 1.0 gm. of pure phenol, transfer to a liter volumetric flask, dilute to a liter with water, and mix. One ml. contains 1 mg. (0.001 gm.) of phenol. Use this stock solution to prepare standard solutions. It is stable for several months in the refrigerator.

b. Preparation of standards.

Dilute 10.0

ml. of the stock solution 6-a to a liter with water, and mix. One ml. contains 10 micrograms (0.00001 gm., 10 gammas, or 10 units) of phenol. Use this standard solution to prepare more dilute standard solutions; e. g., dilute 5, 10, 30, and 50 ml. to 100 ml. with water to prepare standard solutions containing 0.5, 1.0, 3.0, and 5.0 gammas or units of phenol per milliliter, respectively. Keep standard solutions in the refrigerator.

In a similar manner, prepare from the stock solution such more concentrated standard solutions as may be needed, containing, for example, 20, 30, and 40 units per milliliter.

Measure appropriate quantities of the phenol standard solution into a series of tubes (preferably graduated at 5.0 and 10.0 ml.) to provide a suitable range of standards as needed, containing 0 (control blank), 0.5, 1.0, 3.0, 5.0, 10.0, etc., to 30 or 40 units. To increase the brightness of the blue color and improve the stability of the standards, add 1.0 m. of 0.05 percent copper sulfate solution 5-a to each.

Add 5.0 ml. of color dilution buffer 1-c and add water to bring the volume to 10.0 ml. Add 4 drops (0.08 ml.) of BQC 4, mix, and allow to develop for 30 minutes at room temperature. If the butyl alcohol extraction method is to be used in the test, extract the standards as described under III Conducting the Test.

Read the color intensities with a photometer, subtract the value of the blank from the value of each phenol standard, and prepare a standard curve (straight line). When the standards are to be used for visual comparisons they should be stored in a refrigerator.

8

II. Sampling-1. Hard cheese. Take 8 sample from the interior with clean Roquefort trier, place in a small tube, stopper the tube, and keep it in a refrigerator.

2. Soft and semisoft ripened cheese. Harden the cheese by chilling it in the freezing chamber of a refrigerator. Taking special precaution to avoid contaminating the sample with phosphatase that may be present on the surface, use either of the following methods for sampling:

a. Cut a portion from the end of the loaf or from the side of the cheese, extending in at least 2 inches if possible or to a point

somewhat beyond the center in the case of a small cheese. Cut a slit 1⁄4 to 1⁄2 inch deep at least halfway around the portion and midway between the top and bottom. Break the portion into two parts, pulling it apart so that it breaks on a line with the slit, being careful not to contaminate the freshly exposed, broken surface. Remove the sample from the freshly exposed surface at or near the center of the cheese.

b. Remove the surface of the area to be sampled-e. g., the end and the adjacent sides with a clean knife or spatula, to a depth of 1⁄4 inch. Clean the instrument and hands with hot water and phenol-free soap and wipe them dry. Remove the freshly exposed surface to a similar or greater depth and repeat the cleaning. Then take the sample from the center of the freshly exposed area, preferably at or near the center of the cheese in the case of a small cheese.

3. Process cheese, spreads, etc. Take the sample from beneath the surface with a clean knife or spatula.

Avoid the use of samples contaminated with mold.

4. Preservation. If a preservative is necessary, put 1 to 3 ml. of chloroform in the container, cover with a plug of cotton, insert sample and stopper container tightly. Label preserved samples, added."

"Poison-Preservative

II. Conducting the test. 1. Weigh, on a clean balance pan or watch glass, a 0.50-gm. sample (preferably two samples in duplicate) and place in a culture tube 16 or 18 x 150 mm. Similarly, weigh another sample and place in a tube as a control or blank. If the cheese is sticky, weigh the sample on a piece of wax paper about 1 x 1 inch and insert the paper with the sample into the tube. Macerate the blank and the test with a glass rod about 8 x 180 mm.

2. Add to the blank 1.0 ml. of the appropriate (Table 1) barium buffer 1-a (without substrate added), macerate with the rod, leave the rod in the tube, heat for about a minute to at least 85° C. (185° F.) in a beaker of boiling water with the beaker covered so that the entire tube becomes heated to approximately 85° C., cool to room temperature, and macerate again with the rod.

3. Add to the test 1.0 ml. of the appropriate (Table 1) barium buffer substrate 2-a or 2-b, and macerate.

From this point, treat the blank and the test in a similar manner.

Add 9.0 ml. of the appropriate barium buffer substrate 2-a or 2-b (total, 10.0 ml. added), and mix. The rod may be left in the tube during incubation; or, if removing it at this point, cut a piece of filter paper approximately 1 x 1 inch, wrap and hold it tightly around the rod, rotate the rod while withdrawing it from within the tube so as to wipe the rod clean, usert the paper with the adhering fat into the tube, and stopper the tube.

4. Incubate in a water bath at 37°-38° C. (99°-100° F.) for 1 hour, mixing or shaking the contents occasionally.

5. Place in a beaker of boiling water for nearly a minute, heating to 85° C. (185° F.). and cool to room temperature.

6. Pipet in 1.0 ml. of the zinc precipitant 3-b for ripened cheese or the zinc-copper precipitant 3-a for unripened cheese, and mix thoroughly (pH of mixture, 9.0-9.1).

7. Filter (5-cm. funnel, 9-cm. Whatman No. 42 or No. 2 paper recommended), and collect 5.0 ml. of filtrate in a tube, preferably graduated at 5.0 and 10.0 ml.

8. Add 5.0 ml. of color-development buffer 1-b (pH of mixture, 9.3-9.4).

1

9. Add four drops 1 of BQC 4, mix, and allow the color to develop for 30 minutes at room temperature.

10. Determine the amount of blue color by either of two methods:

a. With a photometer. Read the color intensity of the blank and that of the test, subtract the reading of the blank from that of the test, and convert the result into phenol equivalents by reference to the standard curve described under "Phenol standards." The butyl alcohol extraction method is ordinarily unnecessary when using a photometer.

b. With visual standards. For quantitative results in borderline instances, e. g., tests yielding 0.5 to 5 units of color, extract with butyl alcohol 5-b. Add 5.0 ml. of the alcohol and invert the tube slowly several times Centrifuge if necessary to increase the clearness of the alcohol layer. Compare the blue color with the colors of standards in the alcohol.

With samples yielding more than 5 units, compare the colors in aqueous tests with those of aqueous standards.

11. Dilution method for quantitative results. In tests that are observed during color development to be strongly positive, e. g., 20 units or more, in which four drops of BQC may be much less than sufficient to combine with all of the phenol, pipet an appropriate proportion of the contents into another tube, make up to 10.0 ml. with colordilution buffer 1-c, and add two drops more of BQC in the case of unripened cheese or four drops in the case of ripened cheese. With each test, dilute and treat the blank in the corresponding manner. Dilute each strongly positive test thus until the final color is within the range of the standards or photometer. Allow 30 minutes for color development after the last addition of BQC, and make the reading at the end of the 30minute period. Multiply, for example, by 2 for a 5+5 dilution, 10 for a 1+9 dilution, and 50 for a 1+9 followed by a 2+8 dilution.

Alternatively, to reduce the amount of yellow off color, add two instead of four drops of BQC after each dilution, and allow the color to develop. Then test the com

1 For merely detecting underpasteurization, in testing unripened cheese, two drops is sufficient, provided the visual standards are prepared likewise with two drops.