W W ._' ‘ 13: {H (DOUG m MOCHEMICAL STUDY OF DEFFL‘RENT 5: * A BACAEREOLQGICAL AND ' METHODS OF SALT‘NG QNIQNS Them: for the Define of M S: MICHIGAN STATE caLLEGn‘ Arthur Iavxdi jones ‘ This is to certify that the thesis entitled ‘ A Bacteriological and Biochemical Study of Different Methods of Dalting Onions presented by Arthur David Jones I has been accepted towards fulfilment of the requirements for M. g degree in_Bacteriology & Public Health AAAAJ Major professor Date December 14, 1945 \ THESIS A BACTERIOLOGICAL AND BIOCHEMICAL STUD! OF DIFFERENT METHODS OF SALTING ONIONS by Arthur David J ones \. A THESIS Submitted to the School of Graduate Studies of Michigan State College of Agriculture and Applied Science in partial fulfilment of. the requirements for the degree MASTER OF SCIENCE Department of Bacterioloy and Public Health 1945 ACKNOWLEDGEMENT The author wishes to acknowledge his gratitude to Doctor F. W. Fabian for his assistance and guidance throughout this in- veetigation. TABLE OF CONTENTS Page Introduction 1 Review of Literature 2 Methods A. General Salting Procedure I 5 B. Bacterial and Chemical Analysis 6 C. Method A and Results 8 D. \Nethod B and Results 11 E. Method C and Results 13 Physical Condition of Onions Salted by Three Methods 18 Discussion 20 Summary 21 Literature Cited 23 INTRODUCTION Under normal conditions salting is one of the four principal methods for preserving food. During the war and since, there has been a shortage of.critical materials needed for.canning,vdehydra- ting and freeeing foods, so that various methods of brining.have been used extensively for preserving large amounts of vegetables. Some of the methods used have not been satisfactory resulting in considerable loss due to spoilage. One of the vegetables that has always been salted extensively and which gives trouble to the salter is onions. This study was undertaken to compare different methods of salting onions and to determine, if possible, which method pro- duced the best onions with the least waste. Bacteriological studies were used to obtain a picture of the relative numbers of different types of organisms as they developed during the process of brining. Chemical analyses were run in conjunction with the studies on the microscopic flora to determine any relation between changes in chemical environment and changes in the population of the micro- organisms. lith these data a much better idea may be obtained of the bio- logical changes which take place during the preserving process in each of the different methods used, and also.the types of micro- organisms developing during the process. .2... REVIEW OF LITERATURE The literature dealing with the preservation of vegetablesrby the use of salt is quite extensive. Fabian, Bryan and Etchells ( 6) reported extensively on the influence of salting upon cucum- ber fermentation and upon the incidence of certain types of micro- organisms related to the fermentation. Fabian and Erickson (7) stated that 30° salometer brine to which has been added 2.5 per- cent dextrose by weight is the best method for the salting of green tomatoes. Fabian and Blum (5) found that ittakes at least a 70° salometer brine to preserve peas; corn, green string beans and okra being preserved in low brine concentrations (40° salometer) , where- as, a brine strength of 60° salometer appeared to be on the border- line between preservation and spoilage for green lima beans. They found that vegetables with a high protein content were not salted as successfully as those with a low protein content. Etchells and J ones (3) in a study of comercial brining methods stated that green beans, lima beans and peas were satisfactorily preserved by coverning with a 60° salometer brine. Leafy vegetables, such as ; kale, mustard greens, spinach and turnip greens were kept in good condition treated with a 20° salometer acidified brine. Fabian and Wadsworth (9 ) reported that blanched whole kernel corn, green snap beans, carrots, spinach and beets brined in 18 per-cent salt gave the best results with the products comparing favorably with similar products canned at the same time. Wadsworth and Fabian (13) studied methods of salting peas. They recommended at least 18 and not over 20 per-cent salt. Fabian and Rants (8) described a method for '1'- .--u. .. . l . . I . . . 1- I I I I ‘ . I ,L.- I. I -' .1 . . : I ‘v I. . _ . . .~ I I I . . . _ . . _ ..: .l‘ I l I I I _ . .' -- ' I ‘ J 5.. . . . . ‘. ‘l .. I I I l u i - l -3- preserving red mango popper hulls which gave excellent results. They found that covering them with 70° salometer. brine w and than adding 15 pounds of dry salt per 100 pounds of pepper hulls pro-o duced a good quality product and allowed practically no dfementa- tion. Literature pertaining to the salting of. onions is limited and conflicting. Cainpbell (2 ) described a method for salting onions which consisted of soaking them in mterfor severaldays," drain- ing and adding 40° saloneter. brine. - This was allowed to‘stand. for 1. days, then to be replaced with. 60° salometer- brine and finally by 80° salometer brine. ‘ This method allowed an active fermenta- tion. However, Fabian (1.) stated that lactic acid fermentation - will injure the texture of onions. He showed that-a. 20° salometer brine allowing fermentation, loosened the outer layers of the onion . For this reason the salt concentration should. be sufficiently high to prevent fermentation. 7 Until 15 per—cent salt concentration. is reached, fermentation will take place, and spoilage may occur until more than 20 per-centsalt is. present... - The amountof salt to. add to suppress spoilage bacteria and permit large numbers of lactic- acid producing bacteria to grow is from. 2;» to Spar-cent. Certain bacteria, fortunately not directly responsible a ' for spoilage of vegetables, have been reported to grow in very high concentrations of salt.) Folk (10) stated that micrococci‘ and ear- . cinae, because of their form of growth, could withstand up to 15 per-cent concentrations of salt. Wyant and Remington 0.4) reported that Glostridig. botuling -19. not. affected by 10 per-cent salt con- centration. Fischer (11) reported that the ”hog bacillus"- grow well on an infusion containing 9 per-cent salt. -4. Halophiles have been described by Browne (1 ) which grew luxuriantly in a saturated solution of salt, and which would not grow on media containing less than 16 per-cent salt by weight. LeFevre and Round (12) ,1 while studying the microorganisms concerned in the fermentation of cucumber pickles, isolated a group of bac- teria from pickle scum containing 10 per-cent salt, and were. grown readily on a medium containing 25- per-cent salt. ' -5- IlETHODS General Salting . Procedure All the onions were salted according to a general salting procedure. The onions were allowed to become dry by standing at room temperature for several days. The stem and root ends were trimmed, adhering dirt removed, and the rough outer skins rmoved. They were then weighed into three creeks and treated with three different brining procedures» which will be outlined in detail later. In salting onions, as in other vegetables, it is necessary to compensate for the water present in them, some of which will be re- moved when the brine is added. To determine the amount of salt that is necessary to compensate for the water in the onion, the following formula was used: (5) ~ 8 x '- Ar—L-f 3° 00 in which I a weight of salt in pounds per 100 pounds of onions, A s per-cent of moisture in onions, and s : per-cent of salt desired, or in terms of salometer de- grees desired it is: doggees salometer X 26.5 100 To use this formula, it is necessary to know the weight of the onions and the amount of moisture they contain. For comercial pur— poses the amount of moisture listed in tables of chemical composition is satisfactory, but in this work the moisture was determined by dry- ing an accurately weighed sample in an electric drying oven at 100° C. until a constant weight was reached. The loss of weight was taken as the amount of moisture present and the average for five samples was found to be 87.6 per-cent. a , . . ‘ . ." ; . 1 - _ . .I . l ' . ._ . , .. . .. ,I - . _ _ I . - v , . - .' . l . v . . i - ' . - . . I ' . . -§ . - I . i- . . a . - n . . .... I . .. . . . .. ,, - .‘ . . ' . . . - ......_. . ...-... I . .. - . _ . . u - . . . -6-- Bacterial and Chemical Analysis Four media were used to determine the microscopic flora pres- ent in the brine at various intervals throughout the salting pro- cedure. Bacto nutritive caseinate agar was used as a differential me- dium. On these plates a total count of all organisms present was made first. Next, the strong acid forming colonies were counted, which were distinguished by a white zone of precipitated casein surrounding the colonies. The plate was then flooded with brom cresol purple indicator solution for five minutes and a total count made of the acid forming colonies which were yellow against the purple background of the medium. To determine the number of weak acid formers, the number of strong acid formers was subtracted from the total number of acid forming colonies. The plate was! then flooded with dilute acetic acid, and the peptonizing colonies were 1' counted, which were surrounded by a clear zone. ‘ Bacto tryptone glucose extract agar was used to obtain a total count of all bacteria present in the brine. Bacto tomato juice agar was used to detect the umber of acid-producers, especially Ectobacilli. .. To determine the number of yeasts and molds present in the brine, potato dextrose agar wasused. Bacterial growth on 3 this medium was inhibited by acidifying it to pH 3.5 t. with a ster- ile solution of tartaric acid. All plates were incubated 48 hours at 30° C. and counted with the aid of a Quebec counting chamber. Total acid as lactic was determined by titrating with N/lO NaOH. The pH of the brine was determined with a Beckman glass electrode pH .7. meter. Salt was determined in per-cent by titrating with 11/10 Ag303 using dichlorofluorescein as an indicator. Salt strength was also tested by using a ’salometer which is a commercial test based on a scale in which a saturated salt solution is considered 100° salometer. The degrees salometer are measured by a graduated hydrometer calibrated on a 0 to 100° scale, reading direct in terms of degrees salometer. -8- Method A To the first lot of onions (50 pounds) sufficient 40° salometer brine was added to cover them and then an additional 5.19 pounds of salt added to compensate for the water present in the onions. This amount was calculated from the formula described previously. Suffi- cient salt was then added to raise the salcmeter reading at various intervals (refer to Table 1) until a final concentration of 60° sa- lameter was reached. The bacterial and chemical results obtained from the brine of this lot of onions treated by this method are found in Table l. The number of yeasts reached a maximum on the second day, after which they gradually decreased in numbers until the twentieth day where a slight use was evidenced. The total plate count on tryptone- glucose extract agar was not large, the highest count, occurring on the second day, was two hundred thousand per ml. This count de- creased to nine thousand on the eleventh day and later built itself up to eighteen thousand at the end of twenty—six days. The ratio of acid producing organisms to the total count on nutritive casei- nate agar was approximately 1:2 at the beginning with the final ra- tio being approximately 1:16. No visible fermentation of the onions in this lot occurred. However, the acidity did increase from .01 percent and pH 6.50 in the first day to .14 percent and pH 4.85 on the twentieth day, after which a sharp decline was noted. The pH curve seemed to follow that of the percent acidity quite regularly and seemed to bear a direct relationship. Tomato Juice agar generally gave higher counts than the tryptone—glucose extract agar and produced larger, more distin- -9- guishable colonies. The bacterial counts on this medium also fol— lowed the general curve more closely than the tryptone-glucose ex- tract agar and was generally found to be a medium more suited to the optimal conditions of the organisms concerned. 8.: Mg , omé 8. . oz: mam 0.3 o o4 o. 3. do” «own: an at: a 8% “8. 0.3 Q3 QS o 2.. m. on. 5:: mm 8 0.2 $3 .3. an? 4.2 ha o N. m. o 93 om 3. c, , «S can. a. «a. 3. 04m sém o a.» ma m.m .18 an a... , an 8a 3. an; «.3 «.2 o 3. as 3 was 3 3 mi 8.“ 2. o _ ox. one o M.” w. m. um fl 3 u: on.“ S. 8. “.3 «:3 o 34 as. an. «A o m” 3. - Md. 3.“ 8. 3. 8 Q o ,0.“ cm mam .m a S . an." «as 8. mi 8 SH 0 mm 8 m. on m 8 ad 2..“ 8. ma 8 . a: o 8 3 m om m 8 3H one .8. 3 2a . com o 3 7, mm. o . o3 N 8 _ tn __ and 8. , a L fiwmws ”mm. a saw”? . non, mo 30.» Waging .38. an a. mag .. .H as .4 soda: .3 e3 Idea unease you 3.3.. .338vo «sequence was 360: 27.3.02”qu 0.5 sowsuflfiemhoohvwa no hopes: macaw .H 0.33. l .11.. Method B The second lot of onions (50 pounds) was covered with an 80° salometer brine and 11.78 pounds of salt added to maintain the 80° brine strength for the duration of the preserving process. No visible fermentation occurred in these onions. Starting with an initial acidity of 0.07 per cent and a pH 5.70, the maximum acidity reached was only .11 per cent with a pH 4.87 on the tenth day and falling off after that to .02 per cent and pH 5.35 on the twentieth day. The microbial picture showed considerably smaller numbers of organisms than in Method A. A maximum of ten thousand occurring on the first day which was gradually reduced to disappear- ance on the twenty-second day. Six hundred peptonizers were present on the second day after which they disappeared. Yeasts which were present at the beginning, reached a maximum at the end of the second day and disappeared by the sixth day. The ratio of the number of acid—formers to the total number of bacteria present on nutritive caseinate agar reached 1:2 on the second day, 1:4 on the sixteenth day and disappeared entirely on the nineteenth day. The results of bacterial and chemical analyses are given in Table 2. Tomato juice agar again shows higher counts and more cons sistent results than the tryptone-glucose extract agar. I .12- .. . . ._- A ... ... _ .. c... u . .. .. .. ... n ma om . . has. and ._ mo. .. .. .. . .. n . .. ,.. .. . .. _ .. um. i. is... as 8...“ _, s. o a. .3. .. ._ :. .. s. . a 11...; . , w r l ‘ n ,. .... \ a .3. one .88 ,_ 2. o 8.. . R. 9 mm. .3. NH. we. 3 om. 9.8 +36 _ Q. o ...m. .3. .o a. ma. 8. «a. S o» mam} 84 d. o .3. a: c on. em. 3. m». S 8. as i as. S. c we... sum 0 8. no. 8. .... m ,. as , _ as . as 8. o. 3 «.... o . 8. 2. mm. 3 s 2; DOWN “Mom 86 0m. Com Hem.H o on. 0N0 #00 “ON Q I 2., ed 8.0 _ 8. on. in «.3 e. 81‘ .3. o .33 m on . 9mm 23m . 8. mm. 0.3” 025” o o o a 8m H goggm. HOW-Mi . 9351—.” . uvmeH a Hand ad ahvufldw 304 dflod “:04 museums . no.3 , mm . n80 sod Home oogn , 8003» (ended H38. ado»: msonpm H309 sea as 3.8 gouge 389 among, s 33 House {331395. will. H38 338 i est“? .8356 : mama so when L .m 350: an as Ida» unease new 33 .333vo emanated use eaves 853038.” 05 so meninges? no 885: magma .N 0.3.3. .13- Method C The third lot of onions (50 pounds) was treated in a somewhat different manner designed to allow fermentation to proceed. The onions were first covered with tap water and allowed to soak for three days. On the second day a maximum bacterial count on tryptone- glucose extract agar of over six billion bacteria per ml. was at- tained. The soaking in water removed considerable odor and strong taste from the onions and resulted in a cleaner looking brine la- ter on. This water was drained off and the onions were covered with a 80° salometer brine which resulted in a considerable reduction in the numbers of bacteria. After standing three days, this brine was replaced with 60° salometer brine with a resulting further decrease in numbers of organisms. Again this brine was drained off and replaced with 80° salometer brine which was maintained throughout the remainder of the process. Each time the brine was changed, salt was added to com- pensate for the water present in the onions. The 80° salometer brine resulted in a drastic reduction in numbers of organisms so that at the end of twenty~four days only three—thousand viable organisms per ml. remained in the brine. It is interesting to note here that al- though the total number of bacteria was reduced and remained small in number, the number of acid-forming organisms decreased irregular~ ly, showing alternate diminishing and increasing numbers. This phe— nomenon resulted in curves with three peaks, each successively lower than the other. This has been graphically illustrated in Figure l. A summary of the results of bacterial and chemical analyses appears in Table 3. Peptonizers predominated in the second and third days .14. while the onions were in water. The first day after the 40° sa- lometer brine was added there were six thousand peptonizers pres- ent, after which they were completely inhibited. The lactic acid bacterial count on tomato juice agar, Table 3, column 7, rose very high during the period the water was on the onions and were reduced considerably after the addition of the salt but managed to survive in considerable numbers and persisted through- out the duration of the experiment. Yeasts, as shown by the potato dextrose agar, Table 3, column 8, were abundant from the beginning. They increased considerably while the water was on the onions but were reduced upon the addition of the 40° salometer brine; decrea- sed still further when the 60° salometer brine was added and disap- peared entirely upon the addition of the 80° salometer brine. These data confirm the bacteriological findings of previous work on the influence of salt on microorganisms by various inves- tigators. Salt is very toxic to the proteolytic bacteria, less toxic to yeasts and only mildly toxic to the lactic acid group of bacteria. Certain members of this latter group are evidently able to develop strains that will withstand very high concentrations of salt. Tryptone glucose extract agar gave higher counts with the wa- ter than did the tomato—juice agar, however, with the brine, the tomato—juice agar again gave higher and more consistent results. A comparison of the bacterial counts of brines plated on tomato-juice agar is given in Figure 2. Bacterial Count ~ thousands per m1. 50,000 40,000 50.000. 20,000. 1n nng 9000 8000 7000. 6000. 5000- 4000’ 3000- 2000- 1000- Note:units changed ' G , . A _— B ____. Notegunits changed 100 90' 80- 70- 60- 50- 40' 50' 20- 10 .5 04’ .3 .2 .1 Note:units changed 0 \/ , \__n___ 5 10 15 20 25 Time in Days Fig.1. 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NH 0m mém 3:.“ mm. an R. m... 0 3 0e «0 0H 8 «.3. : «0a 0a. 3 05 H8 0 me e 3 mm 0 0e dad 3..» 0m. mew 0% 00m 0 00 0m 0% e 0e .93 $4 . mm. 03 80$ 03.0 0 mm 0 8 e n : 0a..» 8. 0a.} 803a 08.03 08.8 08d~ 000.3 0 08.08 m I u u .. and 08.0% 80.030 08.3 804 084 0 80.02 m .. n .. .u 03. 80K 08.08 0 0m} 03; 0 83.4 a [$340an . www.mowfl speech nwmmLIIMmMo nomads 304 304 g3. moonwou ammo ma name use some ocean $00us , csoom msouwm, H38. : hon , _ we. pass omohpNoc cusses mass“. .3 a 0.3533 wbfipunvflz mfimhirwdflddco H.309 330m 05.5. no .HE goo $5355 ... man He heaven ma .0 sense: 3 so» 1H3 unease no.“ 33 .335vo 93.3209 one .0308 9.300%?” on» so mamHQthogoas mo hangs macaw . m 023. .400,000- Bacterial Count - thousands per ml. -17- 600,000F 500,000' 500,000- 200,000- 100,000' 10,000 Noteaunits nhonona 9000- 8000‘ 7000- 6000- 5000- 4000- 5000r 2000- 1000- 100 ,a 90-, eo-l 70 -: ‘-/ \ l l l I hotezunits changed 60- 50' 40- 30- 20' Notezunits changed H 0 j _ / \ \ OHNMIPUIO‘QQ‘O / i, . . “h . . 10 . . . lb . . ‘20 . . .04 §3_‘ Time in Days Fig.2. Total bacterial plate count on tomato juice agar of the brine from onions preserved at different salt concentrations. .13.. PHYSICAL CONDITION OF ONIONS SALTED BY THREE METHODS The results obtained in this series. of experimentsutend-to show. that of the a three methods employed, Method A appeared to be the most satisfactory. This is easily shown by the results of examination of the physical appearance of the three lots of. on- ions. To general visual inspection little difference was obser- ved between the three methods . However, “ upon manual examination of each onion, it was found that a considerable difference existed between the different methods. ' It was found that lethod. 0. created a product with considerable injury. This injury specifically con- sisted of a loosening and softening of thevouter scales of the product. This injury to the scales was generally concomitant with a soft, mushy interior of the onion. Comte were made. on each lot for injured onions. Method 0 produced 86.85 per cent injured on- ions. llethod B resulted in a lot containing 44.21 per cent in- jured onions. Method» A gave the best results with only 2.59 percent injury. The loss of» these injured onions cannot be attributed to one specific cause- However, it may be caused by fermentation oc- curring with Method 0, or a too high salt concentration at the be- ginning of the process in Method B. The results indicate that a brine concentration of 80° salome- ter is not satisfactory as an initial covering for a preserving onions . The high salt concentration apparently draws the moisture out of onions too fast to allow the brine to enter the onion and, thereby, make it firm and crisp. This fact precludes the possibility of dry- salting onions. The results also ' indicate that fermentation of " ., . ‘ flirt... fluent? A .19. onions is not desirable to produce the best product. It was also evident that the color of the brine has no bear- in on its preservative action on onions . The brine of Method 0 was much cleaner-looking due to the amorous changes but. was least effective in preserving the onions. Discoloration of all the onions in all. three lots was observed. However, this blackening occurred over the entire surface of the onion preserved according to Methods B and C . The onions salted ac- cording to llethod A were merely discolored about the cut edges . This led to the recommendation that the. onions be only trimmed at the root and stem- ends, leaving at least one rough outer. scale ‘ present to. protect the onion from discoloration- Those onions near the surface of the crock showed the most discoloration indicating an oxidation possibly with the productionof tannin or deposition of iron salts . J Freshening the products of the three methods by running. water resulted in a whiter, firmer and crisper onion with those salted according to Method A. * . ' . . - . w ,- .- - . . - .5 . . . I ' . . x n _ . ' . '. . . n . . I . ..' ' ' . - JP ' . - I, e ' "' v .- . ‘ - '« . r . . . . . . .- ....- .. ._ . . v '_ ‘ ... . e u - . -20— DISCUSSION The data presented indicate thatof the three methods used for ealting onions, Method.B was the least satisfactory, whereas, both lethods A and C had merit.and certain distinct advantages. ‘Kethod A resulted in a product of good quality but the micro- scopic flora was not reduced sufficiently to-warrant-storage over a long time. Method 0 gave a less desirable—product but stor- age fer considerable time-without spoilage could be depended upon because of the almost complete inhibition of bacterial growth. It would seem plausible,therefore, on the basis of‘the data ob- tained, that a combination of these two methods could be used to distinct advantage. Such a method as to embody the advantages of both methods and remove the undesirable factors present could be recommended. This method would consist of covering the onions with a4!)9 salometer brine, allowing this to remain.for two days or longer, after which it would be replaced with a-Goo‘brine. This would be allowed to remain on the onions for two days after which thus it would be replaced with.an 80lo salometer brine. Based on data presented, it seems probable that this method would result in the firm, crisp, white product which was produced_byVflethod A and would give the chemical and bacteriological results comparable to lethod G in which bacterial growth-was completely inhibited at the end of the preserving process. some: Three methods of preserving onions by salting were studied. The method that gave the best results was lethod A which consisted of covering the onions with 409 salometer.brine,‘inereasingzther salt concentration gradually-to 50° salometer and finallytoéo9 salcmeter. It was found that the other two methods which utilized 80° salometer brine resulted in an almost complete inhibition of bacterial growth. ilethod B, which consisted of covering the onions with an 80° salometer brine at the“ beginning had a deleterious ef- fact on the physical appearance of the onions. *Method-C allowed fermentation to occur and also produced an undesirable product. With.flethod A, the onions had a.good color, were firm.in texture and only 2.59 per cent showed any injury to the outer scales-of the onions. eBacterial analysis showed the presence of fairly‘ large numbers of bacteria at the termination of the experiments with the lot of onions preserved according to'Hethede. For this reason a combination of methods A and C is recommen~ ded which embodies the advantages of each. rThis method is to ini- tially cover the onions with a 40° salometer brine, to be replaced in two days with a 60° salometer-brtne,-which in.turn is replaced in two days with an 80° salometer brine. This method will insure the production of good quality onions with a maximum of safety from spoilage‘during.storage. Notable effects of salt on the development of various types of microorganisms were in evidence. ‘With the gradual increase in salt concentration there was a gradual decrease in the total number of organisms present in the brines. The peptonizers affected most by -22- the salt were always the first group to disappear. The_toxicity of the salt to yeasts was less than that to the peptonizers but sufficient to cause them to disappear shortly thereafter. ‘The acid forming organisms were the most resistant of any of the or- ganisms to-the salt and maintained_a relatively high ratio to the ‘ total number present throughout the duration of the process. (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (11:) -23. LITERATURE CITED Browne, W. W. Halophilic Bacteria. Proc‘. Soc. Exp. Biol. Campbell, C. B. Campbell's Book. Rev. Ed. Vance Publishing Corp., New York. 1937. Etchells, J. I.., and Jones, I. D. CommerciaLBrine Preserva- tion of Vegetables. Fruit Products J our. ,-. a, 2U» 1943- Fabian, F. W. Wartime Vegetable Salting. Food Ind., _1_6_, 72. 1941.. , and Blum, £1.18. Preserving Vegetables by Salting. Fruit Products. J ournal, _2_2_, 228—236,. 1943. ,‘ Bryan, C. 8., and Etchells, J. 1.. Experimental Work on Cumber Fermentations. Michigan Agr. Exp. Sta., Tech. Bull. 126. 1932. ________,,, and Erickson, F- J. Salting of Green Tomatoes, Fruit Products Journal, 12, 363-367. 191.0. , and. Hontz, L. H. Preservation of Red Mango Pepper Bulls. Fruit Products Journal, a, 198-199. 1945. ,J and Wadsworth, C. K. Salting Beets, Carrots, Corn, Green Beans and Spinach. Fruit Products Journal. 3A,, 231-237. 1945. Folk, I. S. The role of certain ions in bacterial physiology. A review. (Studies on salt action, VII) Abs. Bact. 1: 33-147, 1923- Fischer, A. The structure and functions of bacteria. Transl. by A. Copper Jones- 198 p. Oxford. 1900. LeFevre, E. and Round, L. A. A preliminary report on some halOphilic bacteria. J. Bact., A: 177-182. 1919. Wadsworth, C. K. and Fabian, F. W. Salting Early June and Alaskan Peas .. Fruit Products Journal. _2}_, 298- 301. 191.1,. Wyant, Z. N. and Remington, R. The influence of various chemi- cal and physical agencies upon Bacillus botulinus and its spores. J. Bact., 2, 553-557. 1920. 7 . a a o _ ..w vdtllw. .5! _, . e. I... . .- . .‘ " \dl K u~ s 5 “H ‘ ..'- "k . -: A‘ . . . e x s ' . - A “ 3‘ ' .n _ ' ' . . .- ' ‘ A.»- g 21., _ r . ‘ ‘er. ., ‘ ‘ " , ‘-'.' '. _ ». -A z' 1. «an . to,» My . .‘ y if 21:3: ', : 4‘5!“ {ah-fl W:- *- 1 II ., atom '- 2.9:.r. H37 , .n? .: :, MICHIGAN STATE UNIVERSITY LIBRARIES n 41., ..an 2.1;? . .. .... >5, ... an 77...... ...,..:.:. , . ... ., ...i .7 2.1; 1 i/n , 7.. . r .2”. i. 5. ......j; . ., . . V . . V .. , . . V . . . I . . V ..f.._....,.;,_...,