226 TECHNICAL BULLETIN 15 



Likewise comparisons were made on jellies between refractive index and 

 direct sucrose readings from the refractometer scale. Here the results 

 cliecked very well. For example in 66 determinations the sucrose readings 

 averaged only 0.053 per cent more than the solids calculated from the re- 

 fractive index. The direct reading sucrose scale on the refractometer should 

 not be relied upon in testing apple juices for solids or sugar. The refracto- 

 meter gave more reliable results than the Brix hydrometer. 



Hydrogen Ion Concentration and Titrutable Acidity 

 of Extracted Apple Juices and Jellies. 



Data collected relative to the titratable acidity and pH of apples are pre- 

 sented in Table 1, while the resulting juices and jellies are considered in 

 Table 6. In general, the hydrogen ion concentration of the juice was slightly 

 lower than that of the fruit itself. The second and third extracts were lower 

 than the first. The resulting jellies made from the combined first and second 

 extracts corresponded closely in pH to the juices. Tarr (17) stated that pH 

 3.46 was the minimum at which jelly formation occurred with a relatively 

 pure source of pectin. From Table 6 it is evident that some of the jellies 

 made from apple juice exceeded this value. Apparently natural fruit juices 

 did not behave like pure pectin in this regard. 



The relation existing between total titratable acidity and hydrogen 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 total acidity, calculated 

 to malic, of the finished jelly varied from 0.22 per cent in Mcintosh to 0.66 

 per cent in Red Siberian Crab, while the pH varied from 3.2 in Red Astra- 

 chan to 3.62 in Baldwin, 1925 crop. 



Recovery of Soluble Solids, Pectin and Acid in Successive Extractions 

 Made under Various Conditions 



Data were compiled bearing upon the influence of the following factors 

 upon the percentage composition of the extracts from eight varieties of 

 apples. 



1. Successive extractions 



2. Sliced and chopped apples 



3. Ratio of fruit to water during extraction 



4. Time of extraction 



5. Temperature of extraction 



6. Added acids 



7. Yearly variations of Baldwin apples 



Tables 7 — 12 and Charts 1 — 5 contain condensed analytical data showing 

 the mean percentage of soluble solids and pectin successively extracted from 

 eight varieties of apples by the use of various methods. Weighted averages 

 were used throughout. Due to space limitations, physical and organoleptic 

 observations were omitted. In spite of the number of tests some few incon- 

 sistencies occurred, yet on the whole the results were fairly uniform and 

 showed definite trends. Because of the large nimiber of tests with Baldwin 

 apples under controlled conditions, it is believed that considerable significance 

 may be attached to them. 



