Foods and Their Adulteration / Origin, Manufacture, and Composition of Food Products; Description of Common Adulterations, Food Standards, and National Food Laws and Regulations

Average composition:

 Frazier, of the Cornell station, has collected analyses of a large number of different varieties of potatoes, and finds them to have the following average composition:

The following analyses show in detail the composition of potatoes from different localities:

Analysis of Maine potatoes:

 The Bureau of Chemistry a few years ago made an investigation in connection with the experiment station in Maine of the composition of potatoes grown in that state used for table purposes and for starch making. Some of the best varieties grown in different parts of the state were subjected to analysis, and the following results show them to be of quite uniform composition:

Analyses of Maine Potatoes.[29]

Analysis of Vermont potatoes:

 Analyses made in Vermont and published in the report of the Vermont Experiment Station for 1901 show an average content of starch considerably less than that above given, namely:

Composition of Potatoes used in France for Industrial Purposes.

—The following is regarded in France as an average composition of the potato suitable for industrial purposes:[30]

The total fermentable matter, as seen above, is a little over 19 percent, not allowing anything for the cellulose which is fermented. As a portion of the cellulose may also become a source of alcohol, it is observed that the average percentage of fermented matter in the French potato used for industrial purposes is not far from 20 percent.

The following varieties show a variation in starch content of 6.8 percent, the minimum being 15.9 and the maximum 22.7 percent:

Analysis of Potatoes from German Sources.—Average composition and starch content:

 The content of starch in potatoes examined in the laboratory of the Association of German Spirit Manufacturers during the year 1905 varied from 12.1 to 25.1 percent. Eleven percent of the total number examined contained between 12 and 14 percent of starch, 20 percent between 14 and 16 percent of starch, 13 percent between 16 and 18 percent of starch, 24 percent between 18 and 20 percent, 24 percent also between 20 and 22 percent, and 8 percent between 22 and 25.1 percent.

These data show that 56 percent of the total number of samples examined contained between 18 and 25 percent of starch. It is evident, therefore, that the general average content of starch in the potatoes used in the German distilleries is not far from 18 to 20 percent.

The mean composition of potatoes as given by three German authorities, namely, König, Lintner, and Wolff, is as follows:

Average Analysis of Potatoes by Three German Authorities.

The above data show the average content of fermentable matter in German potatoes, as determined by three of their leading authorities, to be about 20 percent. The potatoes used for the manufacture of alcohol in Germany are not of the variety raised for edible purposes. In a large number of experiment stations in Germany systematic efforts have been made for many years to grow a potato rich in starch without respect to its edible qualities. These potatoes are coarser in structure and less palatable than those grown for the table. The object of the cultivation of this class of potatoes is to produce as much starch and other fermentable matters per acre as possible. It is evident that our own experiment stations should undertake work of a similar character if the potato is to be used to any great extent in the manufacture of industrial alcohol. There is no doubt of the fact that success equal to that attained by the German experimenters will attend any systematic efforts of this kind in our country. Not only will larger crops per acre of potatoes be grown, but these potatoes will contain larger quantities of starch and other fermentable substances. If the crop of potatoes is to remain at the present average, namely, less than 100 bushels per acre, profitable returns for alcohol making can not be expected, either by the farmer or by the manufacturer. A much larger quantity must be grown and, if possible, at less expense, in order that encouraging profits may be realized.

Maercker, one of the most celebrated of German authors, states that in certain instances the potato in Germany reaches a very high starch content. Some varieties, in exceptional instances, have shown as high as 29.4 percent, 28.1 percent, and 27.3 percent, respectively. In warm, dry seasons potatoes often are found containing from 25 to 27 percent of starch. According to Maercker, the sugar content, including all forms of sugar, varies greatly. Perfectly ripe potatoes contain generally no sugar or only a fractional percentage. When potatoes are stored under unfavorable conditions, large quantities of sugar may be developed, amounting to as high as 5 percent altogether. In general, it may be stated that the content of sugar of all kinds will vary from 0.4 percent to 3.4 percent, according to conditions.

While potatoes grown thus to increase the content of starch are not generally used as food, yet they are nutritious but not as palatable as those grown especially for table purposes.

Ash analyses:

 The mineral matters which the potato extracts from the soil or from the fertilizers which are added thereto consist chiefly of phosphate of potash. The mean average composition of the ash of the potato is shown in the following table:[31]

This analysis was made upon the so-called pure ash, deprived of its unburned carbon, and freed of sand and carbon dioxid.

Effect of fertilization on the yield and starch content:

 Experience in Germany has shown not only that liberal fertilization with nitrogen is favorable to the production of a large crop of potatoes, but also that this is accomplished without decreasing the percentage of starch therein. The following table shows the increase in yield, percentage of starch, and amount of starch obtained by nitrogen fertilization, the results being expressed in hectares[32] and kilograms:

Effect of Nitrogen Fertilization on Yield and Starch Content of Potatoes.

It is evident from the data given in the table that the liberal application of nitrogenous fertilizers increases the yield per acre of tubers and of starch to a very marked extent, although the average percentage of starch present is increased very little. Converting the average data given in the foregoing table into their equivalents in pounds per acre, we have the following results: Without nitrogen—yield of tubers, 16,781 pounds per acre; yield of starch, 3,277 pounds per acre. With nitrogen—yield of tubers, 19,629 pounds per acre; yield of starch, 3,856 pounds per acre.

The following varieties of potatoes are considered in Germany the best for the manufacture of alcohol: Wohltman, Silesia, Agricultural Union, Athenena, Prince Bismarck, Richter’s Imperator, and Maercker. The latest consular report on the potato as a source of alcohol in Germany shows the following yields per acre and percentages of starch:

Yield and Starch Content of Potatoes Grown in Germany for Alcohol Production.

Use of the Potato.

—In addition to its value as human food the potato has other economical relations. It is used in many countries almost exclusively in the production of starch for the laundry and for general domestic uses.

The potato is not very extensively used for starch production in the United States except in the state of Maine and perhaps in one or two other localities. The starch of the potato has a particular value for use in the textile industry in the sizing of cloth. Practically all of the potato starch which is produced in the United States is devoted to that purpose, and for this reason it brings a higher price than the ordinary starch made of Indian corn.

Technique of the Production of Starch from Potatoes.

—There is scarcely any manufacturing process which is more simple in its method than the manufacture of starch from potatoes. The process consists simply in the rasping or grinding of the potato to a fine pulp, which is afterward placed upon sieves in a thin layer and sprinkled with water which detaches the starch granules from the pulp matter, carries them through the sieve, and thus separates them from the fibrous portion.

It will be interesting to the general reader, on account of the importance of this product, to give a brief description of the method employed and the results obtained.

Potato Starch.

—In this country potato starch is manufactured chiefly in Maine, Wisconsin, and Colorado. The factories are of a very primitive type, the machinery consisting of a rasper constructed usually by wrapping a wooden cylinder with sheet-iron punctured so that the ragged edges of the hole are on the exterior surface as shown in Fig. 41. Water is added at the time of rasping, and the starch pulp goes onto gauze shaking tables where the starch grains are washed through the sieve, as indicated in Figs. 42 and 43. The separated starch and water go into settling tanks. Where the starch has settled into a firm mass it is broken up and sent to the drying kiln. Potato starch is highly prized as a sizing in the textile industry.

Use of the Potato in the Manufacture of Spirits.

—A much more important technical use of the potato is in the manufacture of distilled spirits. Distilled spirits made from the potato are not generally used for potable purposes but are devoted to industrial uses. In the United States, very little if any distilled spirits are made from the potato. In Europe, however, especially in Germany, the industry is one of great magnitude. Practically all of the industrial spirits used in Germany and in many parts of Europe are made from the potato. The process is a simple one. The pulp of the potato, or starch, separated therefrom is subjected to the action of malt or other diastatic action for the purpose of converting the starch into sugar. In some cases this conversion takes place by more strictly chemical means, namely, by heating the pulpy matter or the starch separated therefrom in a proper state of dilution, in contact with an acid at a high temperature and pressure. Hydrochloric acid or sulfuric acid is usually employed for this purpose. The action of the acid converts the starch into fermentable sugar, namely, dextrose, a form of sugar differing in its quality and character from that produced by malt known as maltose. Both sugars, however, are fermentable to the same degree and produce, for equal quantities of sugar, the same quantity of alcohol. When the starch is converted into sugar by one or the other of these methods it is subjected to fermentation by an appropriate quantity of yeast which is of the same family as that used in the alcoholic fermentation of other saccharine products.

Special characters of yeast, however, are reserved for special purposes, since the variety of yeast determines to a certain extent the character of the secondary products which are formed during fermentation and thus determine the character, flavor, and aroma of the finished product. After the fermentation has been completed the residue is technically known as beer, and is subjected to distillation for the separation of the spirit.

A description of the process of distillation will be found in the second volume of this manual and is therefore omitted here.

Radish.

—The botanical name of the radish is Raphanus sativus L. The French name is radis; German, Radies; Italian, ravanello; Spanish, rabanito.

The radish is a vegetable which is found throughout the whole year in all the principal markets of the United States, being grown under cover during the cold weather. It is ready for market within a short time after sowing, so that crop after crop can be grown during the year on the same soil. It is most highly prized when it is young, as it tends to acquire a pungent and bitter taste as it approaches maturity. The two principal varieties grown, as respects the roots, is the one having a long, tapering root, and the other a short, spherical bulb. The latter are more prized for eating purposes. There are many varieties grown.

Composition of Edible Portion.—

Rhubarb.

—The botanical name for rhubarb is Rheum L. The French name is rhubarbe; German, Rhabarber; Italian, rabarbaro; Spanish, ruibarbo.

Rhubarb is a vegetable which is widely distributed in the United States and grows generally very early in the spring. It is a highly acid plant, and is used chiefly as a sauce and for making pies. It requires a very large addition of sugar to make it palatable. It has medicinal properties which give it additional value. There are many varieties grown. It is a plant that is ready for use very early in the spring, being available in the farmer’s garden almost before any other vegetable, and this makes it of still greater value.

Composition of the Edible Stem.—

The above data show that the rhubarb is practically valueless as food and is chiefly condimental. In regard to its nutrients the fat is in a larger proportion than in that of almost any other succulent vegetable.

Squash.

—Another variety of the gourd family which is highly prized as a food product is the squash. It is used in the same manner as the pumpkin, and is highly valued both as a food for man and domesticated animals.

Composition of the Flesh of the Squash.—

The above data show that the squash is a much more nutritive substance than the pumpkin. In other respects it is little different in its composition, being only a dryer form of pumpkin.

Sweet Potato.

—The vegetable known as sweet potato is known botanically as Convolvulus batatas L.

From the name it is seen that the sweet potato does not belong to the same botanical family as the potato itself. By reason, however, of its similar condition of growth and, to a certain extent, its chemical composition and uses, the term potato has, in this country at least, become to be universally applied to both, although the prefix “sweet” is quite commonly used with the sweet potato, whereas if any prefix is used with the potato, properly so-called, it is the word “white” or “Irish.” The sweet potato is grown extensively in the United States and in other respects, agriculturally, may be regarded as complemental to the potato.

While the potato grows best in the northern parts of the country and in mild climates, the sweet potato flourishes in the greatest abundance in the southern and warmer portions. In respect to the character of the soil the two vegetables are quite similar, both doing best in a sandy or loose soil, provided it is sufficiently supplied with plant food for the use of the growing plant. The sweet potato is a thickened root, and is propagated almost exclusively by means of shoots called “slips.”

Planting and Cultivation.

—There is a very distinct difference between the planting of the sweet potato and that of the potato. The former are rarely planted in the field where the crop is to mature. It is quite a universal custom to plant the sweet potato in beds where the young growth can be forced both by means of artificial heat and by a generous mulch of highly nutritious soil. The plants can then be set very early in the spring and by the time they are ready to be transplanted to the field have acquired a considerable size. When ready for transplanting the seed bed is prepared with the same care as that required for the potato. The ridging of the rows, which in the case of potatoes takes place during cultivation, is accomplished in the case of sweet potatoes before planting. If the soil is moist and the temperature not too high the young plants are removed from the seed bed and set on top of the apexes in the formed rows. The cultivation of the field during the growth of the crop is sufficient to keep the surface in good tilth and prevent the growth of weeds, grass, etc. Care must be exercised in the cultivation not to draw the earth away from the ridges which have been formed, but to increase their size by drawing the earth more and more toward the apex of the ridge. The cultivation is continued until the growing vines practically cover the surface of the soil and thus form a natural mulch, which not only conserves the moisture and tilth of the soil but also prevents the growth of weeds and grass. The sweet potato, in respect of its flavor, is particularly sensitive to the influence of frost, also the leaves are more sensitive to frost than those of the potato. If a heavy frost is experienced before the tubers are harvested it is apt to impart an unpleasant taste to the potato and injure its edible qualities. For this reason, if it is not possible to harvest the potato before the advent of frost, it is advisable to cut the vines at the point where they emerge from the soil. When this has been done the injurious effects of the frost, above mentioned, are not experienced. In the southern portion of the country the sweet potato is often allowed to remain in the soil during the greater part of the winter, and, if the vines are removed, it keeps in excellent condition.

Yield and Composition of the Sweet Potato.

—As has already been mentioned, there is a general resemblance, in so far as chemical and nutritive properties are concerned, between the sweet potato and the potato. The sweet potato is usually colored a yellowish tint, due to the distribution of more or less xanthophyll throughout its substance. The sweet potato also contains notable quantities of cane sugar, to which its name is due. It, however, contains large quantities of starch and fiber and small quantities of protein, resembling in this general manner the potato itself. The sweet potato has not been used in the United States for the making of alcohol. In the Azores great quantities of sweet potatoes are grown for this purpose, and make an alcohol of fine quality, which is used to a large extent in fortifying port wines. There are large areas in the United States, especially in the Southern States, where the sweet potato can be grown in great abundance. The experiments at the South Carolina station show that as high as 11,000 pounds of sweet potatoes can be grown per acre. The percentage of starch is markedly greater than in the white or Irish potato. In all cases over 20 percent of starch was obtained in the South Carolina sweet potatoes, and in one instance over 24 percent. As high as 2,600 pounds of starch were produced per acre.

In addition to starch, the sweet potato contains notable quantities of sugar, sometimes as high as six percent being present, so that the total fermentable matter in the sweet potato may be reckoned at the minimum at 25 percent. A bushel of sweet potatoes weighs 55 pounds, and one-quarter of this is fermentable matter, or nearly 14 pounds. This would yield, approximately, 7 pounds, or a little over one gallon of 95 percent alcohol. It may be fairly stated, therefore, in a general way, that a bushel of sweet potatoes will yield one gallon of industrial alcohol. The average yield of sweet potatoes, of course, is very much less than that given in the South Carolina reports, where heavy fertilization was practised. On plots to which no fertilizer was added the yield was about 8,000 pounds of sweet potatoes per acre, yielding in round numbers 1,900 pounds of starch. The quantity of sugar in the 8,000 pounds is about 350 pounds, which, added to the starch, makes 2,250 pounds of fermentable matter per acre. This will yield 1,125 pounds of industrial alcohol of 95 percent strength, or approximately 160 gallons per acre.

The yield of sweet potatoes in the above computation must be regarded as exceptionally high. A safer calculation will be based upon the yield of 100 bushels of sweet potatoes per acre, a little above the average of the yield of the potato, or a total of 5,500 pounds per acre. One-quarter of this amount is fermentable matter—about 1,400 pounds—which would yield, approximately, 700 pounds of 95 percent alcohol, or 100 gallons of 95 percent alcohol per acre. In addition to the sugar in the form of sucrose, or common sugar, which the sweet potato contains, there is also an appreciable amount of non-crystallizable sugars. The total sugars in the sweet potato have not been overstated in the above estimate. In fact, the contrary, rather, is true, since the two sugars together probably average about six percent of the weight of the potato. If the average quantity of starch in the sweet potato is 20 percent, which is rather a low estimate, the total fermentable matter in the sweet potato is 26 percent instead of 25 percent, as estimated above.

Changes in Composition of the Sweet Potato of Different Varieties on Storing.[33]