238 TECHNICAL BULLETIN 15 



3. Long extraction periods were unsatisfactory because of destruction of 

 the jellifying power of tlie pectin. Jelly yields and quality were injured 

 materially. For example, two 15-minute extractions removed from 50 to 80 

 per cent more soluble solids, pectin and acid than a single 30-minute ex- 

 traction. 



4. Although fair yields of solids, pectin and acid were obtained at an 

 extraction temperature of 88° C. (190° F.), the optimum was found to be 

 100°C. (212°F.). Retorts or pressure cookers at 109°C. (228°F.) gave only 

 slightly higher yields of solids and pectin in the juice than were obtained at 

 the boiling point, and their use is not recommended for juice extraction. 



5. The best ratio of fruit to water was 3:2 in the case of sliced apples, or 

 3:3 where chopped or grated apples were used. The yield of jelly per pound 

 of fruit was greater where the ratio was 3:i and least when it was 3:2. 



6. Tartaric acid added to the apple-water mixture in concentrations of 

 0.2 to 0.4 per cent slightly increased the yield of solids and pectin in the 

 extract as well as the total jelly yield. Added acid always improved the 

 color and often the flavor and consistency of apple jellies. 



7. Finely chopped apples gave a slightly more concentrated juice and 

 greater jelly yield than sliced apples, but because of the difficulty of filtering 

 and the cloudiness of the finished jellies, chopping is not recommended. 



8. In short extraction periods the jelly strength of the jellies increased 

 with the percentage of pectin present. In longer extractions where the 

 jellifying power of the pectin had been injured by prolonged heat, this rela- 

 tion did not hold. 



Apples suitable for jelly should yield approximately 20 ounces of jelly per 

 pound of fruit. 



Jelly yields depended primarily upon the amount of jellifying pectin pres- 

 ent in the juice, and the amount of sugar used. Less sugar should be used 

 where pectin is present only in limited amounts or where its jellifying power 

 has been injured by hydrolysis. 



In general those jellies containing the most pectin were very firm and 

 tough in consistency unless additional sugar was used. The hydrogen ion 

 concentration of the varieties tested was suitable for the formation of good 

 yields of well flavored jellies. 



There was a fair degree of correlation between the total titratable acidity 

 and hydrogen ion concentration in apples, apple juice and jelly. That is, high 

 total acidity and high hydrogen ion concentration were present in the same 

 samples of apples, juices or jellies. 



The sugar content of apple jellies ranged from 65 to 70 per cent with an 

 average of 67.5 per cent. Jellies containing less than 65 per cent sugar were 

 often tough while those with over 70 per cent were uniformly soft or syrupy. 

 In making jellies from fruit, it was found much more desirable to proportion 

 the sugar to the original weight of fruit than to an vmcertain yield of juice of 

 questionable composition. 



The determination of jelly strength by means of the Bloom gelometer gave 

 very concordant results. 



Brix hydrometer readings on extracted apple juice gave an average of 0.18 

 per cent higher than by the Abbe refractometer and 0.15 per cent higher 

 than by the gravimetric determination of solids in solution. The mean sugar 

 content of the soluble solids in heat extracted apple juice was 76.5 per cent. 



