APPLE JUICE EXTRACTION FOR JELLY 225 



(see Table 3) in the residual pulp than was obtained in the first extract 

 from the fruit. However, since the weiglit of juice obtained in tiie several 

 extractions was nuich greater than that of the pulp, the actual amount of 

 pectin remaining in tiie pulp was much less. This is shown clearly in Tables 

 10 and 11. An average of 31 tests, where the ratio of fruit to extraction 

 water was 3:2 and the tune 15 minutes at 100°C., showed that 25.5 per cent 

 of the pectin remained in the pulp. AVliere the ratios were 3:3 and 3:4, the 

 percentages of pectin in the pulps were 20.4 and 19.1 respectively. 



In Table 4 are found the mean actual amounts of soluble solids, pectin and 

 acid calculated to malic, in the combined first, second and third extracts plus 

 that found in the residual pulp. These figures approximated the composition 

 of the fruit itself. Altliough some differences existed among the several 

 varieties, there were only slight variations between tests on the same variety. 

 For example, in 91 different tests on Baldwin apples, the mean value for 

 soluble solids was 134.7 grams per kilogram of fruit with an average devia- 

 tion from the mean of 9.55 grams. Similarly the values for pectin were 4.84zt 

 0.50 and for acid calculated as malic, 4.01 ±0.57. Red Siberian Crab, Wine- 

 sap, and King David gave the highest yields of soluble solids; Red Astrachan 

 and Wealthy were among the lowest. The Winesap and Baldwin varieties 

 carried the most pectin while Mcintosh, Red Astrachan and King David 

 contained the least. Red Siberian Crab, Red Astrachan and King David 

 produced the juice of highest acidity for jelly, while Mcintosh and Baldwin 

 yielded juice of low acidity. 



Comparison of Brix Hydrometer and Abbe Refractometer 

 for Solids and Sugar D eterndnations in Apple Juice. 



Check determinations of soluble solids (mainly sugar) were made by both 

 the Brix hydrometer and the Abbe refractometer, to ascertain which gave 

 the more accurate results. Percentages of sugar from a direct reading suc- 

 rose scale on the refractometer also were compared with the refractive index 

 values as computed from the Tables by Schonrock (2) and with the total 

 sugars as determined gravimetrically. Temperature corrections were made 

 according to Stanek (2), though every effort was used to make readings at 

 20° C. so that such corrections usually were unnecessary. The A. O. A. C. 

 table (2) for correcting saccharonieters for temperature variations was used. 

 The results obtained from the chemical determinations of solids and sugar 

 made according to the A. O. A. C. methods are given for comparison in 

 Table 5. 



The sugar constituted an average of only 76.5 per cent of the soluble solids 

 present in the juice. For this reason care must be exercised to report Brix 

 or refractometer readings in terms of solids rather than sugar. The Brix 

 reading was too high consistently as were the values olitained from the 

 direct reading sucrose scale on the refractometer. The latter registered a 

 mean difference of 1.45 per cent over the total sugars actually present. The 

 computation of solids from refractive index gave good results, though they 

 were usually slightly lower than those obtained by use of the gravimetric 

 method. As a result of 263 comparisons between Brix and refractometer 

 readings on total solids in heat extracted Baldwin apple juices, the Brix 

 method gave a mean increase in solids of 0.308 per cent. In 101 tests on 

 other apple varieties the increase was only 0.22 per cent. These results 

 corroborated certain data recently reported by Slierwood (15) on the re- 

 fractometer analysis of sugar beet juice. 



