10 MASS. EXPERIMENT STATION BULLETIN 440 



iodine content of apples and applesauce has been determined by Nebraska and 

 Ohio investigators, who found that dried Nebraska apples contain from 89 to 340 

 parts per billion of iodine. Dried apples in the Oregon goitrous region contained 

 only 3 parts per billion; whereas Ohio applesauce showed 125 parts per billion of 

 iodine (American Can Company.) 



Acids 



The chief organic acid of the apple is malic acid, which is found to the extent 

 of from 0.5 to 1.0 percent. Citric acid has been found in only a few varieties. 

 Crab apples may contain as much as 0.03 percent citric acid. Yellow Transparent 

 0.02 percent, and Winesap a trace. Apples also contain a small quantity of 

 tannic acid (which contributes astringency to their flavor) and uronic acid. 

 Uronic acid is closely related to pectin, as discussed previously. Ursolic acid, a 

 complex organic acid, is one of the principal components of the waxy coating of 

 the skin of the apple. 



Apples as eaten have an acid reaction, but because of their buffering capacity 

 they influence the acid-base balance of the body as an alkaline food. The organic 

 acids of the apple are oxidized in the body to furnish energy and leave a basic 

 residue in the blood. The preponderance of base-forming elements in the apple 

 leads to the formation of a urine less acid than normal. The apple thus safe- 

 guards the body from reduction of the bicarbonate concentration or alkali reserve 

 of the blood. 



One of the first studies of the titrable acidity and hydrogen-ion concentration 

 of New England apples was made by Fellers (1928), who found that the acidity 

 of Massachusetts varieties of apples varied only in very narrow limits, namely 

 from pH 3.6 to pH 3.2. The relation between total titratable acidity and hydro- 

 gen-ion concentration was reasonably constant; i.e., the higher the hydrogen-ion 

 concentration the higher the acidity and vice versa. Some varieties appeared to 

 contain more buffer substances than others. The titratable acidity of apple juice 

 and jelly manufactured from these apples was also determined. The juice was 

 slightly lower in hydrogen-ion concentration than the fruit itself; the second and 

 third extracts were lower than the first. The total acidity of the finished jelly, 

 calculated as malic acid, varied from 0.22 percent in Mcintosh to 0.66 percent in 

 Red Siberian Crab; while the pH value ranged from 3.2 in Red Astrachan to 3.6 

 in Baldwin. 



The hydrogen-ion concentration and the titratable acidity of thirteen varieties 

 of New York apples was determined by Pfund (1939). Nearly all had pH values 

 between 3.0 and 4.0; and if all the titrable acid is considered to be malic, the 

 molarity values are between 0.070 M and 0.013 M. Of all the apple fruits ex- 

 amined, approximately 86 percent had pH values between 3.1 and 3.7 and molar- 

 ity values between 0.055 M and 0.18 M. The differences between the pH values 

 of raw apple juice, baked apples, and applesauce were not significant; therefore, 

 the pH value of the raw apple juice may be considered as representative for the 

 acidity of the cooked product. The data are shown in Table 6. 



The basic effect of apples on the alkali reserve of the blood and acidity of the 

 urine was studied by Shea and Fellers (1942). The term "alkali reserve" refers 

 to the amount of basic elements (such as calcium, magnesium, potassium, and 

 sodium) combined as bicarbonates in the blood. These bicarbonates provide a 

 readily available source of base for the neutralization of acids. Nine healthy men 

 from 22 to 27 years of age were placed on two diets; one group received an acid- 



