THE EFFECTS OF PROCESS PARAMETERS ON THE FORMATION OF VOLATILE ACIDS AND FREE FATTY ACIDS IN QUICK RIPENED BLUE CHEESE Thesis for the Degree of M. S. MICHIGAN STATE UNIVERSITY BRUCE RUSSELL. HARTE 1974 - aaar 5.61 -- 1st 5.02 25.5 2nd 4.99 21.0 3rd 5.13 12.4 4th 5.34 14.1 5th 5.62 17.2 6th 6.11 20.2 7th 6.50 23.5 _—_—————_—_——_-——_——-—‘——————__———— Salted Days 1, 4, 5 O 5.59 -- 1st 5.02 25.6 2nd 4.85 20.7 3rd 5.13 18.8 4th 5.84 15.5 5th 6.39 19.6 6th 6.78 31 2‘ 7th 6.78 3122 53 Table 6.--Continued. Day of ACIDITY Ripening pH VOlatile acidity Salted Days 2, 4, 5, 6 O 5.50 -- 'lst 4.88 23.5 , 2nd 4.86 21.8 . 3rd 4.89 19.7 - 4th 5.16 25.6 5th 5.30 27.9 6th 5.49 30.3 7th 5.71 40.3 8th 6.26 43.5 In all four modifications a decrease in volatile acidity and pH occurred from the first to the second day. The two Blue cheeses that were salted initially on day 1 exhibited a pronounced decelera- tion in the production of volatile acids. During the remainder of the ripening period, small increases in volatile acidity occurred. The cheese salted on days 1, 2 and 3 had a final volatile acidity of only 23.5. Cheese salted on days 1, 4 and 5 was similar in character to that of the previous cheese though the reduction in volatile acidity was not as severe. Gould (1941) and Stadhouders (1956) demonstrated the retarding effect of sodium chloride on lipase activity. Willart and Sjostrom (1959) found that when the salt content was increased from 1.5 to 4.0%, the amount of liberated FFA decreased with increasing salt concentration. An increase in the salt content from 3.0 to 3.9% was found by Poznanski, Jaworski and 54 D'Obyrn(1967) to reduce the fat acidity in Roquefort cheese. The small concentration of volatile acids in the cheese salted on days 1, 2 and 3 was probably a result of salting the cheese early in the ripening period.. This also may hold for the cheese salted on days 1, 4 and 5 as early salting can change the microflora of the cheese. Most microorganisms cannot survive salt concentrations greater than 6% and generally none can survive a concentration of 10% (Morris . 1969) P. roqueforti can survive salt brines of approximately 16%. Cheese salted early in the ripening process will not benefit from the same enzymatic degradations of the starter organisms as cheese salted later in the process. A decrease in lipolytic activity by the starter organisms may also be a factor involved in the low vOlatile acidities observed. The rise in pH values in the cheese salted on days 1, 2 and 3 and l, 4 and 5 are probably not due to rampant proteolysis but to the small amount of liberated FFA. The QR Blue cheese salted days 0, 4 and 6 and 2, 4, 5 and 6 had larger volatile acidities and lower final pH values. These. cheeses were permitted to ripen for 8 days.- Cheeses salted on days 0, 4 and 6 received 1/2 of the net total of salt immediately follow- ing draining. It was hoped that contamination would be lessened by this early salting. .A moderate amount of volatile acidity developed in this cheese. The modification salted on days 2, 4, 5 and 6 pro- duced an intermediate amount of volatile acidity consistent over an eight.day period. -It is questionable whether there is any advantage in a four day salting period. 55 Table 7 shows the FFA for QR Blue cheese as affected by salting times. The cheeses salted on days 1, 2 and 3 and 1, 4 and 5 are quite similar in their FFA profiles. The ratio of butyric acid to the higher acids remains approximately the same regardless of salt concentration (Willart and Sjostrom, 1959). Salting early in the ripening period results in an apparent reduction in total FFA. The low volatile acidities found in the Cheese salted on days 1, 2 and 3 and l, 4 and 5 correlated with the low amounts of volatile fatty acids (C4-C10) in the cheese. The cheese salted on days 0, 4 and 6 Table 7.--The effect of salting sequence on the free fatty acid content of quick ripened Blue cheese. FFA (mg/Kg) Acid Salted on days 0, 4, 6 1, 2, 3 1, 4, 5 2, 4, 5, 6 Butyric 950 550 530 830 Caproic 420 230 300 240 Caprylic 310 200 230 320 Capric 1,470 690 590 1,970 Lauric 2,620 1,000 760 2,420 Myristic 5,740 2,240 2,410 5,230 Palmitic 15,700 5,560 8,170 11,900 Stearic 8,470 3,220 5,750 5,510 Oleic 17,600 9,220 12,100 11,500 Linoleic 1,640 510 420 1,210 Linolenic 860 380 340 710 56 and on 2, 4, 5 and 6 had higher levels of FFA, indicating less inhibition of the lipolytic activity of E, roqueforti. Higher levels of volatile fatty acids were found. Table 8 presents the subjective analysis of the QR Blue cheese salted at various times. The OR cheese salted on days 1, 2 and 3 was criticized for its mild flavor, weak texture and lack of color. This was not an atypical flavored cheese, merely mild in flavor. The evaluation for the cheese, salted on days 1, 4 and 5 was basically the same. Flavor was Slightly better, though color was excessive. The cheese salted on days 0, 4 and 6 was criti- cized for being slightly bitter, light in color and weak in texture. The cheese evaluated as the best of the salting modifications was that salted on days 2, 4, 5 and 6. It was criticized for being slightly bitter, excessive in color and slightly mealy in texture. Table 8.--Sensory evaluation of quick ripened Blue cheese as affected by salting sequence. Salted on days Fa°t°r 0, 4, 6 ‘1, 2; 3 1, 4, 5 2, 4, 5, 6 Color 12.5 12.7 10.5 15.3 Flavor 13.3 10.7 12.7 12.0 Texture 6.0 5.6 6.0 7.3 Tota1 31.8 29.0 29.2 34.6 57 The levels and times of salting play significant roles in the manufacturing of QR Blue cheese. Lipolysis, proteolysis and contamination by other organisms are affected by salt concentration. The knowledge of when to salt is thus an important factor in the manufacture of.high quality QR Blue cheese. Effect of Ripening Temperatures on Quick Ripened Blue Cheese Four modifications of QR Blue Cheese were prepared at various curing temperatures. Two of these modifications involved manufacture at 48° F with different salting times. Modification #1 at 48° F was salted on days 4, 5 and 6. Modification #2 at 48° F was salted on days 11, 12 and 13. Both modifications required longer ripening (14 days) at the lower temperature. Modification #3 was ripened at 57° F for 9 days and salted on days 5, 6 and 7. Modification #4 was ripened at 72° F for 7 days and salted on days 4, 5 and 6. Table 9 presents the volatile acidities and pH measurements for the cheese ripened at various temperatures. The combined effect of low temperature and early salting was inhibitory to the production of volatile acidity in modification #1 at 48° F. The low temperature itself reduced lipase action and combined with early salting, re- tarded the release of FFA and resulted in an increased pH. In modifi- cation #1, the volatile acidity of the cheese failed to increase. However, a very significant drop in volatile acidity occurred on the thirteenth and fourteenth days. This decrease may reasonably be 58 Table 9.--The development of acidity during the quick ripening of Blue cheese at various ripening temperatures. Days of ACIDITY Ripening pH Volatile acidity R1pened at 48° F No. l 0 5.57 -_ lst 5.01 21.2 2nd 4.93 19.1 3rd 4.93 18.4 4th 4.95 17.7 5th 4.91 16.6 6th 4.97 18.1 7th 4.96 17.3 8th 4.98 21.5 9th 5.02 22.5 10th 5,15 25.1 11th 5.13 17.6 12th 5.38 12.6 13th 5.60 12.3 14th 5.99 11.5 Ripened at 48° F No. 2 O 5.56 -- lst 5-01 17.0 2nd 4.88 14.0 3rd 4.94 15.7 4th 4.92 14.1 5th 4.94 12.2 6th 4.97 12 4 7th 4.98 14.9 8th 5.15 7.50 9th 5.42 6.50 10th 5.58 12.3 11th 5.69 24.6 12th 5.84 26.5 13th 5.90 28.1 14th 5.85 35.6 59 Table 9.-—Continued Days of ACIDITY Ripening pH Volatilé’acidity Ripened at 57° F 0 5.53 -- lst 4.95 17.0 2nd 4.88 10.0 3rd 4.88 13.3 4th 5.05 24.5 5th 5.62 28.5 6th 6.06 42.1 7th 6.23 43.3 8th 6.23 46.5 9th 6.09 49.0 Ripened at 720 F O 5.65 -- 1st 5.01 28.7 2nd 5.34 31.0 3rd 6.38 34.5 4th 6.46 36.5 5th 6.66 38.7 6th 6.58 42.7 7th 6.57 47.0 assumed to be the result of utilization of the volatile acids by the mold. The pH did not increase until the tenth day. On the thirteenth and fourteenth days pH increased, coinciding with the decrease in volatile acidity. Modification #2 at 48° F was not salted until sporulation occurred (evidenced by color develOpment). Pro- duction of volatile acidity was quite slow until the tenth day where it began to increase to the final moderate amount. The pH was also 60 very slow to rise, no increase being observed until the eighth day. On day 14 a slight decrease was noted probably due to liberation of FFA by the enzymes of E, roqueforti. Modification #3 was ripened at 57° F for 9 days and salted days 5, 6 and 7. Volatile acidity and pH are similar to the cheese cured at 62° F for 7 days and salted on days 4, 5 and 6. The lower temperature slowed the hydrolysis of fatty acids by the lipase of E, roqueforti and lengthened the ripening period to 9 days. Modification #4 was ripened at 72° F for 7 days and salted on days 4, 5 and 6. The curing temperature employed in this pro- cedure was closer to the optimum for mold lipase activity, 30-32C (Morris and Jezeski, 1953) and for the lipolytic activity of streptococci and lactobacilli, 15-30 C (Carini, 1969) than the pre- vious ripening temperatures. Volatile acidity did not decrease on day 2 as it had in all of the previous cheese made. Instead, an increase was observed on the second day, indicating rapid hydrolysis of the triglycerides. However, the final volatile acidity was not greater than for cheese ripened at 62° F for 7 days. Alford (1971) demonstrated that release of FFA in large amounts might retard lipase activity. It is possible a large amount of volatile acids were released in this cheese in the early stages of ripening thus in- hibiting further hydrolysis. The pH also rose very rapidly indicat- ing advanced proteolysis. The data in Table 10 illustrate the FFA formed in OR Blue cheese cured at various ripening temperatures. The QR cheese 61 Table lO.--The effect of ripening temperature on the free fatty acid content of quick ripened Blue cheese. FFA,(mg/Kg) Acid Curing temperature, F 48 (#1) 48 (#2) 57 72 Butyric 380 760 900 920 Caproic 60 320~ 320 270 Caprylic 50 f 290 480 260 Capric 340 1,910 1,440 1,070 Lauric 314 3,940 2,770 2,000 Myristic 456 7,180 6,720 6,140 Palmitic 1,170 19,400 13,900 17,200 Stearic 600 7,500 3,860 8,790 Oleic 2,340 18,400 8,160 12,400 Linoleic 310 1,130 850 1,450 Linolenic 290 880 830 1,890‘ ripened at 480 F #1 was representative of cheese made with early, salting and low curing temperature. The quantities of FFA found are very low. The small amounts of volatile (C4-C10) fatty acids present in the cheese correlate with the low total volatile acidity. QR Blue cheese #2 cured at 48° F had a FFA profile consisting of moderate amounts of short chained fatty acids and larger amounts of long chain fatty acids. The FFA of modification #3 (ripened at 57° F for 9 days) is similar to that of cheese cured at 62° F for 7 days. QR Blue cheese cured at 72° F for 7 days did not show the large amounts of FFA one might anticipate as a result of a higher curing temperature. 62 Again, this may be due to an inhibitory effect by the FFA (released in the early stages of curing) on further hydrolysis of the fat. The subjective analysis of the Cheese ripened at these temperatures is presented in Table 11. The cheese ripened at 48° F Table ll.--Sensory evaluation of quick ripened Blue cheese cured at various ripening temperatures. Ripening temperature, F Factor 48 (#1) 43 (#2) 57 72 Color 4.9 12.5 12.0 6.5 Flavor 8.0 15.5 ,12'0 8.0 Texture 3.2 7.0 6.0 3.7 Total 16.1 35.0 30.0 18.2 #1, was criticized for lack of color, weakness of texture and mild- ness of flavor. The Cheese was very clean with no apparent contamina- tion or off flavors. This was the result of the low temperature and early salting. However, for the same reasons, little Blue cheese flavor developed. The quick ripened Blue cheese ripened at 48° F, #2, was one of the best cheeses produced. It was a well balanced, moderately flavored Cheese with no trace of any off flavor. Color was slightly insufficient and texture was weak. The QR Blue cheese ripened at 57° F was bitter, lacking in odor and weak in texture. 63 Cheese ripened at 720 F had a bitter, atypical flavor, dark color and a gummy texture. Temperature of ripening is of course, very important in the production of a desirable cheese. Cheese can be cured at a low temperature to produce a desirable flavor. However, with a low temperature a longer time is necessary to complete ripening. Higher_ ripening temperatures may enhance fat breakdown and protein degrada- tion but in this research proved to be detrimental to the flavor, body and texture of quick ripened curd. Effect of Homogenization, Pasteurization and_One Hfiur Delay_on the Pro- pene ue eese Homogenized raw milk, pasteurized unhomogenized milk and milk homogenized one hour befOre pasteurization were investigated as variables in the preparation of QR Blue cheese. The homogenized raw milk was preheated to 130° F, homogenized and then cooled to 84° F where starter culture was added. The pasteurized unhomogenized milk was heated to 1440 F and held at this temperature for 30 minutes.' In an effort to obtain increased lipolysis and possibly increased ketone production through subsequent beta oxidation of the FFA, milk was homogenized one hour prior to pasteurization. The volatile acidities and pH values of cheese prepared by the three variations described above are presented in Table 12. The 64 Table 12.--The development of acidity during the quick ripening of Blue cheese as affected by pasteurization and homogeni- zation. Day of , ACIDITY ripening pH Volatile acidity Homogenized raw 0 5.52» -- lst 5.06 24.6 2nd 4.97 16.0 3rd 5.12 23.4 4th 5.59 29.6 5th 6.23 35.6 6th 6.49 44.5 7th 6.56 48.6 Homogenized one hour prior to pasteurization 0 5.68 -- 1st 5.65 24.6 2nd 5.51 _ 11.5 3rd 6.09 15 8 4th 6.30 17 9 5th 6.50 22 5 6th 6.34 31 3 7th 6.21 34 2 Pasteurized, unhomogenized 0 5.48 -- lst 4.99 19.6 2nd 4.981 15.8 3rd 5.32 16.6 4th 5.54 28.6 5th 5.60 33.1 6th 5.61 42 0 7th 5.65 36:2 65 development of volatile acidity in the homogenized raw milk cheese occurred more rapidly in the early stages of ripening than in the cheese ripened at 620 F for 7 days. This may be the result of the activity of natural milk lipases which were not destroyed by heating. The final volatile acidities were comparable to those of cheese ripened at 620 F for 7 days. Higher levels of volatile acidities did not result possibly because of early release of large amounts of FFA. The pH increased rapidly during the initial stages of the curing perhaps due to a more active protease system. The volatile acidity of the pasteurized unhomogenized QR Blue cheese increased slower than did the homogenized raw milk cheese. Morris (1961) demonstrated that pasteurization destroyed the natural milk lipases. Homogenization of milk increases the surface area of the fat, thus permitting greater lipolysis by the milk and mold lipase systems. QR Blue cheese manufactured without homogenization but with pasteuri- zation would suffer from this twofold decrease in lipolysis. The cheese made from milk homogenized one hour prior to pasteurization had only a moderate amount of volatile acidity. This was not the anticipated effect. Harper and Gould (1959) found that milk held at 120° F for 5 minutes between homogenization and pasteurization resulted in a rancid product. The cheese milk that was held for one hour had a rancid odor though that was probably not the reason for the atypical characteristics of this cheese. Contamination was pos- sibly the main cause for the poor quality of this cheese. The one hour holding period at a temperature of approximately 125° F would 66 have been an ideal medium for the proliferation of many undesirable organisms normally found in milk. Heavily contaminated cheese could inhibit mold growth and subsequently less FFA would be liberated by the enzymes of E, roqueforti. The pH values also were erratic, , possibly due to the contamination present. Additional research is. needed to confirm these speculations. Table 13 presents the total FFA for QR Blue cheese modified as described. The cheese prepared by homogenizing milk one hour I before pasteurization had less total FFA than the homogenized raw Table 13.--The effect of varying homogenization and/or pasteurization treatments on the free fatty acids’of quick ripened Blue cheese. Acid . FFA (mg/Kg) Homog. raw Homog. one hr. Past.-Unhomog. Butyric 970 650 770 Caproic 320 390 310 Caprylic 320 240 230 Capric 1,440 1,080 1,350 Lauric 2,930 1,690 1,700 Myristic 6,600 4,230 3,530 Palmitic 19,700 8,030 11,000 Stearic 11,600 3,470 7,570 Oleic 19,900 8,170 12,800 Linoleic 1,230 620 1,290 Linolenic 1,150 610 850 67 milk cheese. This was probably due to the partial effect of con- tamination on E, roqueforti. The pasteurized unhomogenized cheese also had smaller concentrations of FFA present in the final product. Less FFA would be liberated because of the previously mentiOned decrease in rate of lipolysis.) The homogenized raw milk cheese had a FFA level similar in amount to that cheese ripened at 620 F for 7 days. Table 14 shows the subjective analysis of the three modified QR Blue cheeses. Quick ripened Blue cheese that was made from Table l4.--Sensory evaluation of quick ripened Blue cheese as affected by pasteurization and homogenization. Factor: ._ Homog. raw Homog. one hr. Past.-Unhomog. Color 10.0 5.0 5.4 Flavor 12.0 7.5 9.4 Texture 5.7 4.5 5.0 Total 27.7 17.0 19.8 pasteurized unhomogenized milk was criticized for being mild in flavor, mealy in texture and having no blue color. The QR Blue cheese manufactured from homogenized raw milk was excessive in color, mealy in texture and bitter in flavor. QR Blue cheese produced from milk homogenized one hour prior to pasteurization was criticized for 68 being atypical in flavor, gummy in texture and for the absence of any blue color. Lane and Hammer (1938) found that homogenized milk produced cheese that was lighter in color, softer in texture and ripened faster. They found that pasteurizing the milk and then homogenizing gave cheese which ripened slower but developed volatile acidity more rapidly and had a more typical flavor. Dozet et a1. (1972) produced a soft white cheese from homogenized milk that had a Soft firm consistency and pronounced flavor. In order to produce the best quality QR Blue cheese it appears that both pasteurization and homogenization are necessary. Effect of Cookin the Curd and the 'EAHHI ion of a Commerélal Lipase "oniQuTCkiRipened'Blue Cheese A commercial lipase preparation was added to cheese milk after pasteurization. Cheese produced with the added lipase was cured at 620 F for 7 days and salted on days 4, 5 and 6. It was. hoped the lipase would encourage the liberation of the volatile fatty acids. A problem that often occurred in the manufacture of QR Blue cheese was shattering of the curd prior to drainage.‘ This resulted in poor drainage and loss of cheese. In an attempt to alleviate this problem the curd was cooked to firm the curd particles. The tempera- ture of the curd was raised from 84° F to 1000 F in one hour. 69 Table 15 presents the volatile acidities for the cheese with the added lipase and for the cheese cooked prior to drainage. The cooked cheese produced a volatile acidity similar in amount to QR cheese ripened at 620 F for 7 days. The pH values are also very similar. The volatile acidity did not increase as antiCipated when Table 15.--The development of acidity during the ripening of Blue cheese as affected by cooking of the cheese curd and by the addition of a commercial lipase preparation. fi— 7 Day of ACIDITY ripening, _ pH' Volatile acidity Cheese curd cooked 0 5.54 -- lst 4.97, 22.5 2nd 4.92 15.6 3rd 5.21 18.5 4th 5.68 27.0 5th 6.02 35.1 6th 6.20 41.5 7th 6.17 46.3 Lipase preparation added 0 5.50 -- lst 4.90 17.0 2nd 4.94 15.8 3rd 4.95 14.3 4th 5.18 29.3 5th 5.65 34.7 6th 5.66 42.0 7th 5.71 40.0 70 lipase was added. The reason(s) for this are not known. The pH rose and stabilized on day 5 at a pH lower than that cheese ripened at 620 F for 7 days. This would seem to indicate greater release of FFA or reduced proteolysis. Table 16 lists the total FFA isolated from cheese prepared by the previously described modifications. The FFA profile of cheese that was cooked is not unlike that of the cheese produced at 620 F for 7 days. The cheese prepared with the addition of lipase had low levels of butyrate and oleate in the final product. In most QR Blue Table 16.--The effect of added lipase or cooking cheese curd on the free fatty acids of quick ripened Blue cheese. Acid FFAimglKg) Lipase added Cooked Butyric 570 710 Caproic 390 350 Caprylic 340 460 Capric 1,260 1,560 Lauric 1,880 1,880 Myristic 4,490 3,970 Palmitic 11,100 12,300 Stearic 5,140 4,140 Oleic 5,260 10,300 Linoleic 1,010 1,110 Linolenic 830 850 71 cheeses the ratio of stearate to oleate is 1:2 or 1:2.5. In this cheese the ratio was approximately 1:1._ The low levels of butyrate and oleate found in the cheese may be a result of the addition of a commercial lipase to the cheese milk. Other unelucidated factors may also be responsible for the differences. Table 17 shows the subjective analysis for the two modified Cheeses. The cheese produced with the addition of lipase was Table l7.-~Sensory evaluation of quick ripened Blue cheese as affected by cooking of the cheese curd and by the addi- tion of a commercial lipase preparation. Factor Lipase added Cooked Color 14.8 11.0 Flavor 12.0 14.3 Texture 7.7 7.0 Total 34.5 32.3 criticized for being bitter in flavor and mealy in texture. The cheese had an excellent color. This cheese scored well overall because of the superior color. Coulter and Combs (1938) accelerated the ripening of Blue cheese by the addition of steapsin. The cheese had a distinct bitter flavor. Shehata (1967) reported on a procedure where the flavor of Blue cheese was improved by the addition of lipase. 'In the QR process the addition of lipase does not appear to 72 increase hydrolysis of FFA nor does it appear to improve flavor.. The short ripening time involved in the QR procedure may not be long. Venough to allow the lipase to function to the extent that it does in conventional curing. The lipolytic action that normally occurs in QR takes place in a short time and may limit further lipolysis by foreign agents, such as added lipases. 'The OR Blue cheese manufactured from cheese curd which was cooked was criticized for being slightly bitter in flavor, mealy in texture and excessive in color. By cooking the curd the particles of cheese became toughened. Drainage time was reduced and loss of cheese due to shattering was lessened. Shehata (1966) reported that cooking the curd made it stronger, which resulted in less shattering. Cooking the curd did not appear to adversely effect the quality of the cheese.. Effect of Direct Acidification on OUTER—RTEEHEU—BTUE'Cheese ‘T Three lots of QR Blue cheese were manufactured by direct. acidification of the cheese milk with hydrochloric acid, lactic acid and by a combination of lactic acid and starter culture. A11 cheeses were ripened at 620 F for 7 days and salted on days 4, 5 and 6. The lots containing lactic acid and lactic acid plus starter attained a pH of 5.7.! This was approximately the pH used by Singh and Kristoffersen (1972) in developing cheese flavor. The starter culture 73 was added at a concentration of 1% to the lot containing lactic acid and starter. Table 18 presents the volatile acidity and pH values for the directly acidified cheeses.. The pH of the two modifications con- taining lactic acid are considerably different on day l. The cheese manufactured without starter culture exhibited a pH approximately the same as on the day of.manufacture.i The pH of the cheese made with starter culture fell to 5.11 by day 1. This drop in pH may have been due to the production of lactic acid by the starter culture. There was-little difference found in the volatile acidities of cheese acidified with lactic acid and cheese acidified with lactic acid plus starter. The somewhat higher volatile acidity in the lactic acid and starter cheese may have been due to lipolysis by the starter culture (Dovat et a1. 1970). At the conclusion of curing, cheese made by both modifications exhibited volatile acidities similar in amounts to that found for other adaptations.of QR Blue cheese. The volatile acidity found in cheese made by hydrochloric acid direct acidification is approximately the amount present in the other acid acidifications. A low volatile acidity was recorded on day 1 perhaps' due to the lack of starter culture. The pH values were high and inconsistent. Table 19 lists the FFA distribution of the directly acidified cheeses. There are inconsistencies from trial to trial. The levels of the long chain fatty acids present fluctuates in each modification. 74 Table 18.--The development of acidity during the quick ripening of Blue cheese as affected by direct acidification of the cheese milk. Day of yACIDITY ripening pH Volatile acidity Lactic acid, direct acidification O 5.70 -- lst 5.79 10.3 2nd 5.67 15.7 3rd 5.66 21.4 4th 5.37 27.5 5th 5.50 35.6 6th 5.57 40.8 7th 5.70 46.6 Lactic acid and starter, direct acidification 0 5.70 -- lst 5.11 14.8 2nd 5.15 16.6 3rd 5.20 28.5 4th 5.58 32.5 5th 5.88 36.5 6th 5.81 38.4 7th 5.42 42.6 Hydrochloric acid, direct acidification 0 5.20 -- lst 6.88 8.16 2nd 6.59~ 9.23 3rd 6.60 11.0 4th 6.71 13.7 5th 6.82 24.8. 6th 6.58 39.2 7th 6.53: 44.1 75 Table l9.--The effect.of direct acidification on the free fatty acids in quick ripened Blue cheese. FFA (mg/K9) Acid Acid used for direct acidification Lactic acid Lactic acid & starter HCl Butyric 850 610 890 Caproic 470 470 390 Caprylic 520 410 200 Capric 2,010 1,840 810 Lauric 2,580 1,840 990 Myristic 6,720 4,240 2,980 Palmitic 9,780 14,400 8,390 Stearic 4,370 5,570 7,600 Oleic 10,930 7,040 17,100 Linoleic 1,060 1,210 1,900 Linolenic 860 820 2,020 These differences may in part be reSponsible for the atypically flavored cheeses produced by direct acidification. Table 20 shows the subjective analysis of the directly acidified cheeses. None of the cheeses prepared by these methods developed any blue color. Body and texture were gummy. The flavor of all three cheeses was atypical. Direct acidification of Blue cheese was shown to produce a curd of good body and texture by Shehata (1966). Flavor was not judged as the cheese was not ripened. Manufacture of QR Blue cheese by direct acidification failed to produce a cheese of typical flavor 76 Table 20.--Sensory evaluation of quick ripened Blue cheese as affected by direct acidification. Factor i Lactic acid Lactic acid 8 starter HCl Color 4.5 4.5 5.0 Flavor. 7.3 8.7 6.7 . Texture , 5.0 5.0 4.7 Total 15.8 18.2’ 16.4 and color. Whether the time involved in OR was insufficient for the ' cheese to ripen properly is unknown.. Regardless of the reason QR Blue cheese prepared by direct acidification was unacceptable under the conditions used in this research. The Suggested Methods for the_ ro uction of Qu c R pene Blue Cheese I Based upon the information obtained from the preceding trials the procedure of Kondrup and Hedrick (1963) for the manu- facture of QR Blue cheese was modified.. The following are the sug- gested methods. Procedure #1 involved a ripening temperature of 52° F for 11 days and salted on days 7,v8 and 9. The cheese curd was cooked following cutting of the curd to provide better drainage. A ripening temperature of 52° F was chosen because it is low enough to prevent undesirable contamination. Furthermore, the ripening time 77 involved was shorter than curing at 480 F. The initial salting took place on day 7 when the first color appeared. Samples of cheese made by this procedure were stored for four weeks at 400 F to determine what effect such additional storage would have on the quality of the cheese. Suggested procedure #2 was ripened at 520 F for 11 days and salted on days 1, 9 and 10. The cheese curd was cooked following cutting of the curd. The primary purpose for the initial salting on day 1 was to further reduce the possibility of contamination in the cheese. Samples of this cheese were also pressed into a loaf to determine the possibility of storing and marketing in a loaf form. Table 21 presents the volatile acidities and pH values for the two alternative methods. The low ripening temperature retarded early increases in volatile acidity and pH. The volatile acidities and pH values found in the cheese produced by method #1 increased gradually throughout the later stages of ripening. This slow, con- sistent increase may have been beneficial in the production of cheese of balanced flavor spectrum. Samples of this cheese held in storage showed small increases of volatile acidity throughout the storage period. These increases are indicative of continued lipolysis by the enzymes of E, roqueforti. The pH decreased as storage continued which again corresponded to the increase of volatile acidity. The volatile acidity in cheese produced by MethOd #2increased more rapidly than that of method 1. The initial salting on day 1 did not appear to adversely effect the production of volatile acidity. Earlier in this discussion lipolysis of cheeses salted on days 1, 2 78 Table 2l.--The development of acidity during the quick ripening of Blue cheese by the suggested methods. Day of ACIDITY. ripening pH Volatile acidity 0 5.39 —- 1st 4.90 19.3 2nd 4.88 17.2 3rd 4.84 16.8 4th 5.08 12.8 5th 5.13- 13.5- 6th 5.46 22.4 7th 5.53 31.6 8th 5.86 34.7 9th 5.95 37.6 10th 6.24 42.3 11th 6.13 43.1 After 1 week* 5.89 51.1 After 2 weeks 5.87 52.2 After 3 weeks 5.83 52.5 After 4 weeks- 5.76 53.7 *Storage at 40° F Method No. 2 0 5.60 -- lst 5.35 16.0 2nd 5.35 14.8 3rd 5.34 12.0 4th 5.46 13.6 5th 5.51 16.5: 6th 5.79 24.4 7th 5.94 29.4 8th 6.09 32.3 9th 6.20- 36.3 10th 6.42. 39.8 11th 6.30 46.0 79 and 3, and l, 4 and 5 was said to have been retarded by the early addition of sodium chloride. The difference between those Cheeses and the cheese produced by method 2 involves the time span between the initial, secondary and final salting. In those earlier cheeses the total amount of salt was added prior to the normal salting times. There was little time between the initial and final addition of salt. The time Span between the initial and final salting for method 2 was extended over a much longer interval. The secondary and final salting occurred after the normal salting times (days 7, 8 and 9 as in method #1). Table 22 lists the FFA for the suggested improved methods. The FFA distribution of the Cheese stored at 40° F from method 1 are also Shown. Cheese stored at 40° F for one week definitely increased In the volatile (C4'ClO) fatty acids over that not stored. Butyric acid Showed the greatest increase and after one week of storage the amount of butyrate present had almost doubled. Throughout the remain- ing storage time little change occurs in the level of butyrate pres- ent in the cheese. Over the four week storage period the long chain FFA increased slightly. The fatty acids (°6'°12) increased during the first weeks of storage, but then decreased on subsequent storage. Continued lipolytic activity by E, roqueforti resulting in further hydrolysis of fatty acids is probably the reason for the increased amounts of fatty acids. Loss of these fatty acids may then occur as a result of beta oxidation. Beta oxidation of these FFA would yield methyl ketones (Hawke, 1966). After four weeks of storage small 80 Table 22. --Free fatty acids produced in quick ripened Blue cheese by - Results after suggested alternate methods of manufacture. four weeks of storage are also presented. e-Linolenic 613 , . , FFA (mg/Kg) ” ' ’ ACId Mfig°°° 1 week* 2 week 3 week. '4.week.”¥ Mfi§°g°-- ’Butyric 650 1,260 1,230 1,270 ‘.1.270 875- ' Caproic 244 484 344 .383 - 522 ‘ ~401— Caprylic 314 408 464 , 686 . 529 _ 306. Capric 950 ‘ 1,030 1,740 , 3,090 .f '2,5sor ; 2,350 Lauric 1,540 1,630 2,500 ' 3,080., 3,460 ,' 2,560" Myristic 4,630 ’ 3,880 4, 780 ' 7,290." 7,000 . 4,520 Palmitic 13,1001 12,600' 13, 000 _ 13,100 .‘ 14,000 12,400 Stearic' 4,730 4,660 4,690 5,850" ”6,260 , 5,600 Oleic 12,900 13,200 13,200 . 14,500 14,900 ~ 13,000 Linoleic 834- 823 ‘- 798. 857 ' 925,, 1,260. 762 ‘ 742 ' 644 595. . 914 *Stored at 400 F. increases were still being noted in some long chain fatty acids. ‘The_ FFA distribution of cheese prOduced by method 2 is similar to that cheese ripened at 62°F for 7 days. Table 23 Shows the subjective analysis of the cheese produced Q by the SuggeSted methods. .marked improvement when the cheeSe was stored at. 400 F. improved through the third week. The cheese produced by method 1 shows Flavor “I. Color and texture rémained quite constant throughout the storage study. 81 Table 23.--Sensory evaluation of quick ripened Blue cheese by the suggested methods. Factor No.1 1 week* 2 week 3 week 4 week No.2: Color 13.0 12.8 13.0 12.8 12.8 12.0: Flavor 13.0 14.7‘ 15.8 16.7 16.7 14.0 Texture 7.7' 8.3 8.7 8.7 8.3 8.0 Total 33.7 35.8 37.5 38.2 37.8 34.0 Quick ripened Blue cheese manufactured by suggested method 1 had a well balanced flavor when stored at 40° F for a week or more. The overall quality of the cheese in storage remained fairly stable even though the concentrations of FFA (and undoubtedly methyl ketones) were changing. The flavor improvement that occurred as storage progressed probably was due to the increase in short chain fatty acids and methyl ketones. Due to the lower temperature used to ripen the cheese produced by method 1 the development of flavor was slower but more consistent from trial to trial. After four weeks of storage the quality of the cheese had not deteriorated. Flavor development of cheese produced by method 2 was satis- factory after the 11 day ripening period. This cheese had a clean, mild flavor. The early salting may help to eliminate contamination. Samples of this cheese were pressed into loaf shape. This resulted in a cohesive product, well flavored and light colored. In trials with other batches of cheese it became evident that salting times, 82 mold development and curd breakdown were critical in the formation of'a cohesive product. It is suggested that cheese ripened by the quick ripened loose curd method may have longer shelf life when pressed into a loaf. Preparation of Quick Ripened to o .. eeses Cheese was made~with a white mutant of E, roqueforti obtained from Midwest Mold Company. The suggested methods were used in the production of this cheese with the exception of different salting times.. White mold cheese 1 was ripened at 52° F for 10 days and salted on days 5, 6 and 7. The curd was cooked after cutting. White mold cheese 2 was ripened at 520 F for 10 days and salted on dayS‘ l, 6 and 7. The primary purpose of making quick.ripened white mold cheese dealt with the absence of blue color in the final product. To some individuals the blue color in a Blue cheese is offensive. Therefore, a white mold cheese would be ideal from the_standpoint' of producing the mold flavor without the blue color. In quick ripened Blue cheese the initial salting took place when color first developed. With no color developing there was no set guide as to when the first salt should be applied. Table 24 presents the volatile acidities and pH values for the white mold cheeses. Possibly both white mold cheeses may have been salted too early. Both cheeses demonstrated volatile acidities that were developing normally until the addition of salt. 83 Table 24.--The development of acidity during the quick ripening of a cheese made with a white mutant of E, roqueforti. if. Days of ACIDITY. ripening pH VOlatile acithy Cheese No. l 0 5.55 -- lst 5.05 22.4 2nd 4.99 18.0 3rd 4.90 15.3 4th 5.01 18.8 5th 5.20- 24.5 6th 5.42 26.9 7th 5.48 28 0 8th 5.56 28 7 9th 5.68 31 9 10th 5.75 34.1 0 5.58 -- 1st 5.06 22 5 2nd 5.03 21 8 3rd 5.02 20.1 4th 4.98 19.1 5th 5.11 20.8 6th 5.22 21.8 7th 5.33 23.5 8th 5.45 29.5 9th 5.62 31.3 5.91 38.6 10th 84 Table 25 presents the FFA of the quick ripened white mold cheeses. The data found in this table are similar to those of the. previous table. The total FFA are low, probably because salt was‘ added to the cheese too early in the ripening process. A difference» was noted in the profile of FFA for the white mold cheeses compared, Ito the blue mold Cheese. The ratio of butyrate to caprylate was approximately 1:1 while in the blue mold cheese it was about 1:3.v Table 25.4-Free fatty acid (FFA) content of quick ripened.white mold cheese made with a white mutant of E, roqueforti. A°1°- CheeseNo.lFFA (mSLEQIheese.No.,2— Butyric 520 660 Caproic 290 230 Caprylic 570 650- Capric 1,500 1,460 Lauric, 2,530 2,380 Myristic 5,840~ 4,630 Palmitic 9,210 10,200 Stearic 3,470- 4,910 Oleic 9,190 11,100 Linoleic 1,030 940 Linolenic 990 840 85 Table 26 shows the results of subjective analysis of the white mold cheeses. Both variations were criticized for being mild in flavor and weak in texture. The quick ripened white mold cheese had a flavor typical of a mild Blue mold cheese. It was concluded that the white mutant of E, regueforti can be used to produce a cheese with the blue-veined flavor without the blue color. A means by which the correct times of salting can be accurately detected remains to be developed. Table 26.--Sensory evaluation of quick ripened white mold cheeses made with a white mutant of 3,.roqueforti. Factor Cheese No. 1 Cheese No. 2 Color 12.3 11.0 Flavor 10.0 9.7 Texture 7.3 7.3 Total 29.6 28.0 SUMMARY AND CONCLUSIONS A well flavored Blue cheese can be manufactured by the QR process. The time involved in ripening the cheese is substantially less than that for commercially ripened cheese., Overhead costs are reduced due to the need for less equipment. The amount of physical labor required during ripening is also substantially less because of the short ripening time. In QR cheese the final product is very suitable for direct use in salad dressings and dips because of the small, well-veined loose curd particles. It is also possible to press QR Blue cheese into loaf form. This would imprOve color con- sistency, texture and overall appearance. If additional research with pressing proves to be successful this would enable QR cheese to compete with traditional cured cheese in wheels. The short ripening time of QR cheese makes salting times, ripening temperatures and the presence of contamination critical in developing a good quality cheese. Salt must not be applied in large amounts too early in the ripening process. Addition of excessive salt retards lipolysis by E, roqueforti, resulting in a mild flavored cheese. Some salt may be applied in the early stages of ripening to aid in the control of contaminating organisms. When salting the cheese correctjudgement must be used by the cheesemaker in order to produce a well flavored, well blended cheese. A higher ripening 86 87 temperature (620 F) produced a cured cheese in approximately 7 days (for a summation of data comparing a conventional QR Blue cheese, commercial Blue cheese and alternative QR Blue cheese, see Table 27). The lower temperature of 52° F required an additional 4 days to ripen properly. However, there are benefits which overshadow the need for the additional ripening time.* Lower temperature reduces the Table 27.-~FFA, volatile acidities and pH values for a conventional quick ripened Blue cheese, a commercial Blue cheese and a Blue cheese produced by a suggested method. FFA Commercial Convgegional 2 weeks* Mfi§°°d 2 weeks* Butyric 720 1,270 1,680 650 1,230 Caproic 64 490 490 240 340 Caprylic 74 420 360 310 460 Capric 870 820 2,240 950 1,740 Lauric 1,440 1,240 1,500 1,540 2,500 Myristic 5,700 4,090 4,660 4,630 4,780 Palmitic 12,700 12,500 12,500 13,500 13,000 Stearic 6,020 6,590 6,460 4,730 4,690 Oleic 13,800 13,900 13,000 12,900 13,200 Linoleic 610 790 750 830 800 Linolenic 630 ~ 710 650 760 640 :;Q§}t¥2;3t"° 26.3 47.5 55.0 43.1 52.2 Clijlsp” 5.69 6.22 5.78 6.13 5.87 *Stored at 40° F. 88 possibility of contamination and thus the production of off flavors. The creation ofga good, well blended flavor occurred more readily when the ripening period was lengthened by the lower temperature.- The loose curd form by which QR cheese is cured makes it more prone to contamination than traditionally cured Blue cheese. The surface area is greatly expanded because of the many curd particles. 'This results in: l) a greater surface for contaminating organisms to grow on, and 2) less chance for the off colors produced by contami- nating organisms to be scraped off. A heavily contaminated QR cheese will have off flavors and off colors probably resulting in destruction of the cheese. Contamination can be controlled by salting time, ripening temperature and most importantly, the use of proper sanitary procedures during the manufacture and ripening of the cheese. QR Blue cheese was produced by direct acidification with lactic and hydrochloric acids. The cheese did not develop proper flavor nor the blue-green color associated with Blue cheese.‘ Future experimentation may hold the answers to successful application of direct acidification to OR cheese. Homogenization of the cheese milk enlarges the fat surface thus allowing increased lipolysis by milk and mold lipase systems. Pasteurization inactivates the milk lipase but more importantly destroys many contaminating organisms. It appears that both are necessary for the development of a clean, full flavor in OR Blue cheese. Iii! 1.!l 89 A commercial lipase preparation was added to cheese milk used in the manufacture of QR Blue cheese. A satisfactory cheese was produced, though any benefits derived from addition of the lipase were questionable. In the manufacture of QR Blue cheese the coagulum was cut one hour prior to drainage. This was found to be unsatisfactory due to excessive curd shattering, resulting in cheese loss and prolonged drainage time. A cook procedure was devised which strengthened the curd particles and resulted in faster drainage and less cheese loss. The cooking did not appear to adversely effect the quality of the cheese. A white mutant of B, roqueforti was obtained, cultivated and utilized in the production of a QR White mold cheese. A cheese having the Blue cheese flavor without the blue color was produced. QR white mold cheese may be used where blue color is undesirable. Cheese ripening is a complicated procedure involving many physical and biochemical changes. Many of these changes can be directly or indirectly controlled by the actions of the cheesemaker. Therefore, it may be true that the success or failure of QR Blue cheese will depend upon the cheesemaker's skills, patience and deter- mination. i III-ill! Ill-nil APPENDIX APPENDIX Determination of Butyric and Higher Acids Reagents Silicic acid: Mallinckrodt 2847, lOO mesh, activated 175° c for l8 hours. Stored in a desiccator.. Glycol reagent: Dissolved 700 mg bromocresol green, sodium salt, in 700 ml ethylene glycol by warming on a steam bath. Cooled. Added 200 ml water to the 700 ml ethylene glycol-bromocresol green. solution; then added 40 ml 0.l N ammonium hydroxide and enough water to make one liter., Cglumg packing: Mixed 100 g of silicic acid/95 ml glycol solution in a mortar with a pestle to form a homogeneous powder. Stored in tightly stoppered bottle. Isopropanol-KOHz. Twenty-five grams.of KOH pellets (85 per! cent) was dissolved in 400 ml of isopropanol by warming on.a steam bath and swirling.. The supernatant isopropanol-KOH solution was decanted from aqueous KOH clinging to the bottom of the flask. Solution was cooled and stored at 40° F. 90 9l Isolation of FFA from Cheese (l) Five grams of a representative sample of cheese were acidified to pH l.9, as determined by acidifying a separate sample with 50 per cent sulfuric acid. (2) Five to ten milligrams each of 7:0 and 17:0 fatty acids were added in about 5 ml of Skellysolve B to the cheese with thorough mixing. (3) Nine grams of silicic acid were added to the cheese with thorough mixing. (4) The chromatographic column, described by Keeney (1956), was prepared by mixing 35 g of packing with l50 ml of l per cent Butanol in hexane to form a slurry. The slurry was added to a 25 x 500 mm column, equipped with a fritted-glass filter, 2 mm Teflon stopcock and a detachable 500 ml separatory funnel. The column was packed using S-lO psi nitrogen pressure so as to obtain a flow rate of approximately 3.5 ml/min. The silicic acid, cheese mixture was“, added as a cap to the column packing. (5) Fat was extracted with 400 ml of Skellysolve B containing l per cent butanol. The eluate was saved to be passed over a silicic acid-KOH column. 92 Removal of FFA from Fat Materials Silicic acid. Coarser particles of silicic acid were selected by suspending 100 g in 400 ml methanol-and decanting and discarding the silicic acid that did not settle within 5 minutes. This procedure was repeated once with methanol and once with 400 ml of acetone.) The remaining silicic acid was rinsed with ethyl ether and air dried.“ (l) Fifty grams of the coarse particle preparation were washed 3 times with l50 ml ether containing 2.5 per cent phoSphoric acid and then washed 2 times withLlSO ml ether. (2) The silicic acid was air dried, after which it was exhaustively washed with distilled water and redried. (3) Silicic acid was activated at 175° C for l8 hours and stored in a desiccator. Procedure (1) Four grams of prepared silicic acid were weighed into a 50 ml beaker. Eight ml of isopropanol-KOH and 24 ml of ethyl ether were added to the silicic acid with mixing. After standing 5 minutes, the silicic acid was slurried into a 18 x 180 mm chromato- graphic column, equipped with a fritted glass filter, 2.mm Teflon stopcock and a detachable 250 ml liquid reservoir.. The column wast washed with 100 ml of ether and air bubbles removed with a glass rod. 93 (2) The eluate from the fat extraction column was passed over the silicic acid-KQH column at a rate of 5 ml/min. (3) The column was washed with 75 ml of ether to remove the lipids. (4) The FFA were eluted with 60 ml of ether containing con-. centrated phosphoric acid (2.5 per cent, v/v at a flow rate of l0 ml/min. The eluate was collected in a 250 ml centrifuge bottle. (5) Column was washed 2 times with 40 ml portions of ethyl ether and eluate collected in centrifuge bottle. (6) Methanol (70-80 ml) was added to the combined eluates and the solution titrated to the phenolphthalein end point with l N methanolic-KOH under nitrogen. (7) The precipitated potassium salts of acidic constituents other than fatty acids were removed by centrifugation (l200 rpm) and the clear supernatant containing soluble salts of the fatty acids transferred to a 500 ml round bottom flask. The supernatant was evaporated at 500 C, to a volume_of 5-l0 ml, using a rotany evaporater. (8) The 5 ml sample was transferred to a 16 x 125 mm screw-cap round bottomed test tube and evaporated to dryness at 500 C under a stream of nitrogen. 94 Preparation of Butyl Esters (l) One-half ml of n-butanol along with l drop of 0:03 per cent methyl red indicator in n-butanol was placed in a 5 ml beaker. (2) A 0.025 ml quantity of concentrated sulfuric acid was added to the test tube containing the dried salts. The tube was sealed and placed in a boiling water bath until the dried.salts had dissolved. The tube was removed and cooled. (3) Additional concentrated sulfuric acid was added until the methyl red end point was reached. A 0.025 ml excess sulfuric acid was added and the tube resealed. (4) Butyl esters of FFA were formed by heating the sealed tube in a 1000 C water bath for 1.5 hours. (5) Tube was removed from the water bath and cooled. Anhydrous sodium sulfate was added and the mixture allowed to stand at room temperature for 45 minutes. (6) The butyl alcohol solution was transferred quantita- tively to a Babcock skimmilk bottle by washing the tube with 5-l0 ml of l per cent sodium bicarbonate. The skimmilk bottle was shaken vigorously. (7) The esters were brought up to the neck of the bottle by adding, without agitation, 20 per cent sodium chloride brine. (8) The bottle was spun briefly in a Babcock centrifuge and the esters brought into the neck of the bottles with brine. Appro- priate aliquots of the butyl alcohol solutions were withdrawn 95 directly from the necks of the Babcock bottles with a Hamilton 5 microliter syringe and injected in the gas-liquid chromatograph. Correction Factors Correction factors were obtained for 4:0, 6:0 and 8:0 com- pared to 7:0, and for 10:0, 12:0, 14:0, 16:0, 18:0, 18:1, 18:2 and 18:3 compared to 17:0. A mixture of standard fatty acids consisting of 5-10 mg of each standard acid was dissolved in ether and applied to the silicic acid-KOH column and treated as outlined above to obtain the butyl esters. I The appropriate factor for each acid was calculated from the resulting peak areas of the butyl esters (Bills, Khatri and Day, 1963). The factors were used in solving for the weight of the fatty acids present in the cheese sample. Table 28.--Moisture content of quick ripened Blue cheese. ——v Cheese %M Cheese %M Commercial 42.5 Past.-Unhom. 43.5 62 F-7 days 42.9 Homog. raw 48.0 Sugg. proc. #1, 44.9 Homog. one 45.0 Sugg. proc. #2 46.2 Lactic acid 42.7 Salt 0, 4, 6 45.1 Lactic & Star. 41.1 salt 1, 2, 3 45.2 H01, 0 51.3 Salt 1, 4, 5 44.0 Temp.x48o F~#1, 44.1 Salt 2, 4, 5, 6 44.0 Temp..48o F #2 44.4 White mold #1 49.1 Temp. 570 F 43.2 White mold #2 44.8 Temp. 72, F 39.0 Lipase 42.7 Cooked / 42.2 BIBLIOGRAPHY BIBLIOGRAPHY Albrecht, T. w. and H. 0. Jaynes. Milk lipase. J. Dairy Sci. 38; 1955. 137. Alford, J. A., J. L. Smith and H. D. Lilly. Relationship of micro- 1971. bial activity to changes in lipids of-food. J. Appl. Microbio. 1§§3133. Anderson, 0. F. and E. A.-Day. Quantitative analysis of the major_ 1965. fatty acids in Blue cheese. J. Dairy Sci. 48:248. Anderson, 0. F. and E. A. Day. Quantitation, evaluation and effect 1966. of certain microorganisms on flavor components of Blue cheese. J. Agri. 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