D I S T R I B U T I O N OF D I A C E T Y L AND A C E T Y L M E T H Y L C A R B I N O L B E T W E E N F A T AND W A T E R , W I T H S P E C I A L R E F E R E N C E TO B U T T E R 1 W. H. t I O E C K E R AI#D B. ~V. t t A M M E R
Department of Dairy Industry, Iowa State College, Ames, Iowa
I n b u t t e r made with butter culture, diacetyl and acetylmethylcarbinol are derived largely from the culture added to the cream and from the fermentation of citric acid during holding or ripening of the cream. Only small portions of these compounds present in the cream at churning appear in the finished butter. They are carried out in the buttermilk (2, 4, 5, 6, 8, 9, 15, 16, 17, 19) in relatively large amounts and also may be removed by the water used to wash the butter (6, 11, 13, 1 7 ) . F a t and water, the two constituents of b u t t e r which are present in large amounts, have v e r y different solvent properties. The data reported herein deal with the distribution of diacetyl and acetylmethylcarbinol between f a t and water and involve studies on (a) mixtures of " W e s s o n " oil and water or brine, (b) mixtures of b u t t e r f a t and water or brine and (c) unsalted and salted butter. ANALYTICAL PROCEDURES
Diacetyl was determined by the colorimetric method of Prill and Hammer (18), with minor modifications used by Hoecker and H a m m e r (9). Color intensities were obtained with a Klett-Summerson photoelectric colorimeter. Acetylmethylcarbinol also was determined colorimetrically, using the procedure described b y ttoecker and H a m m e r (9) for its estimation in butter. EXPERI)SENTAL
Distribution of Diacetyl and Acetylmethylcarbinol in Mixtures of " W e s s o n " Oil and ~Vater or Brine 2 The distribution of diacetyl between " W e s s o n " oil and water or brine was studied (a) by adding various amounts of an oil solution of diacetyl to 100 ml. portions of oil and then adding 100 ml. of either water or brine to each portion and (b) by adding various amounts of a water solution of diacetyl to 100 ml. portions of either water or brine and then adding 100 ml. of oil to each portion. The mixtures were held 2 days at room t e m p e r a t u r e in closed containers, with f r e q u e n t shaking. The oil and water or brine were separated by centrifuging, the oil was pipetted off and diacetyl contents of' Received for publication October 16, 1941. 1/journal Paper No./[-713 of the Iowa Agricultural Experiment Station, Ames, Iowa. Project No. 127. 2 Brine regularly consisted of 14 gm. sodium chloride made up to 100 ml. with distilled water. 175
ml. ml. ml. soln. A or B + 100 ml. brine ml.
ml. ml. ml. soln. C§ or DII + 100 ml. oil nil.
0.5 1.0 2.0 3.0
0.5 1.0 2.0 3.0
0.5 ml. 1.0 ml. 2.0 nil. soln. C or D + 100 ml. oil 3.0 ml.
+
+
100 ml. oil
100 ml. oil
100 ml. w a t e r +
100 ml. brine +
0.5 ml. 1.0 ml. 2.0 ml. soln, A t or B$ + 100 ml. water 3.0 ml.
Description of mixture
1.53 3.31 6.40 9.75
1.85 3.82 7.78 12.31
1.41 3.07 5.75 9.34
1.86 3,54 6.55 10.38
p..p.m. in mixture cale.*
* Calculated f r o m analyses of oil and w a t e r or brine. t Soln. A = 100 ml. ' ' Wesson ' ' oil + 0.1 ml. diacetyl. $ Soln. B = 100 ml. ' ' Wesson ' ' oil + 0.2 gm. aeetylmethylcarbinol. § Soln. C = 100 ml. w a t e r + 0.1 ml, diacetyl. ]1 Soln. D = 100 ml. w a t e r + 0.2 gin. aeetylmethylearbinol.
No.
Series
TABLE 1
2.15 4.71 9.47 14.70
3.00 6.40 12.92 21.00
1.98 4,19 7.73 12.50
0.91 1.91 3.33 4.80
0.70 1.24 2.64 3,62
0.83 1.95 3.77 6.18
0.78 1.33 2.69 4.35
in oil
m water 2.93 5.75 10.40 16,40
p.p.m.
p..p.m,
Diacetyl
29.8 28.9 26.0 24.6
18.9 16.3 17.0 14.7
29.5 31.8 32.8 33.1
, 21.0
21.0 18.8 20.5
in oil
%
4.42 7.90 15.87 24.27
3.92 13.60 16.71 26.11
3.87 8.83 15.62 23.10
4.62 8.79 14.78 22.56
p.p.m. m mixture eale.
8.10 14.70 29.40 46.20
6.87 15.92 31.80 49.90
7.04 16.40 29.27 43.13
8.45 16.70 28.20 43.30
p.p..m, in water
0.73 1.10 2.34 2.33
0.96 1.27 1.62 2.32
0.69 1.26 1.96 3.07
0.79 0.88 1.36 1.82
p.p.m. in oil
Acetylmethylcarbinol
Distribution of diacetyl and acetylmethylearbinol in mixtures of ' ' Wesson ' ' oil and water or brine Mixtures contained equal volumes of oil and w a t e r or brine and were held 2 days at room t e m p e r a t u r e
0.83 0.70 0.74 0.48
0.12 0.47 0.48 0.45
0.89 0.71 0.63 0.66
0.86 0.51 0.46 0.40
% in oil
DIACETYIJ AND ACETYLMETHYLCARBINOL
177
the oil and water or brine were determined. I n the studies on acetylmethylcarbinol the same general procedures were used. Table 1 gives the details of the trials and also the results of the analyses. I n the mixtures, the water or brine regularly contained higher concentrations of diacetyl and acetylmethylcarbinol than the oil, the differences being greater with acetylmethylcarbinol than with diacetyl. The percentage of diacetyl in a mixture that was contained in the oil was increased by sodium chloride in the water. The concentration of diacetyl in a m i x t u r e a p p a r e n t l y did not affect the percentage in the oil. The concentrations of acetylmethylcarbinol in the oil were v e r y low, and the different concentrations in the mixtures gave essentially the same percentage in the oil. I n the oil-water mixtures, concentrations of diacetyl and acetylmethylcarbinol in water ranged from 2.93 to 21.00 p.p.m, and f r o m 6.87 to 49.90 p.p.m., respectively, and those in the oil varied from 0.70 to 4.35 p.p.m, and from 0.79 to 2.32 p.p.m., respectively. Of the total diacetyl and acetylmethylcarbinol in the mixtures, f r o m 14.7 to 21.0 per cent and f r o m 0.12 to 0.86 per cent, respectively, were in the oil. I n the oil-brine mixtures, concentrations of diacetyl and acetylmethylcarbinol in the brine ranged f r o m 1.98 to 14.70 p.p.m, and f r o m 7.04 to 46.20 p.p.m., respectively, while those in the oil varied from 0.83 to 6.18 p.p.m, and from 0.69 to 3.07 p.p.m., respectively. The percentages of the total diacetyl and acetylmethylcarbinol in the mixtures that were in the oil ranged from 24.6 to 33.1 and from 0.48 to 0.89, respectively. A series of oil-water mixtures, each containing 200 gin. of " W e s s o n " oil and 40 gm. of water, were p r e p a r e d and different amounts of either diacety] or acetylmethylcarbinol added. Additions of the various concentrations of diacetyl or acetylmethylcarbinol were made by using equal amounts of the compounds as oil and water solutions. The mixtures were then treated the same ~as those involving equal volumes of oil and water or brine. Data on the distribution of diacetyl and acetylmethylcarbinol in the mixtures are given in table 2. As in the previous trials, the water regularly contained higher concentrations of diacetyl and acetylmethylcarbinol than the oil, and the differences were greater with the carbinol t h a n with diacetyl. W i t h both diacetyl and acetylmethylcarbinol, the percentages in the mixtures t h a t were contained in the oil varied considerably, b u t with each compound the highest value was obtained with the lowest concentration. I n the mixtures, concentrations of diacetyl and acetylmethylcarbinol in the water ranged f r o m 0.53 to 6.90 p.p.m, and f r o m 10.92 to 118.00 p.p.m., respectively, while those in the oil varied f r o m 0.24 to 2.19 p.p.m, and from 0.87 to 5.43 p.p.m., respectively. Of the total diacetyl and acetylmethylcarbinol in the mixtures, f r o m 56.5 to 69.0 per cent and f r o m 18.5 to 28.7 per cent, respectively, were in the oil.
178
W. H. HOECKER AND B. W. HAMMER TABLE 2
Distribution of diacetyl and aeetylmethylcarbinol in mixtures of ' ' Wesson" oil and water
Mixtures contained 200 gin. oil and 40 gm. water and were held 2 days at room temperature Diacetyl
Trial I p.p.m, No. [ in mixture talc.* 0.29 0.47 0.68 0.70 1.09 1.68 2.97
Aeetylmeth dcarbinol
p..p.m, m water
p.p.m. in oil
% in oil
p.p.m. in mixture calc.
p..p.m, m water
p.p.m. in oil
% in oil
0.53 0.96 1.53 1.60 2.43 4.40 6.90
0.24 0.37 0.52 0.52 0.83 1.14 2.19
69.0 66.0 63.3 61.4 63.3 56.5 61.3
2.54 4.00 5.65 6.49 11.33 13.04 24.13
10.92 19.00 26.10 30.70 54.40 64.00 118.00
0.87 1.01 1.57 1.67 2.75 2.89 5.43
28.7 21.0 23.2 21.4 20.2 18.5 18.8
* Calculated from analyses of oll and water. W i t h about the same concentration of diacetyl or acetylmethylcarbinol in mixtures of equal volumes of oil and water and in mixtures of 200 gin. oil and 40 gin. water, the concentrations of the compounds in both the water and the oil were higher in the latter mixtures. Since in these mixtures the oil comprised such a large portion of the total weight, it contained larger percentages of the diacetyl and acetylmethylcarbinol than in mixtures of equal volumes of oil and water. D i s t r i b u t i o n of D i a c e t y l and A c e t y l m e t h y l c a r b i n o l in M i x t u r e s of B u t t e r f a t and W a t e r or B r i n e
I n studying the distribution of diacetyl between b u t t e r f a t and water or brine, b u t t e r f a t was obtained by melting sweet cream butter (made without butter culture), allowing the fat and serum to separate at 45 ° C. and then decanting and filtering the f a t at 45 ° C. lV[ixtures of 84 per cent melted fat and 16 per cent water or brine were placed in q u a r t jars and various amounts of diacetyl added, the additions consisting of equal amounts of diacetyl as " W e s s o n " oil and water solutions. The jars were closed and placed in a small experimental c h u r n where the mixtures were agitated for 1 hour. A f t e r holding the mixtures at 4 ° C. for various periods, the fat and water or brine were separated by placing the mixtures at 45 ° C. until the fat had melted, centrifuging and then pipetting off the fat. Diacetyl concentrations in the fat and the water or brine were determined. I n the trials with acetylmethylcarbinol, the same procedures were employed. Table 3 gives the data on one trial which is representative of the five carried out. The diacetyl and aeetylmethylcarbinol showed the same general distribution as in the mixtures involving " W e s s o n " oil, with the water or brine regularly containing higher concentrations of the compounds than the fat and the differences being greater with acetylmethylcarbinol than with diacetyl. Sodium chloride increased the percentages of the compounds in the
179
DIACETYL AND ACETYLMETttYLCARBINOL TABLE 3
Distribution of diacetyl and acetylmethylcarbinol in mixtures of butterfat and water or brine
Mixtures contained 84 p e r cent b u t t e r f a t and 16 per cent w a t e r or brine and were held 7 and 30 days at 4 ° C. Diacetyl Description of mixture
Days held at 4oC.
Butterfatwater 30
Butterfatbrine 30
p..p.m,
Acetylmethylearbinol
p.p,m, in water
p.p.m. in oil
% in oil
p..p.m, m mixture ca]c.
1.11 2.25 4.06 4.78 6.15 7.50
2.23 4.90 8.60 10.91 13.59 17.44
0.90 1.75 3.19 3.61 4.74 5.61
68.0 65.3 66.0 63.4 64.7 62.9
2.81 4.85 8.34 12.81 20.56
0.86 1.58 3.38 3.60 4.93 5.04
1.87 3.50 7,60 7.60 10.60 10.30
0.67 1.21 2.56 2.83 3.84 4.04
65.2 64.6 63.7 66.2 65,5 65.4
0.81 1.40 2.67 3.46 5.07 6.01
1.08 1.90 3.92 5.04 8.08 9.12
0.76 1.31 2.43 3.16 4.50 5.42
78.7 78.4 76.5 76.7 74.5 75.7
8.85 12.94 18.70 21.75
0.62 1.25 2.14 3.25 3.85 5.81
0.80 1.75 3.11 5.11 6,46 8.78
0.59 1.15 1.95 2.89 3.35 5.23
79.0 78.4 75.3 74.7 73.3 75.7
m
mixture calc. ~
p.p.m, in" water
p.p.m. " in oil
% in oil
I 12.50 22.30 38.00
0.97 1.52 2.70
28.9 26.4 27.1
; 53.00 i 97.58
5.15 5.89
33.7 24.0
I 1.93 2.71 4.30 5.27 5.89
31.6 26.2 33.4 29.8 24.5
3.31
'! 10.00"" i 2.04
513
i 2030
35.00 54.20 77.60 89.20
3.88 5.10 7.48 8.88
51.7 36.7 36.7 33.1 33.6 34.3
3.34 5.21 9.47 13.62 18.66 22.24
11.80 [ 20.40 1' 37.30 56.10 76.70 91.60
1.73 2.33 ~ 4.16 5.54 7.60 9,00
43.4 37.4 37.0 34.1 34.2 34.0
I 5.14 8.67 10.81 14.83 19.76
22.00 40.00 45.00 65.50 ! 93.60
224
Calculated f r o m analyses of f a t and w a t e r or brine.
m i x t u r e s that were contained in the fat. 1Kixtures held 7 days and 30 days showed essentially the same distribution of diaeetyl and the carbinol. I n the b u t t e r f a t - w a t e r mixtures, concentrations of diacetyl and acetylmethylcarbinol in the water r a n g e d f r o m 1.87 to 17.44 p.p.m, and f r o m 12.50 to 97.58 p.p.m., respeetively, and those in the f a t varied f r o m 0.67 to 5.61 p.p.m, a n d f r o m 0.97 to 5.89 p.p.m., respectively. The f a t contained f r o m 62.9 to 68.0 per cent of the diaeetyl and f r o m 24.0 to 33.7 per cent of the acetylmethylcarbinol in the mixtures. I n the b u t t e r f a t - b r i n e mixtures, concentrations of diaectyl and acetylmethylearbinol in the brine r a n g e d f r o m 0.80 to 9.12 p.p.m, and f r o m 10.00 to 91.60 p.p.m., respectively, while those in the f a t varied f r o m 0.59 to 5.42 p.p.m, a n d f r o m 1.73 to 9.00 p.p.m., respectively. The f a t contained f r o m 73.3 to 79.0 per cent o3 the diaeetyl and f r o m 33.1 to 51.7 p e r eent of the aeetylmethylcarbinol in the mixtures.
180
W. H. HOECKER AND B. W. HAMMER
T h e r e s u l t s on t h e five t r i a l s w i t h b u t t e r f a t a n d w a t e r o r b r i n e a r e summ a r i z e d i n t a b l e 4, t h e d a t a b e i n g d i v i d e d on t h e basis o f t h e c o n c e n t r a t i o n s of d i a c e t y l o r a c e t y l m e t h y l c a r b i n o l in t h e m i x t u r e s . TABLE 4 Summary of the distribution of diacetyl and avetylmethylearbinol i~ all the butterfat and water or brine mixtures Mixtures contained 84 per cent butterfat and 16 per cent water or brine and were held various periods at 4 ° C. Description of mixtures and groupings
p.p.m. in
l~umber of mixtures
mixture calc. *
Average p.p.m, in Water or brine
I
Fat
Average % in fat
Diacetyl Butterfat-water mixtures Group 1 ................................. Group 2 ................................. Group 3 ................................. Butterfat-brine mixtures Group 1 .............................. Group 2 ................................. Group 3 ..............................
0 to 1.51 to above
1.50 5.00 5.00
13 21 17
1.60 6.45 12.01
0.64 2.60 5.85
71.8 69.2 71.5
0 to 1.51 to above
1.50 5.00 5.00
11 18 23
4.08
1.23
12.96
0.95 2.96 9.54
80.6 78.9 79.0
Acetylmeth lcarbinol Butterfat-water mixtures Group 1 ............................... Group 2 .............................. Group 3 ................................. Butterfat-brine mixtures Group 1 .............................. Group 2 ................................. Group 3 .................................
0 to 8.00 8.01 to 24.00 above 24.00
13 18 18
23.46 73.86 185.17
1.90 4.93 12.13
30.0 26.4 22.9
0 to 8.00 8.01 to 24.00 above 24.00
13 20 18
20.26 63.68 149.30
2.47 6.41 14.54
40.3 34.9 33.9
* Calculated from analyses of fat and water or brine. T h e a v e r a g e v a l u e s in t h e t a b l e s u p p o r t t h e v a r i o u s p o i n t s a l r e a d y noted. T h e y also s h o w t h a t as t h e c o n c e n t r a t i o n of d i a c e t y l i n a m i x t u r e increased, t h e p e r c e n t a g e i n t h e f a t d i d n o t c h a n g e a p p r e c i a b l y , w h i l e as t h e concent r a t i o n of a c e t y l m e t h y l c a r b i n o l i n a m i x t u r e i n c r e a s e d , t h e p e r c e n t a g e in t h e f a t d e c r e a s e d . T h e s e r e l a t i o n s h i p s a r e s u g g e s t e d b y t h e d a t a on t h e indiv i d u a l m i x t u r e s , b u t i r r e g u l a r i t i e s in th e r e s u l t s t e n d to o b s c u r e them.
D i s t r i b u t i o n of D i a c e t y l and A c e t y l m e t h y l c a r b i n o l in Unsalted and S a l t e d B u t t e r I n t h e s t u d i e s on t h e d i s t r i b u t i o n of d i a e e t y l a n d a c e t y l m e t h y l c a r b i n o l b e t w e e n t h e f a t a n d s e r u m of u n s a l t e d a n d s a l t e d b u t t e r , t h e s e r u m was s e p a r a t e d f r o m t h e f a t ( a ) b y s u b j e c t i n g c h i l l e d b u t t e r to h i g h p r e s s u r e s a n d (b) b y c e n t r i f u g i n g m e l t e d b u t t e r . T h e u n s a l t e d b u t t e r w as of t h e high-flavor type, being c h u r n e d from cream that had been ripened with a b u t t e r c u l t u r e to a r e l a t i v e l y h i g h a c i d i t y . T h e s a l t e d b u t t e r e i t h e r was
DIACETYL AND ACETYLMETHYLCARBINOL
181
churned f r o m sweet cream held over night at about 4 ° C. a f t e r addition of 8 per cent b u t t e r culture or was churned f r o m sweet c r e a m (containing no culture) with addition of a solution of diacetyl or a distillate of b u t t e r culture d u r i n g working of the butter. F o r the separation of the serum and f a t by pressing, the b u t t e r was held at a p p r o x i m a t e l y - 1 8 ° C. for 24 hours, a f t e r which it was shredded and 400 gin. mixed with 900 gm. of fine sand. The m i x t u r e was then subjected to a p p r o x i m a t e l y 1200 lbs. pressure per square inch in a hydraulic press (12). The sand and the p a r t s of the press coming in contact with the m i x t u r e were cooled to a p p r o x i m a t e l y 4 ° C. before use so t h a t the t e m p e r a t u r e of the b u t t e r would not increase too rapidly. W i t h the procedure employed, a portion of the b u t t e r serum was obtained. Also, a small a m o u n t of the mixture came t h r o u g h the filter cloth; this m a t e r i a l was held at 45 ° C. a n d the f a t recovered b y centrifuging and pipetting. F o r the separation of the serum a n d f a t b y melting, the b u t t e r was held in a closed container at 45 ° C. until the f a t had melted, and the m i x t u r e was then c e n t r i f u g e d a n d the f a t pipetted off. Diacetyl a n d acetylmcthylcarbinol determinations were made on the original b u t t e r and on the f a t a n d serum. The percentages of f a t and w a t e r in the b u t t e r were determined b y the Mojonnier method, and f r o m these values and the analyses on the f a t a n d serum the amounts of diacetyl a n d acetylmethylcarbinol in the b u t t e r were also calculated. Table 5 gives the data. As with the mixtures of b u t t e r f a t and w a t e r or brine, the serum of b u t t e r contained higher concentrations of diacetyl and acetylmethylcarbinol than the fat, with the greatest differences again involving the carbinol. The averages of the percentages of diacetyl and acetylmethylcarbinol contained in the f a t were smaller in unsalted t h a n in salted butter. The percentage of diacetyl contained in the f a t a p p a r e n t l y was i n d e p e n d e n t of the concentration in the butter, whereas the percentage of acetylmethylcarbinol contained in the f a t usually decreased somewhat as the concentration in the b u t t e r increased. Addition of a solution of diacetyl or a distillate of b u t t e r culture to salted b u t t e r resulted in essentially the same distribution of diacetyl as when the b u t t e r was made f r o m cream containing b u t t e r culture. W h e n the serum was separated b y pressing the butter, the f a t usually contained slightly higher percentages of diacetyl and acetylmethylcarbinol t h a n when the serum was separated b y melting the butter. The amounts of diacetyl and acetylmethylcarbinol in the butter, as calculated f r o m its composition and analyses of the f a t and serum, agree f a i r l y closely with the determined amounts.
I n the unsalted butter, diacetyI and acetylmethylcarbinol concentrations in the serum r a n g e d f r o m 0.25 to 3.55 p.p.m, and f r o m 4.85 to 119.16 p.p.m., respectively, and those in the f a t varied f r o m 0.19 to 1.11 p.p.m, and f r o m
0.92 0.24
0.57 0.57
1.29 1.29
1.42 1.42
0.99 0.99
0.16
0.08
0.11
0.10 0.10
0.05 0.05
0.69 0.69
0.92 0.92
0.50 0.50
pressing melting
pressing melting
pressing melting
pressing melting
pressing
pressing
pressing
pressing melting
pressing melting
pressing melting
pressing§ melting§
pressing melting
7
8
9
10
11
12
13
14
Ii
0.44 0.52
0.96 0.97
0.71 0.73
0.03 0.03
0.10 0.09
0.11
0.09
0.19
0.91 0.94
1.39 1.33
1.09 1.11
0.58 0.50
0.81 0.20
0.96
eale.
0.73 0.80
2.00 ] .33
1.55 1.15
0.07 0.11
0.21 0.14
0.26
0.20
0.44
2.70 1.75
3.55 2.50
3.13 2.34
1.79 1.54
2.27 0.25
2.88
p.p.m, in serum
Diacetyl
0.39 0.48
0.76 0.92
0.55 0.66
0.02 0.02
0.08 0.09
0.09
0.07
0.14
0.58 0.79
1.04 1.11
0.72 0.89
0.33 0.35
0.45 0.19
0.61
% in fat
63.2 78.4
61.3
66.1
63.2
70.5 72.8
61.6 74.6
61.8 72.3
65.5 48.5
Salted
52.7 70.3
62.1 69.4
55.0 67.5
46.6 58.0
44.4 75.0
53.2
Unsalted
p.p.m. m fat
Determined. Calculated on b a s i s of composition of b u t t e r a n d a n a l y s e s of s e r u m a n d fat. B u t t e r held 2 weeks at 4 ° C. Solution of diacetyl a d d e d to sweet c r e a m b u t t e r . II Distillate of b u t t e r culture a d d e d to sweet e r e a m b u t t e r ,
1.16
detr-~
p.p.m, in b u t t e r
pressing pressing$
separated by
Serum
pressing
Sample No.
TABLE 5
13.85 13.85
0.54 0.54
2.40 2.40
3.00
3.18
4.56
10.10 10.10
20.90 20.90
23.20 23.20
1.58 1.58
19.75
detr,
I
13.50 11.83
0.50 0.54
2.69 2.58
3.03
2.69
4.23
7.94 8.34
20.25 20.08
23.05 20.44
1.60 1.56
17.41
talc.
p.p.m, in b u t t e r fat
serum
59.00 45.40
1.72 1.93
11.00 8.66
13.00
12.30
18.53
32.00 33.50
92.40 88.90
119.16 96.00
5.08 4.85
78.65
4.00 4.87
0.29 0.30
1.04 1.25
1.09
0.91
1.76
3.40 3.60
6.40 6.86
5.46 6.61
0.89 0.88
6.20
p.p.m. in
In
p..p.m.
Acetylmethylcarbinol
Distribution of diaeetyl and aeetylmethylcarbinol in unsalted and salted butter
23.6 32.8
46.0 44.4
30.8 43.4
29.0
27.5
34.2
35.6 35.9
26.2 28.2
19.5 27.1
45.6 46.8
29.8
in fat
%
0
QO t~
DIACETYL AND ACETYLMETHYLCARBINOL
183
0.88 to 6.86 p.p.m., respectively. The f a t contained f r o m 44.4 to 75.0 per cent of the diacetyl and f r o m 26.2 to 46.8 per cent of the acetylmethylcarbinol in the butter. I n the salted butter, diacetyl a n d acetyhnethylcarbinol concentrations in the s e r u m r a n g e d f r o m 0.07 to 2.00 p.p.m, a n d f r o m 1.72 to 59.00 p.p.m., respectively, while those in the f a t varied f r o m 0.02 to 0.92 p.p.m, and f r o m 0.29 to 4.87 p.p.m., respectively. Of the total diacetyl and aeetylmethylcarbinol in the butter, the f a t contained f r o m 48.5 to 78.4 per cent and f r o m 23.6 to 46.0 per cent, respectively. DISCUSSION OF RESULTS
The presence of diacetyl and acety]methylcarbinol in the f a t of b u t t e r and of m i x t u r e s of f a t and water or brine is in agreement with various investigations (3, 7, 8, 10, 15, 17). However, !V[akar'in (13, 14) f o u n d diacetyl (a trace) in the f a t of only one of eight samples of butter, whereas the serum always contained diacetyl. H e believed that the aroma of b u t t e r is influenced largely b y the concentration of the aqueous constituents of the cream t h a t are retained in the butter. On the basis of averages of the percentages of diacetyl a n d acetyhnethylearbinol in cream t h a t were retained in butter, Barnicoat (1, 2) suggested t h a t these compounds are present only in the serum. I f this were the case, the percentages of the compounds in the cream t h a t are retained in the b u t t e r should be the same, a n d actually a higher percentage of diacetyl t h a n of acetylmethylcarbinol is retained (19). Since large percentages of the diacetyl and acetylmethylcarbinol in cream at churning are removed with the buttermilk, higher concentrations of the compounds would be expected in the serum t h a n in the f a t of butter. Although the concentrations in the f a t are relatively low, the percentages of the compounds in b u t t e r t h a t are contained in the f a t are c o m p a r a t i v e l y high because b u t t e r contains a p p r o x i m a t e l y 80 p e r cent fat. The difference in the partitioning of diacetyl and acetylmethylcarbinol between f a t a n d serum of b u t t e r (or between f a t and w a t e r or brine in the mixtures) is what would be expected f r o m the chemical constitution of the compounds. Davies (8) stated t h a t since the v a p o r pressure of diacetyl is much higher t h a n t h a t of acetylmethylcarbinol, a greater portion of diacetyl than of the carbinol would be expected in the fat. A p p a r e n t l y , the partitioning of diacetyl and carbinol between the serum and f a t in b u t t e r reaches an equilibrium in a relatively short time. The distribution of diacetyl in b u t t e r into which a solution of diacetyl or a distillate of butter culture has been worked should be essentially the same as in b u t t e r made f r o m cream containing b u t t e r culture; diacetyl is produced b y the organisms in the s e r u m of cream (or b u t t e r ) and therefore in both cases the partitioning of the diacetyl is f r o m the serum to the fat. The g r e a t e r percentage of diacetyl and acetylmethylcarbinol in the f a t
184
W. H. HOECKER AND B. W. HAMMER
in mixtures of fat and brine than in mixtures of fat and water presumbly is due to the salting-out effect of the sodium chloride. Some of the older procedures for distilling diacetyl from solutions made use of this effect through the addition of sodium chloride to a solution before distillation. Comparative solubilities in f a t probably explain why with diacetyl the concentration in b u t t e r does not affect the percentage of the total that is retained in the fat, while with acetylmethylcarbinol an increase in the concentration in b u t t e r decreases the percentage of the total that is retained in the fat. The low solubility of acetylmethylcarbinol soon limits the amount taken up by the fat. The variations among samples of b u t t e r in the percentages of the total diacetyl or acetylmethylcarbinol that is contained in the fat probably are due to several factors, such as the composition of the butter, the physical state of the fat, the churning procedure and the degree to which water is dispersed in the butter. Also, analytical errors involved in determining Yery small quantities of the compounds m a y be of minor significance. SUMMARY
I n unsalted and salted butter, both the serum and the fat contained diacetyl and also acetylmethylcarbinol. The serum contained higher concentrations of the compounds than the fat, the differences being greater with acetylmethylcarbinol than with diacetyl. I n each type of butter, a larger percentage of the total diacetyl than of the total acetylmethylcarbinol was contained in the fat. B u t t e r into which a solution of diacetyl or a distillate of b u t t e r culture had been worked showed the same general distribution of diacetyl as butter made from cream containing butter culture. I n general, the data obtained on mixtures of " W c s s o n " oil and water or brine and mixtures of b u t t e r f a t and water or brine agree with the results obtained on butter. I n such mixtures, and also in butter although the results were not as definite as with the mixtures, the addition of sodium ch]n~'ide increased the percentage of diacetyl or acetylmethylcarbinol t h a t was in the fat. The concentration of diacetyl in the mixtures or in butter a p p a r e n t l y did not affect the percentage contained in the fat, b u t as the concentration of acetylmethylcarbinol increased the percentage contained ~n the fat decreased. Mixtures of b u t t e r fat and water or brine held at 4 ° C. showed essentially the same distribution of diacetyl and acetylmethylcarbinol after 30 days as after 7 days. REFERENCES (1) BARNICOAT, C . R . Diacetyl in Cold-stored Butters. Jour. Dairy Res., 6: 397-406. 1935. (2) BARNICOAT,C.R. Diacetyl in Cold-stored Butters. II. Jour. Dairy Res., 8: 15-30. :1937.
DIACETYL AND ACETYLMETHYLCARBINOL
185
(3) BOGDON0V, V . M . Ways of Increasing the Aroma of Butter. Molochnaya Prom., 4, No. 4: 5-9. 1937. Original not seen. Abstracted in Chem. Abs., 33: 7411. 1939. (4) BRIOUX, CH., AND JOUIS, Elm. Le Diac~tyle dans ]es Beurres l~ormands. Compt. Rend., 205: 526-528. 1937. (5) BRIOUX, CH., AND JOUIS, EDG. Le Diac~tyle dans les Beurres Normands. Le Lait~ 18: 11-22. 1938. (6) BtiNeER, H. Die Preussische Versuchs- und Forschungsanstalt fiir Milchwirtschaft in Kiel in J a h r e 1936-37. Landw. Jahrb., 84: 887-927. 1937. (7) DAVIES, W . L . Flavour and Aroma of Butter. Dairy Indus., 1: 165-167. 1936. (8) DAVIES, W . L . The Development of Aroma in Butter. l l t h W o r l d ' s Dairy Congr. Proc., Berlin, 2: 76-78. 1937. (9) I-IOECKER, W. 1=[., AND HAMI~IER, B . W . Flavor Development in Salted Butter by Pure Cultures of Bacteria: Preliminary Results. Iowa Agr. Expt. Sta., Res. Bul. 290. 1941. ( 1 0 ) KING, N. ~3ber die Einwerkung des Diaeetyls a u f das Butterfett. Milchw. Forsch., 12: 172-182. 1931. (11) KRENN, ffOSEF. Ober die Bildung yon Diacetyl bei der l~eifung des Rahmes und dessert Schicksal bei der Butterung. l l t h W o r l d ' s Dairy Congr. Proc., Berlin, 2: 78-80. 1937. (12) LANE, C. B., AND HAMMER, B . W . Bacteriology of Cheese. I. Effect of Pasteurizing the Milk on the Nitrogenous Decomposition in Cheddar Cheese. Iowa Agr. Expt. S t a , Res. Bul. 183. 1935. (13) MAKAR'IN, A. M. The Distribution of Biacetyl in the Process of Production of Butter Both in the Individual Products and in the B u t t e r in the Various Phases of Production. Molochnaya Prom., 4, No. 5: 20-22. 1937. Original not seen. Abstracted in Chem. Abs., 33: 9467. ]939. (14) MAKAR'IN, A . M . The Production of Aroma in Butter. Molochno-Maslodel'naya Prom., 5, No. 6: 10-13. 1938. Original not seen. Abstracted in Chem. Abs., 35: 2988. 1941. (15) MICHAELIAN, M. B., AND HAMMER, B. W. Studies on Acetylmethy]carbino] and Diacetyl in Dairy Products. Iowa Agr. Expt. Sta., Res. Bul. 179. 1935. (16) MOttLER, H., AND HERZFELD, E. Diacetyl in Milehprodukten. Mitt. aus dem Geb. der Lebensmtl. Untersuch. u. Hyg., 26: 34-41. 1935. (17) MOH~, W., AND WELLM, J. Der Diaeetylgehalt in deutscher Butter und Einfluss des Herstellungsverfahrens auf den Diacetylgehalt der Butter. 11th W o r l d ' s Dairy Congr. Proc., Berlin, 2: 89-97. 1937. (18) PRILL, E. A., AN]) H A ~ E E , B . W . A Colorimetric Method for the Mierodetermination of Diaeetyl. Iowa State Col. flour. Sci., 12: 385-395. ]938. (19) PRILL, E. A., AND tIAM~ER, B . W . Changes in the Diacetyl and the Acetylmethylcarbinol Contents During the Manufacture of Butter. flouR. DAIRY SCI., 22: 79-88. 1939.