rying sweet skim milk. It contains not ore than 5 percent of moisture, as deermined by the method prescribed in Official and Tentative Methods of nalysis of the Association of Official gricultural Chemists," Fourth Edition, 935, page 282 [Ed. note, 9th edition, 960, p. 203, sec. 15.102], under the capon "Moisture-Tentative." The term skim milk" as used in this section, eans cow's milk from which the milk at has been separated. NOTE: 70 Stat. 486, 21 U.S.C. 321c, provides statutory definition for this food under me name "nonfat dry milk." 20 F.R. 9582, Dec. 20, 1955, as amended at F.R. 6566, Aug. 31, 1956] ART 19-CHEESES; PROCESSED CHEESES; CHEESE FOODS; CHEESE SPREADS, AND RELATED FOODS; DEFINITIONS AND STANDARDS OF IDENTITY c. 4.500 Cheddar cheese, cheese; identity; label statement of optional ingredients. .502 Cheddar cheese for manufacturing; identity. .505 Washed curd cheese, soaked curd cheese; identity; label statement of optional ingredients. .507 Washed curd cheese for manufacturing; identity. .510 Colby cheese; identity; label statement of optional ingredients. .512 Colby cheese for manufacturing; identity. .515 Cream cheese; identity; label statement of optional ingredients. .520 Neufchatel cheese; identity; label statement of optional ingredients. .525 Cottage cheese; identity. .530 Creamed cottage cheese; identity; label statement of optional ingredients. 19.660 19.665 of optional ingredients. Asiago medium cheese; identity. Cook cheese, koch kaese; identity. Gammelost cheese; identity. Hard cheeses; identity. Semisoft cheeses; identity; label statement of optional ingredients. Semisoft part-skim cheeses; identity; label statement of optional ingredients. 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. Sec. 19.755 19.760 Pasteurized 19.763 Pasteurized blended cheese with fruits, vegetables, or meats; 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; label statement of optional ingredients. 19.782 19.783 Cream cheese with other foods; identity; label statement of optional ingredients. 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: §§ 19.500 to 19.790 issued under sec. 701, 52 Stat. 1055, as amended; 21 U. S. C. 371. Interpret or apply sec. 401, 52 Stat. 1046, as amended; 21 U. S. C. 341. § 19.500 Cheddar cheese, cheese; iden. tity; label statement of optional ingredients. (a) Cheddar cheese, cheese, is the food prepared from milk and other ingredients specified in this section, by the procedure set forth in paragraph (b) of this section, or by another procedure which produces a finished cheese having the same physical and chemical properties as the cheese produced when the pr section is used. It contains not n than 39 percent of moisture, and its ids contain not less than 50 percen milk fat, as determined by the meth prescribed in paragraph (c) of this tion. If the milk used is not pasteur the cheese so made is cured at a t perature of not less than 35° F. for less than 60 days. (b) Milk, which may be pasteur or clarified or both, and which ma warmed, is subjected to the actio harmless lactic-acid-producing bact present in such milk or added the Harmless artificial coloring may added. Sufficient rennet (with or w out purified calcium chloride in a q tity not more than 0.02 percent, ca lated as anhydrous calcium chlorid the weight of the milk) is added t the milk to a semisolid mass. The is so cut, stirred, and heated with tinued stirring, as to promote and late the separation of whey and The whey is drained off, and the is matted into a cohesive mass. mass is cut into slabs, which are so and handled as to promote the dra of whey and the development of ac The slabs are then cut into pieces, may be rinsed by sprinkling or po water over them, with free and con ous drainage; but the duration of rinsing is so limited that only the or the surface of such pieces is rem The curd is salted, stirred, fu drained, and pressed into forms harmless preparation of enzymes of mal or plant origin capable of aidi the curing or development of flav cheddar cheese may be added durin procedure, in such quantity tha weight of the solids of such prepa is not more than 0.1 percent o weight of the milk used. (c) Determine moisture by the m prescribed on page 262 (15.124) note, 9th edition, 1960, p. 210 15.1401, under "Moisture-Official, milk fat by the method prescrib page 263 (15.131) [Ed. note, 9th e 1960, p. 210 ec. 15.1471, und Official," official Me** ysis of cultur 1950 fr ocia+ i) Cheddar cheese in the form of es or cuts in consumer-sized packages 7 contain an optional mold-inhibiting redient consisting of not more than percent by weight of sorbic acid, posum sorbate, sodium sorbate, or any bination of two or more of these. :) For the purposes of this section: 1) The word "milk" means cow's I, which may be adjusted by separatpart of the fat therefrom or by addthereto one or more of the following: am, skim milk, concentrated skim , nonfat dry milk, water in a quansufficient to reconstitute any contrated skim milk or nonfat dry milk i 2) Milk shall be deemed to have been teurized if it has been held at a temature of not less than 143° F. for a od of not less than 30 minutes, or a time and at a temperature equiva: thereto in phosphatase destruction. ddar cheese shall be deemed not to e been made from pasteurized milk 25 gm. shows a phenol equivalent of re than 3 micrograms when tested by method prescribed in paragraph (f) his section. 3) During the cheese-making procthe milk may be treated with hydroperoxide solution followed by addiof a suitable catalase preparation to ninate the hydrogen peroxide. The trogen peroxide solution shall comply h the specifications of the United es Pharmacopeia, except that it may eed the concentration specified thereAnd it does not contain added prerative. The amount of the hydrogen oxide solution used shall be such that weight of the hydrogen peroxide ed thereby does not exceed 0.05 perof the weight of the milk treated. : catalase preparation shall be a stabuffered solution, neutral in pH, ng a potency of not less than 100 : units per milliliter. The catalase rein shall have been extracted from vers of meat animals, which livers e been inspected and passed by the it Inspection Division, Agricultural earch Service, of the United States artment of Agriculture. The amount catalase preparation used shall be that the weight of the catalase ed thereby does not exceed 20 parts million of the weight of the milk Ited. ! The method referred to in para(e) (2) of this section is as fol I. Reagents-1. Buffers-a. Barium boratehydroxide buffer. Dissolve 25.0 gm. of c. p. barium hydroxide (Ba(OH),:8H2O, 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.1 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-8. Zinc-copper precipitant for unripened cheese. Dissolve 6.0 gm. of zinc sulfate (ZnSO, 7H2O) 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-chloroimine 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. 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, 1All pH values reported herein were determined at 25° C. or corrected to that temperature. 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. more In a similar manner, prepare from the stock solution such 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 refrig erator. II. Sampling-1. Hard cheese. Take a sample from the interior with a 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 the center of the cheese. b. Remove the surface of the area t sampled-e. g., the end and the adja sides-with a clean knife or spatula, depth of 4 inch. Clean the instrument hands with hot water and phenol-free and wipe them dry. Remove the freshl posed surface to a similar or greater c and repeat the cleaning. Then take sample from the center of the freshly posed area, preferably at or near the c of the cheese in the case of a small chee 3. Process cheese, spreads, etc. Tak sample from beneath the surface with a knife or spatula. Avoid the use of samples contami: with mold. 4. Preservation. If a preservative is r sary, put 1 to 3 ml. of chloroform in container, cover with a plug of cotton, sample and stopper container tightly. preserved added." samples, "Poison-Preser III. Conducting the test. 1. Weigh, clean balance pan or watch glass, a 0.5 sample (preferably two samples in dupl and place in a culture tube 16 or 18 x 15 Similarly, weigh another sample and pl a tube as a control or blank. If the c is sticky, weigh the sample on a piece c paper about 1 x 1 inch and insert the with the sample into the tube. Macera blank and the test with a glass rod 8 x 180 mm. 2. Add to the blank 1.0 ml. of the a priate (Table 1) barium buffer 1-a (wi substrate added), macerate with the leave the rod in the tube, heat for al minute to at least 85° C. (185° F.) in a of boiling water with the beaker cove that the entire tube becomes heated proximately 85° C., cool to room temper and macerate again with the rod. 3. Add to the test 1.0 ml. of the priate (Table 1) barium buffer substrɛ or 2-b, and macerate. From this point, treat the blank an test in a similar manner. Add 9.0 ml. of the appropriate b buffer substrate 2-a or 2-b (total, 10 added), and mix. The rod may be the tube during incubation; or, if re it at this point, cut a piece of filter approximately 1 x 1 inch, wrap and tightly around the rod, rotate the roc withdrawing it from within the tube to wipe the rod clean, insert the pape the adhering fat into the tube, and s the tube. 4. Incubate in a water bath at 37° (99°-100° F.) for 1 hour, mixing or s the contents occasionally. 5 Place in a beaker of boiling wa nearly a minute, heating to 85° C. (18 and cool to room temperature. 6. Pipet in 1.0 ml. of the zinc prec 3-b for ripened cheese or the zinc. precipitant 3-a for unripened chees mix thoroughly (pH of mixture, 9.0–$ Filter (5-cm. funnel, 9-cm. Whatman 42 or No. 2 paper recommended), and eet 5.0 ml. of filtrate in a tube, preferagraduated at 5.0 and 10.0 ml. Add 5.0 ml. of color-development buffer pH of mixture, 9.3-9.4). Add four drops of BQC 4, mix, and allow scar to develop for 30 minutes at room erature 9 Determine the amount of blue color ther of two methods: With a photometer. Read the color inty of the blank and that of the test, subthe reading of the blank from that of Test, and convert the result into phenol Talents by reference to the standard described under "Phenol standards." butyl alcohol extraction method is orrty unnecessary when using a photom With visual standards. For quantitaSe results in borderline instances, e. g., tests ng 0.5 to 5 units of color, extract with alcohol 5-b. Add 5.0 ml, of the alcohol invert the tube slowly several times trifuge if necessary to increase the cleare of the alcohol layer. Compare the blue with the colors of standards in the h samples yielding more than 5 units, re the colors in aqueous tests with me of aqueous standards. Dilution method for quantitative reIn tests that are observed during color opment to be strongly positive, e. g., its or more, in which four drops of may be much less than sufficient to Ee with all of the phenol, pipet an priate proportion of the contents into the tube, make up to 10.0 ml. with color--on buffer 1-c, and add two drops more QC in the case of unripened cheese or drops in the case of ripened cheese. reach test, dilute and treat the blank Se corresponding manner, Dilute each y positive test thus until the final Bra within the range of the standards tometer. Allow 30 minutes for color ment after the last addition of BQC, make the reading at the end of the 30me period. Multiply, for example, by 2 #15-5 dilution, 10 for a 1+9 dilution, and & 1+9 followed by a 2+8 dilution. ratively, to reduce the amount of dew of color, add two instead of four of BQC after each dilution, and allow to develop. Then test the comof color development by adding a top: repeat the dilution procedure the addition of an extra drop does not any further increase in the amount of Calculation and evaluation of results. Eng 0.5 gm. of sample and adding a 110 ml. of liquid, multiply the value merely detecting underpasteurizatesting unripened cheese, two drops eat, provided the visual standards pared likewise with two drops. of the reading by 1.1 to convert it to units of color or phenol equivalents per 0.25 gm. of cheese. The result may, if desired, be converted to phenol equivalents per 1 gm. by multiplying by 4.4. To read IV. Photometric determination. the color in aqueous solution, use a filter with maximum light transmission in the region of 610 mu wave length. To read the color in butyl alcohol, extract the color as described above. If necessary, centrifuge the sample for 5 minutes to break the emulsion and to remove the moisture suspended in the alcohol layer. A Babcock centrifuge can be adapted for this purpose by making special tube holders as follows: Slice a section 4 inch thick from a rubber stopper of suitable diameter to fit in the bottom of the centrifuge cup. Glue together two cork stoppers of appropriate diameter. bore through the center a hole of proper size to hold the tube snugly, and insert the double-cork section into the cup. After centrifuging, remove nearly all of the butyl alcohol by means of a pipet with a rubber bulb on the top end. Filter the alcohol into the photometer cell and read with a filter with maximum light transmission in the region of 650 mμ wave length. If more than approximately 4 ml. of butyl alcohol is required for the photometer used, conduct the test in a larger tube and extract the color, in both the test and the standards, with the necessary quantity of butyl alcohol rather than with 5 ml. specified above. V. Precautions. The length of time that the crystalline disodium phenyl phosphate and the BQC powder will remain stable can be increased greatly by keeping them in the freezing chamber of a refrigerator, and by keeping them dry. The glassware, stoppers, and sampling tools should be scrupulously clean, and it is desirable to soak them in hot, running water after cleaning. The solid barium hydroxide and the barium buffer must be kept stoppered tightly to prevent absorption of carbon dioxide. Phenolic contamination from plastic closures on reagent bottles has been encountered, and therefore the use of plastic closures should be avoided. Rubber stoppers should not be used in flasks in which butyl alcohol is stored. Glass or cork stoppers should be used. VI. Modifications for different cheeses Different kinds of cheese and cheeses of different ages have different buffering capacities, and therefore some of them require modification of concentrations of the reagents. The modifications of the barium buffer needed to produce optimal pH conditions during incubation (9.85-10.20), and of the precipitant to yield uniformly clear filtrates and to minimize interference during color development under optimal pH conditions (9.3-9.4), are specified in Table I. With some samples, especially those of unknown history, slight deviations from the |