INDUSTRIAL AND ENGINEERING CHEMISTRY
1292
tion of 2 cc., but the pH value still remained 6.8. It was not until 5 cc. of acid had been added that the pH changed. Then it suddenly jumped to 5.0. Coagulation was practically complete. To a similar sample 0.5 cc. of the acid was then added. After standing for one hour it showed no sign of curdling. The sample was bottled and put through the sterilization process. Complete precipitation resulted. This proved that the milk was highly buffered and could tolerate only a very small amount of acid without showing a t least partial curdling on sterilizing. As there was practically no difference in the titratable acid in the various ingredients, their pH afforded the only indication of their fitness. pH values less than 6.0 should be adjusted with a suitable alkali to p H 7.0. Sometimes the cause of curdling can be traced to bottling plant conditions and lack of facilities to properly reveal acid conditions. It is of the utmost importance that no carbon dioxide be present in milk chocolate. In one plant visited, batch after batch was curdled owing to a small amount of carbon dioxide which leaked past a closed valve. It was not until the gas line was removed that a satisfactory batch could be obtained.
Vol. 20, No. 12
Conclusion
Such has been the progress of the industry under the guidance of its chemists, until now the carbonated beverage is as much a part of American life as work, food, and sports. No picnic, ball game, or other sporting event could develop its normal enthusiasm without the sustaining effect that the pop bottle exerts on mob lung power. Dressed in a more stately package and consumed under more dignified surroundings, our soda water has become a standard factor in promoting good cheer a t home and a t the club. It is a great industry, and the chemist is a t work, improving here, developing a novelty there, and defending it against arbitrary and fanatical legislation, seeking to impose prejudiced and impractical standards. He will, in the future, as in the past, draw copiously on the sister sciences of bacteriology and applied mechanics for inspiration and suggestion. And he is cheered by the hope that he too may, along the highways and byways of his work, find new facts, and that these, when classified and added to that great body of organized knowledge which constitutes our science, will make it more complete and extend its service.
Chemistry and the Baking Industry C . B. Morison A-RICAN INSTITUTE OF BAKING, CHICAGO, ILL.
HE importance of chemistry and the related sciences
T
for the better understanding and for the improvement of the art of baking has been emphasized by chemists for over one hundred and fifty years. This is a comparatively short time in the history of baking, but not in the history of chemistry, since it runs parallel with the modern development ,pf this science from the time of Lavoisier to contemporary theories of atomic structure. The chemist’s interest in baking did not have its origin in the theoretical aspects of t.he problem. Chemistry was first brought to the attention of the bakers on the basis of its utility and application for a better knowledge of the art, improvement of baking conditions, and the technical education of bakers. This was surely the original interest of those eighteenth century chemists in France who first began to study French bakery methods and conditions by actual contact with the baker. These men have a just claim t o the title of pioneers in this field of applied chemistry. I n 1767 Malouin published his “Description,”’ which greatly expanded the article on baking in the Encyclopedie of Diderot of 1763. Malouin’s work called attention to the value of science and its methods for the improvement of baking, and provided a basis for the work of the great French food chemist Parmentier, who early in his useful career became interested in the art and labored until his death for the education and advancement of the craft. Parmentier’s great work on baking,2 published in 1778, received the approbation of the Royal Academy of Science as a work which gave t o the art “une heureuse application des conoissances Physiques et Chemiques.” It is a landmark in the history of chemistry as applied to baking. It soon became the recognized authority in the scientific literature of the “Description et Details des Arts du Meunier, du Vermicellier et du Boulanger, avec une Histoire abregee de la Boulengerie, et un Dictionnaire de ces Arts,” Paris, 1767. 8 “Le Parfait Boulanger. ou Trait6 Complet sur la Fabrication et IC Commerce du Pain,” Paris, 1778.
subject and a handbook for the progressive baker, and was translated into foreign languages. This work had a real influence in bringing some appreciation of the value of science in baking practice by giving the baker information which even now is of practical value. Parmentier was the original advocate of technical education for bakers, and his influence led to the foundation of a school of baking in Paris, which was destroyed in the midst of a flourishing career by the French revolutionists, who had no need for chemists and sent Lavoisier to the guillotine. After Parmentier, who is entitled to the credit of having brought some measure of appreciation for scientific control into the bakery and a better understanding of the art, but little progress was made in the chemistry of baking until the work of Dumas in the 1840’s. Between the time of Parmentier and Dumas the rise of analytical chemistry had made possible a better knowledge of the composition of wheat and other cereals, flours, and bread, in common with other foods, but no one had published a comprehensive study of the chemistry of baking comparable to the original work of Parmentier. I n 1843 Dumas published an article on chemistry as applied t o baking, which brought the subject of baking up t o date and included a r6sumb of some of his own investigations.s This article was a mine of information for those interested, and was used by many writers of textbooks and encyclopedias for the preparation of original articles. Dumas, who made a thorough study of baking, came to the optimistic conclusion that, ‘(l’artde la Boulangerie, naguere si arri6re, tend B s’elever au rang des industries manufacturieres les mieux raisone6s.” He also concluded that the most satisfactory way to determine the baking value of flour W R S by a carefully controlled baking test, which in 1928 is the opinion of most cereal chemists. The work of Parmentier and Dumas has been mentioned for the purpose of indicating that the chemist’s interest in 8
“Traite de Chimie, AppKqu6e aux Arts,“tome 6, Paris, 1843.
INDUSTRIAL AND ENGINEERING CHEMISTRY
December, 1928
baking is no new development in tlie history of the science and that, while bakers generally have not until recently greatly appreciated the value of chemistry, in terms of utility tlierc has existed a chemical interest in baking which is as old as modern chemistry. Need for Chemists in Baking Industry Thirty years ago a trained chemist working in a flour mill Today most flour mills OS any size cmploy chemists, and within t.lic last 15 years laboratories have been established in the larger bakery organizations. This has been due to various causes asid conditions, but very probahly the most significant cause is an economic one--the recent entrance of the baking industry int,o miiss production. Ijaking is no longer conducted on the olrl-fashioned series of halid operations which limit production. The development of machinery has reduced hand operntions to a minimum. Douglis are now mixed, divided, and molded Iry various types of machines. The fermentation of doughs may be carried on under controlled temperature and humidity conditions made possible by mechanical systems of control. Macliines and traveling ovens have greatly speeded production, and it is now possible to operate an aot.omatic machine bakery with the elimination of manual operation, as was recently demonstrated at Wcmbley in England. The mechanical equipment for the inass produrtion of bread has been designed by engineers in cooperation with practical bakers, and in this development the chemist has played but little part. The mass production of bread in its nrechanical features has not been due to the work OS the chemist, but he is B necessary Sactor in it io spite of ingenious machines and ovens. The ingredients, processes, and productR must be controlled by the aid OS the chemist if economy and uniformity of production are to be expected, since the major problem of large-scale production of bread is the efficient and economical conversion of flour and other ingredients into bread of standard quality. The basic materials or essential ingredients in bread-making are flour, yeast, water, and salt. In addition to these, American baking practice requires sugar, shortening, and milk, in comparatively high amounts, which is not customary in Brit.ish or European bread production. or hakcry was a rarity.
Chemistry of Flour
1293
posed a tentative method for study.6 The interpretation of the results of the baking test and its appiication to bakery requirements and conditions must he based on the experience of the operator. The control chemist must become a baking technologist. The scientific aspect. of tlie Hour problem, especially in the relation of physico-chemical propwties to baking value, has heen the subject of extensive investigations by chemists. Many Snctors have been studied, :tnd in recent years the contemporary methods of pliysicnl chemistq and colloid investigation have been used by workers in the ficld, with the production of a new literature. l3:iiley has given a good review of the present8status of tho Hour prot>lem.r Aiiotlier flour problem that is now being reviewed is the emi1u:itioil of Rour for cako-making, ivtiicli has heen broil&
Laboratory of a Large Raking Company
to tlsc attent,ion of chemists because of the growt,h of the cake-making brancli of the baking industry to large-scale production. The evaluation of cake flour will probahly be bascd largely on controlled baking tests, unless future scientific research leads t o better methods. Other ingredient control problems are handled by the laboratory in relation to plant requirements. Methods of analysis are available for baking ingredients, and their grade and the claims of the manuiseturer are checked by the chemist. Chemistry has been responsible for the improvement of ingredient quality in those industries whose products are the raw materials of bread-making, and sriitable shortenings, milk products, snlt, sugar, malt extract, and other Fermentable earbohydrat,es may be obtained from reliable manufact,urers.
As flour is the most irnport.ant ingrcdient in bread-making, the determination of its baking value, or its evaluation for use in the bakery, is the chief ingredient control problem of tlie clscmist. This has been a problem for five generations and it still rema.ins a complex and puzzling field of study. The purely analyticsl side OS the flour problem presents little Studies on Yeast difficulty. Methods for moisture, protein, and ash have been subjects of contiiiucd critical study by the Association Yeast, a result of biological and biiiclieinical study, has of Official Agricultural Clicmists4 and the American Asso- been tlic suhjcct of continued investigation and research. ciation of Cereal chemist^,^ as a result of which official The prodoctioil of coinpressed yeast has been placed on a methods have beeii adootcd in the interests OS imiformitv t,eelmical hsis that has mfide possible a yeast of relatively and aceurscy. high uniformity for s i biological product. It is not overWide niany methods have been mroposed for drtermininrc empliasizing the facts to state that the large-scale produot,ion the baking v&e of a bread flour ind-miich work has been of coinpressed yeast especially adapted to the fermentation of done on the problem of why some flours we “strong” and dough, that can be delivered to tlie bakery in good biological others “weak” and how “Teak’ flours may he improved, condit,ion, is one of the most important factors in the progress modern cereal chemists in the baking industry still agree with of the baking industry. Dumas‘ opinion, that the most satisfactory method for the Control of Fermentation evaluation OS a bread flour is by a controlled baking test. Ttse American Association of Cereal Chemists, which Iias been The distinctive feature of the bread-making process is the working on the baking test for several years, has lately pro- fermentation of the dough, in which higlily complex physico-
‘ Asrocn.
Ot3ciai Agr. Chrm., Methods, 1926. “Methods for the Ailaivsis of Cereals and Cereal Productr. American Ars&-isfion of C e ~ aChemists,” l Lancnster, 19%. I
. C a r d Chem., a, 310 (1825): 8 , 85 (1926); 4, 270, 281, 299 (1927);
S, 158.277, 301 (S9%8); Norlhiurslrrn Miller. 6. 1 (1’328). “Chemistry of Wheat Flour:
New Yolk, 1925.
1394
INDLTSTRIAL A N D BNGINEERING CHEMISTRY
chemical and biochemical phenomena me involved. Each generation of chemists restates what is going on in terms of its own theories and conceptions, and, while this has led to a progressively better understanding of the general and special problems of dough fermentation, it caimot be maintained that as a result all the variables may he scientifically controlled. It is well recognized by the industry that the control of fermeiita,tion conditions is essential for efficient production and that failure here is responsible for most of the difficult.ics included in the frrmiliar term "shop trouble." I n well-equipped plant,s, temperatures aid humidities may be controlled in dough or fermentation rooins providcd wit.h suit,nble apparatus. Temperatures best adapted to fermcntation have been esta.blishcd as tlve result of experience and confirmed by biochemical study. Scientific methods for t,lie determination of the time of fermentation of the dough, so that it may be taken at exactly the right time or stage for make-up, d i d i a g , proofing, and baking into the most satisfactory bread, have not yet been made amilahle to the industry.
Voi. 20. No. 12
terest has timed away from the older studies of composition, digestibility coefficients, and calories to the protein quality factors, vitamins, and inorganic constituents. There should be little misunderstanding of the nutritive properties of bread, but, strange t o say, the new knowledge has been confusing t o some, misunderstood by others, and improperly oriented b y those who see in every new fact sometbing sensational for popular exploitat,ion. A t a time when the nutritive properties of bread should be better understood tliere is still much popular confusion and misunderst.anding, which require correction by reference to the established facts. The problem of the mold and rope infection of bread has been greatly clarified by biological and biochemical investigcttiun and as a result may be prevented in efficientlyoperated bakeries. The growing stale of hresd, its physicochemical mechanism, and its prevention havc not yet been satisfsetorily solved by the chemist. Various theories have been evolved to explain it and methods have been pat,ent.cd for kceping bread fresh." Kone of these are considered satisfactory for tlie practical elimiiiation of stale hread. The study of why bread stales aiid how it may he kept fresh without deterioration is commcndcd to chemists who :ire looking for problems in whicli to apply methods of colloid iiivcstig&tioiim. Progress of Industry
The services OS chemistry and related sciences to t,he baking industry liwe msde possibla :I better uiidersta,ridiiig OS t,lie baking process, the composition and properties of flour and other ingredients, dough fermentation, baking and tlic (!liaracteristics and nutritive properties of bread, the prevention of mold and rope, and the development of irnprovcd metliods of control. The technical education of bakers was initint.ed and fostered by chemists. Ilaki~igin the present stnge of its rlcvelopment utilizes Iiiglily iiigenious automatic machinery, from mixers t o traveling ovens for large-scale or mass production, and includes some measure oi scientific cont,rol in Maxine Room the methods of production, especially in rclation to Rour and o t l m ingredients and tlie characteristics and composition of Srience iias not yet caught u p vith practice, and uone of the baked prodiict. It is still an srt, due to the many inthe methods proposed by the laboratory appcar to be satis- lierent variables in flour and other iiigredients, the process of factory in competition with the judgment of the experienced icrmenitation, and baking. T l i e progrcss of the bakiug iiidustry to more scientific baker. It nray he that t,he present empirical methods, hasrd on the individual experience of the practical baker, will at prodiiction methods will largely depend npon the research soiue future time gire ~ v a yto a scientific method for the a.otirities of chemist,^ i n nctuttl contact wit,li the industry, determination of tlie t,ime PS fcrmrntation, but t,here is no who must dram upon the contrihiit.ions of fundament,al rercli workers in the various iields of chemistry that may be reason to predict on tlie basis of present knowledge that t,his will be accomplished in the w a r future. Modern baking has applicd to the study of the many liaming variables in the its ingredients, formulas, and the mixing of ingredients in a mi of 1~:iking. Team rvork between the chemist in the bakery ~ c r ~ t awirker ,l should make possible fsirly good state OS control, but the Sameritation of dough, and the f , ~ ~ ~ d n ~ ~rewwch as far as the time factor is coiceriml. still rests on an em- tlie dedopnicnt of metiiods of ront,rol more scicntific than pirical basis and is nom most pra.nctirally controlled by those tlrort? \w have a t present rriiri ~vliichtlie future hakine industry skilled in the art. The climirratioii OS cmpirirism in the \>-illrequire if the art is crer to be rcpnrded as a science. The control of the timp factor in dough fermcntatioii ~i-ouldhe an rcrcrit, ent,r;mce of tlie chemist into tlic hakery is the best, important :~dinoccin thc ntific p r o p e ~ sof the baking evidence tdiat thc baking industry has come to a recogindiistrq. nitir)n of tlir value of chemistry for its precut development nnd future pro~;ress.
-
Nutritive Properties of Bread Ingredients
The nutritive properties of v;licat flour, other cereal pains, and bread have been the subject of considerable rcviexv and new work by various biological chemists in recent years, The contrihotions of Orlborne and Llendel,s ;\IcCollun~,*and S h e ~ m n nliave ' ~ greatly cxt,endedaiid clarified our knodedge in tliis field. As the result. of this xork, contemporary inJ. B i d Chem.. S1, 557 (1919); "Proteins of the Wheat Kernel," U'ashington, 1907; "The Vogetnblc Proteins,'' London. 1924. "The Nencr Knowledse of Nutrition," New Yark. 1925. ,'"Chemistry of Food and Nutiition," h-eew Pork, 1925.
11 Jaro. "Thc Trchnoiogy of HreadmakinK." Liverpool, 1921: PSeumanil, "Rioteefreidc unrl Broi," Rerlin, 1923: Mrurizio. "Die NrhiungPm i t i c l *us Getreidc," Berlin, 1928: Katz, "Oiidcrzoekiege" N a i i Hlet Oudbakken \X.aidcn \'an Brood Tin De Middrlci Om Dit T e Voorkommen,"
Amiteidrm, 1917.
Glucose from Wood in Germany and Switzerland-German technical papers r e ~ e n t l ylivve devoted space to the manufacture of carbohydrates from wood. Since about 60 per cent of the chemical contents of wood represents cellulose, the wood need not be in thc form of high-priccd lurnbcr, but sawmill waste may be employed conveniently. A prnccss is now being worked on a commercial scale by a factory in Geneva, Switzerland.
