The Vitamine Manual

by Walter Hollis Eddy

d. Acids and alkalies have apparently little effect on this particular vitamine.

It may be well to state here however that owing to variability in behavior with variation in conditions it is dangerous to draw too general conclusions and until a given source has actually been investigated under specific cooking conditions one should not rely too strongly on analogies based on comparative experiments. This statement applies to all vitamines and presents one of the live subjects of investigation for the cooking schools and the food factories.

e. Little has been learned further about the chemistry of this substance. [Footnote: Since the above was put in type Steenbock has shown that the A vitamine resists saponification and that by saponifying fats which contain the A it may be possible to secure a fraction rich in the vitamine and free of fat.] Butter fat, nitrogen free and phosphorus free is shown to carry the vitamine and it is therefore assumed that the vitamine lacks these elements. It has been claimed that it may be removed from butter fat by prolonged extraction with water but this has not been confirmed by more recent experimenters. Steenbock was the first to call attention to the association of the A vitamine with yellow pigment in plant and animal sources. Butter, egg yolk, carrots, yellow corn contain it while white corn and white roots are less rich in this vitamine. This observation suggested the chemical relation between the vitamine and carotin. It has however been shown by Palmer and others that carotin is not vitamine A. This association of the pigment with the vitamine is therefore apparently a coincidence and this clue has failed as yet to throw light on the chemical nature of vitamine A.

II. THE CHEMICAL PROPERTIES OF VITAMINE "B"

When Funk first studied this substance he conducted all his evaporations in vacuo from fear that higher temperatures would prove destructive. Subsequent investigation however has shown that 100° has very little if any destructive effect if the vitamine is held in acid or neutral solution. Temperatures between 100° and 120° maintained in an autoclave at 15 pounds above normal pressure do tend to slowly destroy the factor. The extent of this destruction also varies with the character of the crude extract. In general, then, there is little fear of injuring this vitamine in ordinary cooking temperatures if the use of alkali is avoided.

The effect of alkali depends upon the temperature to a very marked degree. Osborne has recently reinvestigated this matter and finds that in the presence of a 0.1N solution of alkali at 20°C. there is very little destruction but that raising the temperature to 90°C. brings about a marked destruction. Seidell has shown that if the vitamine is absorbed by Lloyd's reagent and this reagent be then extracted with dilute alkali the vitamine passes into the alkaline solution. If the latter is neutralized quickly it is possible to recover most of the vitamine by this method. The effect of alkali becomes of practical importance to the housewife because of certain cooking habits. I refer to the well known practice of adding soda to the water in which vegetables are cooked to soften the vegetable and accelerate the cooking. Daniels and Loughlin in this country investigated this matter and came to the conclusion that this procedure did not produce enough destruction to be dangerous. Later the matter was studied by Chick and Hume in England and these investigators brought out a feature that had perhaps been overlooked in the previous work. Their point was that in ordinary feeding tests the results merely tell whether there is enough vitamine present to produce normal growth. Hence if the substance tested has much vitamine, a large part of it might be destroyed and this fact not appear in the test because enough might still be left to induce normal growth. By reducing the amount tested so that it was just adequate for normal growth and then applying the soda-cooking experimentation they showed that this method of cookery does do serious harm to the vitamine. From the practical point of view it is of course sufficient to show that enough is left after a cooking process to suffice for normal growth when the substance is taken in the portion sizes ordinarily eaten. The effect of alkali deserves more attention on the part of cooks and food preparateurs and we need more data concerning the minimal dose necessary to protect the human animal.

In neutral and acid solution it is perfectly safe to assume little destruction of this vitamin through heat and it is now common practice to boil sources with the extracting reagent and to use the steam bath freely to concentrate and evaporate these extracts. We have recently investigated the effect upon cabbage of cooking in a pressure cooker at eight pounds pressure. The cabbage so cooked, when dried and mixed so as to form 10 per cent of a basal vitamine free diet, yielded all the "B" vitamine necessary to produce normal growth in rats.

The very name of this vitamine indicates its ready solubility in water. It is also soluble in 95 per cent alcohol and either of these extractants may be used to obtain the vitamine. It is not readily soluble in absolute alcohol and 95 per cent is not as good an extractant as water. Substances rich in the vitamine apparently yield the latter more readily if they have first been subjected to autolysis or if the extracting fluid is acidified. Funk was the first to show that yeast produced a greater yield if it was allowed to autolyse before extraction with alcohol. However, Osborne and Wakeman have produced a method of treating fresh yeast by boiling it with slightly acidified water which seem as efficient as autolysis in the yield produced.

The various methods of extraction now in vogue have already been discussed in Chapter II and need not be repeated here. In general it is apparent that to obtain concentrates of high potency it is permissible to employ temperatures of 100°C. if we will maintain an acid or neutral reaction but that alkali should be avoided wherever possible and when its use is imperative the temperature must be kept below 20°C. or destruction will result. In applying this rule to cooking operations the results should be determined by direct tests rather than by assumptions based on these generalizations. It should also be noted that the alkalinity of a solution should be determined on the basis of hydrogen ion concentration and not on amount of alkali added since many substances have a marked buffer reaction.

The water-soluble "B" is not only soluble in water but can be dissolved in other reagents. Thus McCollum has shown that while benzene is of little value as an extractant of this vitamine, if we will first extract the vitamine with alcohol or water and deposit this on dextrin by evaporation it is then possible by shaking the activated dextrin with benzene to cause the vitamine to pass into solution in benzene. Voegtlin and Meyers have recently shown that it is soluble in olive oil and in oleic acid and their data suggest a new means of concentrating the substance which may be of value in tracing its character.