Sauerkraut from Pre-Treated Cabbage C. H. KEIPPER,W. H. PETERSON, AKD E. B. FRED, University of Wisconsin, Madison, Wis., W. E. J-AUGHN.American Can Co., Maywood, Ill. The effect of washing and other treatments of cabbage on the quality of sauerkraut has been tested over a period of three years on both laboratory and factory scale. I n all, 199 barrels of kraut hare been packed at the laboratory and 468 tons at a commercial plant. I n the barrel experiments 84 per cent of the kraut made f r o m washed cabbage graded "good to fancy," whereas only 19 per cent of the kraut made f r o m unwashed cabbage reached this grade. I n factory experiments an increase of from 17 to 50 per cent in the output of quality product was obtained by washing the cabbage. This treatment
removes a large number of undesirable micro-organisms which reside on the outside of the cabbage head, and permits the desirable iypes, which are most abundant on the inner tissue, to bring about a satisfactory fermentation. Bacteriological and chemical data are given to show the effect of washing the cabbage on theflora and composition of the sauerkraut. Inoculation of the washed cabbage with pure cultures of lactic acid producing bacteria gave, in general, further improvement, but the increase was not suficient to warrant recommending its adoption in commercial practice.
S
AUERKRAUT is made by adding salt to shredded cabbage, packing the mixture in a suitable container, and allowing the plant tissue to undergo natural fermentation. The effect of salting and packing is to bring about liberation of large quantities of plant sap. This juice contains sugars, proteins, and mineral salts, and provides an excellent medium for the development of some of the microorganisms originally present on the cabbage tissue and for the suppression of others. The lactic acid forming types, which convert the sugars into lactic acid, acetic acid, ethyl alcohol, and carbon dioxide, sooner or later dominate the fermentation. While the natural process of fermentation thus brings about ultimate destruction of the undesirable microorganisms, their number and persistence for a certain length of time are important factors in affecting the quality of the sauerkraut. I n the past decade attempts have been made to control the flora of sauerkraut by regulating the temperature and inoculating the cabbage with pure or mixed cultures of lactic acid forming bacteria. While these are important control measures, they are inadequate to cope with the mixed mass of organisms carried into the vat on the cabbage tissue. If the types of organisms which enter the vat could be controlled to some extent, the production of uniformly good kraut would become an easier problem. I n another report (4)it has been shown that the outer leaves of the cabbage plant carry a large number of bacteria which are of no value in the production of sauerkraut. The inner leaves, on the other hand, are almost free from such bacteria and carry a flora in which the useful lactic acid formers predominate, It follows that the removal of as many organisms as possible from the outer tissue will increase the proportion of beneficial organisms and favor the development of a satisfactory fermentation. I n the present investigation the reduction of undesirable forms has been accomplished by washing the trimmed heads with a heavy spray of water or by treating the heads with chlorinated water. As a further means of controlling the fermentation, the treated cabbage has been inoculated with a heavy suspension of desirable organisms. During a three-year period 199 barreIs, each containing 300 pounds (136 kg.) of cabbage, have been packed a t the laboratory; and in the fall of 1930, 468 tons were packed a t a commercial plant. Of the total, 190 tons were unwashed and
AND
served as controls, while the remainder was treated in various ways to satisfy the purpose of the experiments. EXPERIMENTAL METHODS LABORATORY EXPERIMENTS. Because of the desirability of using cabbage of as uniform grade as possible, only wellmatured heads of a single variety (All Seasons) grown on upland Miami soil were used. The heads were trimmed of outer green leaves and were then washed by rotating under a heavy spray of either cold water (45-50' F. or 7.2-10' C.) or hot water (140-180" F. or 60-82.2' C.). They were then cored and shredded in the usual manner. When necessary, the shredded cabbage was heated to about 60" F. (15.6" C.) by passing live steam into the chute through which it dropped from the cutter to the coIlecting box. Salt was added to the shredded cabbage in the proportion of 2.5 pounds (1.1kg.) of salt to 100 pounds (45.4 kg.) of cabbage, and the two were thoroughly mixed. Three hundred pounds (136 kg.) of the salted cabbage were then packed into freshly paraffined 45gallon (170.6-liter) barrels and covered with cheese cloth and the barrel head. Clean stones were placed on the boards until about 2 inches (5 cm.) of juice appeared above the boards. The barrels were placed in a cellar, which was kept a t 64-67' F. (17.8-19.4' C.) during the fermentation period. I n order to secure representative samples of juice, 6-inch (15.2-cm.) Buchner funnels, fitted with pressure tubing, were placed in the center of each barrel a t the time of packing and were connected with the outside by passing the tube through a hole in the side. A pinchcock closed the tube outside the barrel and permitted the drawing of samples for chemical and bacteriological analysis. In the inoculation experiments 3 liters of a vigorous culture of lactic acid forming bacteria were well mixed with each 300 pounds (136 kg.) of cabbage just before salting. The inoculum consisted of two strains of mannitol-forming bacteria, L. niannitopr~us(culture 20) and L. pentoaceticus (culture 13). As a control on the effect of the various treatments, untreated cabbage was packed and fermented in the same manner. The general plan was to pack in one day a series of barrels covering the different treatments and thus furnish a proper basis for comparison. The make-up of a series varied from year to year, and only the plan followed in 1930 will be
884
iii &.tail: 2 I,arreIs of uiiwashcd culA,agc; 2 kJiiTPt?lS tif u-aslied calhagc,; 2 barrels oS waslied and iooculiited cabbage; 1 barrel of caiibagc waslied, t.heii placed in cliloriiiated water (100 p. p. trl.) for 3 oiiiiutes; I barrel of waslied, cliloriiiated, and rcwislied caiilmgc; t barrel of ivaslietl, cliloriniited, and inoculated cabiiage. l n 1929 eacli series cuiisisteil i d 6 liarrels a i d iii l'J28 of 4 lmrels. Ihring the tlirce years the total pack x a s :is fdlows: 1928, 40 imrels; 1!V29, 72 barrds; 1930, H i harrrls. Tlie rlitiwciit treatnients ainl nitrriiicrs of iiriits eniployed are soiiimariaed in Tatile 11. FA~OH I ~YV E H I M E ~After T ~ . the cabbage wax cured and trinimed: it was wrtslied ill a squirrel-cagc corn wnsiier,
yivw
fermctited ii days aiid was added in aiiioiiiits varyiiig frvm 1 . 6 to 6.6 per cent. In order to coniliare the results with pliysiaal, clielnical, atid bacteriological data previoiisly oiitaitied (i,(I), sarriplcs OS juice and temperature readings were taken in the first series. The saniplcs of juice were obtained by Iiieatis of IlCtclrner fuiiiiels and tubes leading through tlir ~vallsof the vat. Twnprratnren were recorded by iiieaiis of three thmnocouples, located as follows: numlrer I, 2 feet from bottoiri and 2 feet froin d e ; nuintirr 2, crnter; iiuiriher 3, 2 feet helciw surface and 2 feet from side opposite the bottoiri thermoeouple. Readings were recorded daily by nienns of a pot,entiioiiieter. The tiierinucouples were ciieoked before and after use arid nixe found correct at both times. In addition to tlie miall vats, tliret: 5O-tm vats were tilled n-itli wshed eabbagc:. So csperinierttal data were taken during the fermentation, as the object was merely to compare the quality of the kraut ill these 50-ton vats with that io vats filled with unwashed cabbage. IETHOI~S.Titratalile acid was dtiteriiiiiied iiniwdiately after packiiig the cnlil~agcand at frequent. intervals diiririg tlie fenneiitatior\. Ton oubjc emitiiiic+m of juic(. :*id 10 ec. of disbilled water wcre heated to lioiling tri espcl earbon dioxide, aiid titratcrl hilt, with 0.1 .V sodium liydniririe to the plienoiplitlia.leiri end poitit. T l i c saucrkrarit was malyaed for unferiiimted sugar, ctliyl alcirliol, mlatile a d , and nonvolatile acid by met,horls descriiied i l l a previmis publication (0). The salt cootrut of tlie brine was read I>? riieairs of a
salimetcr. This hydrotiteter reads percentage saturat,ion of iodiuiii cliirsidt. in tlie solui,ioii,but asother solnhle compounds, meh as sugars, acids, proteiiis, etc., affect the readings, the values are usi:fiil orily for cotuliarative piirinises. As a result of erpcricncc, N reading of 1G to 18 is gerierally regarded as irrdicatirig the preseiicc of an adeqnate ariiiiunt of salt. ~ ~ , \ ~ ' i ~ E K l O r , ( ~ a rf!N,Al.Ysls. ~Ar. At the tioie Of filling the barn& or vats, Lotlr washed arid iinwaslied heads \sere sampled and Iilatea were rnadeto rletcrrriiiie tlie perretitage of organisms reniovcd from the outer leaves by wa%hing. The method used is descri1,rd in detail iti tlie author's pitper on t.he Aura of cabbage (.,$I. The riiiinlier of r,rraiiiarw ill the fcmiwting enlibare - n-as determined from sainples of juice taken at v n r i o u s tiiiies ditriirg t h e i(:riii(!ii t Htion. I'lrrte c o u n t s were made oii glucost: yeast-wiitcr agar uf plI 6.8, tu wliicli n stnail h r n o u r l t o f potassitmi phosphate was added. Direct c o u n t s were made l i y t h e nletliod hf Breed and Brew (1). .\ f u r t l i e r index of liaeteriiii activity was o b t a i n e d from tlie methylciie b l u e rediretion test (8). The types of organisms in the fermenti n g m a t e r i a l were d e t c r n ~ i n e din n rougli w a y iiy examination of the agar . . p l a t e s aiid the direct-count mounts. After the preliminary observations, a careful typing was tirade by picking all of tlie colonies in a sectioii of a randoni plate and culturing these organisms on various bacteriological media. The chief diagnostic tests used were: changes produced in Minus milk, type of g o w t h arid formation of acid and gas in glucose yeast water, production of catalase, slime formation on sircrose gelatin, fermetitalrility of various sugars and other carlioliydrates, morphological appearance (coccus, rod, capsule formation), and reactim to various stains. On tire basis nf these tests some 800 orgaiiisnis olitaiiied frurri kraiit iii various stages of fertncirtation have been classified. Exl~E,nr\rE,lr.kL
Uh-rl
xu.llnas OP Oxolsrslrs AS lt8SULT or Sirice the efkct of wasliiiig ealhage tissue is the Irasisof this study,aii idea o i tlieefiicieiicy of the processsliould lxl givwi. From an (if 40.3 lieadi, 198 of which u-ere i1I.y IS
ui,waslieil il3lll 205 w
was fouiid tliat wnshing redneed tlie organisins on the outer tissues more than 80 per cent. This figure is representative of the results obtained from liotli fiictory arid laliirratory experiincnts. Complete data are assemi~ledin Table I. Since the couiit,s of individual lirads varied widely, only uveragns are gil-en in the table. of tlie uixvasheil outer tissue ranged friiiii 84,000 to 10 orgmisms per gratii. Tlie waslied outer tissue from 14,000 to 793,000 organisms per grain. The average of 1,ti95,O(K)orgaaisnls per gram on unwaslied tissue
INDUSTRIAL AND ENGINEERING CHEMISTRY
886
as compared with 228,000 on washed tissue shows the striking reduction which washing effects. TABLE I. XUMBER O F MICROORGANISMS FOGSD ON ASD UNWASHED CABBAGE TISSUE SERIES
UKWASHED
Headsa
Bacteriab
\~ASHED
w 4SHED
Heads"
Bacteriab
BARREL EXPERIMENTS
-1 B C D E F G H I
16 10 10 10 10 10 10 10
2,400,000 420,000 241,000 307,000 105,000 120,000 84,000 638,000 1,360,000
6 10
10 10 10 10 10 10
10
793,000 136,000 65,000 105,000 67,000 28,000 14,000 8S,OOO 32,000
VAT E X P E R I M E N T S (FACTORY)
.I
1,863,000 33 2,553,000 16 2,417,000 24 2.000,000 24 35 3,663,000 22 C Number of heads used in each series. b Average number of bacteria per gram of tissue.
B
C D E
31 10 12 24
55 1,000 191,000 219,000 26 1,000 179,000
I n order to reduce still further the number of organisms on the outer tissues, some heads were treated with chlorinated water, containing at least 100 p. p. m. of chlorine. Although the heads were thoroughly washed to remove any traces of chlorine, all of the sauerkraut made from cabbage treated in this way had a peculiar musty odor and an unpleasant taste. The use of chlorine in wash water therefore seems inadvisable. A study of the organisms in fermenting FERMESTATION. cabbage offers a means of following the rate at which changes occur and of detecting the rise of any abnormal conditions. After a rapid increase in the number of organisms during the first few days, there is a marked decline because of lack of free oxygen, depletion of readily available food, and the retarding effect of accumulated by-products such as lactic and acetic acids. The number of organisms found as fermentation progresses is given for three of the experiments in Figure 1, and for all of them in Table 11. The figures are the average of three to fifty-five separate fermentations and therefore do not show the irregularities that occur in a single fermentation. Examples of the variations that occur in single experiments are given in previous publications on sauerkraut fermentation (6, 6). The barrel experiments show that a rapid rise in the number of organisms began immediately after packing, and continued until a maximum was reached on the third day. There was then a sharp drop for 2 or 3 days, after which a gradual decline took place throughout the remainder of the fermentation period. A comparison of the figures for washed and unwashed cabbage shows what a marked effect washing has upon the early stages of fermentation. At the beginning of fermentation, the number of organisms on cabbage washed with cold water was only 700,000 per cubic centimeter as compared with 2,300,000 on unwashed cabbage (Table 11). However, the organisms on the washed cabbage increased more rapidly, as the steeper curve shows, until by the third day there were 187,800,000 as compared with 158,100,000on the unwashed cabbage. After the first 2 days cabbage washed with hot water showed a greater number of microorganisms than that washed with cold water. Inoculation with pure cultures of lactic acid forming bacteria resulted in high initial counts and a high count for the first 2 days. After the first 2 days the effect was less marked. If inoculation is beneficial, a study of the types of organisms will be more important than a determination of their number. The results of only the first series of factory experiments are given here, because less complete records were kept of the
Vol. 24, No. 8
second series. That the vats were slower to react is shown by a more gradual increase in the number of organisms during the early stages of fermentation. The peak was reached on the fifth to tenth day, with a considerably lower number of organisms than in the barrel experiments. The barrel experiment in which unwashed tissue was used reached a maximum of 158,100,000 bacteria per cubic centimeter on the third day, while the vat experiment reached the maximum of 75,300,000 on the tenth day. Titration of acids produced during various stages of fermentation is one means of reckoning progress toward completion of the curing process. A study of the results listed in Table I11 and represented by graphs in Figure 1 shows a fairly rapid rise in acidity during the first few days. Since the curves are the average of a large number of fermentations, the rise is
85
250
200
I 2
150
09
100
Y
?
50
03:
b .
3 I 5
b v)
p J
i
AGE IN DAYS
FIGURE1. NUMBER OF ORGAUISMS AXD TITRATABLE ACIDITY, BARREL EXPERIMENTS not as rapid as that exhibited by curves for some single fermentations. Likewise they do not show the degree of flattening that is characteristic of the latter curves. An acidity between 0.4 and 0.6 per cent lactic acid was attained at the beginning of the drop in number of organisms, after which the increase in acidity was more gradual. Although the increase of titratable acidity in the vats was somewhat slower for the first 3 days than in the barrels, after 5 days the acidities in the vats were greater than in the barrels. Since there were fewer organisms in the vats, their efficiency in the production of titratable acids seems to have been greater. Washing the cabbage increased the acidity of the vat kraut but had no consistent effect in the barrel experiments. Inoculation had no clearly defined effect on the development of acid. TYPESOF ORGANISMS.It is evident that the types of organisms present are of primary importance, for it is their action upon the tissue and the accumulation of their byproducts which largely determine the quality of kraut. These organisms may be classified roughly upon a basis of physiological and morphological characteristics into three groups: The first group of aerobic, Gram-negative, nonacid producers, which usually liquefy gelatin, is composed of chromogens, such as B. herbicoh and B. jluorescens, miscellaneous spore-formers, yeasts, and m coderms. The secondYgroup, which may be designated as low acid tolerant, is composed chiefly, if not wholly, of cocci-like, Gramositive, nonmotile, gas-forming organisms which Pederson ( 7 ) gas shown have the general characteristics of Leuconostoc rnesenteroides. Hucker and Pederson ( 3 ) have made an extensive study of this species and believe that it is abundant in all types of fermenting vegetable material.
Tire third or high mid-tolernnt group the I,adobanllus type. They grow mure isms o? the firs1 tlV0 groups and '4':" oh scant, granul?r growth on gelatin. lhis gruup may bc divided into gm-?ormmg and nongus-?orming t,ypes. The former rlosely rcsemble I,. pcntoncelicua while the Intter ;we similar to L . cuetinieriu and I,. planlarum. ibotimi OS tlie urgilnisrw ~ < , I I I aI ~i iariuiii iiit,wvsla formation of sauorkraut Srooi washed and unbage is recorded in 'Mde IV. The e a b t ~ ~ gase it ,vent into the vat carried a large nuluiier of nonacid-fuming iwganisms. The conditions esistiug in the kraut vat were iinfavorable for the development of these organisms, and after 3 or 4 days most of them disappeared. They probably *ewe no useful purpose, aud their rrductim in nrmiiiors by mashing increases the perccntage oS acid f o r m e r s and, in eousequence, promotes the early estahiishlilent. OS a 1mm:r . . sauerkraut flora. The luw a c i d - i o le ra 11 t 1, ii e t e r i a pr e d o m i Ita ted during the early period of Ecrmeritatim. They cornprisixl a larger percentage of the total aiid persisted f o r a l o n g e r time in the washed than in the uri,\.aslied eabirage. The third or high ncidtuicrant group was in the a s c e n d a n t a f t e r 5 or 6 days when the acidit,y had reached 0.4 to 0.6 per cent, a n d c o n t i n u e d as t h e dominant type throughout tlie remainder of the fer-
inentation. linfortilnateiy, 110 data are given for the distribution
SALTING AND p.4crUNQ SHREDDED CABRAGE
IN VAT
than at t,he center or near tire top. Tiio three readings f o r e a c h da), v e r e averaged and are :I 1o t t e d in Figure 2 . 4 s a result of the mshing operations, the waslied cabbage went into tlie vats from 3" to 5' C. warmer than tlie untreated. This difference in temperature w a s maintained during the fust 12 days of fermentation, after which the t e m p e r a t u r e s in all the vats hecame approximately the same. 9 rise of about 5" C. took plaeo in all the vats during the first 5 days of f e r m e n t a t i o n , a f t e r wlricli the temperatures of the t r e a t e d c a b b a g e remained approximately constant for a xeek. The t e m p e r a t u r e of the unwashed cabbage continued to rise irregularly until the
Ihge was iiot eunsidered, l>ecause it varied only slightly and is tradc rather tliaii a fermentatiw prol~lcm. Acidity was disregarded except in cases where it iirjrired the flavor, since all the sanip11:a of kraut w r c r:onsiilcraljly higher tlinii the standard, 1.5 per m i t . CT OF OF
~ ~ A S W i S i CAxxAUE ; OS ~ I s T N I B o T l o N
ONGANISMSPnmem
.AT
V ~ n m u sS~a
