224 TECHNICAL BULLETIN 15 t 



from a given weight of apple was somewhat less than where greater dilu- 

 tions were used. On the other hand since longer heating was required for 

 the conversion of a dilute juice into jelly, there was a more or less serious 

 loss in the jellifying power of the pectin. In other words the total amount 

 of pectin maj' be greater in the more dilute extracted juices, yet because of 

 deesterification (10) of pectin by heat and acid, its jellifying qualities may 

 be impaired. This hydrolysis of the pectin may affect seriously the yield and 

 the quality of the resultant jelly if the extraction period is too extended. 

 This readily became apparent when a 30-minute extraction period was used, 

 and caused irreparable loss in jelly yield and in quality if extended to 60 

 minutes. (See Table 14). 



Due to evaporation during extraction, the yields of juice from the longer 

 extraction periods were less in general than those from shorter periods, 

 though the former contained more solids including pectin. As already stated, 

 this may mean little, because the pectin may be partly demethoxylated and 

 of poorer quality (7, 9, 10). The results here presented indicate clearly that 

 a loss occurred. The least amount of pectin was extracted in the 15-minute 

 extraction period, the most in the 60-minute period. There was little differ- 

 ence in either juice yields or composition in the 15-minute extraction period 

 as compared with a 15-minute extraction period followed by 10 minutes 

 standing removed from the source of heat. An additional column in Table 

 2 was inserted to show the actual amounts of pectin obtained in the com- 

 bined first and second extracts from one kilogram of apples. The amount 

 increased with both the length of the extraction period and the widening of 

 the apple-water ratio. The same observation applied though in a different 

 degree in the case of soluble solids and acidity. 



Composition of Heat Extracted Apple Juice (8 varieties) 



(Extraction Period, 15 Minutes at 100°C.) 

 Table 3 is largely self-explanatory and was prepared to show the general 

 composition of the juice obtained from the first, second, and third extrac- 

 tions and of the residual marc or pulp. Since different temperatures or 

 periods of extraction showed only minor variations in the composition of the 

 juices, they have not been included. The chopped fruit yielded slightly more 

 concentrated juices than the sliced; similarly tlie longer the extraction, the 

 more concentrated became the juice, but for practical purposes these dif- 

 ferences were insignificant. 



The averages reported in Table 3 were found to be very similar to others 

 compiled using different methods of extraction and even distinct apple va- 

 rieties. Some varieties were better for jelly making than others (see Tables 

 10 and 11), but as previously shown in Table 1, there were no striking varia- 

 tions in solids among the eight varieties analyzed. The differences in pectin 

 content were marked and merited some attention. The large amount of pectin 

 remaining in the residual pulp was striking. The A. O. A. C. methods (2) 

 of analysis, no doubt, were responsible for a part of this high percentage. 

 The method required boiling 300 grams of the pulp with 800 c. c. of water 

 for 60 minutes, replacing from time to time the water lost by evaporation. 

 Thus, much additional pectin was brought into solution. Moreover, by re- 

 peating the operation still more pectin was obtained. The method yielded/ 

 arbitrary results only, and did not indicate the absolute amount of pectin 

 present in the pulp. Nevertheless it proved of value in comparative work 

 such as this. In general, a slightly higher percentage of pectin was found 



